Characterization of Recharge Mechanisms and...

21
Research Article Characterization of Recharge Mechanisms and Sources of Groundwater Salinization in Ras Jbel Coastal Aquifer (Northeast Tunisia) Using Hydrogeochemical Tools, Environmental Isotopes, GIS, and Statistics Jamila Hammami Abidi, 1 Boutheina Farhat, 1 Abdallah Ben Mammou, 1 and Naceur Oueslati 2 1 Faculty of Sciences of Tunis, Laboratory of Mineral Resources and Environment, University of Tunis El Manar, 2092 Tunis, Tunisia 2 Regional Commission for Agricultural Development, av. Hassen Nouri, 7000 Bizerte, Tunisia Correspondence should be addressed to Jamila Hammami Abidi; [email protected] Received 25 November 2016; Accepted 5 February 2017; Published 8 May 2017 Academic Editor: Franco Frau Copyright © 2017 Jamila Hammami Abidi et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Groundwater is among the most available water resources in Tunisia; it is a vital natural resource in arid and semiarid regions. Located in north-eastern Tunisia, the Metline-Ras Jbel-Raf Raf aquifer is a mio-plio-quaternary shallow coastal aquifer, where groundwater is the most important source of water supply. e major ion hydrochemistry and environmental isotope composition ( 18 O, 2 H) were investigated to identify the recharge sources and processes that affect the groundwater salinization. e combination of hydrogeochemical, isotopic, statistical, and GIS approaches demonstrates that the salinity and the groundwater composition are largely controlled by the water-rock interaction particularly the dissolution of evaporate minerals and the ion exchange process, the return flow of the irrigation water, agricultural fertilizers, and finally saltwater intrusion which started before 1980 and which is partially mitigated by the artificial recharge since 1993. As for the stable isotope signatures, results showed that groundwater samples lay on and around the local meteoric water line LMWL; hence, this arrangement signifies that the recharge of the Ras Jbel aquifer is ensured by recent recharge from Mediterranean air masses. 1. Introduction e hydrogeology of coastal aquifers has been studied inten- sively during the past decades, stimulated by both scientific interest and societal relevance [1]. Coastal areas throughout the Mediterranean face salinization problems of groundwater which is the major source of water supply especially for drink- ing and agricultural sector. e imbalance between abstrac- tion and natural recharge rates causes an overexploitation of groundwater resources resulting in declining groundwater table, water quality degradation, and crop damage. A number of aquifers in coastal zones are being increas- ingly exploited and affected ([2–6]). For instance, ground- water contamination and decline of water levels have been reported in Tunisia [7–13] and in many countries around the world. It has been reported in India [14], Jordan [15], Australia [16], USA [17], China ([18, 19]), Netherland [1], and among many others. In semiarid coastal regions of north-eastern Tunisia, such as Ras Jbel plain, the groundwater is usually the main resource used for irrigation and drinking purposes. Never- theless, salinization is becoming a common problem affecting groundwater resources. Groundwater exploitation of the Ras Jbel aquifer began in 1949 and has increased each year since 1980. Under pressures of population, climate change, and pollution, the aquifer faces substantial challenges in the management of scarce freshwater resources. During the last four decades, the shallow aquifer groundwater has been over- exploited through excessive, uncontrolled pumping mainly for domestic and agricultural purposes [20]. Salinization Hindawi Journal of Chemistry Volume 2017, Article ID 8610894, 20 pages https://doi.org/10.1155/2017/8610894

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Research ArticleCharacterization of Recharge Mechanisms and Sources ofGroundwater Salinization in Ras Jbel Coastal Aquifer (NortheastTunisia) Using Hydrogeochemical Tools EnvironmentalIsotopes GIS and Statistics

Jamila Hammami Abidi1 Boutheina Farhat1

Abdallah BenMammou1 and Naceur Oueslati2

1Faculty of Sciences of Tunis Laboratory of Mineral Resources and Environment University of Tunis El Manar 2092 Tunis Tunisia2Regional Commission for Agricultural Development av Hassen Nouri 7000 Bizerte Tunisia

Correspondence should be addressed to Jamila Hammami Abidi hammamijamilayahoofr

Received 25 November 2016 Accepted 5 February 2017 Published 8 May 2017

Academic Editor Franco Frau

Copyright copy 2017 Jamila Hammami Abidi et alThis is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Groundwater is among the most available water resources in Tunisia it is a vital natural resource in arid and semiarid regionsLocated in north-eastern Tunisia the Metline-Ras Jbel-Raf Raf aquifer is a mio-plio-quaternary shallow coastal aquifer wheregroundwater is the most important source of water supplyThe major ion hydrochemistry and environmental isotope composition(12057518O 1205752H) were investigated to identify the recharge sources and processes that affect the groundwater salinization Thecombination of hydrogeochemical isotopic statistical and GIS approaches demonstrates that the salinity and the groundwatercomposition are largely controlled by the water-rock interaction particularly the dissolution of evaporate minerals and the ionexchange process the return flow of the irrigation water agricultural fertilizers and finally saltwater intrusion which started before1980 and which is partially mitigated by the artificial recharge since 1993 As for the stable isotope signatures results showed thatgroundwater samples lay on and around the local meteoric water line LMWL hence this arrangement signifies that the rechargeof the Ras Jbel aquifer is ensured by recent recharge fromMediterranean air masses

1 Introduction

The hydrogeology of coastal aquifers has been studied inten-sively during the past decades stimulated by both scientificinterest and societal relevance [1] Coastal areas throughouttheMediterranean face salinization problems of groundwaterwhich is themajor source ofwater supply especially for drink-ing and agricultural sector The imbalance between abstrac-tion and natural recharge rates causes an overexploitationof groundwater resources resulting in declining groundwatertable water quality degradation and crop damage

A number of aquifers in coastal zones are being increas-ingly exploited and affected ([2ndash6]) For instance ground-water contamination and decline of water levels have beenreported in Tunisia [7ndash13] and in many countries around the

world It has been reported in India [14] Jordan [15] Australia[16] USA [17] China ([18 19]) Netherland [1] and amongmany others

In semiarid coastal regions of north-eastern Tunisiasuch as Ras Jbel plain the groundwater is usually the mainresource used for irrigation and drinking purposes Never-theless salinization is becoming a commonproblem affectinggroundwater resources Groundwater exploitation of the RasJbel aquifer began in 1949 and has increased each yearsince 1980 Under pressures of population climate changeand pollution the aquifer faces substantial challenges in themanagement of scarce freshwater resources During the lastfour decades the shallow aquifer groundwater has been over-exploited through excessive uncontrolled pumping mainlyfor domestic and agricultural purposes [20] Salinization

HindawiJournal of ChemistryVolume 2017 Article ID 8610894 20 pageshttpsdoiorg10115520178610894

2 Journal of Chemistry

a

D

Qp-t

Recent Alluvia

Dunes

Upper Pleistocene-Tyrrhenian

Old soils and eboulisAa

Upper Pleistocene

Deposits of beaches and littoral cordons

Quaternary sailor and old dune

Pliocene Maris of Raf Raf Pontien red sandy maris Brownclays brown maris and sand coarse

Maris of the Bel Khedim Wadi

Flysh of Kechabta Alternation of maris and sandstone

Wadis

Faults

Mediterranean sea

m2a

m2b

qm1

m3

PIa

Qpa

qm2

N

5 km

440

435

430

440

435

430515 520 525 530

515 520 525 530

Figure 1 Geological and location map of the study area [28ndash30]

due to seawater intrusion and decreasing groundwater levelshas recently been identified [21] Unplanned and substantialwithdrawals of groundwater from the shallow aquifer of RasJbel have resulted in severe water level decline of up to7m in some areas and high total dissolved solids (TDS)contents reaching 8000mgl Reports of increasing salinity ofgroundwater supplies in the area suggest a need to define thesources of salt water It is also useful to study the rechargemechanisms as well as the mixing fresh watersaline water

Stable isotope and geochemical techniques have beenused in groundwater studies of coastal aquifers worldwide[22ndash25] for determining the origins of groundwater salin-ization in aquifers and processes that affect water chem-istry such as rock weathering evaporation atmosphericprecipitation and cation exchange Consequently studyingstable isotope and geochemical techniques can significantlyimprove our understanding of groundwater hydrodynamicalprocesses and chemical evolution [26] In the present studyenvironmental isotopes (12057518O 1205752H) in conjunction withhydrochemistry (major ions) were employed (1) to define thepotential sources and different mechanisms of groundwatersalinization in the study area (2) to discuss the chemicalevolution of groundwater and (3) to explain groundwaterrecharge and discharge in the coastal plain of Metline- RasJbel- Raf Raf

2 Study Area

TheMetline-Ras Jbel-Raf Raf plain which covers a total areaof about 50 km2 represents one of the most important

0100200300400500600700800900

1000

Prec

ipita

tions

(mm

)

1993

1967

1965

1963

1997

1999

1973

1975

2001

1985

1983

1995

2003

1979

1977

1971

1969

1961

1981

1959

1989

1987

2005

2007

1991

Year

Figure 2 Yearly precipitation inMetline-Ras Jbel-Raf Raf plain [6465]

agricultural regions in north-eastern Tunisia (Figure 1) It ischaracterized by a semiarid ldquoMediterraneanrdquo climate withmild wet winters and warm dry summers [27 28]The aver-age annual precipitation ranges from approximately 258 to993mm (Figure 2) Geologically it is limited to the south byJbelDjaouf EnNadhour and EdDemina to the southwest byJbel Sidi Saleh Hakima and El Faouar to northwest by JbelBab Banzart Sidi Bou Choucha and Touchela to the northandnortheast by theMediterranean seaTheplain ofMetline-Ras Jbel-Raf Raf is a wide basin of collapse formed by a sub-sidence followed by an alluvial and recent sedimentation Itis affected by folding and faults in NW-SE and SSW-NNEdirections Sedimentary series extend fromMiocene to Qua-ternary The lithological description of these sediments [28ndash30] reveals that the Miocene is represented by the Kechabta

Journal of Chemistry 3

844 Mm3 water resources

Number of monitoring wellsExploitation (Mm3year)

02468

10121416

Expl

oita

tion

(Mm

3y

ear)

020040060080010001200140016001800

Num

ber o

f mon

itorin

g w

ells

1980 1985 1990 1995 2000 20051966

Figure 3 Evolution of the exploitation rate and the monitoring wellnumber of the shallow aquifer of Ras Jbel during 1966 and 2005 [3031]

and Wadi Bel Khedim formations The Kechabta formationhas a thickness of about 1000m and consists of alternationof marls and fine sandstone benches The Wadi Bel Khedimformation is of 250m thickness At the east of Raf Raf itis composed of large outcrops of gray marls with gypsumbenches The Quaternary series unconformably overlie theMiocene series and is divided into seven units (from bottomto the top qm1 Aa qm2 Qpa Qp-t D and a)

Hydrologically theQuaternary series and the current for-mations characterized by their extension and their good per-meability host the shallow aquifer of Ras Jbel This aquifer isrecharged by local infiltration on the plain by water flowingfrom the surrounding hills and from the different riverscrossing the plain Wadi Beni Ata and Wadi Ali in Beni AtaregionWadi El Kantra El Blaat and ElMa in Ras Jbel regionWadi Sandid draining the zone of Raf Raf andWadi El Kantrain the region of Dar El Khaddar Pumping tests showed thattransmissivity can reach 1510minus4m2s The most transmissiveareas are the low alluvial plain of Bahirat Beni Ata the lowalluvial area ofWadi ElKrib andElAouinet and the upstreamarea of Ain Cherchar Ain Ezzaouia Ain Kassa and Ain ElHammam as well as the sandstone dune of Ain ElMestir andAin Mahloul

The shallow aquifer of Ras Jbel is affected by natu-ral and anthropogenic factors like evaporation irrigationpumping and so forth The aquifer is tapped by severalprivate and state owned wells In the period between 1985and 1990 the exploitation rate was estimated at 135Mm3year which exceeded the renewable resources evaluated at844Mm3year [31] The total number of dug wells has beenestimated to be 1387 in 1985 1396 in 1990 and 1563 in 2005 In2005 the exploitation rate was estimated at 1027Mm3year(Figure 3) The massive exploitation of aquifer resources inresponse to the heavy pumping caused a drop in the waterlevel (Figure 4) and the deterioration of water quality In1949 the salinity of the groundwater varied between 648and 1692mgl [32] The investigations carried out by theDGRE between 1985 and 1993 through several monitoringwells revealed the existence of a very saline groundwaterThedegradation of the water quality has been detected mainly incoastal areas where salt concentrations exceeded 15 gl in 1985

and 8 gl in 1993 and in the depression of Bahirat Beni Atawhere the ante-quaternary substratum is below the sea level[21]

3 Methods

31 Water Sampling and Chemical Analysis Ninety-foursamples (including pumpingwells and piezometers)were col-lected for geochemical analysis (major elements) and isotopes(1205752H 12057518O) during the wet and the dry season of Marchand July 2007 (Figure 5) Sampling locations were recordedusing a potable GPS device Prior to sampling all wellswere pumped for several minutes to eliminate the influencefrom stagnant water Samples were collected in cleanedpolyethylene bottles tightly capped and stored at 4∘C untilanalysis Electrical conductivity (EC) salinity and pH weremeasured in the field using a portable conductivity salinityand pH meter

Chemical analyses were done using a Varian 730-ES ICPOptical Emission Spectrometer for cations and using ionchromatography (DX-120 Dionex USA) for anions HCO3

minus

was measured by titration (Hach USA) Samples for stableisotope analysis were collected according to the proceduresdescribed by Clark and Fritz [33] Isotopic analyses wereconducted in the isotopic laboratory of the department ofHydrology andGeo-environmental Sciences of the Faculty ofEarth and Live Sciences of the Free University of AmsterdamIsotopic ratios are expressed in per mil (120575) and oxygen andhydrogen isotope analyses were reported to 119889 notation rel-ative to Vienna Standard Mean Oceanic Water (V-SMOW)where 119889 = [(RsRVSMOW) minus 1] times 1000 Rs represents eitherthe 18O16Oor the 2H1H ratio of the sample and RSMOW is18O16O or the 2H1H ratio of the SMOW Typical precisionsare plusmn01 and plusmn1 for oxygen-18 and deuterium respectively

32 Statistical Analysis The physicochemical parametersand chemical composition of the groundwater samples arepresented inTable 1 All the acquired datawere integrated intohydrogeochemical database in order to study the ground-water quality and to identify the groundwater salinizationprocesses that contributed to the acquisition of the actualchemical composition

Piper plots [34] considered as the common method for amultiple analyses on the same graph are used to representthe different water samples and to distinguish graphicallybetween different water types defined by the Stuyfzand clas-sification (1993) Sample points with similar hydrochemistrytend to cluster together in the diagram [35]

Principal component analysis method (PCA) and correla-tions are a popular method to assess groundwater qualityOne of the principle advantages of multivariate techniquessuch as principal component analysis (PCA) is that they areable to rapidly reveal relationships between a large numberof variables In this study PCA and correlations are used toidentify the possible sources of major ions in groundwaterhydrogeological reactions that may occur in the study areaand dominant factors that control groundwater quality

Gibbs diagrams which are a simple plot of the TDS versusthe weight ratio of Na+(Na+ + Ca2+) or Clminus(Clminus +HCO3

minus)

4 Journal of Chemistry

N

Mediterranean sea

15

0 05 1 2 3 4(Km)

Piezometric map (1988)

Pizometric contour (m)

Limit of Ras Jbel plain

Wadis

514000 516000 518000 520000 522000 524000 526000 528000

514000 516000 518000 520000 522000 524000 526000 528000

438000

436000

434000

432000

430000

438000

436000

434000

432000

430000

Figure 4 Piezometric contour maps of the study area [31]

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Sampling points

Dams

Large urban agglomeration

Wadis

Limit of the plain of Ras Jbel

0 05 1 2 3 4

(Km)

Figure 5 Location of sampled wells and piezometers in the study area

are widely used to establish the relationships between thewater composition and the lithological characteristics of theaquifer [36] Three distinct fields including precipitationdominance evaporation dominance and rock weatheringdominance constitute the segments in the Gibbs diagram

Hydrogeochemical Modeling The equilibrium state of thewater with respect to a mineral phase can be determined bycalculating saturation index (SI) using analytical data In thisstudy saturation indices (SI) were calculated in terms of thefollowing equation [37]

SI = log( IAP119896119904 (119879)) (1)

where IAP is the relevant ion activity product which can becalculated by multiplying the ion activity coefficient 120574iand the composition concentration 119898119894 and 119896119904(119879) is theequilibrium constant of the reaction considered at the sam-ple temperature [35] The geochemical modeling programPHREEQC has been used to evaluate the water chemistry

SI gt 0 indicates oversaturation and minerals may be subjectto precipitation SI lt 0means undersaturation and mineralswill dissolve and SI = 0 suggests saturation and minerals arein equilibrium status with respect to the solution [38]

4 Results and Discussion

41 Hydrogeochemical Characterization Groundwater qual-ity depends on various chemical constituents and theirconcentrations which are mostly derived from the geologicalstratum of the particular region [6] The pH was one of theprimary indicators of the water chemistry evolution Theaquifer groundwater was neutral to slightly alkaline waterwith a mean pH value of 723 and 715 in the wet anddry season respectively Electrical conductivity (EC) of thewater samples was medium to high suggestive of very highlymineralized waters EC values ranged between 1240 and6300 120583Scm in the wet season and between 1131 and 5430 120583Scm in the dry season A problem to the water supply devel-opment in the area is the increasing electrical conductivity

Journal of Chemistry 5

Table1Ch

emicaldataof

sampled

wellsandpiezom

etersintheR

asJbelaquifer

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

13670

741

2369

225

8944

310

999

298

305

5430

723630

299

140

757

121792

343

287

23990

705

2519

447

57413

41022

307

270

3760

721

2446

447

58376

1989

326

250

33840

68

2649

442

54425

11997

384

338

3480

705

2451

421

48392

9918

356

308

44120

713166

368

72647

51021

742

311

3900

722612

327

63506

2789

626

299

56300

69

4110

520

89738

71390

1005

361

5530

706

4323

501

94731

41599

1040

354

65080

695

3345

403

8166

68

1160

661

366

3850

715

2832

363

66499

5953

598

348

75790

69

3630

560

115

550

41457

635

309

4740

73231

523

103

471

3118

1633

317

83730

69

2306

286

115

284

20895

377

329

3560

711

2407

353

135

294

12876

421

317

95660

703

3800

368

129

881

111487

563

361

4660

716

3126

339

9660

97

1248

498

329

103530

732384

249

59388

25788

589

287

2840

763

1989

258

46347

20610

489

220

1144

80712

3260

379

7264

618

989

820

337

3650

719

2674

334

59500

13774

683

311

123250

72142

230

55346

37705

477

293

3160

735

2360

285

55434

37720

543

287

132770

71658

216

45264

31474

352

277

2540

735

1710

243

41262

29487

380

268

142480

765

1972

278

46337

24659

382

246

2860

749

2040

263

50343

23662

462

238

156250

796

4089

466

86857

961463

811

310

4230

735

3049

353

71605

26866

684

445

164190

762480

258

7844

422

830

619

231

3520

738

2392

276

70421

19766

598

244

173990

752715

274

49550

107

775

460

500

3290

772497

280

50426

80652

413

598

182920

722046

221

56330

79472

444

445

2240

729

1841

199

45289

7544

4363

427

192730

775

1817

236

54285

25451

382

381

2250

731680

215

46256

31427

395

311

204020

723

2747

208

131

525

61011

481

386

3360

733

2389

206

124

410

3872

384

390

211240

778

819

4836

165

7289

102

173

2120

755

1317

104

57270

5639

108

134

223280

705

2358

258

55377

35844

515

275

2910

765

1835

230

42338

32589

366

238

231573

768

924

8419

200

6276

89250

1131

782

783

7312

182

3217

88207

245170

715

2891

505

75510

81185

407

201

4060

705

2697

490

67433

51066

436

201

254610

732910

189

113

576

7916

652

458

3880

733

2889

211

123

590

4878

650

433

265050

732330

733

1666

216

55270

1246

4264

387

273400

755

1938

255

65287

27594

415

296

2720

733

1928

257

62312

35568

371

323

283160

761662

178

48289

87478

356

226

2520

739

1910

279

57280

16593

393

293

292950

789

2176

187

66419

6713

587

198

303580

722353

199

80437

11819

613

195

3240

752217

205

72427

11732

582

189

313090

752187

225

71394

10710

560

217

3240

754

2330

228

68424

7766

637

201

323490

762317

231

69479

10749

560

221

3830

735

2804

269

80572

7866

723

287

334290

712886

358

7040

420

954

729

351

5080

775

3608

454

90654

231107

884

397

343640

725

2648

292

66520

15851

591

315

3410

735

2429

305

67401

12764

575

305

6 Journal of Chemistry

Table1Con

tinued

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

353860

725

2836

326

81550

27874

634

344

3420

751

2487

304

71455

14756

571

317

364820

795

3253

398

81472

361084

789

393

4110

743

3015

348

74539

38922

729

366

373740

745

2390

230

78412

17829

607

218

3320

732

2441

265

70474

16757

609

250

382720

771881

197

55332

9591

465

232

3650

752628

292

71491

6821

654

293

392080

771378

169

32251

11470

336

1101817

749

1269

158

30213

8391

319

153

403540

742454

231

75419

8823

620

278

3770

719

2727

273

81489

7865

696

317

415030

713010

402

81456

14116

6689

201

3130

767

2233

232

68431

7734

578

183

422820

793

2061

179

65371

6683

580

177

442980

712

1817

236

43324

78531

337

270

2090

752

1694

198

42234

64502

355

299

452670

711694

215

43277

69493

316

281

2130

741553

203

40258

67437

294

256

462840

741741

200

55267

9555

375

281

3050

732277

285

69390

3770

516

244

473310

705

1749

300

59217

3680

233

256

3170

732257

389

57249

2807

522

232

484990

706

2856

555

8240

05

1210

355

250

4120

712601

560

73327

21084

372

183

EC(120583scm

)TD

SCa2+M

g2+N

a+K+C

lminusSO42minusH

CO3minus(m

gl)

Journal of Chemistry 7

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

CE wet season (microsiemenscm)

1240ndash20802081ndash31603161ndash38603861ndash48204821ndash6300

Large urban agglomerationWadis

Limit of Ras Jbel plain

0 05 1 2 3 4

(Km)

(a)

0 05 1 2 3 4

(Km)

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Large urban agglomerationWadis

CE dry season(microsiemenscm)

1131ndash23302331ndash29102911ndash3560

3561ndash42304231ndash5530

Limit of Ras Jbel plain

(b)

Figure 6 Spatial distribution of electrical conductivity (a) wet season and (b) dry season in Ras Jbel aquifer

(EC) values of near-coastal shallow groundwater The highEC of groundwater from wells located along the coast and inBahirat Beni Ata can be explained by the seawater intrusioneffect caused by the groundwater level drawdown due tooverexploitation (Figures 6(a) and 6(b))

Based on the conductivity values the groundwater systemcould be classified into four groups fresh water (lt500 120583Scm) marginal water (500ndash1500 120583Scm) brackish water(1500ndash5000 120583Scm) and saline water (gt5000 120583Scm) Basedon our conductivity values it is evident that groundwaterin Ras Jbel aquifer is in marginal and brackish waters Fewsamples are of saline water type

The study area is characterized by a wide range of salini-ties Salinity values ranged between 500 and 3600mgl in thewet season and between 500 and 3500mgl in the dry seasonThe higher values of EC and salinity are indicators of higherionic concentrations probably due to the high anthropogenic

activities in the region and geological weathering conditionsbut also due to the intrusion of seawater into the groundwatersystem

The relative content of a cation or an anion is definedas the percentage of the relative amount of that ion to thetotal cations or anions respectively [39] In the study area thestrong acid anions (Clminus and SO4

2minus) exceed weak acid anions(HCO3

minus andCO32minus)On the other hand sodiumand calcium

concentrations exceed magnesium and potassium contentsThe triangular diagram (Figure 7) shows that the groundwa-ter chemistry was mainly characterized by two groups Thefirst group was ClminusndashNa+ type in which Na+ accounted formore than 52ndash65 of the total cations the second group wasClminusndashNa+Ca2+ type in which Na+ and Ca2+ accounted for37ndash48 and 36ndash53 of the total cations respectively Chem-ical facies in the phreatic aquifer of Ras Jbel seem to bedirectly related to the configuration of the ante-quaternary

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 2: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

2 Journal of Chemistry

a

D

Qp-t

Recent Alluvia

Dunes

Upper Pleistocene-Tyrrhenian

Old soils and eboulisAa

Upper Pleistocene

Deposits of beaches and littoral cordons

Quaternary sailor and old dune

Pliocene Maris of Raf Raf Pontien red sandy maris Brownclays brown maris and sand coarse

Maris of the Bel Khedim Wadi

Flysh of Kechabta Alternation of maris and sandstone

Wadis

Faults

Mediterranean sea

m2a

m2b

qm1

m3

PIa

Qpa

qm2

N

5 km

440

435

430

440

435

430515 520 525 530

515 520 525 530

Figure 1 Geological and location map of the study area [28ndash30]

due to seawater intrusion and decreasing groundwater levelshas recently been identified [21] Unplanned and substantialwithdrawals of groundwater from the shallow aquifer of RasJbel have resulted in severe water level decline of up to7m in some areas and high total dissolved solids (TDS)contents reaching 8000mgl Reports of increasing salinity ofgroundwater supplies in the area suggest a need to define thesources of salt water It is also useful to study the rechargemechanisms as well as the mixing fresh watersaline water

Stable isotope and geochemical techniques have beenused in groundwater studies of coastal aquifers worldwide[22ndash25] for determining the origins of groundwater salin-ization in aquifers and processes that affect water chem-istry such as rock weathering evaporation atmosphericprecipitation and cation exchange Consequently studyingstable isotope and geochemical techniques can significantlyimprove our understanding of groundwater hydrodynamicalprocesses and chemical evolution [26] In the present studyenvironmental isotopes (12057518O 1205752H) in conjunction withhydrochemistry (major ions) were employed (1) to define thepotential sources and different mechanisms of groundwatersalinization in the study area (2) to discuss the chemicalevolution of groundwater and (3) to explain groundwaterrecharge and discharge in the coastal plain of Metline- RasJbel- Raf Raf

2 Study Area

TheMetline-Ras Jbel-Raf Raf plain which covers a total areaof about 50 km2 represents one of the most important

0100200300400500600700800900

1000

Prec

ipita

tions

(mm

)

1993

1967

1965

1963

1997

1999

1973

1975

2001

1985

1983

1995

2003

1979

1977

1971

1969

1961

1981

1959

1989

1987

2005

2007

1991

Year

Figure 2 Yearly precipitation inMetline-Ras Jbel-Raf Raf plain [6465]

agricultural regions in north-eastern Tunisia (Figure 1) It ischaracterized by a semiarid ldquoMediterraneanrdquo climate withmild wet winters and warm dry summers [27 28]The aver-age annual precipitation ranges from approximately 258 to993mm (Figure 2) Geologically it is limited to the south byJbelDjaouf EnNadhour and EdDemina to the southwest byJbel Sidi Saleh Hakima and El Faouar to northwest by JbelBab Banzart Sidi Bou Choucha and Touchela to the northandnortheast by theMediterranean seaTheplain ofMetline-Ras Jbel-Raf Raf is a wide basin of collapse formed by a sub-sidence followed by an alluvial and recent sedimentation Itis affected by folding and faults in NW-SE and SSW-NNEdirections Sedimentary series extend fromMiocene to Qua-ternary The lithological description of these sediments [28ndash30] reveals that the Miocene is represented by the Kechabta

Journal of Chemistry 3

844 Mm3 water resources

Number of monitoring wellsExploitation (Mm3year)

02468

10121416

Expl

oita

tion

(Mm

3y

ear)

020040060080010001200140016001800

Num

ber o

f mon

itorin

g w

ells

1980 1985 1990 1995 2000 20051966

Figure 3 Evolution of the exploitation rate and the monitoring wellnumber of the shallow aquifer of Ras Jbel during 1966 and 2005 [3031]

and Wadi Bel Khedim formations The Kechabta formationhas a thickness of about 1000m and consists of alternationof marls and fine sandstone benches The Wadi Bel Khedimformation is of 250m thickness At the east of Raf Raf itis composed of large outcrops of gray marls with gypsumbenches The Quaternary series unconformably overlie theMiocene series and is divided into seven units (from bottomto the top qm1 Aa qm2 Qpa Qp-t D and a)

Hydrologically theQuaternary series and the current for-mations characterized by their extension and their good per-meability host the shallow aquifer of Ras Jbel This aquifer isrecharged by local infiltration on the plain by water flowingfrom the surrounding hills and from the different riverscrossing the plain Wadi Beni Ata and Wadi Ali in Beni AtaregionWadi El Kantra El Blaat and ElMa in Ras Jbel regionWadi Sandid draining the zone of Raf Raf andWadi El Kantrain the region of Dar El Khaddar Pumping tests showed thattransmissivity can reach 1510minus4m2s The most transmissiveareas are the low alluvial plain of Bahirat Beni Ata the lowalluvial area ofWadi ElKrib andElAouinet and the upstreamarea of Ain Cherchar Ain Ezzaouia Ain Kassa and Ain ElHammam as well as the sandstone dune of Ain ElMestir andAin Mahloul

The shallow aquifer of Ras Jbel is affected by natu-ral and anthropogenic factors like evaporation irrigationpumping and so forth The aquifer is tapped by severalprivate and state owned wells In the period between 1985and 1990 the exploitation rate was estimated at 135Mm3year which exceeded the renewable resources evaluated at844Mm3year [31] The total number of dug wells has beenestimated to be 1387 in 1985 1396 in 1990 and 1563 in 2005 In2005 the exploitation rate was estimated at 1027Mm3year(Figure 3) The massive exploitation of aquifer resources inresponse to the heavy pumping caused a drop in the waterlevel (Figure 4) and the deterioration of water quality In1949 the salinity of the groundwater varied between 648and 1692mgl [32] The investigations carried out by theDGRE between 1985 and 1993 through several monitoringwells revealed the existence of a very saline groundwaterThedegradation of the water quality has been detected mainly incoastal areas where salt concentrations exceeded 15 gl in 1985

and 8 gl in 1993 and in the depression of Bahirat Beni Atawhere the ante-quaternary substratum is below the sea level[21]

3 Methods

31 Water Sampling and Chemical Analysis Ninety-foursamples (including pumpingwells and piezometers)were col-lected for geochemical analysis (major elements) and isotopes(1205752H 12057518O) during the wet and the dry season of Marchand July 2007 (Figure 5) Sampling locations were recordedusing a potable GPS device Prior to sampling all wellswere pumped for several minutes to eliminate the influencefrom stagnant water Samples were collected in cleanedpolyethylene bottles tightly capped and stored at 4∘C untilanalysis Electrical conductivity (EC) salinity and pH weremeasured in the field using a portable conductivity salinityand pH meter

Chemical analyses were done using a Varian 730-ES ICPOptical Emission Spectrometer for cations and using ionchromatography (DX-120 Dionex USA) for anions HCO3

minus

was measured by titration (Hach USA) Samples for stableisotope analysis were collected according to the proceduresdescribed by Clark and Fritz [33] Isotopic analyses wereconducted in the isotopic laboratory of the department ofHydrology andGeo-environmental Sciences of the Faculty ofEarth and Live Sciences of the Free University of AmsterdamIsotopic ratios are expressed in per mil (120575) and oxygen andhydrogen isotope analyses were reported to 119889 notation rel-ative to Vienna Standard Mean Oceanic Water (V-SMOW)where 119889 = [(RsRVSMOW) minus 1] times 1000 Rs represents eitherthe 18O16Oor the 2H1H ratio of the sample and RSMOW is18O16O or the 2H1H ratio of the SMOW Typical precisionsare plusmn01 and plusmn1 for oxygen-18 and deuterium respectively

32 Statistical Analysis The physicochemical parametersand chemical composition of the groundwater samples arepresented inTable 1 All the acquired datawere integrated intohydrogeochemical database in order to study the ground-water quality and to identify the groundwater salinizationprocesses that contributed to the acquisition of the actualchemical composition

Piper plots [34] considered as the common method for amultiple analyses on the same graph are used to representthe different water samples and to distinguish graphicallybetween different water types defined by the Stuyfzand clas-sification (1993) Sample points with similar hydrochemistrytend to cluster together in the diagram [35]

Principal component analysis method (PCA) and correla-tions are a popular method to assess groundwater qualityOne of the principle advantages of multivariate techniquessuch as principal component analysis (PCA) is that they areable to rapidly reveal relationships between a large numberof variables In this study PCA and correlations are used toidentify the possible sources of major ions in groundwaterhydrogeological reactions that may occur in the study areaand dominant factors that control groundwater quality

Gibbs diagrams which are a simple plot of the TDS versusthe weight ratio of Na+(Na+ + Ca2+) or Clminus(Clminus +HCO3

minus)

4 Journal of Chemistry

N

Mediterranean sea

15

0 05 1 2 3 4(Km)

Piezometric map (1988)

Pizometric contour (m)

Limit of Ras Jbel plain

Wadis

514000 516000 518000 520000 522000 524000 526000 528000

514000 516000 518000 520000 522000 524000 526000 528000

438000

436000

434000

432000

430000

438000

436000

434000

432000

430000

Figure 4 Piezometric contour maps of the study area [31]

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Sampling points

Dams

Large urban agglomeration

Wadis

Limit of the plain of Ras Jbel

0 05 1 2 3 4

(Km)

Figure 5 Location of sampled wells and piezometers in the study area

are widely used to establish the relationships between thewater composition and the lithological characteristics of theaquifer [36] Three distinct fields including precipitationdominance evaporation dominance and rock weatheringdominance constitute the segments in the Gibbs diagram

Hydrogeochemical Modeling The equilibrium state of thewater with respect to a mineral phase can be determined bycalculating saturation index (SI) using analytical data In thisstudy saturation indices (SI) were calculated in terms of thefollowing equation [37]

SI = log( IAP119896119904 (119879)) (1)

where IAP is the relevant ion activity product which can becalculated by multiplying the ion activity coefficient 120574iand the composition concentration 119898119894 and 119896119904(119879) is theequilibrium constant of the reaction considered at the sam-ple temperature [35] The geochemical modeling programPHREEQC has been used to evaluate the water chemistry

SI gt 0 indicates oversaturation and minerals may be subjectto precipitation SI lt 0means undersaturation and mineralswill dissolve and SI = 0 suggests saturation and minerals arein equilibrium status with respect to the solution [38]

4 Results and Discussion

41 Hydrogeochemical Characterization Groundwater qual-ity depends on various chemical constituents and theirconcentrations which are mostly derived from the geologicalstratum of the particular region [6] The pH was one of theprimary indicators of the water chemistry evolution Theaquifer groundwater was neutral to slightly alkaline waterwith a mean pH value of 723 and 715 in the wet anddry season respectively Electrical conductivity (EC) of thewater samples was medium to high suggestive of very highlymineralized waters EC values ranged between 1240 and6300 120583Scm in the wet season and between 1131 and 5430 120583Scm in the dry season A problem to the water supply devel-opment in the area is the increasing electrical conductivity

Journal of Chemistry 5

Table1Ch

emicaldataof

sampled

wellsandpiezom

etersintheR

asJbelaquifer

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

13670

741

2369

225

8944

310

999

298

305

5430

723630

299

140

757

121792

343

287

23990

705

2519

447

57413

41022

307

270

3760

721

2446

447

58376

1989

326

250

33840

68

2649

442

54425

11997

384

338

3480

705

2451

421

48392

9918

356

308

44120

713166

368

72647

51021

742

311

3900

722612

327

63506

2789

626

299

56300

69

4110

520

89738

71390

1005

361

5530

706

4323

501

94731

41599

1040

354

65080

695

3345

403

8166

68

1160

661

366

3850

715

2832

363

66499

5953

598

348

75790

69

3630

560

115

550

41457

635

309

4740

73231

523

103

471

3118

1633

317

83730

69

2306

286

115

284

20895

377

329

3560

711

2407

353

135

294

12876

421

317

95660

703

3800

368

129

881

111487

563

361

4660

716

3126

339

9660

97

1248

498

329

103530

732384

249

59388

25788

589

287

2840

763

1989

258

46347

20610

489

220

1144

80712

3260

379

7264

618

989

820

337

3650

719

2674

334

59500

13774

683

311

123250

72142

230

55346

37705

477

293

3160

735

2360

285

55434

37720

543

287

132770

71658

216

45264

31474

352

277

2540

735

1710

243

41262

29487

380

268

142480

765

1972

278

46337

24659

382

246

2860

749

2040

263

50343

23662

462

238

156250

796

4089

466

86857

961463

811

310

4230

735

3049

353

71605

26866

684

445

164190

762480

258

7844

422

830

619

231

3520

738

2392

276

70421

19766

598

244

173990

752715

274

49550

107

775

460

500

3290

772497

280

50426

80652

413

598

182920

722046

221

56330

79472

444

445

2240

729

1841

199

45289

7544

4363

427

192730

775

1817

236

54285

25451

382

381

2250

731680

215

46256

31427

395

311

204020

723

2747

208

131

525

61011

481

386

3360

733

2389

206

124

410

3872

384

390

211240

778

819

4836

165

7289

102

173

2120

755

1317

104

57270

5639

108

134

223280

705

2358

258

55377

35844

515

275

2910

765

1835

230

42338

32589

366

238

231573

768

924

8419

200

6276

89250

1131

782

783

7312

182

3217

88207

245170

715

2891

505

75510

81185

407

201

4060

705

2697

490

67433

51066

436

201

254610

732910

189

113

576

7916

652

458

3880

733

2889

211

123

590

4878

650

433

265050

732330

733

1666

216

55270

1246

4264

387

273400

755

1938

255

65287

27594

415

296

2720

733

1928

257

62312

35568

371

323

283160

761662

178

48289

87478

356

226

2520

739

1910

279

57280

16593

393

293

292950

789

2176

187

66419

6713

587

198

303580

722353

199

80437

11819

613

195

3240

752217

205

72427

11732

582

189

313090

752187

225

71394

10710

560

217

3240

754

2330

228

68424

7766

637

201

323490

762317

231

69479

10749

560

221

3830

735

2804

269

80572

7866

723

287

334290

712886

358

7040

420

954

729

351

5080

775

3608

454

90654

231107

884

397

343640

725

2648

292

66520

15851

591

315

3410

735

2429

305

67401

12764

575

305

6 Journal of Chemistry

Table1Con

tinued

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

353860

725

2836

326

81550

27874

634

344

3420

751

2487

304

71455

14756

571

317

364820

795

3253

398

81472

361084

789

393

4110

743

3015

348

74539

38922

729

366

373740

745

2390

230

78412

17829

607

218

3320

732

2441

265

70474

16757

609

250

382720

771881

197

55332

9591

465

232

3650

752628

292

71491

6821

654

293

392080

771378

169

32251

11470

336

1101817

749

1269

158

30213

8391

319

153

403540

742454

231

75419

8823

620

278

3770

719

2727

273

81489

7865

696

317

415030

713010

402

81456

14116

6689

201

3130

767

2233

232

68431

7734

578

183

422820

793

2061

179

65371

6683

580

177

442980

712

1817

236

43324

78531

337

270

2090

752

1694

198

42234

64502

355

299

452670

711694

215

43277

69493

316

281

2130

741553

203

40258

67437

294

256

462840

741741

200

55267

9555

375

281

3050

732277

285

69390

3770

516

244

473310

705

1749

300

59217

3680

233

256

3170

732257

389

57249

2807

522

232

484990

706

2856

555

8240

05

1210

355

250

4120

712601

560

73327

21084

372

183

EC(120583scm

)TD

SCa2+M

g2+N

a+K+C

lminusSO42minusH

CO3minus(m

gl)

Journal of Chemistry 7

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

CE wet season (microsiemenscm)

1240ndash20802081ndash31603161ndash38603861ndash48204821ndash6300

Large urban agglomerationWadis

Limit of Ras Jbel plain

0 05 1 2 3 4

(Km)

(a)

0 05 1 2 3 4

(Km)

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Large urban agglomerationWadis

CE dry season(microsiemenscm)

1131ndash23302331ndash29102911ndash3560

3561ndash42304231ndash5530

Limit of Ras Jbel plain

(b)

Figure 6 Spatial distribution of electrical conductivity (a) wet season and (b) dry season in Ras Jbel aquifer

(EC) values of near-coastal shallow groundwater The highEC of groundwater from wells located along the coast and inBahirat Beni Ata can be explained by the seawater intrusioneffect caused by the groundwater level drawdown due tooverexploitation (Figures 6(a) and 6(b))

Based on the conductivity values the groundwater systemcould be classified into four groups fresh water (lt500 120583Scm) marginal water (500ndash1500 120583Scm) brackish water(1500ndash5000 120583Scm) and saline water (gt5000 120583Scm) Basedon our conductivity values it is evident that groundwaterin Ras Jbel aquifer is in marginal and brackish waters Fewsamples are of saline water type

The study area is characterized by a wide range of salini-ties Salinity values ranged between 500 and 3600mgl in thewet season and between 500 and 3500mgl in the dry seasonThe higher values of EC and salinity are indicators of higherionic concentrations probably due to the high anthropogenic

activities in the region and geological weathering conditionsbut also due to the intrusion of seawater into the groundwatersystem

The relative content of a cation or an anion is definedas the percentage of the relative amount of that ion to thetotal cations or anions respectively [39] In the study area thestrong acid anions (Clminus and SO4

2minus) exceed weak acid anions(HCO3

minus andCO32minus)On the other hand sodiumand calcium

concentrations exceed magnesium and potassium contentsThe triangular diagram (Figure 7) shows that the groundwa-ter chemistry was mainly characterized by two groups Thefirst group was ClminusndashNa+ type in which Na+ accounted formore than 52ndash65 of the total cations the second group wasClminusndashNa+Ca2+ type in which Na+ and Ca2+ accounted for37ndash48 and 36ndash53 of the total cations respectively Chem-ical facies in the phreatic aquifer of Ras Jbel seem to bedirectly related to the configuration of the ante-quaternary

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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Analytical Methods in Chemistry

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Theoretical ChemistryJournal of

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Analytical ChemistryInternational Journal of

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Quantum Chemistry

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Organic Chemistry International

ElectrochemistryInternational Journal of

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CatalystsJournal of

Page 3: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 3

844 Mm3 water resources

Number of monitoring wellsExploitation (Mm3year)

02468

10121416

Expl

oita

tion

(Mm

3y

ear)

020040060080010001200140016001800

Num

ber o

f mon

itorin

g w

ells

1980 1985 1990 1995 2000 20051966

Figure 3 Evolution of the exploitation rate and the monitoring wellnumber of the shallow aquifer of Ras Jbel during 1966 and 2005 [3031]

and Wadi Bel Khedim formations The Kechabta formationhas a thickness of about 1000m and consists of alternationof marls and fine sandstone benches The Wadi Bel Khedimformation is of 250m thickness At the east of Raf Raf itis composed of large outcrops of gray marls with gypsumbenches The Quaternary series unconformably overlie theMiocene series and is divided into seven units (from bottomto the top qm1 Aa qm2 Qpa Qp-t D and a)

Hydrologically theQuaternary series and the current for-mations characterized by their extension and their good per-meability host the shallow aquifer of Ras Jbel This aquifer isrecharged by local infiltration on the plain by water flowingfrom the surrounding hills and from the different riverscrossing the plain Wadi Beni Ata and Wadi Ali in Beni AtaregionWadi El Kantra El Blaat and ElMa in Ras Jbel regionWadi Sandid draining the zone of Raf Raf andWadi El Kantrain the region of Dar El Khaddar Pumping tests showed thattransmissivity can reach 1510minus4m2s The most transmissiveareas are the low alluvial plain of Bahirat Beni Ata the lowalluvial area ofWadi ElKrib andElAouinet and the upstreamarea of Ain Cherchar Ain Ezzaouia Ain Kassa and Ain ElHammam as well as the sandstone dune of Ain ElMestir andAin Mahloul

The shallow aquifer of Ras Jbel is affected by natu-ral and anthropogenic factors like evaporation irrigationpumping and so forth The aquifer is tapped by severalprivate and state owned wells In the period between 1985and 1990 the exploitation rate was estimated at 135Mm3year which exceeded the renewable resources evaluated at844Mm3year [31] The total number of dug wells has beenestimated to be 1387 in 1985 1396 in 1990 and 1563 in 2005 In2005 the exploitation rate was estimated at 1027Mm3year(Figure 3) The massive exploitation of aquifer resources inresponse to the heavy pumping caused a drop in the waterlevel (Figure 4) and the deterioration of water quality In1949 the salinity of the groundwater varied between 648and 1692mgl [32] The investigations carried out by theDGRE between 1985 and 1993 through several monitoringwells revealed the existence of a very saline groundwaterThedegradation of the water quality has been detected mainly incoastal areas where salt concentrations exceeded 15 gl in 1985

and 8 gl in 1993 and in the depression of Bahirat Beni Atawhere the ante-quaternary substratum is below the sea level[21]

3 Methods

31 Water Sampling and Chemical Analysis Ninety-foursamples (including pumpingwells and piezometers)were col-lected for geochemical analysis (major elements) and isotopes(1205752H 12057518O) during the wet and the dry season of Marchand July 2007 (Figure 5) Sampling locations were recordedusing a potable GPS device Prior to sampling all wellswere pumped for several minutes to eliminate the influencefrom stagnant water Samples were collected in cleanedpolyethylene bottles tightly capped and stored at 4∘C untilanalysis Electrical conductivity (EC) salinity and pH weremeasured in the field using a portable conductivity salinityand pH meter

Chemical analyses were done using a Varian 730-ES ICPOptical Emission Spectrometer for cations and using ionchromatography (DX-120 Dionex USA) for anions HCO3

minus

was measured by titration (Hach USA) Samples for stableisotope analysis were collected according to the proceduresdescribed by Clark and Fritz [33] Isotopic analyses wereconducted in the isotopic laboratory of the department ofHydrology andGeo-environmental Sciences of the Faculty ofEarth and Live Sciences of the Free University of AmsterdamIsotopic ratios are expressed in per mil (120575) and oxygen andhydrogen isotope analyses were reported to 119889 notation rel-ative to Vienna Standard Mean Oceanic Water (V-SMOW)where 119889 = [(RsRVSMOW) minus 1] times 1000 Rs represents eitherthe 18O16Oor the 2H1H ratio of the sample and RSMOW is18O16O or the 2H1H ratio of the SMOW Typical precisionsare plusmn01 and plusmn1 for oxygen-18 and deuterium respectively

32 Statistical Analysis The physicochemical parametersand chemical composition of the groundwater samples arepresented inTable 1 All the acquired datawere integrated intohydrogeochemical database in order to study the ground-water quality and to identify the groundwater salinizationprocesses that contributed to the acquisition of the actualchemical composition

Piper plots [34] considered as the common method for amultiple analyses on the same graph are used to representthe different water samples and to distinguish graphicallybetween different water types defined by the Stuyfzand clas-sification (1993) Sample points with similar hydrochemistrytend to cluster together in the diagram [35]

Principal component analysis method (PCA) and correla-tions are a popular method to assess groundwater qualityOne of the principle advantages of multivariate techniquessuch as principal component analysis (PCA) is that they areable to rapidly reveal relationships between a large numberof variables In this study PCA and correlations are used toidentify the possible sources of major ions in groundwaterhydrogeological reactions that may occur in the study areaand dominant factors that control groundwater quality

Gibbs diagrams which are a simple plot of the TDS versusthe weight ratio of Na+(Na+ + Ca2+) or Clminus(Clminus +HCO3

minus)

4 Journal of Chemistry

N

Mediterranean sea

15

0 05 1 2 3 4(Km)

Piezometric map (1988)

Pizometric contour (m)

Limit of Ras Jbel plain

Wadis

514000 516000 518000 520000 522000 524000 526000 528000

514000 516000 518000 520000 522000 524000 526000 528000

438000

436000

434000

432000

430000

438000

436000

434000

432000

430000

Figure 4 Piezometric contour maps of the study area [31]

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Sampling points

Dams

Large urban agglomeration

Wadis

Limit of the plain of Ras Jbel

0 05 1 2 3 4

(Km)

Figure 5 Location of sampled wells and piezometers in the study area

are widely used to establish the relationships between thewater composition and the lithological characteristics of theaquifer [36] Three distinct fields including precipitationdominance evaporation dominance and rock weatheringdominance constitute the segments in the Gibbs diagram

Hydrogeochemical Modeling The equilibrium state of thewater with respect to a mineral phase can be determined bycalculating saturation index (SI) using analytical data In thisstudy saturation indices (SI) were calculated in terms of thefollowing equation [37]

SI = log( IAP119896119904 (119879)) (1)

where IAP is the relevant ion activity product which can becalculated by multiplying the ion activity coefficient 120574iand the composition concentration 119898119894 and 119896119904(119879) is theequilibrium constant of the reaction considered at the sam-ple temperature [35] The geochemical modeling programPHREEQC has been used to evaluate the water chemistry

SI gt 0 indicates oversaturation and minerals may be subjectto precipitation SI lt 0means undersaturation and mineralswill dissolve and SI = 0 suggests saturation and minerals arein equilibrium status with respect to the solution [38]

4 Results and Discussion

41 Hydrogeochemical Characterization Groundwater qual-ity depends on various chemical constituents and theirconcentrations which are mostly derived from the geologicalstratum of the particular region [6] The pH was one of theprimary indicators of the water chemistry evolution Theaquifer groundwater was neutral to slightly alkaline waterwith a mean pH value of 723 and 715 in the wet anddry season respectively Electrical conductivity (EC) of thewater samples was medium to high suggestive of very highlymineralized waters EC values ranged between 1240 and6300 120583Scm in the wet season and between 1131 and 5430 120583Scm in the dry season A problem to the water supply devel-opment in the area is the increasing electrical conductivity

Journal of Chemistry 5

Table1Ch

emicaldataof

sampled

wellsandpiezom

etersintheR

asJbelaquifer

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

13670

741

2369

225

8944

310

999

298

305

5430

723630

299

140

757

121792

343

287

23990

705

2519

447

57413

41022

307

270

3760

721

2446

447

58376

1989

326

250

33840

68

2649

442

54425

11997

384

338

3480

705

2451

421

48392

9918

356

308

44120

713166

368

72647

51021

742

311

3900

722612

327

63506

2789

626

299

56300

69

4110

520

89738

71390

1005

361

5530

706

4323

501

94731

41599

1040

354

65080

695

3345

403

8166

68

1160

661

366

3850

715

2832

363

66499

5953

598

348

75790

69

3630

560

115

550

41457

635

309

4740

73231

523

103

471

3118

1633

317

83730

69

2306

286

115

284

20895

377

329

3560

711

2407

353

135

294

12876

421

317

95660

703

3800

368

129

881

111487

563

361

4660

716

3126

339

9660

97

1248

498

329

103530

732384

249

59388

25788

589

287

2840

763

1989

258

46347

20610

489

220

1144

80712

3260

379

7264

618

989

820

337

3650

719

2674

334

59500

13774

683

311

123250

72142

230

55346

37705

477

293

3160

735

2360

285

55434

37720

543

287

132770

71658

216

45264

31474

352

277

2540

735

1710

243

41262

29487

380

268

142480

765

1972

278

46337

24659

382

246

2860

749

2040

263

50343

23662

462

238

156250

796

4089

466

86857

961463

811

310

4230

735

3049

353

71605

26866

684

445

164190

762480

258

7844

422

830

619

231

3520

738

2392

276

70421

19766

598

244

173990

752715

274

49550

107

775

460

500

3290

772497

280

50426

80652

413

598

182920

722046

221

56330

79472

444

445

2240

729

1841

199

45289

7544

4363

427

192730

775

1817

236

54285

25451

382

381

2250

731680

215

46256

31427

395

311

204020

723

2747

208

131

525

61011

481

386

3360

733

2389

206

124

410

3872

384

390

211240

778

819

4836

165

7289

102

173

2120

755

1317

104

57270

5639

108

134

223280

705

2358

258

55377

35844

515

275

2910

765

1835

230

42338

32589

366

238

231573

768

924

8419

200

6276

89250

1131

782

783

7312

182

3217

88207

245170

715

2891

505

75510

81185

407

201

4060

705

2697

490

67433

51066

436

201

254610

732910

189

113

576

7916

652

458

3880

733

2889

211

123

590

4878

650

433

265050

732330

733

1666

216

55270

1246

4264

387

273400

755

1938

255

65287

27594

415

296

2720

733

1928

257

62312

35568

371

323

283160

761662

178

48289

87478

356

226

2520

739

1910

279

57280

16593

393

293

292950

789

2176

187

66419

6713

587

198

303580

722353

199

80437

11819

613

195

3240

752217

205

72427

11732

582

189

313090

752187

225

71394

10710

560

217

3240

754

2330

228

68424

7766

637

201

323490

762317

231

69479

10749

560

221

3830

735

2804

269

80572

7866

723

287

334290

712886

358

7040

420

954

729

351

5080

775

3608

454

90654

231107

884

397

343640

725

2648

292

66520

15851

591

315

3410

735

2429

305

67401

12764

575

305

6 Journal of Chemistry

Table1Con

tinued

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

353860

725

2836

326

81550

27874

634

344

3420

751

2487

304

71455

14756

571

317

364820

795

3253

398

81472

361084

789

393

4110

743

3015

348

74539

38922

729

366

373740

745

2390

230

78412

17829

607

218

3320

732

2441

265

70474

16757

609

250

382720

771881

197

55332

9591

465

232

3650

752628

292

71491

6821

654

293

392080

771378

169

32251

11470

336

1101817

749

1269

158

30213

8391

319

153

403540

742454

231

75419

8823

620

278

3770

719

2727

273

81489

7865

696

317

415030

713010

402

81456

14116

6689

201

3130

767

2233

232

68431

7734

578

183

422820

793

2061

179

65371

6683

580

177

442980

712

1817

236

43324

78531

337

270

2090

752

1694

198

42234

64502

355

299

452670

711694

215

43277

69493

316

281

2130

741553

203

40258

67437

294

256

462840

741741

200

55267

9555

375

281

3050

732277

285

69390

3770

516

244

473310

705

1749

300

59217

3680

233

256

3170

732257

389

57249

2807

522

232

484990

706

2856

555

8240

05

1210

355

250

4120

712601

560

73327

21084

372

183

EC(120583scm

)TD

SCa2+M

g2+N

a+K+C

lminusSO42minusH

CO3minus(m

gl)

Journal of Chemistry 7

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

CE wet season (microsiemenscm)

1240ndash20802081ndash31603161ndash38603861ndash48204821ndash6300

Large urban agglomerationWadis

Limit of Ras Jbel plain

0 05 1 2 3 4

(Km)

(a)

0 05 1 2 3 4

(Km)

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Large urban agglomerationWadis

CE dry season(microsiemenscm)

1131ndash23302331ndash29102911ndash3560

3561ndash42304231ndash5530

Limit of Ras Jbel plain

(b)

Figure 6 Spatial distribution of electrical conductivity (a) wet season and (b) dry season in Ras Jbel aquifer

(EC) values of near-coastal shallow groundwater The highEC of groundwater from wells located along the coast and inBahirat Beni Ata can be explained by the seawater intrusioneffect caused by the groundwater level drawdown due tooverexploitation (Figures 6(a) and 6(b))

Based on the conductivity values the groundwater systemcould be classified into four groups fresh water (lt500 120583Scm) marginal water (500ndash1500 120583Scm) brackish water(1500ndash5000 120583Scm) and saline water (gt5000 120583Scm) Basedon our conductivity values it is evident that groundwaterin Ras Jbel aquifer is in marginal and brackish waters Fewsamples are of saline water type

The study area is characterized by a wide range of salini-ties Salinity values ranged between 500 and 3600mgl in thewet season and between 500 and 3500mgl in the dry seasonThe higher values of EC and salinity are indicators of higherionic concentrations probably due to the high anthropogenic

activities in the region and geological weathering conditionsbut also due to the intrusion of seawater into the groundwatersystem

The relative content of a cation or an anion is definedas the percentage of the relative amount of that ion to thetotal cations or anions respectively [39] In the study area thestrong acid anions (Clminus and SO4

2minus) exceed weak acid anions(HCO3

minus andCO32minus)On the other hand sodiumand calcium

concentrations exceed magnesium and potassium contentsThe triangular diagram (Figure 7) shows that the groundwa-ter chemistry was mainly characterized by two groups Thefirst group was ClminusndashNa+ type in which Na+ accounted formore than 52ndash65 of the total cations the second group wasClminusndashNa+Ca2+ type in which Na+ and Ca2+ accounted for37ndash48 and 36ndash53 of the total cations respectively Chem-ical facies in the phreatic aquifer of Ras Jbel seem to bedirectly related to the configuration of the ante-quaternary

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

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CatalystsJournal of

Page 4: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

4 Journal of Chemistry

N

Mediterranean sea

15

0 05 1 2 3 4(Km)

Piezometric map (1988)

Pizometric contour (m)

Limit of Ras Jbel plain

Wadis

514000 516000 518000 520000 522000 524000 526000 528000

514000 516000 518000 520000 522000 524000 526000 528000

438000

436000

434000

432000

430000

438000

436000

434000

432000

430000

Figure 4 Piezometric contour maps of the study area [31]

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Sampling points

Dams

Large urban agglomeration

Wadis

Limit of the plain of Ras Jbel

0 05 1 2 3 4

(Km)

Figure 5 Location of sampled wells and piezometers in the study area

are widely used to establish the relationships between thewater composition and the lithological characteristics of theaquifer [36] Three distinct fields including precipitationdominance evaporation dominance and rock weatheringdominance constitute the segments in the Gibbs diagram

Hydrogeochemical Modeling The equilibrium state of thewater with respect to a mineral phase can be determined bycalculating saturation index (SI) using analytical data In thisstudy saturation indices (SI) were calculated in terms of thefollowing equation [37]

SI = log( IAP119896119904 (119879)) (1)

where IAP is the relevant ion activity product which can becalculated by multiplying the ion activity coefficient 120574iand the composition concentration 119898119894 and 119896119904(119879) is theequilibrium constant of the reaction considered at the sam-ple temperature [35] The geochemical modeling programPHREEQC has been used to evaluate the water chemistry

SI gt 0 indicates oversaturation and minerals may be subjectto precipitation SI lt 0means undersaturation and mineralswill dissolve and SI = 0 suggests saturation and minerals arein equilibrium status with respect to the solution [38]

4 Results and Discussion

41 Hydrogeochemical Characterization Groundwater qual-ity depends on various chemical constituents and theirconcentrations which are mostly derived from the geologicalstratum of the particular region [6] The pH was one of theprimary indicators of the water chemistry evolution Theaquifer groundwater was neutral to slightly alkaline waterwith a mean pH value of 723 and 715 in the wet anddry season respectively Electrical conductivity (EC) of thewater samples was medium to high suggestive of very highlymineralized waters EC values ranged between 1240 and6300 120583Scm in the wet season and between 1131 and 5430 120583Scm in the dry season A problem to the water supply devel-opment in the area is the increasing electrical conductivity

Journal of Chemistry 5

Table1Ch

emicaldataof

sampled

wellsandpiezom

etersintheR

asJbelaquifer

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

13670

741

2369

225

8944

310

999

298

305

5430

723630

299

140

757

121792

343

287

23990

705

2519

447

57413

41022

307

270

3760

721

2446

447

58376

1989

326

250

33840

68

2649

442

54425

11997

384

338

3480

705

2451

421

48392

9918

356

308

44120

713166

368

72647

51021

742

311

3900

722612

327

63506

2789

626

299

56300

69

4110

520

89738

71390

1005

361

5530

706

4323

501

94731

41599

1040

354

65080

695

3345

403

8166

68

1160

661

366

3850

715

2832

363

66499

5953

598

348

75790

69

3630

560

115

550

41457

635

309

4740

73231

523

103

471

3118

1633

317

83730

69

2306

286

115

284

20895

377

329

3560

711

2407

353

135

294

12876

421

317

95660

703

3800

368

129

881

111487

563

361

4660

716

3126

339

9660

97

1248

498

329

103530

732384

249

59388

25788

589

287

2840

763

1989

258

46347

20610

489

220

1144

80712

3260

379

7264

618

989

820

337

3650

719

2674

334

59500

13774

683

311

123250

72142

230

55346

37705

477

293

3160

735

2360

285

55434

37720

543

287

132770

71658

216

45264

31474

352

277

2540

735

1710

243

41262

29487

380

268

142480

765

1972

278

46337

24659

382

246

2860

749

2040

263

50343

23662

462

238

156250

796

4089

466

86857

961463

811

310

4230

735

3049

353

71605

26866

684

445

164190

762480

258

7844

422

830

619

231

3520

738

2392

276

70421

19766

598

244

173990

752715

274

49550

107

775

460

500

3290

772497

280

50426

80652

413

598

182920

722046

221

56330

79472

444

445

2240

729

1841

199

45289

7544

4363

427

192730

775

1817

236

54285

25451

382

381

2250

731680

215

46256

31427

395

311

204020

723

2747

208

131

525

61011

481

386

3360

733

2389

206

124

410

3872

384

390

211240

778

819

4836

165

7289

102

173

2120

755

1317

104

57270

5639

108

134

223280

705

2358

258

55377

35844

515

275

2910

765

1835

230

42338

32589

366

238

231573

768

924

8419

200

6276

89250

1131

782

783

7312

182

3217

88207

245170

715

2891

505

75510

81185

407

201

4060

705

2697

490

67433

51066

436

201

254610

732910

189

113

576

7916

652

458

3880

733

2889

211

123

590

4878

650

433

265050

732330

733

1666

216

55270

1246

4264

387

273400

755

1938

255

65287

27594

415

296

2720

733

1928

257

62312

35568

371

323

283160

761662

178

48289

87478

356

226

2520

739

1910

279

57280

16593

393

293

292950

789

2176

187

66419

6713

587

198

303580

722353

199

80437

11819

613

195

3240

752217

205

72427

11732

582

189

313090

752187

225

71394

10710

560

217

3240

754

2330

228

68424

7766

637

201

323490

762317

231

69479

10749

560

221

3830

735

2804

269

80572

7866

723

287

334290

712886

358

7040

420

954

729

351

5080

775

3608

454

90654

231107

884

397

343640

725

2648

292

66520

15851

591

315

3410

735

2429

305

67401

12764

575

305

6 Journal of Chemistry

Table1Con

tinued

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

353860

725

2836

326

81550

27874

634

344

3420

751

2487

304

71455

14756

571

317

364820

795

3253

398

81472

361084

789

393

4110

743

3015

348

74539

38922

729

366

373740

745

2390

230

78412

17829

607

218

3320

732

2441

265

70474

16757

609

250

382720

771881

197

55332

9591

465

232

3650

752628

292

71491

6821

654

293

392080

771378

169

32251

11470

336

1101817

749

1269

158

30213

8391

319

153

403540

742454

231

75419

8823

620

278

3770

719

2727

273

81489

7865

696

317

415030

713010

402

81456

14116

6689

201

3130

767

2233

232

68431

7734

578

183

422820

793

2061

179

65371

6683

580

177

442980

712

1817

236

43324

78531

337

270

2090

752

1694

198

42234

64502

355

299

452670

711694

215

43277

69493

316

281

2130

741553

203

40258

67437

294

256

462840

741741

200

55267

9555

375

281

3050

732277

285

69390

3770

516

244

473310

705

1749

300

59217

3680

233

256

3170

732257

389

57249

2807

522

232

484990

706

2856

555

8240

05

1210

355

250

4120

712601

560

73327

21084

372

183

EC(120583scm

)TD

SCa2+M

g2+N

a+K+C

lminusSO42minusH

CO3minus(m

gl)

Journal of Chemistry 7

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

CE wet season (microsiemenscm)

1240ndash20802081ndash31603161ndash38603861ndash48204821ndash6300

Large urban agglomerationWadis

Limit of Ras Jbel plain

0 05 1 2 3 4

(Km)

(a)

0 05 1 2 3 4

(Km)

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Large urban agglomerationWadis

CE dry season(microsiemenscm)

1131ndash23302331ndash29102911ndash3560

3561ndash42304231ndash5530

Limit of Ras Jbel plain

(b)

Figure 6 Spatial distribution of electrical conductivity (a) wet season and (b) dry season in Ras Jbel aquifer

(EC) values of near-coastal shallow groundwater The highEC of groundwater from wells located along the coast and inBahirat Beni Ata can be explained by the seawater intrusioneffect caused by the groundwater level drawdown due tooverexploitation (Figures 6(a) and 6(b))

Based on the conductivity values the groundwater systemcould be classified into four groups fresh water (lt500 120583Scm) marginal water (500ndash1500 120583Scm) brackish water(1500ndash5000 120583Scm) and saline water (gt5000 120583Scm) Basedon our conductivity values it is evident that groundwaterin Ras Jbel aquifer is in marginal and brackish waters Fewsamples are of saline water type

The study area is characterized by a wide range of salini-ties Salinity values ranged between 500 and 3600mgl in thewet season and between 500 and 3500mgl in the dry seasonThe higher values of EC and salinity are indicators of higherionic concentrations probably due to the high anthropogenic

activities in the region and geological weathering conditionsbut also due to the intrusion of seawater into the groundwatersystem

The relative content of a cation or an anion is definedas the percentage of the relative amount of that ion to thetotal cations or anions respectively [39] In the study area thestrong acid anions (Clminus and SO4

2minus) exceed weak acid anions(HCO3

minus andCO32minus)On the other hand sodiumand calcium

concentrations exceed magnesium and potassium contentsThe triangular diagram (Figure 7) shows that the groundwa-ter chemistry was mainly characterized by two groups Thefirst group was ClminusndashNa+ type in which Na+ accounted formore than 52ndash65 of the total cations the second group wasClminusndashNa+Ca2+ type in which Na+ and Ca2+ accounted for37ndash48 and 36ndash53 of the total cations respectively Chem-ical facies in the phreatic aquifer of Ras Jbel seem to bedirectly related to the configuration of the ante-quaternary

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CatalystsJournal of

Page 5: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 5

Table1Ch

emicaldataof

sampled

wellsandpiezom

etersintheR

asJbelaquifer

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

13670

741

2369

225

8944

310

999

298

305

5430

723630

299

140

757

121792

343

287

23990

705

2519

447

57413

41022

307

270

3760

721

2446

447

58376

1989

326

250

33840

68

2649

442

54425

11997

384

338

3480

705

2451

421

48392

9918

356

308

44120

713166

368

72647

51021

742

311

3900

722612

327

63506

2789

626

299

56300

69

4110

520

89738

71390

1005

361

5530

706

4323

501

94731

41599

1040

354

65080

695

3345

403

8166

68

1160

661

366

3850

715

2832

363

66499

5953

598

348

75790

69

3630

560

115

550

41457

635

309

4740

73231

523

103

471

3118

1633

317

83730

69

2306

286

115

284

20895

377

329

3560

711

2407

353

135

294

12876

421

317

95660

703

3800

368

129

881

111487

563

361

4660

716

3126

339

9660

97

1248

498

329

103530

732384

249

59388

25788

589

287

2840

763

1989

258

46347

20610

489

220

1144

80712

3260

379

7264

618

989

820

337

3650

719

2674

334

59500

13774

683

311

123250

72142

230

55346

37705

477

293

3160

735

2360

285

55434

37720

543

287

132770

71658

216

45264

31474

352

277

2540

735

1710

243

41262

29487

380

268

142480

765

1972

278

46337

24659

382

246

2860

749

2040

263

50343

23662

462

238

156250

796

4089

466

86857

961463

811

310

4230

735

3049

353

71605

26866

684

445

164190

762480

258

7844

422

830

619

231

3520

738

2392

276

70421

19766

598

244

173990

752715

274

49550

107

775

460

500

3290

772497

280

50426

80652

413

598

182920

722046

221

56330

79472

444

445

2240

729

1841

199

45289

7544

4363

427

192730

775

1817

236

54285

25451

382

381

2250

731680

215

46256

31427

395

311

204020

723

2747

208

131

525

61011

481

386

3360

733

2389

206

124

410

3872

384

390

211240

778

819

4836

165

7289

102

173

2120

755

1317

104

57270

5639

108

134

223280

705

2358

258

55377

35844

515

275

2910

765

1835

230

42338

32589

366

238

231573

768

924

8419

200

6276

89250

1131

782

783

7312

182

3217

88207

245170

715

2891

505

75510

81185

407

201

4060

705

2697

490

67433

51066

436

201

254610

732910

189

113

576

7916

652

458

3880

733

2889

211

123

590

4878

650

433

265050

732330

733

1666

216

55270

1246

4264

387

273400

755

1938

255

65287

27594

415

296

2720

733

1928

257

62312

35568

371

323

283160

761662

178

48289

87478

356

226

2520

739

1910

279

57280

16593

393

293

292950

789

2176

187

66419

6713

587

198

303580

722353

199

80437

11819

613

195

3240

752217

205

72427

11732

582

189

313090

752187

225

71394

10710

560

217

3240

754

2330

228

68424

7766

637

201

323490

762317

231

69479

10749

560

221

3830

735

2804

269

80572

7866

723

287

334290

712886

358

7040

420

954

729

351

5080

775

3608

454

90654

231107

884

397

343640

725

2648

292

66520

15851

591

315

3410

735

2429

305

67401

12764

575

305

6 Journal of Chemistry

Table1Con

tinued

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

353860

725

2836

326

81550

27874

634

344

3420

751

2487

304

71455

14756

571

317

364820

795

3253

398

81472

361084

789

393

4110

743

3015

348

74539

38922

729

366

373740

745

2390

230

78412

17829

607

218

3320

732

2441

265

70474

16757

609

250

382720

771881

197

55332

9591

465

232

3650

752628

292

71491

6821

654

293

392080

771378

169

32251

11470

336

1101817

749

1269

158

30213

8391

319

153

403540

742454

231

75419

8823

620

278

3770

719

2727

273

81489

7865

696

317

415030

713010

402

81456

14116

6689

201

3130

767

2233

232

68431

7734

578

183

422820

793

2061

179

65371

6683

580

177

442980

712

1817

236

43324

78531

337

270

2090

752

1694

198

42234

64502

355

299

452670

711694

215

43277

69493

316

281

2130

741553

203

40258

67437

294

256

462840

741741

200

55267

9555

375

281

3050

732277

285

69390

3770

516

244

473310

705

1749

300

59217

3680

233

256

3170

732257

389

57249

2807

522

232

484990

706

2856

555

8240

05

1210

355

250

4120

712601

560

73327

21084

372

183

EC(120583scm

)TD

SCa2+M

g2+N

a+K+C

lminusSO42minusH

CO3minus(m

gl)

Journal of Chemistry 7

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

CE wet season (microsiemenscm)

1240ndash20802081ndash31603161ndash38603861ndash48204821ndash6300

Large urban agglomerationWadis

Limit of Ras Jbel plain

0 05 1 2 3 4

(Km)

(a)

0 05 1 2 3 4

(Km)

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Large urban agglomerationWadis

CE dry season(microsiemenscm)

1131ndash23302331ndash29102911ndash3560

3561ndash42304231ndash5530

Limit of Ras Jbel plain

(b)

Figure 6 Spatial distribution of electrical conductivity (a) wet season and (b) dry season in Ras Jbel aquifer

(EC) values of near-coastal shallow groundwater The highEC of groundwater from wells located along the coast and inBahirat Beni Ata can be explained by the seawater intrusioneffect caused by the groundwater level drawdown due tooverexploitation (Figures 6(a) and 6(b))

Based on the conductivity values the groundwater systemcould be classified into four groups fresh water (lt500 120583Scm) marginal water (500ndash1500 120583Scm) brackish water(1500ndash5000 120583Scm) and saline water (gt5000 120583Scm) Basedon our conductivity values it is evident that groundwaterin Ras Jbel aquifer is in marginal and brackish waters Fewsamples are of saline water type

The study area is characterized by a wide range of salini-ties Salinity values ranged between 500 and 3600mgl in thewet season and between 500 and 3500mgl in the dry seasonThe higher values of EC and salinity are indicators of higherionic concentrations probably due to the high anthropogenic

activities in the region and geological weathering conditionsbut also due to the intrusion of seawater into the groundwatersystem

The relative content of a cation or an anion is definedas the percentage of the relative amount of that ion to thetotal cations or anions respectively [39] In the study area thestrong acid anions (Clminus and SO4

2minus) exceed weak acid anions(HCO3

minus andCO32minus)On the other hand sodiumand calcium

concentrations exceed magnesium and potassium contentsThe triangular diagram (Figure 7) shows that the groundwa-ter chemistry was mainly characterized by two groups Thefirst group was ClminusndashNa+ type in which Na+ accounted formore than 52ndash65 of the total cations the second group wasClminusndashNa+Ca2+ type in which Na+ and Ca2+ accounted for37ndash48 and 36ndash53 of the total cations respectively Chem-ical facies in the phreatic aquifer of Ras Jbel seem to bedirectly related to the configuration of the ante-quaternary

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CatalystsJournal of

Page 6: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

6 Journal of Chemistry

Table1Con

tinued

Well

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

ECpH

TDS

Ca2+

Mg2+

Na+

K+Clminus

SO42minus

HCO3minus

Wetseason

Dry

season

353860

725

2836

326

81550

27874

634

344

3420

751

2487

304

71455

14756

571

317

364820

795

3253

398

81472

361084

789

393

4110

743

3015

348

74539

38922

729

366

373740

745

2390

230

78412

17829

607

218

3320

732

2441

265

70474

16757

609

250

382720

771881

197

55332

9591

465

232

3650

752628

292

71491

6821

654

293

392080

771378

169

32251

11470

336

1101817

749

1269

158

30213

8391

319

153

403540

742454

231

75419

8823

620

278

3770

719

2727

273

81489

7865

696

317

415030

713010

402

81456

14116

6689

201

3130

767

2233

232

68431

7734

578

183

422820

793

2061

179

65371

6683

580

177

442980

712

1817

236

43324

78531

337

270

2090

752

1694

198

42234

64502

355

299

452670

711694

215

43277

69493

316

281

2130

741553

203

40258

67437

294

256

462840

741741

200

55267

9555

375

281

3050

732277

285

69390

3770

516

244

473310

705

1749

300

59217

3680

233

256

3170

732257

389

57249

2807

522

232

484990

706

2856

555

8240

05

1210

355

250

4120

712601

560

73327

21084

372

183

EC(120583scm

)TD

SCa2+M

g2+N

a+K+C

lminusSO42minusH

CO3minus(m

gl)

Journal of Chemistry 7

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

CE wet season (microsiemenscm)

1240ndash20802081ndash31603161ndash38603861ndash48204821ndash6300

Large urban agglomerationWadis

Limit of Ras Jbel plain

0 05 1 2 3 4

(Km)

(a)

0 05 1 2 3 4

(Km)

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Large urban agglomerationWadis

CE dry season(microsiemenscm)

1131ndash23302331ndash29102911ndash3560

3561ndash42304231ndash5530

Limit of Ras Jbel plain

(b)

Figure 6 Spatial distribution of electrical conductivity (a) wet season and (b) dry season in Ras Jbel aquifer

(EC) values of near-coastal shallow groundwater The highEC of groundwater from wells located along the coast and inBahirat Beni Ata can be explained by the seawater intrusioneffect caused by the groundwater level drawdown due tooverexploitation (Figures 6(a) and 6(b))

Based on the conductivity values the groundwater systemcould be classified into four groups fresh water (lt500 120583Scm) marginal water (500ndash1500 120583Scm) brackish water(1500ndash5000 120583Scm) and saline water (gt5000 120583Scm) Basedon our conductivity values it is evident that groundwaterin Ras Jbel aquifer is in marginal and brackish waters Fewsamples are of saline water type

The study area is characterized by a wide range of salini-ties Salinity values ranged between 500 and 3600mgl in thewet season and between 500 and 3500mgl in the dry seasonThe higher values of EC and salinity are indicators of higherionic concentrations probably due to the high anthropogenic

activities in the region and geological weathering conditionsbut also due to the intrusion of seawater into the groundwatersystem

The relative content of a cation or an anion is definedas the percentage of the relative amount of that ion to thetotal cations or anions respectively [39] In the study area thestrong acid anions (Clminus and SO4

2minus) exceed weak acid anions(HCO3

minus andCO32minus)On the other hand sodiumand calcium

concentrations exceed magnesium and potassium contentsThe triangular diagram (Figure 7) shows that the groundwa-ter chemistry was mainly characterized by two groups Thefirst group was ClminusndashNa+ type in which Na+ accounted formore than 52ndash65 of the total cations the second group wasClminusndashNa+Ca2+ type in which Na+ and Ca2+ accounted for37ndash48 and 36ndash53 of the total cations respectively Chem-ical facies in the phreatic aquifer of Ras Jbel seem to bedirectly related to the configuration of the ante-quaternary

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

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Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

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Advances in

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

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Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

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Applied ChemistryJournal of

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Analytical ChemistryInternational Journal of

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Quantum Chemistry

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ElectrochemistryInternational Journal of

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CatalystsJournal of

Page 7: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 7

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

CE wet season (microsiemenscm)

1240ndash20802081ndash31603161ndash38603861ndash48204821ndash6300

Large urban agglomerationWadis

Limit of Ras Jbel plain

0 05 1 2 3 4

(Km)

(a)

0 05 1 2 3 4

(Km)

NMediterranean sea

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

Large urban agglomerationWadis

CE dry season(microsiemenscm)

1131ndash23302331ndash29102911ndash3560

3561ndash42304231ndash5530

Limit of Ras Jbel plain

(b)

Figure 6 Spatial distribution of electrical conductivity (a) wet season and (b) dry season in Ras Jbel aquifer

(EC) values of near-coastal shallow groundwater The highEC of groundwater from wells located along the coast and inBahirat Beni Ata can be explained by the seawater intrusioneffect caused by the groundwater level drawdown due tooverexploitation (Figures 6(a) and 6(b))

Based on the conductivity values the groundwater systemcould be classified into four groups fresh water (lt500 120583Scm) marginal water (500ndash1500 120583Scm) brackish water(1500ndash5000 120583Scm) and saline water (gt5000 120583Scm) Basedon our conductivity values it is evident that groundwaterin Ras Jbel aquifer is in marginal and brackish waters Fewsamples are of saline water type

The study area is characterized by a wide range of salini-ties Salinity values ranged between 500 and 3600mgl in thewet season and between 500 and 3500mgl in the dry seasonThe higher values of EC and salinity are indicators of higherionic concentrations probably due to the high anthropogenic

activities in the region and geological weathering conditionsbut also due to the intrusion of seawater into the groundwatersystem

The relative content of a cation or an anion is definedas the percentage of the relative amount of that ion to thetotal cations or anions respectively [39] In the study area thestrong acid anions (Clminus and SO4

2minus) exceed weak acid anions(HCO3

minus andCO32minus)On the other hand sodiumand calcium

concentrations exceed magnesium and potassium contentsThe triangular diagram (Figure 7) shows that the groundwa-ter chemistry was mainly characterized by two groups Thefirst group was ClminusndashNa+ type in which Na+ accounted formore than 52ndash65 of the total cations the second group wasClminusndashNa+Ca2+ type in which Na+ and Ca2+ accounted for37ndash48 and 36ndash53 of the total cations respectively Chem-ical facies in the phreatic aquifer of Ras Jbel seem to bedirectly related to the configuration of the ante-quaternary

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 8: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

8 Journal of Chemistry

1

2

5

6

7

89

9

NaCl typeNaCaCl type

Ca+

Mg

Na+

KMg

Ca

100

100

100100

0

0

0

100

0

0

0

100

100 0

4

3

0 100

SO4+Cl +

NO3

SO4

CO3+HCO3

Cl + NO3

Figure 7 Piper diagram of groundwater zone 1 alkaline earths(Ca + Mg) exceed alkalis (Na + K) zone 2 alkalis exceed alkalineearths zone 3 weak acids (CO3 + HCO3) exceed strong acids (SO4+ Cl) zone 4 strong acids exceed weak acids zone 5 carbonatehardness gt 50 (alkaline earths and weak acid dominate) zone 6noncarbonate hardness gt 50 zone 7 noncarbonate alkali gt 50zone 8 carbonate alkali gt 50 (groundwater is inordinately soft inproportion to the content of TDS) zone 9 no cationndashanion pairgt50 [34]

substratum and the proximity of several sampled wells fromthe sea

The NandashCl-type indicated the presence of high chlorideconcentrations in the aquifer which may originate from thedissolution of halite influx of sewage or waste water andmainly intrusion of sea water [40] In the downstream part ofthe plain near the sea and in Bahirat Beni Ata where amarineintrusion was detected since 1980 the groundwater is mainlyof ClminusndashNa+ type (Figure 8) The distribution maps of Clminus inboth wet and dry seasons (Figures 9(a) and 9(b)) are wellcorrelated with those of electrical conductivity and facies

42 Processes Controlling Groundwater Salinization Under-standing the water salinization mechanism is the basis forregional salt management Groundwater salinization is large-ly a function of the mineral composition of the aquiferthrough which it flows and hydrogeochemical processes suchas mineral dissolution precipitation evaporation and tran-spiration ion exchange and the residence time along the flowpath It is also linked to various anthropogenic activities suchas agriculture overexploitation of groundwater resourcesand sewage disposal

421 Water-Rock Interaction and Origin of GroundwaterMineralization Reactions between groundwater and aquiferminerals have a significant role onwater qualityThe119901times119901 cor-relationmatrix revealing the existence of bivariate linear cor-relations between variables allows a better understanding ofthe dominant water-rock interactions or source of the ionsover the study area Additionally the use of multivariate

Table 2 Principal component matrix

1198651 1198652 1198653CE 097 minus003 005TDS 098 minus004 008pH minus041 minus042 075Ca2+ 082 017 minus010Mg2+ 078 013 002Na+ 089 minus020 017K+ minus011 minus086 minus016Clminus 096 014 007SO42minus 077 minus020 028

HCO3minus 043 minus057 minus049

Eigenvalue 586 140 095 Explication 5864 14 953 Cumulative 5864 7264 8217Bold values loadings ge 05

statistics in hydr(geo)logical studies is a very common prac-tice and numerous applications can be found in the literature([10 19 41]) though most hydrologists consider that valueslarger than 05 indicate significant correlation In the presentstudy PCA was carried out for 10 parameters (Ca MgNa K HCO3 SO4 Cl pH TDS and EC) and more than90 observations (Tables 2 and 3) The first two factors 1198651and 1198652 were always retained explaining about 73 of thetotal variance (Table 2) Factors of a higher order generallyexplained the variance of a single parameter or establishedpoorer and less significant correlations with two parameters[42]

The correlations established between the TDS and con-centrations of major elements (Table 3) show that the TDSis well correlated with the concentrations of chloride (1199032 =096) sodium (1199032 = 087) calcium (1199032 = 083) magnesium(1199032 = 073) and sulphates (1199032 = 076) The high correlationof TDS with chloride sodiummagnesium sulphate and cal-cium indicated that these elements are mostly contributed bymineralization These ions have been dissolved into ground-water continuously and resulted in the rise of TDS Thecontribution of carbonates and potassium is negligible (1199032 =037 and 1199032 = minus005 resp)The low correlation between TDSand pH suggests that the dissolution of the salts is not relatedto acidic conditions of groundwater but it is related to theirdegrees of solubility HCO3

minus and pH apparently have littleassociation with the other variables

Bicarbonates are not correlated to calcium r(HCO3Ca)= 020 indicating another source other than the calcitedissolution However considerable correlation coefficientsbetween sodium and chlorides r(NaCl) = 084 and betweencalcium and sulphates r(CaSO4) = 050 suggest halite andgypsum dissolution respectively

The first factor 1198651 accounts for 58 of the total varianceand it is contributed by the following variables EC TDSMgCa Na Cl and SO4 This factor is associated with the salinitycomponent (NaCl salt source with Ca and SO4 enrichment)and the cation exchange The second factor 1198652 accounts for14 of the total variance and it is negatively determined by K

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

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CatalystsJournal of

Page 9: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 9

Table 3 Correlation matrix of dissolved species and the TDS for the study area in wet season

CE TDS pH Ca2+ Mg2+ Na+ K+ Clminus SO42minus HCO3

minus

CE 1TDS 098 1pH minus034 minus032 1Ca2+ 084 083 minus044 1Mg2+ 073 073 minus030 043 1Na+ 084 087 minus018 060 065 1K+ minus004 minus005 023 minus011 minus028 001 1Clminus 095 096 minus037 084 076 084 minus019 1SO42minus 073 076 minus012 050 052 075 minus002 065 1

HCO3minus 036 037 minus020 020 037 042 030 027 032 1

N

Mediterranean sea

514000 516000 518000 520000 522000 524000 526000

514000 516000 518000 520000 522000 524000 526000

438000

436000

434000

432000

430000

428000

438000

436000

434000

432000

430000

428000

Limit of Ras Jbel plainWadisNaCl typeNaCaCl type

0 05 1 2 3 4

(Km)

Figure 8 Distribution map of the groundwater facies in the shallow aquifer of Ras Jbel

and HCO3 (Figure 10) It suggests carbonates weathering andpollution by fertilizer application

In order to understand the origin of groundwater min-eralization in Ras Jbel plain the saturation index (SI) wascalculated The mineral facies are chosen based on the anal-ysis result of groundwater quality the main components ofgroundwater and the occurrences conditions ([6 43 44]) Inthe study area the main cations are Na+ Ca2+ andMg2+ andthe main anions are HCO3

minus SO42minus and Clminus thus gypsum

anhydrite calcite dolomite aragonite and halite are chosento be the mineral facies

The positive values of the calculated SI with respect tocalcite and dolomite for all groundwater samples (Figure 11)suggest their oversaturation in respect to these minerals(005 lt SIcalcite lt 132 and 008 lt SIcalcite lt 118 in the wetand dry seasons resp and minus010 lt SIdolomite lt 229 and006 lt SIdolomite lt 198 in the wet and dry seasons resp) Asdescribed by Appelo and Postma [45] the dissolution ofcalcite and dolomite is as follows

Calcite

CaCO3 + CO2 +H2Olarrrarr Ca2+ + 2HCO3minus (2)

Dolomite

CaMg (CO3)2 + 2CO2 + 2H2Olarrrarr Ca2+ +Mg2+ + 4HCO3

minus(3)

However focusing on the scatter plots of bicarbonate versuscalcium and calcium + magnesium versus bicarbonate wenotice that groundwater samples are not plotted on the 1 1straight lines of calcite and dolomite dissolution (Figures12(a) and 12(b)) Groundwater samples show an excess ofCa2+ that can be explained by the gypsum dissolution

The plot of SIGypsum and SIAnhydrite versus TDSexhibits a proportional and parabolic shape evolution withnegative values of the saturation indexes (Figure 11) (minus186 ltSIgypsum lt minus034 and minus172 lt SIgypsum lt minus035 in the wet anddry seasons resp and minus208 lt SIanhydrite lt minus056 andminus194 lt SIanhydrite lt minus056 in the wet and dry seasons resp)Thus both calcium and sulphate are derived from the sameorigin which is the dissolution of gypsum and anhydrite

Gypsum CaSO4sdot2H2Olarrrarr Ca2+ + SO42minus + 2H2O (4)

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

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Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

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Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 10: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

10 Journal of Chemistry

NMediterranean sea

0 05 1 2 3 4

(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl wet season (mgl)276ndash531532ndash710711ndash954955ndash12101211ndash1487

(a)

NMediterranean sea

0 05 1 2 3 4(Km)

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000Limit of Ras Jbel plainWadisLarge urban agglomerations

Cl dry season (mgl)217ndash502503ndash720721ndash953954ndash12481249ndash1792

(b)

Figure 9 Spatial distribution of chlorides (a) wet season and (b) dry season in Ras Jbel aquifer

However the plot of sulphate versus calcium (Figure 12(c))shows an excess of Ca2+ ions for the majority of the ground-water samples For these samples the (Ca(Ca + SO4)) ionicratio greater than 05 ratio (from 053 and 079) confirms theionic exchange process [46] The (Ca(Ca + SO4)) ionic ratioclose to 05 confirms that the main source of Ca2+ is the gyp-sum dissolution [46]

A bivariate diagram of sodium versus chloride (Fig-ure 12(d)) reveals two main groups for the first group halitedissolution was maintained for a slope equal to unity wheremajority of the samples are situated on the 1 1 straight ofhalite dissolution given by the following reactions [45]

Halite NaCllarrrarr Na+ + Clminus (5)

The second group includes the high-salinity samples (NandashCltype) which donot follow the halite dissolution line and show

enrichment in chloride compared to sodium Thus anotherphenomenon other than geological effect is controlling theirsalinization and this may be the salt water intrusion

Water samples were plotted in the Gibbs diagrams whichtakes into account themajor role of naturalmechanisms (rockweathering evaporation and precipitation) Figure 13 clearlyshows that themechanism controllingwater chemistry seemsto be a combination of the weathering of carbonates mineralsas well as the evaporation-precipitation processes Howeverlow rates of the groundwater samples were obtained in areasthat were dominated by rock-water interactions

Samples with Na+(Na+ + Ca2+) or Clminus(Clminus + HCO3minus)

ratios greater than 05 and TDS levels between 783 and4323mgl showed that the groundwater chemistry was con-trolled mainly by the saline water mixing or evaporationEvaporation results in increasedTDS in relation to high ratios

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Theoretical ChemistryJournal of

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Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

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Journal of

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Quantum Chemistry

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Organic Chemistry International

ElectrochemistryInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 11: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 11

CERS

pH

CaMg

Na

K

Cl

CETDS

SO42minus

Na+

minus48 minus36 minus24 minus12 12 24 36 48minus6

Component 1

minus36

minus3

minus24

minus18

minus12

minus06

06

12

Com

pone

nt 2

Ca2+

Mg2+

Clminus

SO4

HCO3

(a)

CERS

pH

Ca

Mg

Na

K

Cl

minus48 minus36 minus24 minus12minus6 12 24 36 48

Component 1minus2

minus15

minus1

minus05

05

1

15

2

25

Com

pone

nt 3 SO4

HCO3

(b)

Figure 10 Representation of variables into two principal factors 1198651-1198652 (a) and 1198651ndash1198653 (b)

of dominant cations and anions and CaCO3 precipitates bylosing Ca2+ and HCO3

minus

422 Ionic Exchange Processes and Freshwater-Saline WaterMixing Ion exchange is one of the important natural pro-cesses responsible for the concentration of ions in groundwa-ter and has significant impact on the evolution of groundwa-ter chemistry [18]The dominance of salty groundwater dom-inated by sodiumand chloride ions inRas Jbel shallow aquiferprovides evidence of mixing with an external salinity sourcewhich could be the seawater from the coastal part of theaquifer Cation exchange responsible for the salinity signa-ture is described by twomixingmechanisms (freshening andsaline water intrusion) Equations (6) and (7) show the gain

or loss related toNa+ and (Ca2+ +Mg2+) within the exchangerX

The freshening process or direct ion exchange whereCa2+ from freshwater displaced the marine cations Na+ andMg2+ from the exchanger complexThe resulting loss of Ca2+from solution decreases the saturation state for calcite andpossibly causes calcite dissolution

12Ca2+ + NandashX 997888rarr Na+ + 12CandashX (6)

The intrusion of seawater or reverse ion exchange alsotriggered cation exchange reactions where Ca2+ was expelledfrom the exchanger by seawater Na+ and Mg2+ The released

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

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Carbohydrate Chemistry

International Journal ofInternational Journal of

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Medicinal ChemistryInternational Journal of

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Chromatography Research International

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CatalystsJournal of

Page 12: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

12 Journal of Chemistry

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

1500 2500 3500 4500500TDS (mgl)

minus10

minus05

00

05

10

15

SI ar

agon

ite

minus10

minus05

00051015202530

SI d

olom

iteminus10

minus05

00

05

10

15

SI ca

lcite

minus65

minus60

minus55

minus50

minus45

minus40

SI h

alite

minus25

minus20

minus15

minus10

minus05

00

SI an

hydr

ite

minus25

minus20

minus15

minus10

minus05

00

SI g

ypsu

m

Figure 11 Variation of saturation indices of selected minerals in wet and dry seasons

Ca2+ is being flushed from the aquifer by groundwater flow[45 47]

12Na+ + CandashX 997888rarr Ca2+ + 12NandashX (7)

The plot of [(Ca2+ + Mg2+)ndash(HCO3minus + SO4

2minus)] versus(Na+ndashClminus) determines the exchange of Na+ against (Ca2+ orMg2+) through the clay matrix The relationship [(Ca2+ +Mg2+)ndash(HCO3

minus+SO42minus)] is the gain or loss of (Ca2+ +Mg2+)due to the carbonates and gypsum dissolution The relation-ship of (Na+ndashClminus) determines the gain or loss of Na+ rela-tive to the halite dissolution If there is no ion exchange allwater samples will be placed in the origin of diagram [46]

Figure 14 shows that reverse ion exchange is a dominantprocess To confirm the effect of reverse ion exchangechloroalkaline index CAI-1 was calculated inmilliequivalents

per liter according to the relationship proposed by Schoeller[48]

CAI-1 = [Clminus minus (Na+ + K+)]

Clminus(8)

If reverse ion exchange occurs in groundwater CAI-1 valuesare positiveThe calculated CAI-1 values are positive formorethan 70 of the water samples which confirmed that reverseion exchange is a dominant processThis shows that the inter-action between the seawater and groundwater in the studyarea is playing a major role in the contamination of theaquifer by seawater intrusion These results indicate thatseawaterfreshwater interface is in a continuous evolutiondespite the artificial recharge operations since 1993 and thisprobably because of the permanent heavy pumping

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

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CatalystsJournal of

Page 13: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 13

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Calcite dissolution

0

5

10

15

20

25

30HCO

3minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(a)

Increase in Ca2+

(slope 1 1)

Wet seasonDry season

Dolomite dissolution

0

10

20

30

40

Ca2

++M

g2+

(meacuteq

l)

10 20 30 400HCO3

minus (meacuteql)

(b)

(slope 1 1)

Wet seasonDry season

Gypsum dissolution

0

5

10

15

20

25

30

SO42minus

(meacuteq

l)

5 10 15 20 25 300Ca2+ (meacuteql)

(c)

Increase in Clminus

(slope 1 1)

Wet seasonDry season

Halite dissolution

10 20 30 40 500Na+ (meacuteql)

0

10

20

30

40

50

Clminus

(meacuteq

l)

(d)

Figure 12 Water-rock interaction relationships between different solutes of Na+ Ca2+ Mg2+ Clminus SO42minus and HCO3

minus (a b c d)

Water samples concentrated in the origin of the plot[(Ca2+ + Mg2+)ndash(HCO3

minus + SO42minus)] versus (Na+ndashClminus) indi-cated the absence of the ion exchange process which can beattributed to the evaporation process followed by carbonateprecipitation [49] This result confirmed the results obtainedusing saturation states of minerals and Gibbs diagrams

The seawater fraction in the groundwater is often esti-mated using chloride concentration [50] Chloride ion has

been considered as a conservative tracer not affected by ionexchange [51] For conservative mass balance of the mixturethe equation used is as follows [45]

119891 = (Clmix minus Clfreshwater)(Clseawater minus Clfreshwater) times 100 (9)

where Clmix is the Clminus concentration of the sample Clseawater

is the Clminus concentration of the Mediterranean Sea and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

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Carbohydrate Chemistry

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CatalystsJournal of

Page 14: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

14 Journal of Chemistry

Evaporationdominance

Rock dominance

Precipitationdominance

Transitionalseries

Transitional series

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000ClminusClminus + HCO3

minus

(a)

Evaporationdominance

Rock dominance

Precipitationdominance

1

10

100

1000

10000

100000

TDS

(mg

l)

02 04 06 08 1000Na+Na+ + Ca2+

(b)

Figure 13 Gibbs diagram showing TDS versus (a) Na(Na + Ca) and (b) Cl(Cl + HCO3)

Reverseionicexchange

Direct ionicexchange

Absence ofionic exchange

minus25

minus20

minus15

minus10

minus5

0

5

10

15

20

25

(Ca2

++M

g2+)ndash

(HCO

3minus+SO

42minus)

(meacuteq

l)

minus20 minus15 minus10minus25 minus5 5 10 15 20 250(Na+ + K+ndashClminus) (meacuteql)

Figure 14 Plot of [(Ca2+ +Mg2+)ndash(HCO3minus + SO42minus)] versus (Na+ +

K+ndashClminus) for ion exchange

Clfreshwater represents the Clminus concentration of the freshwater

The fresh water sample will be chosen considering the lowestmeasured value of the electrical conductivity

The rate of mixture varies from 032 (well n∘23) in thenorth of the Raf Raf region andwhere the configuration of theante-quaternary substratum prevents the marine intrusion to13 (well n∘1) near the shoreline (close to the coast)Thehigh-est value of the mixing fraction corresponds to the highestmeasured values of Clminus and EC (1792mgl and 5430 120583Scmresp)

43 Isotopes and Groundwater Origin The stable isotoperatios of oxygen and hydrogen in the groundwater are usefultools to differentiate between salinity origins [52 53] and tohelp us understand various sources of recharge processes togroundwater because they are sensitive to physical processessuch as atmospheric circulation groundwater mixing andevaporation ([33 54])

In arid and semiarid regions evaporation could be animportant process influencing groundwater chemistry [19]To understand the relationship between isotopic compositionof groundwater of the shallow aquifer of Ras Jbel and thoseof precipitation measured at the station of Tunis Carthagesituated at 50 km from the plain of Metline-Ras Jbel- Raf Rafa bivariate diagram 1205752Hversus 12057518O is plotted in Figure 15(a)

A local meteoric water line (LMWL) for Tunis Carthagewas used to interpret the data in this studyThe local meteoricwater line (LMWL) is controlled by local hydrometeorolog-ical factors including the origin of the vapor mass reevap-oration during rainfall and the seasonality of precipitation[33]The isotope composition of the precipitationwas plottedalong the LMWL using the following equation 1205752H (permil) =8 lowast 12057518O (permil) + 124 (which had a correlation coefficient1198772 = 099) [55 56]

Figure 15(a) shows that the isotopic composition of mostof the groundwater samples collected in the wet season(except for sampling site number 35) lies within a narrowrange confirming that these groundwater samples had thesame recharge source Furthermore all groundwater samplesare scattered around the LMWL indicating that the rechargeof the Ras Jbel shallow aquifer originates from infiltration ofrecent precipitation fromMediterranean vapormasses Basedon their isotopic composition two groups of groundwatersamples were identified (Table 4) The first group is relativelydepleted in isotopic values and includes samples with 12057518O

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 15: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 15

R2 = 083

y = 309x minus 1181

R2 = 082

y = 401x minus 837

y = 8x + 124

Wet season samplesDry season samples

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

훿2H

(0 )

vs S

MO

W

0minus5 minus4 minus3 minus2 minus1minus6minus7

훿18O (0) vs SMOW

(a)

minus35

minus30

minus25

minus20

minus15

훿2H

(0

vs S

MO

W)

1780 2780 3780 4780780TDS (mgl)

(b)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(c)

1780 2780 3780 4780780TDS (mgl)

minus35

minus30

minus25

minus20

minus15

minus10

minus5

훿2H

(0

vs S

MO

W)

(d)

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

1780 2780 3780 4780780TDS (mgl)

(e)

Figure 15 Isotopic relationships of groundwater in the study area

and 1205752H values ranging from minus603 to minus537permil versus V-SMOW and from minus3394 to minus2966permil versus V-SMOWrespectively This may be explained by the fact that nonevap-orated water is rapidly infiltrated to the saturated zone

As per the second group values vary from minus535 tominus350permilversusV-SMOWand fromminus2937 tominus2215permilversus

V-SMOW for 12057518O and 1205752H respectively The relativelyenriched isotopic values of the group 2 samples demonstratethat this groundwater is affected by evaporated open water orsoil water

The groundwater samples collected in the dry seasonwereenriched compared to those collected in the wet season The

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 16: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

16 Journal of Chemistry

Table 4 Isotopic data of sampled wells and piezometers in Ras Jbel aquifer

Parameters 12057518O (permil versus SMOW) 1205752H (permil versus SMOW) 12057518O (permil versus SMOW) 1205752H (permil versus SMOW)Wet season Dry season

Minimum minus603 minus3394 minus574 minus3146Maximum minus35 minus2215 minus006 minus1031Average minus491 minus2806 minus378 minus2333

results show isotopic content ranging from minus574 to minus006permilversus V-SMOW for 12057518Oand fromminus3146 tominus1031permilversusV-SMOW for 1205752H This may be explained by heavy isotopeenrichment in the groundwater caused by strong evaporationgiven that there was effectively no precipitation in the studyarea between the two sampling periods meanwhile thegroundwater may have been mainly recharged by lateralinflow from outside the study area resulting in seasonalfluctuations in the isotopic valuesThe enriched groundwatersamples (n∘15 20 25 30 32 35 38 41 45 and 48) might bean indicator for evaporation of the recharge water before itsinfiltration to the aquifer

The isotopic data for the groundwater collected in the wetseason were linearly fit using the regression equation 1205752H(permil) = 401 lowast 12057518O (permil) minus 837 (1198772 = 082) This regressionline can be interpreted as the groundwater evaporation line(GEL)The gel has a 1205752H12057518O slope lt8 which reflects evap-oration during or after rainfall andormixingwith an externalwater source (eg return of irrigation water) with high 12057518Oand 1205752H values Furthermore the GEL of the wet seasonintersected the LMWL at values of 12057518O = minus522permil versusV-SMOW and 1205752H = minus2937permil versus V-SMOW Thesevalues are estimated as baseline for 1205752H and 12057518O in recharg-ing rainfall (Figures 15(b) and 15(c)) If samples are plottedabove the lines significant groundwater evaporation processcan be confirmed

Additionally the isotopic data from the dry season werelinearly fit using the regression equation 1205752H (permil) = 309 lowast12057518O(permil)minus 1181 (with a correlation coefficient1198772 =083)TheGELhas a smaller slope than the LMWL because evaporationtends to enrich heavy isotopes inwater ([19 57])The increasein groundwater salinity due to evaporation can thus result insimultaneous increase in heavy isotopes ([19 35])TheGELofthe dry season intersects the LMWL at values of 12057518O =minus493permil versus V-SMOW and 1205752H = minus2732permil versus V-SMOW which are chosen as baselines (Figures 15(d) and15(e)) It is observed that 80 of the groundwater sampleswere plotted above the baselines and this demonstrates thatevaporation has a significant contribution to groundwatersalinity in the study area

Furthermore the deuterium excess calculated as d-excess= 1205752H minus 812057518O [54] has been widely used in hydrologicalstudies The d-excess is used to identify secondary pro-cesses that influence the atmospheric vapor content in theevaporationndashcondensation cycle in nature ([54 58]) The d-excess plotted against 12057518O shows a negative correlation forthe whole set of samples (Figure 16)The decrease in d-excess

Wet seasonDry season

minus20

minus15

minus10

minus5

0

5

10

15

20

d-ex

cess

minus6 minus5 minus4 minus3 minus2 minus1minus7 0훿18O (0) vs SMOW

Figure 16 Plot of d-excess versus 12057518O

is an indication that evaporation has occurred during the re-charge process which again confirms the previous results

44 Irrigation Return Flow Irrigation return flow is definedas the excess of irrigation water that is not evapotranspiratedor evacuated by direct surface drainage and which returns toan aquifer or surface water [59 60] Irrigation return flowsmay induce salt and nitrate pollution of receiving waterbodies [61] Indeed NO3

minus is the most common watercontaminant and NO3

minus pollution is increasing because thenumber of anthropogenic sources is increasing [26]

71 of groundwater samples are contaminated by nitrateswhere the concentration exceeds the permissible value of 50mgl set by WHO [62] The spatial distribution of nitrates(Figure 17) shows that high nitrate contents are observedespecially in the upstream of Ras Jbel aquifer Groundwatercontamination by nitrate is due to the intensive use ofnitrogen fertilizers (Ca(NO3)2 KNO3 andMgSO4) In recentyears the agricultural land area inRas Jbel plain has increasedand copious amounts of nitrogenous fertilizer have beenused which have increased the groundwater NO3

minus concen-trations

Furthermore return flow from irrigation water alsoseems to contribute notably to the recharge process Most ofgroundwater samples shows a correlation between NO3 and12057518O reflecting the significant role of evaporated and con-taminated irrigation water to the groundwater salinization(Figure 18(a)) Huge quantities of irrigation return flow

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 17: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 17

Mediterranean SeaN

515000 520000 525000

515000 520000 525000

436000

432000

428000

436000

432000

428000

0 05 1 2 3 4

(Km)

0ndash5960ndash130131ndash232233ndash337338ndash491

Large urbanagglomerationsWadisLimit of Ras Jbel plain

NO3 (mgl)

Figure 17 Spatial distribution of nitrate concentrations in the shallow aquifer of Ras Jbel during the dry season

Return flow of irrigation water

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0

1

훿18

O (

0vs

SM

OW

)

0 100 200 300 400 500NO3

minus (mgl)

(a)21

16

11

6

1

Wat

er ta

ble d

epth

(m)

0 100 200 300 400 500NO3

minus (mgl)

(b)

Figure 18 Plots of NO3minus versus water table depth and 12057518O versus NO3

minus

elevated groundwater level hence increasing evaporation andinducing salinization [63] As highlighted in Figure 18(b) thecontamination by return of irrigation water is observed in theshallower horizons (depth le 13m)

5 Conclusions

This paper aimed to discuss the origin processes and mech-anisms of groundwater salinization as well as the chemicalevolution of groundwater in the Ras Jbel coastal aquifer usingisotopic tools and hydrochemical tracers

Most of the groundwater is considered to be of brackish tosaline water and contains high ion concentrations Thegroundwater in the study area is influenced by both naturaland anthropogenic factorsThemajor geochemical processescontrolling hydrochemical evolution are the inverse cationicexchange due to the phenomena of seawater intrusion disso-lution of evaporates minerals (halite gypsum andor anhy-drite) irrigation return flow water-rock interactions and

evapo(transpi)ration (Figure 19) The mixing rate amongfreshwater and saline water ranges between 1 and 13

In addition groundwater in the shallow aquifer of RasJbel is also contaminated by agricultural fertilizers containinghigh amounts of nitrates Nitrates are transported to theaquifer by natural recharge process and by return flow fromirrigation water

Hydrogen and oxygen-18 stable isotopes signatures ofgroundwater have identified recent groundwater recharge byinfiltration of local precipitations The enrichment in stableisotope of groundwater confirms that return flow of irriga-tion waters is an important factor influencing groundwaterquality

The results of this study can be used to improve ourunderstanding of hydrogeochemical processes and enable theprotection and sustainable use of water resources It there-fore calls for more comprehensive research for better waterresources management

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 18: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

18 Journal of Chemistry

Precipitation

Discharge area

Precipitation

Mediterranean Sea Return flow

N

Return flow

Evaporation and transpiration

Seawater

CaGypsumNa Halite Cl

Ca Mg

Cation exchange

Na K

Flow direction

Return flow (NO3)

(NO3)

(NO3)

intrusion (Clminus) Seawaterintrusion (Clminus)

SO4

Figure 19 Schematic conceptual model summarizing salinization sources of groundwater in the plain of Ras Jbel

Conflicts of Interest

The authors declare no conflicts of interest

Acknowledgments

The authors would like to gratefully acknowledge all mem-bers of the Regional Commission for Agricultural Devel-opment of Bizerte for their guidance and support in fieldcampaigns Special thanks are due to Dr Maarten WaterlooSenior hydrologist Acacia Water (Formerly Professor inHydrology Free University Amsterdam) Netherlands

References

[1] V E A Post Groundwater salinization processes in the coastalarea of the Netherlands due to transgressions during the Holocene[PhD thesis] University of Amsterdam Amsterdam theNetherlands 2004

[2] G de Marsily ldquoImportance of the maintenance of temporaryponds in arid climates for the recharge of groundwaterrdquo Compt-es RendusmdashGeoscience vol 335 no 13 pp 933ndash934 2003

[3] D Han X Song M J Currell G Cao Y Zhang and Y KangldquoA survey of groundwater levels and hydrogeochemistry inirrigated fields in the Karamay Agricultural Development Areanorthwest China implications for soil and groundwater salinityresulting from surface water transfer for irrigationrdquo Journal ofHydrology vol 405 no 3-4 pp 217ndash234 2011

[4] M U Igboekwe and A Ruth ldquoGroundwater recharge throughinfiltration process A Case Study of Umudike SoutheasternNigeriardquo Journal of Water Resource and Protection vol 3 no5 pp 295ndash299 2011

[5] P Banerjee and V S Singh ldquoStatistical approach for compre-hensive planning of watershed development through artificialrechargerdquo Water Resources Management vol 26 no 10 pp2817ndash2831 2012

[6] J Jing Q Hui C Yu-Fei and X Wen-Juan ldquoAssessment ofgroundwater quality based onmatter element extensionmodelrdquoJournal of Chemistry vol 2013 Article ID 715647 7 pages 2013

[7] L Kouzana R Benassi A Ben mammou and M Sfar felfoulldquoGeophysical and hydrochemical study of the seawater intru-sion in Mediterranean semi arid zones Case of the Korbacoastal aquifer (Cap-Bon Tunisia)rdquo Journal of African EarthSciences vol 58 no 2 pp 242ndash254 2010

[8] R Trabelsi K Abid K Zouari and H Yahyaoui ldquoGroundwatersalinization processes in shallow coastal aquifer of Djeffaraplain of Medenine Southeastern Tunisiardquo Environmental EarthSciences vol 66 no 2 pp 641ndash653 2012

[9] AChekirbaneMTsujimuraAKawachiH Isoda J Tarhouniand A Benalaya ldquoHydrogeochemistry and groundwater salin-ization in an ephemeral coastal flood plain Cap Bon TunisiardquoHydrological Sciences Journal vol 58 no 5 pp 1097ndash1110 2013

[10] H Bouzourra R Bouhlila L Elango F Slama and N OuslatildquoCharacterization ofmechanisms and processes of groundwatersalinization in irrigated coastal area using statistics GIS andhydrogeochemical investigationsrdquo Environmental Science andPollution Research vol 22 no 4 pp 2643ndash2660 2015

[11] A Kharroubi S Farhat B Agoubi and Z Lakhbir ldquoAssessmentof water qualities and evidence of seawater intrusion in a deepconfined aquifer case of the coastal Djeffara aquifer (SouthernTunisia)rdquo Journal ofWater Supply vol 63 no 1 pp 76ndash84 2014

[12] I Triki N Trabelsi M Zairi and H Ben Dhia ldquoMultivariatestatistical and geostatistical techniques for assessing ground-water salinization in Sfax a coastal region of eastern TunisiardquoDesalination and Water Treatment vol 52 no 10ndash12 pp 1980ndash1989 2014

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 19: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Journal of Chemistry 19

[13] M F BHamouda A J KondashN Lauer LMejri J Tarhouniand A Vengosh ldquoAssessment of groundwater salinity mecha-nisms in the coastal aquifer of el haouaria Northern TunisiardquoProcedia Earth and Planetary Science vol 13 pp 194ndash198 2015

[14] S K Ambast N K Tyagi and S K Raul ldquoManagement ofdeclining groundwater in the Trans Indo-Gangetic Plain(India) some optionsrdquoAgriculturalWaterManagement vol 82no 3 pp 279ndash296 2006

[15] A El-Naqa and A Al-Shayeb ldquoGroundwater protection andmanagement strategy in JordanrdquoWater Resources Managementvol 23 no 12 pp 2379ndash2394 2009

[16] J L McCallum R S Crosbie G R Walker and W R DawesldquoImpacts of climate change on groundwater in Australia asensitivity analysis of rechargerdquo Hydrogeology Journal vol 18no 7 pp 1625ndash1638 2010

[17] J D Ayotte M Belaval S A Olson et al ldquoFactors affectingtemporal variability of arsenic in groundwater used for drinkingwater supply in the United Statesrdquo Science of the Total Environ-ment vol 505 pp 1370ndash1379 2015

[18] J Wu and Z Sun ldquoEvaluation of shallow groundwater contam-ination and associated human health risk in an alluvial plainimpacted by agricultural and industrial activities Mid-westChinardquo Exposure and Health vol 8 no 3 pp 311ndash329 2016

[19] P Li J Wu and H Qian ldquoHydrochemical appraisal of ground-water quality for drinking and irrigation purposes and themajor influencing factors a case study in and around HuaCounty Chinardquo Arabian Journal of Geosciences vol 9 no 1article 15 2016

[20] DGRE Annuaire de Surveillance Piezometrique Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 2007

[21] A Choura Impact de la surexploitation et de la rechargeartificielle de la nappe de Ras Jbel par les systemes drsquoinformationgeographiques [MS thesis] Faculty of Sciences of Tunis 1993

[22] L Bouchaou J L Michelot A Vengosh et al ldquoApplication ofmultiple isotopic and geochemical tracers for investigation ofrecharge salinization and residence time of water in the Souss-Massa aquifer southwest ofMoroccordquo Journal of Hydrology vol352 no 3-4 pp 267ndash287 2008

[23] F El Yaouti A El Mandour D Khattach J Benavente and OKaufmann ldquoSalinization processes in the unconfined aquiferof Bou-Areg (NE Morocco) a geostatistical geochemical andtomographic studyrdquoApplied Geochemistry vol 24 no 1 pp 16ndash31 2009

[24] F Sdao S Parisi D Kalisperi et al ldquoGeochemistry and qualityof the groundwater from the karstic and coastal aquifer ofGeropotamos River Basin at north-central Crete Greecerdquo Envi-ronmental Earth Sciences vol 67 no 4 pp 1145ndash1153 2012

[25] G Mongelli S Monni G Oggiano M Paternoster and RSinisi ldquoTracing groundwater salinization processes in coastalaquifers a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia Italyrdquo Hydrologyand Earth System Sciences vol 17 no 7 pp 2917ndash2928 2013

[26] Y Lu C Tang J Chen and J Chen ldquoGroundwater recharge andhydrogeochemical evolution in leizhou peninsula Chinardquo Jour-nal of Chemistry vol 2015 Article ID 427579 12 pages 2015

[27] M Ennabli ldquoHydrogeologie de la plaine de Ras Jbel-Raf RafrdquoAnnales des Mines et de la Geologie vol 26 pp 537ndash561 1973

[28] M H Hamza Evaluation de la vulnerabilite a la pollution desnappes phreatiques de Ras Jbel et de Guenniche par les methodesparametriques DRASTIC SINTACS et SI appliquees par lessystemes drsquoinformations geographiques [PhD thesis] Faculty ofSciences of Tunis Tunis Tunisia 2007

[29] P F Burollet ldquoEtude geologique des bassins Mio-Pliocenes duNord Est de la Tunisierdquo Annales des Mines et de la Geologie no7 p 82 1951

[30] M Ennabli ldquoEtat des travaux realises dans la plaine deMetlinemdashRas JbelmdashRaf Raf en vue de lrsquoetude hydrogeologiquede la plaine cotiererdquo Rapp Interne Bureau de lrsquoInventaire et desRessources Hydrauliques 1969

[31] DGRE ldquoAnnuaires de surveillance piezometriquerdquo DGRERapports Techniques des Piezometres et des Forages Rapp IntMinistere de lrsquoAgriculture Tunis Tunisia 1986ndash2006

[32] Pimienta Etude hydrogeologiquede Ras Jebel Fasc1 et 2Service Geologique (BIRH 3-10 et 3-11) 1949

[33] I D Clark and P Fritz Environmental Isotopes in HydrogeologyLewis Publishers New York NY USA 1997

[34] A M Piper ldquoA graphic procedure in the geochemical interpre-tation of water-analysesrdquo Eos Transactions American Geophys-ical Union vol 25 no 6 pp 914ndash928 1944

[35] F Liu X Song L Yang et al ldquoIdentifying the origin and geo-chemical evolution of groundwater using hydrochemistry andstable isotopes in the Subei Lake basin Ordos energy baseNorthwestern ChinardquoHydrology and Earth System Sciences vol19 no 1 pp 551ndash565 2015

[36] R J Gibbs ldquoMechanisms controlling world water chemistryrdquoScience vol 170 no 3962 pp 1088ndash1090 1970

[37] J W Lloyd and J Heathcote Natural Inorganic Hydrochemistryin Relation to Groundwater Oxford University Press New YorkNY USA 1985

[38] D L Parkhurst and C Appelo ldquoPHREEQC2 userrsquos manual andprogramrdquoWater-Resources Investigations Report US Geologi-cal Survey Denver Colo USA 2004

[39] K Pazand A Hezarkhani Y Ghanbari and N AghavalildquoGroundwater geochemistry in the Meshkinshahr basin ofArdabil province in Iranrdquo Environmental Earth Sciences vol 65no 3 pp 871ndash879 2012

[40] D Sujatha andB R Reddy ldquoQuality characterization of ground-water in the south-eastern part of the Ranga Reddy districtAndhra Pradesh Indiardquo Environmental Geology vol 44 no 5pp 579ndash586 2003

[41] A Kharroubi F Tlahigue B Agoubi C Azri and S BourildquoHydrochemical and statistical studies of the groundwater sali-nization in Mediterranean arid zones case of the Jerba coastalaquifer in southeast Tunisiardquo Environmental Earth Sciences vol67 no 7 pp 2089ndash2100 2012

[42] J C Rozemeijer Dynamics in groundwater and surface waterquality from field-scale processes to catchment-scale monitoring[PhD thesis] Utrecht University Utrecht The Netherlands2010

[43] Q B Luo W D Kang Y L Xie and B F Zhao ldquoGroundwaterhydro-geochemistry simulation in the Jingbian area of theLuohe of Cretaceousrdquo Ground Water vol 30 no 6 pp 22ndash242008

[44] N Ettayfi L Bouchaou J L Michelot et al ldquoGeochemical andisotopic (oxygen hydrogen carbon strontium) constraints forthe origin salinity and residence time of groundwater from acarbonate aquifer in the Western Anti-Atlas MountainsMoroccordquo Journal of Hydrology vol 438-439 pp 97ndash111 2012

[45] C A J Appelo and D Postma Geochemistry Groundwater andPollution Balkema Rotterdam The Netherlands 2nd edition1993

[46] A W Hounslow Water Quality Data Analysis and Interpreta-tion Lewis Publishers Boca Raton Fla USA 1995

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 20: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

20 Journal of Chemistry

[47] M S Andersen V Nyvang R Jakobsen and D PostmaldquoGeochemical processes and solute transport at the seawaterfreshwater interface of a sandy aquiferrdquo Geochimica et Cos-mochimica Acta vol 69 no 16 pp 3979ndash3994 2005

[48] H Schoeller ldquoQualitative evaluation of groundwater resourcesrdquoin Methods and Techniques of Groundwater Investigations andDevelopment pp 53ndash83 UNESCO Paris France 1965

[49] B C Richter and C W Kreitler ldquoIdentification of sources ofground-water salinization using geochemical techniquesrdquo p273 1993

[50] E Custodio and K A Bruggeman Groundwater Problems inCoastal Areas Studies and Reports in Hydrology UNESCOParis France 1987

[51] E Custodio Groundwater Problems in Coastal Areas Studiesand Reports in Hydrology UNESCO Paris France 1987

[52] W M Edmunds A H Guendouz A Mamou A Moulla PShand and K Zouari ldquoGroundwater evolution in the Conti-nental Intercalaire aquifer of southernAlgeria andTunisia traceelement and isotopic indicatorsrdquo Applied Geochemistry vol 18no 6 pp 805ndash822 2003

[53] TW Butler II ldquoApplication of multiple geochemical indicatorsincluding the stable isotopes of water to differentiate waterquality evolution in a region influenced by various agriculturalpractices and domestic wastewater treatment and disposalrdquoScience of the Total Environment vol 388 no 1ndash3 pp 149ndash1672007

[54] W Dansgaard ldquoStable isotopes in precipitationrdquo Tellus vol 16no 4 pp 436ndash468 1964

[55] M Ahmed Maliki M Krimissa J Michelot and K ZouarildquoRelation entre nappes superficielles et aquifere profond dans lebassin de Sfax (Tunisie)rdquo Comptes Rendus de lrsquoAcademie desSciences Series IIA vol 331 no 1 pp 1ndash6 2000

[56] A Ben Moussa S B H Salem K Zouari and F Jlassi ldquoHydro-chemical and isotopic investigation of the groundwater compo-sition of an alluvial aquifer Cap Bon Peninsula Tunisiardquo Car-bonates and Evaporites vol 25 no 3 pp 161ndash176 2010

[57] H Qian P Li J Wu and Y Zhou ldquoIsotopic characteristics ofprecipitation surface and ground waters in the Yinchuan plainNorthwest Chinardquo Environmental Earth Sciences vol 70 no 1pp 57ndash70 2013

[58] H Craig ldquoIsotopic variations in meteoric watersrdquo Science vol133 no 3465 pp 1702ndash1703 1961

[59] B Dewandel J-M Gandolfi D de Condappa and S AhmedldquoAn efficient methodology for estimating irrigation return flowcoefficients of irrigated crops at watershed and seasonal scalerdquoHydrological Processes vol 22 no 11 pp 1700ndash1712 2008

[60] Z Kattan ldquoEstimation of evaporation and irrigation return flowin arid zones using stable isotope ratios and chloride mass-balance analysis case of the Euphrates River Syriardquo Journal ofArid Environments vol 72 no 5 pp 730ndash747 2008

[61] J Causape D Quılez and R Aragues ldquoAssessment of irrigationand environmental quality at the hydrological basin level II Saltand nitrate loads in irrigation return flowsrdquo Agricultural WaterManagement vol 70 no 3 pp 211ndash228 2004

[62] WHO Guidelines for Drinking Water Quality World HealthOrganization Geneva Switzerland 3rd edition 2004

[63] H Wu J Chen H Qian and X Zhang ldquoChemical characteris-tics and quality assessment of groundwater of exploited aquifersin Beijiao water source of Yinchuan China a case study fordrinking irrigation and industrial purposesrdquo Journal of Chem-istry vol 2015 Article ID 726340 14 pages 2015

[64] M A Haddad Evolution de lrsquoEtat de la Nappe de Ras Jebel de1949 a 2005 et eValuation des Impacts de la Recharge Artificielle(Periode 1992ndash2005) PFE duCycle drsquoIngenieur enGeosciencesFaculte des Sciences de Tunis 2006

[65] DGRE ldquoAnnuaires drsquoexploitation des nappes phreatiques enTunisierdquo DGRE Tunis Tunisia 1993ndash2008

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 21: Characterization of Recharge Mechanisms and …downloads.hindawi.com/journals/jchem/2017/8610894.pdf[22–25] for determining the origins of groundwater salin ization in aquifers and

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal ofInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of


Linear Ization

Linear Ization

Glop Tim Ization

Glop Tim Ization

Quant Ization

Quant Ization

CHARACTER IZATION

CHARACTER IZATION

Kb Pasca Salin

Kb Pasca Salin

Virtual Ization

Virtual Ization

Christian Ization

Christian Ization

Sens It Ization

Sens It Ization

Inhalator Salin

Inhalator Salin

Jurnal Normal Salin Klp 1 + KEMASAN

Jurnal Normal Salin Klp 1 + KEMASAN

Program Kerja Multimedia 1415 - Salin

Program Kerja Multimedia 1415 - Salin

JChem for SharePoint Microsoft SharePoint · 2017-06-27 · JChem for SharePoint JChem for Excel Instant JChem Standardizer Reactor JChem Web Services JChem Base

JChem for SharePoint Microsoft SharePoint · 2017-06-27 · JChem for SharePoint JChem for Excel Instant JChem Standardizer Reactor JChem Web Services JChem Base

De Mutual Ization

De Mutual Ization

Discret Ization

Discret Ization

Taliban Ization

Taliban Ization

De Vulcan Ization

De Vulcan Ization

Seawater Temp Salin Dense

Seawater Temp Salin Dense

Infeksi Pasca Salin

Infeksi Pasca Salin

Escher Ization

Escher Ization

Salin Artikel PR903 Org Final

Salin Artikel PR903 Org Final