ORIGINAL ARTICLE

Ecological risk assessment of surficial sediment by heavy metalsfrom a submerged archaeology harbor, South Mediterranean Sea,Egypt

Maha Ahmed Mohamed Abdallah1• Ahmed Mohamed Badr-ElDin2

Received: 6 December 2018 / Revised: 13 March 2019 / Accepted: 8 April 2019 / Published online: 25 April 2019

� Science Press and Institute of Geochemistry, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Abstract A protected semi-enclosed embayment, the

Eastern Harbor (EH), is situated in the central sector of the

Mediterranean coast of Alexandria, Egypt. It is a famous

fishing dock and water-sport center and its importance

arose after the discovery of the Ptolemaic royal quarter of

ancient Alexandria. To protect this national treasure and

improve its environmental health, the untreated anthro-

pogenic effluents, which continued for decades into the EH

since 1992, must be totally stopped. Accordingly, it is an

important issue to continually monitor and asses the envi-

ronmental status of the EH. The sediment texture, total

organic carbon, and the accumulation, distribution, and

ecological risks of Cd, Cr, Pb, As, Hg and Al were deter-

mined with a total of 14 surficial sediments samples col-

lected in the EH during 2010. Metal contents were

compared to the literature data to assess the pollution status

of sediments. Enrichment factors, Degree of contamination

(mCd) and potential ecological risk were calculated as a

criterion of possible contamination. Since mCd calculation

produces an overall average value for a range of pollutants,

in the present study the contamination factor that provides

a measure of the degree of overall contamination in the

surface layers in a particular sampling site may provide a

better indication of the state of pollution in the EH sedi-

ments than other indicators.

Keywords Heavy metals � Eastern harbor � Enrichment

factors � Degree of contamination � Potential ecological risk

1 Introduction

Alexandria is the largest city on the Mediterranean coast-

line of Egypt. It is the main commercial harbor, industrial

center and summer resort with a population of nearly 6.5

million inhabitants. Alexandria was one of the main centers

of Hellenistic civilization. It is celebrated for its unique

blend of Ancient Egyptian, Greek, Roman and Islamic

cultures. The eventful history of the city’s history has

resulted in a variety of archaeological relics, which remain.

This is due to the fact that the coastal region, where

Alexandria is situated in, has subsided since ancient times.

The straight coastline of Alexandria extends to about

80 km with slight undulations forming small embayments

(El-Wakeel and El-Sayed 1978). One of these embayments

was artificially transformed into the Eastern Harbor (EH).

The Harbor has a surface area of about 2.53 km2.

Accordingly, its volume is about 15.2 9 106 m3 (Abdallah

2007). The harbor is also one of the fishing docks and acts

as an important water-sporting center in Alexandria city.

The importance of the harbor was boosted after the exca-

vations of a historic site at the foot of Qait Bey Fort, which

discovered thousands of submerged archaeological artifacts

and part of the Ptolemaic royal quarter that represents a

significant era of ancient Alexandria (Goddio 1998). To

protect and conserve this historical human heritage, it was

proposed to implement an under-water museum in part of

the EH, yet the Harbor environmental health could limit the

success of this project.

The marine environment of the EH experienced about

25 years of receiving a considerable amount (20,000 m3/

& Maha Ahmed Mohamed Abdallah

mahaahmed72007@yahoo.com

1 Marine Pollution Lab, National Institute of Oceanography

and Fisheries, Alexandria, Egypt

2 Oceanography Department, Faculty of Science, Alexandria

University, Alexandria, Egypt

123

Acta Geochim (2020) 39(2):226–235

https://doi.org/10.1007/s11631-019-00340-2

day) of untreated sewage flow that was discharged directly

through several marine submerged minor sewage out falls

distributed along the Eastern Harbor coast or indirectly

from Qait Bey Sewage pumping station through El-Boug-

haz inlet (Abdallah 2017). Most of these outfalls were

originally made to serve as disposal sites only for storm

(rainy) waters of the seaside (Cornish) street during the

rainy season (in winter) as a fast solution to protect

Alexandria’s coast from drowning in the storm water. In

addition to raw sewage, the pollutants in the harbor include

wastes from various small industries such as: photo

development shops, car cleaning and repairing, foodstuff

plants, gas stations, small dairy plants and foundries (Ab-

dallah 2007, 2017). Currently, the EH receives anthro-

pogenic wastes from anchored fishing boats and the

shipyard situated at its western part. Beside these, and due

to local water circulation, the Harbor occasionally receives

an additional amount of untreated sewage wastes through

its two openings from two marine outfalls, one of them lies

at Qait Bey Outfall with a discharge rate about

150 9 103 m3/d and the other at El-Silsila Outfall with a

discharge rate about 50 9 103 m3/d (El-Rayis and Hinck-

ely 1999). Additionally, a continuous risk from the existing

oil and fuel related activities (fishing boats, bunker-

ing…etc.) is present. Therefore, the Harbor sediments were

highly affected by anthropogenic inputs and progressively

undergone several changes in character (Abdallah and

Mohamed 2015). These effluents had led to a considerable

increase in the level of nutrients and trace metals in the

Harbor waters and sediments (Abdallah 2007; Kremling

and Petersen 1981). It was believed that the best way to

protect these sites was to stop the discharges from land-

based sources so that sewage outfalls inside the EH were

partially closed since 1993. This work is one of many

studies that aim to continuously monitor and assess the

environmental conditions in the EH. The objectives of the

present work are to illustrate the distribution of trace metals

in the surficial sediments and their assessment by sediment

quality guideline as indicators to identify the present

degree of sediment contamination, to assess the potential

ecological risk of contamination and to predict sediment

toxicity in the EH.

2 Materials and methods

2.1 Sampling

A total of 14 surface sediment samples (0–5 cm) were

collected. The samples represented the whole area of the

Eastern Harbor (EH) during March 2010 (Fig. 1). Samples

were collected with a van Veen grab sampler and the upper

3–5 cm of sediment was removed with a PTFE spatula.

The samples were taken with a polyethylene spoon to avoid

contamination by the metallic parts of the sampler. Sam-

ples were then stored in plastic cups that were cleaned by

1:1 HCl and 1:1 HNO3 and were stored refrigerated at 4 �C

until analysis (American Society for Testing and Materials

(ASTM) 1991).

2.2 Textural and geochemical analyses

In the laboratory, samples were dried in an oven at 50 �C

for 3–4 days. Later, they were lightly ground in an agate

mortar for homogenization, sieved to pass \ 63 mm

(Morillo et al 2004) and prepared for analysis. Laser

technique for grain size analysis was performed using

SALD 3100 (Shimadzu-laser analyzer). The inclusive

graphic mean size (Mz U) was calculated according to Folk

and Ward (1957) in addition to the percentages of sand

(S%), silt (Z%) and clay (C%). Loss-on-ignition proce-

dures were applied for total carbon and total inorganic

carbon determination using TOC-SSM-5000 a solid sample

module, TOC-V CSH/CSN (Shimadzu-total organic carbon

analyzer) at 980 �C and 200 �C, respectively. Total organic

carbon (TOC%) was calculated as the difference of total

carbon and total inorganic carbon measurements.

For heavy metal analysis, the dried and powdered sed-

iments were digested in a mixture of HF-HClO4-HNO3

(Loring and Rantala 1992) and brought into solution in

0.5 M HCl (25 ml) using deionized double distilled water

(DDDW). All chemicals were supplied by MERK and

Prolabo Central Drug House (P) Ltd. Samples were ana-

lyzed using an ICP Mass Spectrometer (ELAN DRC-e,

Axial Field Technology, Perkin Elmer Sciex). Ultrapure

distilled water was used in all procedures of heavy metals

determination. The reagent blanks were included in each

batch of analysis and monitored throughout the analysis

and they were used to correct the analytical results. All

absorbance readings were made in triplicates. Calibration

standard runs were regularly performed to evaluate the

accuracy of the analytical method. The accuracy of the

analytical procedure was checked using a triplicate analysis

of the certified reference materials. The accuracy of the

analytical procedure was checked using a triplicate analysis

of certified reference material (MESS-3) from the National

Research Council of Canada (Table 1).

2.2.1 Degree of contamination (mCd)

According to the following equation that is proposed by

Hakanson (1980) based on the calculation for each pollu-

tant of a contamination factor (Cf):

Cf ¼ C0

Cn

Acta Geochim (2020) 39(2):226–235 227

123

where, C0 and Cn refer to the mean concentration of a

heavy metal in the contaminated sediments and the pre-

industrial ‘‘baseline’’ sediments, respectively. Hakanson’s

equation was used to calculate the modified degree of

contamination (mCd) for the five studied elements (Cd, Pb,

Cr, As and Hg). This modified method can therefore pro-

vide an integrated assessment of the overall enrichment and

impact of contamination of pollutant groups in sediments.

The modified equation for a generalized approach to

calculating the degree of contamination is given as:

mCd ¼Pn

i Cif

n

where, n is the number of analyzed heavy metals and Cif is

the contamination factor.

2.2.2 Potential ecological risk (PER)

The degree of heavy metal pollution in surface sediments

of the EH was assessed by calculating the Toxic Response

Factor (TRF), which depends on the sedimentological toxic

factor (STF) and the sedimentological sensitivity factor

(SSF). STF includes the toxicity variable, assigned by

Hakanson et al. (2003), which reflects the different toxic

effects of each metal in natural aquatic systems. The fol-

lowing metals were classified in decreasing order of

toxicity:

Hg ¼ 40 [ Cd ¼ 30 [ As ¼ 10 [ Pb ¼ 5 [ Cr ¼ 2:

Generally, the negative effect of metals tends to increase

with a decrease of the bio-production. For SSF estimation,

the bio-production ratio (BPR) was calculated. The best

responses were found using the ratio among total

Fig. 1 Sampling location in the

Eastern Harbor

Table 1 Metal extracted from

standard reference material

MESS-3 (n= 3)

Element Metal extracteda (mg Kg-1) Metals extractedb (mg Kg-1) Accuracy (%)

Cd 0.24 0.25 104.2

Pb 21.1 21.52 102.0

Cr 105.0 105.41 100.4

As 21.2 21.67 102.2

Hg 0.091 0.094 103.3

Al 85.9 86.81 101.1

aCertified values corresponding to the total extraction of metals from the standard reference material

MESS-3bValues of the metals extracted from the standard reference MESS-3 in this study

228 Acta Geochim (2020) 39(2):226–235

123

phosphorous and TOC%. Therefore, BPR was calculated as

follows:

SSF ¼ BPR ¼ TP in mg=gð Þ= TOC in %ð Þ½ � � 100

The Toxic Response Factor (TRF) is calculated for each

metal as follows:

Hg ¼ 40� 51=2=BPR1=2; Cd ¼ 30� 51=2=BPR1=2;

Pb ¼ 5� 51=2=BPR1=2;

Cr ¼ 2� 51=2=BPR1=2; As ¼ 10� 51=2=BPR1=2

Thus, the potential ecological risk for each metal was

calculated according to the equation:

PER ¼ TRF � Cf

3 Results and discussion

3.1 Texture and organic carbon

The mean grain size (MzA) and TOC % distribution in the

bottom sediments of the EH are given in Table 2. The

average grain size varied from - 1.13 to 3.43 A with an

average of 0.81 A. The results reveal wide variation in

textural composition observed in the EH sediments and

predominantly composed of sand silt clay at the majority of

the locations. The texture of the EH sediments were

dominated by coarse grained fractions ([ 64%) covering

the north west and south west areas, whereas the harbor

region contained medium grained fraction ([ 21%) to

clayey-silt ([ 14%). The variation of the grain size could

be attributed to the bottom configuration and the current

regime within the Harbor where the fine fractions were

deposited in the depression and the coarse fraction were

deposited on the nearly flat bottom.

Total organic carbon (TOC) is one of the most important

indicators of pollutants in marine sediments, and it gives a

clear idea about the source of runoff in any particular area.

TOC ranged from 0.04% to 3.69% with an average of

0.71%. The average organic carbon content, in the present

study, were generally lower than those recorded previously

in the EH. The TOC has had a steady decrease in level with

time probably due to closure of the outlets of the untreated

discharged domestic waste in the EH since 1993. TOC had

a moderate positive correlation with grain size (r2 = 0.47,

p \ 0.001), indicating that grain sizes control TOC distri-

bution to a certain extent in the EH surface sediments.

There is a general tendency for the finer sediment to have

high contents of TOC. Fine to very fine-grained sediments

tend to have relatively high TOC due to the high specific

surface area of the smaller particles (Horowitz and Elrick

1987). However, this fact is not clearly evident in the

present study because of the contamination of the coarser

sediments covering most of the EH with the allochthonous

organic matter from different land-based sources.

3.2 Elemental concentrations

The trace elements concentrations in the EH surficial sed-

iments are given in Table 3 and illustrated as contour maps

in Fig. 2. Since the sediments from different stations of the

EH are originated from the same environmental sources,

these sediments should have a similar texture and ele-

mental composition type. Recently, the sediments in the

EH are influenced and stressed by natural and anthro-

pogenic pressure (Alves et al. 2016). The most abundant

element in the EH sediments was Al at average concen-

trations [ 2160 lg/g. Pb and As follows Al in abundance

and have with average 81.1 and 78.2 lg/g. Low average

concentration (9.9 l/g) was observed for Cr. Lower con-

centrations were recorded for Cd and Hg (1.33 and

0.59 lg/g), respectively (Table 3). The mean concentra-

tions of elements are comparable to those in other impacted

Harbors elsewhere (Table 4). Aluminum typically displays

a uniform distribution and largely different from pollution-

derived elements (Fig. 2). This is expected, since soil-re-

lated elements such as Al exist in the alumino-silicate

matrix of sediments (Chen et al 2007; Kumar et al. 2001).

Significant correlation between Al concentrations and MzAwas observed (r2 = 0.62, p \ 0.001), indicating that Al

concentrations are mainly controlled by the grain size as a

result of natural weathering processes.

The remaining studied elements (As, Cr, Cd, Pb, Hg)

have exhibited similar patterns with maximal

Table 2 Mean grain size and TOC% of studied metals in surface

sediments from the Eastern Harbour

Site Grain size (U) TOC (%)

1 0.00 0.27

2 - 0.55 0.11

3 1.65 0.74

4 0.88 0.40

5 0.05 1.02

6 1.68 3.69

7 0.15 0.04

8 - 1.13 0.27

9 0.63 0.39

10 2.60 0.76

11 3.43 1.06

12 1.07 0.18

13 0.92 0.06

14 - 0.08 0.92

Mean 0.81 1.23

SD 0.71 0.93

Acta Geochim (2020) 39(2):226–235 229

123

concentrations found in sediments near the shipyard (site

No. 6), suggesting common sources or similar geochemical

behavior of these elements (Fig. 2). This could be related

to three factors: (1) high concentration of urban wastes; (2)

prevailing anticlockwise marine currents; and (3) several

outfalls located in the EH southern margin (Fig. 1).

Unfortunately, concentrations of these elements are used as

markers or tracers of metal industries (Kumar et al. 2001;

Gallego et al. 2002; Loska et al 2004).

The grain size is a major factor controlling natural

concentrations of trace metals in sediments (Zhang et al.

2001; Abdallah 2014). The fine sediments tend to have

relatively high metal contents, due to the high specific

surface of the finer particles. This is evidenced by the

strong correlation between grain size and trace elements

concentration (r [ 0.73). This confirms that the high

dependence and affinity of the studied trace elements for

fine sediments. Also, coatings of organic matter are

prevalent in fine sediments (r [ 0.75), and these coatings

bind a variety of trace elements. The heavy metals are

enriched in clay and organic matter by precipitation as

metallic coatings, incorporation in crystalline structure and

adsorption on cation exchange sites (Armstrong et al.

1976). This might explain the significant correlation

recorded between trace metals with TOC and MzA in the

EH. Fine sediments with high organic matter content retain

more contaminants than does relatively coarse sandy sed-

iment (De Mora et al. 2004).

3.3 Evaluation of pollution status in the EH

Two processes are usually used for assessing the pollution

status of sediments: (1) comparison of metal concentrations

in sediments with those of background concentrations

expressed as enrichment factors (EF) and, (2) comparison

with sediment quality guidelines for each contaminant and

the cumulative effects of contaminants in sediments.

3.3.1 Enrichment factors (EF)

To assess anthropogenic pollution in sediments and soils,

geochemical normalization processes are usually used

(Celik et al. 2009; Esen et al. 2010). Due to the different

magnitude of source contributions at each site in the EH,

the chemical composition of sediments may be different at

each sampling site. Generally, an enrichment factor (EF)

technique is a good tool to differentiate between anthro-

pogenic and naturally occurring sources of metals and is

used to determine the degree of modification in the com-

position. The enrichment factors we calculated for all

analyzed metals in this study are given in Fig. 3. Since Cr

in this studied area has an enrichment factor that is less

than 10, it is considered without enrichment (Zahra et al

2014). This indicates that Cr in the studied sediment is

originated predominantly from lithogenous material. About

57, 50, 14 and 71% of Cd, Pb, As and Hg were in the group

‘‘medium enrichment’’ (10 \ EF \ 100) with increasing

median factors of enrichment. The most enriched elements

(EF [ 100) are 43, 50, 86 and 29% of Cd, Pb, As, and Hg,

respectively.

Plots of the mean enrichment of the studied metals at

each station showed significance for all metals in the sur-

face sediments of the harbor at certain locations (Fig. 3).

This suggests an over-estimation of surface sediment

enrichment, as found for As (its enrichment factor at most

stations was [ 100), indicating that it has a high level of

Table 3 Metals concentrations

(lg/g dry weight) and depth

(m) in sediment samples

Site Depth (m) Cd Pb Cr As Hg Al

1 6.5 0.69 57.37 3.49 58.91 0.09 139.0

2 9.5 0.93 41.23 4.22 57.93 0.19 135.0

3 2.0 0.52 70.63 8.74 71.27 0.74 897.0

4 5.0 0.69 45.82 3.43 75.23 0.23 856.0

5 6.0 0.76 88.79 5.07 75.12 0.88 268.0

6 7.0 5.23 192.94 28.18 132.90 2.40 9312.0

7 5.0 0.97 83.52 5.83 55.44 0.33 267.0

8 4.25 0.64 29.87 2.18 56.19 0.24 74.0

9 4.0 0.81 73.17 3.86 68.33 0.40 551.0

10 9.0 1.74 105.89 26.36 116.45 0.72 11,138.0

11 5.25 3.72 131.59 27.86 128.10 0.77 3982.0

12 7.0 0.69 88.14 7.49 71.16 0.37 523.0

13 6.5 0.53 74.07 8.74 74.89 0.08 351.0

14 4.0 0.71 52.35 2.65 52.71 0.83 1844.0

Mean 1.33 81.10 9.86 78.19 0.59 2166.9

Median 0.73 73.60 5.45 71.21 0.39 535.0

230 Acta Geochim (2020) 39(2):226–235

123

enrichment throughout the EH. Cadmium was highly

enriched at stations numbers 1, 2, 5 and 7 while Pb showed

highest levels of enrichment at 7 stations (representing

50% of all sampling stations). The enrichment plot for Hg

evidenced high enrichment factors in the sediments of

stations 2, 5, 7 and 8 this indicates that there are major

sources of pollution for As, Cd, Pb and Hg in the study

area. However, the high levels of enrichment were found in

Fig. 2 Spatial distribution of Cd, Pb, Cr, As, Hg and Al (mg/g) in surface sediments of the Eastern Harbor

Acta Geochim (2020) 39(2):226–235 231

123

Table 4 Average metal concentrations (lg/g) in sediments from different regions of the world

Region Cd Pb Cr As Hg Reference

Kaohsiung Harbor, Taiwan 0.1–6.8 9.5–470 0.2–900 – 0.1–8.5 Chen et al. (2007)

Montevideo harbor, Uruguay \ 1.0–1.6 44–128 79–253 – 0.6–1.3 Muniz et al. (2004)

Izmir Bay, Turkey 0.22–0.42 36–62 208–308 25–30 – Atgin et al. (2000)

Southern Bay, Brazil 0.07–0.11 42.0–43.5 11–25.1 18.1–56.2 – Da Silva et al. (1996)

Izmit Bay, Turkey 2.5–9.5 55.2–172 38.9–112.4 13.5–28.2 – Pekey (2006)

Eastern Harbour, Egypt 0.08–3.11 37.0–154.0 N.D–39.0 – – Abdallah (2007)

Abu Qir Bay, Egypt 17.21 56.05 63.99 – – Abdallah and Mohamed (2015)

Eastern Harbour, Egypt 0.52–5.23 29.8–192.9 2.2–28.4 52.7–132.9 0.08–2.40 Present study

0200400600800100012001400160018002000

1 2 3 4 5 6 7 8 9 10 11 12 13 14<100

>100

As

0

50

100

150

200

250

300

1 2 3 4 5 6 7 8 9 10 11 12 13 14

>100

<100

Cd

0306090120150180210240270

1 2 3 4 5 6 7 8 9 10 11 12 13 14

<100

>100

Pb

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12 13 14

>100

<100

Hg

0102030405060708090100110

1 2 3 4 5 6 7 8 9 10 11 12 13 14

<100

>100Cr

Fig. 3 The mean enrichment value of studied metal in surface sediments of the EH

232 Acta Geochim (2020) 39(2):226–235

123

the sediments in the vicinity of small sewers which carry

mixed waste discharge from nearby small industries and

domestic sewage as well as in the vicinity of shipyards and

the anchorage of fishing boats, Cd and Pb are known as the

markers of paint industries (Lin et al. 2002). However, Cr

having enrichment factors less than 10, for all sites; fall in

the group of elements without enrichment in the study area.

According to Calmano et al. (1990), the difference in EF

values for the different studied metals in the harbor sedi-

ments may be due to the difference in the magnitude of

input for each metal in the sediment and/or the difference

in the removal rate of each metal from the sediment. When

observing changes in conditions as pH, redox potential,

ionic strength and the concentration of organic complexing

agents, the metals can be released with the water phase.

3.3.2 Degree of contamination (mCd)

For the classification and description of the mCd according

to Abrahim and Parker (2008), about 86% of the studied

sediments were in the range (8 B mCd \ 16) representing

a very high degree of contamination. The contamination

apparently comes from sewers that include industrial

wastes in addition to the outside source. The low move-

ment of sediments also contributed to the contamination.

Extremely high degree of contamination (16 B mCd \ 32)

were observed in about 14% of the EH sediments (at sta-

tions 10 and 11as shown in Fig. 4), which are located near

the shipyards and the outside source of the harbor and its

outlet. Moreover, the ultra-high degree of contamination

(mCd C 32) was recorded in the sediment of station num-

ber 6 which lies in the vicinity of shipyards and the

anchorage of fishing boats, which indicates very serious

anthropogenic pollution at this site (Fig. 4).

3.3.3 Assessment of potential ecological risk (PER)

Higher relative participation of Hg, Cd and As PER was

found for the EH. The harbor is considered a receptor of

industrial effluents. However, it receives significant

amounts of mixed wastes. There is a possibility of trans-

ference of metal contamination from external source

through the El Boghaze opening. Hence, the responsible

substances for sedimentological sensitivity factor (OM,

TP) and the considered metals have the same source or

interdependent sources such as domestic wastes without

treatment and wastes from shipyard installation. The con-

taminant bioavailability is reduced when there is an

increase in sediment anoxia and trophic state of water

column.

According to Hakanson et al. (2003), the sedimento-

logical sensitivity factor (SSF) is related to the trophic

status of the system, which influences the bioavailability of

metals. The EH was found to be a meso-to eutrophic bay,

this is usual for a confined inshore area, but it was not as

eutrophic as a polluted neighboring bay (El Mex Bay),

which receives huge amounts of agricultural drainage

waters contaminated by sewage at a rate of 6 million

m3/day (El-Rayis and Abdallah 2006). In eutrophic aquatic

eco-systems, metals are less bioavailable due to complex-

ation effects and to biological dilution (Hakanson et al.

2003).

About 43, 21 and 14% of the EH sediment has consid-

erable potential ecological risk for Hg, As, and Cd

respectively, in the same context as the high PER represent

14% of Cd and 7% for Hg in the harbor sediment (Fig. 5).

It is reasonable to envisage that Hg and Cd are the two

major ecological risks in the EH sediments.

4 Conclusion

The Eastern Harbor (EH) is one of the most popular tourist

site and fishing location in Alexandria City, Egypt. Iden-

tifying the degree of sediment contamination and assessing

the potential ecological risk of contamination is necessary

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

mC

d

Site

ultra-high

extremely high

very high

Fig. 4 Degree of contamination in each site of the EH sediments

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12 13 14

PER

Site

High

Hg

Cd

As

Considerable

Moderate

Low

Fig. 5 Potential Ecological Risk (PER) of Hg, Cd and As in the EH

sediments

Acta Geochim (2020) 39(2):226–235 233

123

in order to assess the overall level of pollution. This project

studied the fine fraction of surficial sediments from 14

sites. The impact of anthropogenic heavy metal pollution

on EH was evaluated using Enrichment Factors (EF), as

well as modified degrees of contamination (mCd), and the

potential ecological risk (PER) for Cd, Cr, Pb, As and Hg.

Normalized enrichment factor (EF) values for heavy metals

were calculated for EH using the continental shale abun-

dance of Al. The results show that high average EF values

for Cd, Pb, As and Hg. The differences in EF values for the

studied metals may be due to the differences in inputs of

each metal to the sediments and/or the differences in the

removal rates of each metal from the sediments. For the

classification and description of the mCd, about 86% of the

studied sediments represent very high degrees of contam-

ination, which apparently come from sewers that include

industrial wastes. Additionally, extremely high degree of

contamination were observed near the shipyards and the

outside source of the harbor and its outlet. On the other

hand, the ultra-high degree of contamination was recorded

in the vicinity of shipyards and the anchorage of fishing

boats, which indicates very serious anthropogenic pollution

at this site. About 43%, 21%, and 14% of the EH sediments

have considerable potential ecological risks with Hg, As

and Cd, respectively. In the same context, the high PER

represent 14% of Cd and 7% for Hg in the harbor sedi-

ments. It is reasonable to envisage that Hg and Cd are the

two main ecological risks in the EH sediments.

Acknowledgements This study was accomplished as a part of a

fully-funded Grant of Matsumae International Foundation, Japan. We

would like to express our deepest thanks for Prof. Dr. Kimihiko Oki

and Prof. Dr. Takashi Tomiyasu for providing much help and advice.

We wish to thank all members of the Kagoshima University Museum

and Department of Earth and Environmental Sciences, Faculty of

Science, Kagoshima University for their help and support.

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