Inverse and Forward Hydrogeochemical Modeling of Acid Mine Drainage Cihan Güne , Sevgi Tokgöz Güne

Dokuz Eylül University Engineering Faculty Environmental Engineering Department, zmir, Turkey

Flow PathSamples

7 Surfacewater

6 ground-water

8 AMD 9 Mixwith

AMD

12 mix with AMD

11 Mixwith

AMD

10 mix with AMD

EC (µS/cm) 862 1007 4640 1155 1265 1278 1416pH 8.26 7.02 2.7 7.87 7.22 8.05 8.3T (°C) 9 14 12 11 12 12 11Eh (mV) -84 -15 228 -62 -26 -74 -87Na (mg/L) 17.1 15.8 10.7 17.2 17.6 17.8 18.0K (mg/L) 3.1 3.5 4.9 4.1 4.8 5.0 5.2Ca (mg/L) 56.9 79.5 349.4 82.9 92.6 99.3 120.9Mg (mg/L) 73.9 78.0 126.6 102.2 106.6 108.8 117.1SO4 (mg/L) 63.0 63.0 3354.0 204.0 327.0 414.0 573.0Cl (mg/L) 58.0 21.0 54.0 68.0 116.0 152.0 36.0HCO3 (mg/L) 510.0 593.0 0.0 550.0 445.0 370.0 273.0H3BO3 (mg/L) 0.12 0.165 0.142 0.205 0.188 0.263 0.297Al (mg/L) 0.027 0.108 65.6 0.103 2.39 3.69 2.11As (mg/L) 0.002 0.003 2.58 0.045 0.168 0.186 0.104Fe (µg/L) <10 328 649273 742 15133 21891 13896Hg (µg/L) 0.039 0.035 0.173 0.038 0.274 0.21 0.116Mn (µg/L) 3.1 2.0 1276.6 123.9 49.9 118.7 269.1Ni (µg/L) 1.7 76.3 93869.4 1740.5 2114 2838.2 2455.7H2Si03 (mg/L) 23.5 23.1 116.8 20.6 25.2 26.5 23.5Zn (mg/L) 3.4 16.7 1285.6 12.8 19.5 25.5 18.2% Ion Balance -7.9 -2.0 -5.84 -6.5 -7.9 -9.9 -0.0

Formation of Acid WaterSulphur minerals : Coal, metallic mine…

Sulphur minerals + Water + O2 = Sulfuric acidFeS2 + 7/2O2 + H2O => Fe2+ + 2H+ + 2SO4

2-

FeS2 + 14Fe3+ + 8H2O => 15Fe2+ + 16H+ + 2SO42-

FeS2 + 2CaCO3 + 3.75O2 +1.5H2O => Fe(OH)3 +2SO4-2 + 2Ca+2 + 2CO2 (g)

Al+3 + 3H2O <=>Al(OH)3(k) + 3H+

Fe+3 + 3H2O <=>Fe(OH)3(k) + 3H+

Fe+2 + 0.25O2 + 2.5H2O <=> Fe(OH)3(k) + 2H+

Mn+2 + 0.25O2 + 2.5H2O <=>Mn(OH)3(k) + 2H+

Lost of biological activity in abondoned Balya Pb-Zn Mine

2 3 4 5 6 7 8 9 10

pH

Acid DrainageSalty DrainageNeutral Drainage

Acid DrainageHigh pHModerate-High metalHigh suphate…

Neutral DrainageNeutral-alkalin pHlow-moderate metal (Zn,Cd)low-moderate-high sulphate…

Salty DrainageNeutral-alkalin pHLow metal (Fe)Moderate sulphate, calcium,…

Speciation Solubility ModelingDuring the sampling of groundwaters, high sensitiveness in measurements and analyses offield parameters (pH, Eh, dissolved oxygen, temperature, alkanity..), devices withappropriate calibrations, parameters measured in the flow cell closed to atmosphere ifpossible and transfer in an appropriate time for analysis.INPUT:

physical, chemical and biological (limited) components, measurement and analysis data,OUTPUT:Obtained result ensures the distribution of the chemical mass (ion and molecular species) between gas, mineral and solution in an instant image of a dynamic system (admitted) in case of stable balance and potential mineral saturation in accordance with calculated species.Comparison of Flow Path

7* 6 ** 8 AMD 9*** 12*** 11*** 10***pH 8.26 7.02 2.70 7.87 7.22 8.05 8.30

Al mg/L 0.027 0.108 65.560 0.103 2.390 3.690 2.100% Al(OH)2

+ 0 8 0 0 4 0 0% Al(OH)3 0 4 0 1 3 1 0% Al(OH)4

- 100 88 0 99 93 99 100% AlOH+2 0 0 12 0 0 0 0% AlSO4

+ 0 0 88 0 0 0 0Mn mg/L 0.003 0.002 1.276 0.124 0.050 0.119 0.269

% MnCl+ 0 0 83 0 1 1 0% MnCO3 81 22 0 62 25 66 72%MnHCO3

+18 74 0 32 56 22 14

% MnSO4 1 4 17 5 18 11 13Fe mg/L 0.010 0.328 649.27

30.742 15.130 21.891 13.896

% Fe+2 47 61 100 54 64 58 57% FeCO3 28 3 0 14 3 15 18% FeHCO3

+ 23 35 0 27 26 18 13% FeOH+ 1 0 0 0 0 0 1% FeSO4 1 2 0 4 7 8 11

As mg/L 0.002 0.003 2.584 0.005 0.168 0.186 0.104% H2AsO3

- 3 1 0 2 1 2 2% H3AsO3 35 97 100 64 96 42 19% H2AsO4

- 4 1 0 4 1 4 4% HAsO4

-2 59 1 0 29 2 51 76

Inverse Mass Balance ModelsThis model makes it possible to calculate gas and mineral mol transfer in the change

of water chemistry between a final water composition and one or many different initial water compositions, mixing ratio of waters and quantity of exchange in cation.Model works in accordance with mass balance principles with the description of the solutions in flow path, phases in aquifer matrix and uncertainty limits. It may be used

in determination of mixed fraction of many wastewater and natural water and discrimination of anthropogenic effects.

To be able to fulfill the requirements like the comprehension of potential dominant reactions in the medium, accumulation of judgmental knowledge which may

eliminate inappropriate solutions and verification of the reacting ones and products with site observations may offer great advantages in order to produce successful

solutions for the purposes of the validation and confirmation of model results.Dissolution of calcite and albite minerals,

Precipitation of amorphous Fe(OH)3, gibbsite (Al(OH)3), Ca-montmorillonite, allunite(KAl3(SO4)2(OH)6), gypsum (CaSO4:2H2O), CO2(g) and O2(g) as gas phase run away from

the medium and/or dissolved. Changes in sodium in the nullification of the mistakes arising from analysis in mass

balance, in halite in Cl balance and in sodium (NaX), potassium (KX), calcium (CaX2) and magnesium (MgX2) in cation exchange occurring between the surface of solid particles

encountered by water through flow path and them were permitted in mass balance.AMD + groundwater + surface water + reagents (minerals and gases) => result +

products (minerals and gases)

Ca0.95Mg0.05CO3 = CO3-2 + 0.95Ca+2 + 0.05Mg+2

According to the possible scenarios from the results obtained dominant part of water is firstthe acidic waters from the mine (45-80-70-100%) and second groundwater, amount ofdissolved calcite ranges between 6.5 mmol and 18.1 mmol (Model 1-2-5-6). Precipitatedminerals are allunite and gypsum and their quantities range respectively between 0.34-0.79mmol and 9.56-27.5 mmol. CO2(g) is the escaped content of water and oxygen isunderstood to be dissolved and consumed. Furthermore cation change is found to be otherdominant process in the medium and sodium was calculated to be interchanged with Ca+2,Mg+2 and K+.

Hydrogeochemical ModelModels include characteristics and relations required for us to comprehend a real system

with the aspects in which we are interested. Hydrochemical model requires determinative information describing related geological

system, existence of significant chemical reactions and design of formation and knowledge about thermodynamic, kinetic and surface characteristics for private chemical

system.Previously a conceptual behavior trying to comprehend water-rock interaction in the field, what kind of model will be developed and which detailed data will be needed should be

determined.Representative and recognized measurement parameter and sampling planning,

hydraulic and hydrogeological basic directional information are necessary.

REFERENCESAppelo CAJ, Postma D (2005) Geochemistry, groundwater and pollution, 2nd edition-Balkema; Rotterdam

Ball JW, Nordstrom DK (1991) User´s Manual for WATEQ4F -US Geological Survey

Bethke, C.M., (2008) . Geochemical and Biogeochemical Reaction Modeling2nd edition, Cambridge University Press, NewYork, 543 pp.

Blowes, D. W., Ptacek, C. J.; Jambor, J. L.; Weisener, C. G. 2003. The Geochemistry of Acid Mine Drainage Treatise on Geochemistry, Volume 9. Editor: Barbara Sherwood Lollar. Executive Editors: Heinrich D. Hollandand, Karl K. Turekian. pp. 612. ISBN 0-08-043751-6. Elsevier, 2003., s.149-204

Derry G. N. 1999 What Science is and How it Works. Princeton University Press, NJ, 311pp

Gemici, Ü., 2008. Evaluation of the water quality related to the acid mine drainage of an abandoned mercury mine (Ala ehir, Turkey). Environ Monit Assess 147:93–106.

Glynn, P.D., and Brown, J.G., 2011, Integrating field observations and inverse and forward modeling: application at a site with acidic, heavy-metal-contaminated groundwater, in Geochemical Modeling of Groundwater, Vadose and Geothermal Systems, Bundschuh J. & Zilberbrand M. (eds), CRC Press, Chapter 8, p. 181-234.Güne C., Tokgöz Güne S., (2011) Asit Drenaj n Jeokimyasal Modellenmesi. IV. Maden ve Çevre Sempozyumu bildiriler kitab Maden Mühendisleri Odas , zmir

ICOLD, 1996. A Guide to Tailings Dams and Impoundments: Design, Construction, Use and Rehabilitation. International Commission on Large Dams, Bulletin (United Nations Environment Programme) no. 106, 239pp.

Kuipers, J. R., Maest, A.S., K.A. MacHardy, and G. Lawson (2006). “Comparison of Predicted and Actual Water

Quality at Hardrock Mines: The reliability of predictions in Environmental Impact Statements.” Kuipers & Associates, PO Box 641, Butte, MT USA 59703.

Langmuir D (1997) Aqueous environmental geochemistry.-Prentice Hall; New Jersey

Maest, A.S., Kuipers, J.R., Travers, C.L., and Atkins, D.A., 2005. Predicting Water Quality at Hardrock Mines: “Methods and Models, Uncertainties, and State-of-the-Art” (http://www.earthworksaction.org/pubs/PredictionsReportFinal.pdf.).

Merkel, B. J., Planer-Friedrich, B., 2008. Ground-water Geochemistry: A Practical Guide to Modeling of Natural andContaminated Aquatic Systems, Edited by Nordstrom, D. K., 2nd Edition, Springer-Verlag Berlin Heidelberg.

Morin, K. A., Hutt, N.M. 2000. “Lessons Learned from Long-Term and Large-Batch Humidity Cells.” Fifth International Conference on Acid Rock Drainage, Denver, CO, Society for Mining, Metallurgy and Exploration

(SME).

Parkhurst DL, Appelo CAJ (1999) User's guide to PHREEQC (Version 2) -- a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations.- U S Geological Survey Water-Resources Investigations Report 99-4259

Plummer, L.N., Parkhurst, D.L., and Thorstenson, D.C., 1983, Development of reaction models for ground-water systems: Geochim. Cosmochim. Acta, v. 47, p. 665-686.

Stumm, W. and Morgan, J.J., 1996. Aquatic Chemistry: AnIntroduction Emphasizing Chemical Equilibria in Natural Waters, 3rd edn. New York, John Wiley & Sons, 1022 pp.

Zhu, C., Anderson, G. M., ( 2002). Environmental Applications of Geochemical Modeling, Cambridge University Press, New York, 299 pp

Model Number

1 2 3 4 5 6 7

Surface water (%) 0 0 39 0 0 19 98

Groundwater(%) 55 20 59 98 0 0 0

AMD (%) 45 80 2 2 100 81 2Result % 100 100 100 100 100 100 100Calcite 6,58E-03 1,38E-02 0 0 1,81E-02 1,43E-02 0

Fe(OH)3(a) -5,03E-03 -9,07E-03 0 0 -1,14E-02 -9,25E-03 0

Gibbsite 0 0 -3,87E-03 -4,52E-03 0 0 -2,87E-03

Montmlt-Ca 0 0 -2,71E-03 -2,13E-03 0 0 -3,59E-03

Alunite -3,43E-04 -6,23E-04 2,30E-03 2,30E-03 -7,88E-04 -6,36E-04 2,29E-03Gypsum -9,56E-03 -2,09E-02 0 0 -2,75E-02 -2,14E-02 0

Albite 0 0 3,31E-03 2,60E-03 0 0 4,40E-03Halite 0 -3,24E-04 0 4,04E-04 -5,14E-04 -5,34E-04 -6,18E-04CO2(g) -9,03E-03 -1,22E-02 -6,18E-03 -7,54E-03 -1,41E-02 -1,18E-02 -4,11E-03O2(g) 1,27E-03 2,27E-03 7,97E-06 7,97E-06 2,87E-03 2,32E-03 7,97E-06CaX2 9,52E-04 2,68E-03 1,56E-03 1,24E-03 3,69E-03 2,73E-03 2,04E-03

KX 3,70E-04 6,38E-04 -2,25E-03 -2,26E-03 7,95E-04 6,52E-04 -2,24E-03MgX2 6,98E-04 0 1,63E-03 1,57E-03 -4,09E-04 0 1,73E-03NaX -3,67E-03 -5,99E-03 -4,13E-03 -3,37E-03 -7,35E-03 -6,12E-03 -5,30E-03

Reaction Path Modeling (Forward Model)

Models driven by reaction may calculate every step in balance condition covering gradual or incremental mass transfer between phases by subtracting or adding

incrementally an effective component in the system in case of a temperature and/or pressure change. Simulation of instant reactions of solid (chemical compound,

mineral), water and gas mixtures existing in a system may be completed in consecutive interrupted and uninterrupted tests and experiments.

When acidity titration is made with acidic water, calcite mineral in Alasehir mercury mine by the use of PHREEQCv.3.0 code and wateq4f data base, precipitations based on balance reactions of (A) gypsum

(CaSO4), jarosite (Fe3(SO4)2(OH)6), jurbanite (AlSO4(OH).5H2O), kaolinite (Al2Si2O5(OH)4) and (B) gypsum, gibbsite (Al(OH)3) and amorphous Fe(OH)3 minerals up to change in pH were calculated.

As permitted to be precipitated quantity of Al+3 and Fe+3 in the solution is controlled by jarosite((ss:K0.77Na0.03H0.2)Fe3(SO4)2(OH)6), jurbanite and kaolinite in Figure A and gibbsite and

amorphous Fe(OH)3 in Figure B. .Although CO2 partial pressure in unconfined aquifers may have high values, CO2 occurring based on the dissolution of calcite in the solution is balanced in a pressure of 1 atm (0.0035% CO2) and surplus amount was allowed to run away. Mineral phases other than calcite

are defined in the medium in the beginning, they are not allowed to be dissolved but to be precipitated based on neutralization reaction.

According to Figure 1 A neutralization of 1 liter water was balanced in pH 6.01 and 22.5 mmol(2.25 gr) CaCO3 is consumed and calcite saturation was ensured at this point. Interruption of dissolution based on calcite saturation interrupted the precipitation of gypsum. In Figure 1 B

32 mmol (3.2 gr) CaCO3 is consumed, pH 6.01 value is reached. Consumption difference of 50% CaCO3 was caused by the effect of the minerals precipitated on Ph.

In Figure 2 changes in dominant components controlling the pH value in the solution are stated. In this case content of solution has an important effect in AMD characterization as well

as the minerals in the environment.

0

1

2

3

4

5

6

7

0.0E+00

2.0E-03

4.0E-03

6.0E-03

8.0E-03

1.0E-02

1.2E-02

1.4E-02

0 5 10 15 20

mol

/L

CaCO3 (mmol/L)

Gypsum

Jarosite(ss)

Jarosite-Na

Jurbanite

Kaolinite

pH

pHA

0

1

2

3

4

5

6

7

0.0E+00

5.0E-03

1.0E-02

1.5E-02

2.0E-02

2.5E-02

3.0E-02

3.5E-02

4.0E-02

4.5E-02

0 5 10 15 20

mol

/L

CaCO3 (mmol)

Fe Al Ca S(6) pH pH

Figure 2. When calcite and acidity titration of the acidic waters in mercury mine in Alasehir by the use of PHREEQCv.3.0 code, changes in total Fe, Al, Ca and SO4

-2 (S(6)) concentrations dissolved in water upon the precipitations of gypsum, jurbanite, jaroite and kaolinite based on change in pH.

0

1

2

3

4

5

6

7

0.0E+00

5.0E-03

1.0E-02

1.5E-02

2.0E-02

2.5E-02

0 5 10 15 20 25 30 35

mol

/L

CaCO3 (mmol/L)

Fe(OH)3(a)

Gibbsite

Gypsum

pH

pHB

Figure 1. When calcite and acidity titration of the acidic waters in mercury mine in Ala ehir by the use of PHREEQCv.3.0 code, precipitations of (A) gypsum, jurbanite, kaolinite and (B) gypsum, gibbsite and amorphous Fe(OH)3 based on the change in pH.

ConclusionsAn acceptable estimation of acid drainage for mine operation is a critical necessity for both mine industry and control authorities in terms of the protection of

water sources. AMD requires an organized and complete team work from the research stage to closure and recycling. Quality and sensitiveness of many dataproduced in every stage affects directly the reliability of the estimations to be made. Estimation methods, validity limits of methods and field-specificcharacteristics require an essential control planning and course of action. Right estimation of water quality require to understand the potentialproblems as supported by conceptual model with the combination of many complex data like field and laboratory data, hydrology data and mineplanning data obtained from the site. Hydrogeochemical models are used in every stage and in the conceptualization of every analysis and testresult and may ease the audit of all stages and studies. As a result of all studies including conceptual model studies if acidic water will arise out, a newtechnical study to prevent this formation will be necessary. But even the estimation that acidic water won’t arise out based on the sensitiveness of the site interms of water sources requires describing field-specifically simulation models for the prevention, slowdown and stop based on the characterization of mine.Furthermore to come to a conclusion about the whole by studying on a certain part of components constituting the whole in environmental impact assessmentstudies may cause significant mistakes.To make mine plans are of great importance in accordance with the reaction to be shown by the material of mine in atmospheric conditions.

Description of acidic waters formed by any water leakage, overflow of the lake on excavation site and mine process and potential unexpected floodarising from a different source, chemical loads to be brought by it to hydrogeological units (groundwater aquifer) and surface waters and relatedprevention strategies are of vital importance.Size of problem is based on not only many parameters like acid forming potential based on mineral content of wastes, their neutralization potential to reduce,

stop and eliminate the efficacy of this potential, climatic and raining potential of the site and but also point of view to problem. Determination methods to be usedby you and its reliability are the parameters affecting the possibility of your target estimations directly.

Cihan Güne : http://kisi.deu.edu.tr/cihan.gunes/Asit%20Maden%20Drenaj.html cihan.gunes@deu.edu.tr Dokuz Eylül Üniversitesi Mühendilik Fakültesi Çevre Mühendisli i Bölümü T aztepe Kampüsü Buca/ zmir +90232 3017147Sevgi Tokgöz Güne : http://kisi.deu.edu.tr/sevgi.tokgoz/ sevgi.tokgoz@deu.edu.tr Dokuz Eylül Üniversitesi Mühendilik Fakültesi Çevre Mühendisli i Bölümü T aztepe Kampüsü Buca/ zmir +90232 3017128

Flow Cell