-
Turk J Engin Environ Sci25 (2001) , 299 – 313.c© TÜBİTAK
Anthropogenic Pollution in İzmit Bay: Heavy Metal
Concentrationsin Surface Sediments
D. YAŞARInstitute of Marine Sciences and Technology Dokuz
Eylül University
Haydar Aliev Bulvarı, İnciraltı, İzmir 35340, TURKEYA. E.
AKSU
Department of Earth Sciences, Memorial University of
Newfoundland St. John’s,Newfoundland Canada A1B3X5
O. USLUInstitute of Marine Sciences and Technology Dokuz Eylül
University
Haydar Aliev Bulvarı, İnciraltı, İzmir 35340, TURKEY
Received 04.09.1999
Abstract
The extent of marine pollution in İzmit Bay is studied using
geochemical data in surface sediments. Theconcentrations of 41
elements in 24 samples establish that surface sediments in inner
and central İzmit Baydisplay significant enrichments in Ag, As,
Cd, Cr, Co, Cu, Hg, Mo, P, Pb, Sb, Ti, V, and Zn associatedwith
high concentrations of total organic carbon and sulphur.
Geo-accumulation indices indicate that theinner and central İzmit
Bay surface sediments are moderately to very strongly polluted with
respect toAg, Cd, Hg, Mo and Sb, and unpolluted to moderately
polluted with respect to As, Co, Cu, Pb, and Zn.Despite total
sedimentary concentrations above their pre-industrial background
levels, geo-accumulationindices show that the surface sediments in
İzmit Bay are unpolluted with respect to Cr, Ti and V. Exceptfor a
localized area offshore Tuzla, the outer İzmit Bay is generally
unpolluted with respect to heavy metals.
Key Words: İzmit Bay, Marine Pollution, Heavy Metals
İzmit Körfezi’nde Oluşan Antropojenik Kirlilik: Yüzey
sedimanlarındaki AğırMetal Yoğunlukları
Özet
İzmit Körfezindeki deniz kirliliğinin boyutları yüzey
sediman örneklerinde yapılan jeokimyasal çalışmasonucu
incelenmiştir. Toplam 24 örnek üzerinde belirlenen 41 elementin
analizleri sonucu , iç ve orta Körfezyüzey sedimanlarının toplam
organik karbon ve sülfür ile gelişen Ag, As, Cd, Cr, Co, Cu, Hg,
Mo, P, Pb, Sb,Ti, V, ve Zn gibi ağır metal yoğunluklarında
önemli bir artış olduğu saptanmıştır. Yapılan
jeo-akümülasyonhesaplamaları ise iç ve orta Körfezin Ag, Cd,
Hg, Mo ve Sb yönünden kirli ve çok kirli, As, Co, Cu, Pb, andZn
yönünden ise az kirli olduğunu göstermektedir. Yine
jeo-akümülasyon hesaplamaları sonucu, sedimandakiyoğunluklarının
sanayi öncesi yoğunluklarından fazla bulunmasına karşın İzmit
Körfezi sedimanlarının Cr,Ti ve V yönünden kirlenmediği
saptanmıştır. Dış körfez ise, Tuzla bölgesinin bazı bölgeleri
dışında ağırmetal yönünden kirli değildir.
Anahtar Sözcükler: İzmit Körfezi, Deniz Kirliliği, Ağır
Metaller
299
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YAŞAR, AKSU, USLU
Introduction
İzmit Bay is a small east-west trending embay-ment situated
along the northeastern Marmara Sea(Fig. 1). It is naturally divided
into three physio-graphic regions: the inner bay, the central bay
andthe outer bay. The shallower (
-
YAŞAR, AKSU, USLU
tal levels of the following elements in 24 surface and19 core
samples: Ag, Al, As, Ba, Be, Ca, Ce, Cd,Cl, Co, Cr, Cu, Dy, Fe, Ga,
Hg, K, La, Li, Mg, Mn,Mo, Na, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Si, Sr,
Th,Ti, U, V, Y, Zn and Zr. Table 1 gives the full geo-chemical data
from İzmit Bay surface samples andthe MAR97-25 reference site, as
well as the analyti-cal detection limits for these elements. Total
organiccarbon was determined using the technique describedin Aksu
et al. (1995).
For major and trace element determinations us-ing ICP-ES or AAS,
except Ag, As, Cd, Hg, Rband Sb, sediments were powdered and ∼5 g
of pow-der was treated with 30% H2O2 to extract elementsabsorbed by
organic matter and amorphous oxides.Samples were then digested in
15 ml of HF, 5 ml ofconcentrated HCl and 5 ml of 1:1 HClO4 at
200◦Cand subsequently in 50 ml of 20% HCl at 100◦C.Measurements
were carried out using an ARL ICP-ES instrument. Samples for Cd
analyses were pro-cessed as above and Cd was measured using a
VarianModel AA1275 AAS. For the determination of Ag,samples were
digested for 16 hours in 2 ml of con-centrated HNO3 at room
temperature, and then fora further 2 hours in a hot water bath at
90◦C. De-terminations were made using AAS. For As and
Sbdeterminations, samples (5 g each) were partially di-gested in
concentrated HNO3; subsequently, 1 ml ofconcentrated HCl was added
and the samples weredigested for a further 90 minutes. As and Sb
weremeasured using ICP-ES. For Hg determinations sam-ples (5 g
each) were digested in 10 ml concentratedHNO3 and 1 ml of
concentrated HCl for 10 minutes.Samples were then placed in a hot
water bath at90◦C and digested for an additional 2 hours. Hg
wasmeasured using ICP-ES; 4 on-peak and 4 off-peakmeasurements were
made.
For XRF analyses, sediments were powdered and4 g of powder was
mixed with 0.7 g of phenolic resinbinder. After homogenization, XRF
pellets were pre-pared and baked for 15 minutes at 200◦C.
Elementswere determined using an XRF ARL 8420+ sequen-tial
wavelength-dispersive spectrometer, with an Rhend-window X-ray tube
and an LiF200 crystal, spe-cially treated for enhanced heavy
element sensitivity.For energies > 7.471 keV (20◦-50◦ 2Θ), a
scintillationdetector was used with power settings at 75 kV and40
mA. For energies < 6.398 keV (50◦-150◦ 2Θ), aflow-proportional
detector was used with power set-tings at 30 kV and 100 Ma
(Longerich, 1993). Scantimes were 4-6 seconds for the most abundant
el-
ements, 20 seconds for the trace elements and 100seconds for Rb,
Y and Nb. The intensities werethen matrix-corrected by Compton
correction for el-ements with emission energies greater than Fe,
andby the LaChance-Traill algorithm (Longerich, 1993)for elements
with emission energies less than and in-cluding Fe.
Results
Elemental associations
The inorganic geochemical data consist of mea-surements of 41
variables in 24 surface samples (Ta-ble 1). This large data set
does not allow an imme-diate and unambiguous interpretation of
elementalassociations and potential sources in the sediments.Factor
analysis was used to obtain simple patternsfrom this complex data
set. The technique extractsa small number of hypothetical variables
(R mode)or samples (Q mode), referred to as “factors”, whichaccount
for a given percentage of the total variancein the data set. Both Q
and R mode factor analyseswere performed on the geochemical data
from İzmitBay.Factor analysis results show that 3 factors ac-
count for a total of 96.5% of the total variance. Theremaining
3.5% of the total variance not accountedfor by the factor analysis
is assumed to be random.Factor 1 accounts for 37.6% of the total
variance andshows very high factor loadings in Al and Si,
withstatistically significant loadings (i.e. >0.3; Klovanand
Imbrie, 1971) in Be, Ca, Dy, Fe, Ga, K, La, Li,Mg, Mn, Nb, Ni, Rb,
and Y. This factor representsthe aluminosilicates: the most common
constituentof siliciclastic marine sediments. Factor 2 accountsfor
35.9% of the total variance and shows very highloadings in C and S,
but also shows significant load-ings in Ag, As, Cd, Cr, Co, Cu, Hg,
Mo, P, Pb, Sb,Ti, V, and Zn. This factor clearly represents
theorganic matter and the enrichments of those metalswhich are most
commonly associated with high totalorganic carbon in marine
sediments (e.g., Aksu etal., 1998). Factor 3 accounts for 23.0% of
the totalvariance and shows high factor loadings in Ca andMg, with
significant loadings in Sr and Sc. This fac-tor probably represents
the carbonate (biogenic anddetrital) in the study area.
Elemental background concentrations
The average shale values (Turekian and Wede-
301
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YAŞAR, AKSU, USLU
pohl, 1961) commonly used for elemental back-ground
concentrations (e.g., Ergin et al., 1991) can-not account for the
local variations in rock compo-sition and chemistry in the Marmara
Sea, and areunlikely to be representative of the İzmit Bay
sur-face sediments. Instead, the background concentra-tions of the
40 elements used in this study were es-timated in a ∼200 cm-long
core (MAR97-25) recov-ered from the Eastern Marmara Basin,
immediatelywest of İzmit Bay. Nineteen samples between 20 cmand
200 cm depth in MAR 97-25 were selected forthe determination of
elemental background concen-trations. Radiometric dates in cores
from the easternMarmara Sea (e.g., Evans et al., 1989; Ergin et
al.,1994) show that the rate of deposition in deep basinsis ∼100 cm
per 1000 years, suggesting that the sed-iments used for the
calculation of elemental back-ground concentrations were deposited
between 2000and 200 yrBP. Because this core site is far removedfrom
the regions of immediate anthropogenic efflu-ent input, and the
sediments used in the calculationsclearly pre-date the industrial
period, the elementalconcentrations in these samples must
approximatethe background levels in the eastern Marmara Sea.The
background level of each element was calculatedas the average value
of that element in 19 samples incore MAR97-25, presented in Table
1.Anthropogenic pollution in surface sedimentsThe level of
anthropogenic pollution in İzmit Bay
is evaluated using the technique described by Müller(1979),
where the enrichment of an element abovethe background level
(geo-accumulation index) is cal-culated using the following
equation:
Igeo = log2 Cn / 1.5 x Bn
where Igeo = index of geo-accumulation, Cn = mea-sured
concentration of the element in the muddy sed-iment being studied
and Bn = geochemical back-ground value (e.g., MAR97-25); the factor
1.5 isused to compensate for possible variations of thebackground
data due to post-depositional changes(Müller, 1979). Igeo values
were calculated for 40elements (except C) in İzmit Bay surface
sedimentsusing the inorganic geochemical data (Cn) and theelemental
background concentrations (Bn) from thedeep Marmara Sea core
MAR97-25. The data showthat Ag, As, Cd, Cr, Co, Cu, Hg, Mo, P, Pb,
Sb, Ti,V, and Zn, all associated with factor 2, consistentlyexhibit
total sedimentary concentrations above theirbackground levels in
İzmit Bay surface sediments.Enrichments in chalcophile (eg., Cu,
As, Ni
and Zn) and siderophile elements (eg., Cr, Ti andFe) associated
with sediments rich in total or-ganic carbon and sulphur occur
naturally in oxygen-deficient/anoxic basinal settings. In such
environ-ments, sulphate reduction takes place at the seafloor,as in
the Black Sea (Landing and Lewis, 1991),or immediately below the
sediment-water interface,as for the Aegean Sea sapropel S1 (Aksu et
al.,1995), leading to the formation of highly insolublesulphides in
the presence of H2S, and hence en-richments. However, many of the
chalcophile andsiderophile elements are also anthropogenic in
ori-gin. Thus, the distinction between natural and an-thropogenic
sources is often complicated. The oc-currence on İzmit Bay surface
sediments of the rarerbut notorious environmental polluters Ag, Cd,
Hgand Mo in quantities well above their backgroundconcentrations,
and their clear associations and co-variances with total organic
carbon, P and S as wellas the heavy metals As, Cu, Co, Cr, Pb, Sb,
Ti, Vand Zn (e.g., Aksu et al., 1998), strongly suggest thatfactor
2 truly represents anthropogenic pollution inthe study area, rather
than natural enrichment inpoorly oxygenated sediments.
Distribution of TOC, S and heavy metals insurface sediments
Total organic carbon values are high in İzmit Baysurface
sediments, ranging from 1.9-2.6% in the innerbay, to 2.0-3.0% in
the central bay and 0.5-0.7% inthe outer bay, except for 1.8%
offshore of Tuzla (Fig.3; Table 1). These total organic carbon
values areslightly higher than the 0.5-1.7% calculated by Erginet
al. (1991) from İzmit Bay. Total sulphur concen-trations show a
similar trend to that of total organiccarbon, with the highest
values of 0.6-1.0% occurringin inner and central İzmit Bay, and
show a notabledecline in outer İzmit Bay (Fig. 3; Table 1).
Totalsilver concentrations range between 0.1 and 0.7 ppmin İzmit
Bay surface sediments, with moderately highvalues occurring mainly
in the central bay, and thehighest value recorded at station 18
offshore of Tuzla(Figs. 2, 4; Table 1). The background value of
silverin core MAR97-25 is 0.08 ppm, which suggests that itis
moderately enriched in inner and central bay sur-face sediments.
Cadmium concentrations are highin central İzmit Bay (0.5-1.0 ppm)
and moderate inthe inner bay (0.4-0.6 ppm), but are generally
low(
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YAŞAR, AKSU, USLU
Table
1.Elementalconcentrations(µg/g=
ppm)in
İzmitBay
surface
sedim
ents.DL=
detectionlimitin
ppm.EBC=
elem
entalbackgroundconcentrations(inppm)ineasternMarm
ara
Sea,calculatedastheaverageconcentrations
in19samplesfrom
core
MAR97-25.
<DL
Ag
Al
AsBa
BeC
Ca
Cd
CeCl
CoCr
CuDyFe
GaHg
KLaLi
DL0.03
302
10.1—
180.05
125
0.11
10.118
10.05
181
0.1
EBC
0.08
7505815
4001.9—
557720.1
741879928
15934
4.95480919
0.07
2115232
63Station 10.2
8725218
3411.819407388600.5
459188
5623677
3.46152020
1.0
2030124
5920.1
9942817
3171.826009364650.4
431932449
13059
3.56020421
1.0
2247622
5630.2
7720012
4331.723985167240.5
524040342
14361
3.85873919
1.5
1838626
4740.2
7738411
4441.626130304590.5
541995545
40652
2.94192013
1.0
2006927
5150.1
7830119
4951.923238451910.1
608898
3527137
3.34292417
1.3
2220229
4860.4
5621120
3221.928418342961.0
669948047
15049
4.35557519
1.5
2012839
6270.4
4663619
3111.931182363501.0
647860860
21546
5.55980717
1.0
1899444
6680.3
4975728
2761.630762357020.9
558164818
15043
3.55598118
0.6
1902030
5390.3
5017127
2921.826165333690.7
539163320
14445
3.35718418
1.0
1876928
5810
0.2
5622113
2841.822902422000.5
518991018
12741
3.25331715
0.8
1842027
5711
0.2
6958515
2971.822909320420.4
524233519
12339
3.55495317
0.7
2045529
6012
0.3
4801019
2881.823458396010.7
567140317
13438
3.85475217
0.5
1882532
5713
0.2
6078830
2911.312051616950.5
442719722
22547
2.54444311
0.4
1816024
3814
0.1
5866510
2921.27101
970460.3
482124026
28226
2.93632211
<DL1599425
3815
0.2
6494018
2791.66024
417090.3
525238235
16441
3.35317816
<DL1777026
5316
0.3
7795921
2901.75178
473990.4
502534418
13739
3.15242117
<DL1884827
5117
0.1
6329825
2591.35001
956990.4
432765715
11025
2.84067813
<DL1732827
4018
0.7
7020010
3021.812014994800.8
722292511
13282
3.63809815
<DL1966240
3619
0.1
4954026
2901.87124
538870.4
544948417
13538
3.35416317
<DL1752529
5620
0.2
7888714
3041.85146
474760.3
532858519
14839
3.15409518
<DL2018028
5521
0.2
4475713
2711.54190
420020.2
559194731
14438
3.05518015
<DL1624928
5222
0.1
7424915
2891.34056
454080.2
441423727
19926
2.84489214
<DL1608624
4123
0.1
559086
2031.03814
883780.3
362152118
20520
2.1347879
<DL1588822
3324
0.3
5178023
2851.76234
435890.3
539355018
12937
3.05536216
<DL1752228
54
303
-
YAŞAR, AKSU, USLU
Tab
le1.
Continued
Mg
Mn
Mo
Na
NbNi
PPbRb
SSb
ScSi
SrTh
Ti
UV
YZn
ZrDL50
10.1
640.71
11
0.7
9.9
0.03
0.127.8
12.8
13.4
10.61
1.1
EBC
283503325
1.9
1356814
8740927
1194606
0.7
23214626
2508.5
4615
1.5
14825
6399
Station 124969450
4.1
1225411
6660032
958722
1.4
19217210
1346.5
5683
1.0
17923
17177
230329558
4.8
1671212
4959820
917072
1.5
19224613
1244.8
6327
<DL17623
11091
320681427
8.1
2672212
3949827
949048
1.4
19210118
1542.6
5350
0.1
16924
135112
419517411
6.2
1926513
10844429
897707
0.9
12277935
1846.0
4302
2.5
12221
10772
517158999
7.2
1170715
7835522
1068041
1.0
12279826
2268.1
4349
3.3
10723
7580
617089421
8.1
9993712
4652843
1118375
1.8
16172541
1760.9
4872
0.8
18531
15977
713469562
8.5
5701413
6576242
1116254
0.9
16153599
1734.9
4812
4.3
16248
13981
818337893
8.9
6041712
4743141
1089415
0.8
14159822
1910.2
4467
1.2
18422
15872
914285766
5.3
9307312
4740643
1096693
0.8
16164914
1722.0
4795
1.8
17021
16376
1018792591
4.6
7584212
4241031
1036398
0.8
15179249
2032.7
4647
2.1
15919
14778
1124726999
2.8
2636712
4344835
1087611
1.1
15204464
1542.0
4892
1.2
15321
12481
1214501435
3.8
5218713
3640136
1057143
1.8
15159179
1722.0
4699
1.5
15024
13380
1317820507
5.2
1964110
5861943
774926
0.9
9255901
2313.2
3420
2.7
11714
15656
1419481450
2.7
201918
6444721
663878
0.6
9238320
5045.5
3343
0.1
9015
7952
1519371474
1.5
5433012
5145326
903558
0.7
16207449
1805.1
5134
0.4
15020
11283
1625806500
<DL1822912
4653531
953607
0.9
15232452
1973.3
5186
1.9
15320
11473
1720650427
<DL2371510
2452530
782843
0.7
10232238
3135.1
3943
2.4
10517
9954
1815467228
3.3
1653921
2565861
1027417
0.8
10221406
40310.5
5088
3.0
11625
24078
1915087438
<DL3668314
3741939
1022683
1.1
15167256
2185.5
4714
1.0
13420
2576
2028436622
<DL1807713
5852136
1063026
1.1
15228587
2124.5
4924
1.2
15219
11769
2112187468
1.8
9016612
4534828
892137
1.1
15162113
1822.9
5141
1.6
15320
9872
2222033525
<DL1616910
4449227
702214
0.9
13259116
1817.6
4963
0.6
12818
8270
2321065342
1.1
147678
4438821
622785
1.0
8234571
2333.4
3249
0.4
9113
5936
2414757514
<DL8734813
3640428
962219
1.3
16176525
1845.0
5061
0.4
14529
11276
304
-
YAŞAR, AKSU, USLU
Tab
le1.Continued
Mg
Mn
Mo
Na
NbNi
PPbRb
SSb
ScSi
SrTh
Ti
UV
YZn
ZrDL50
10.1
640.71
11
0.7
9.9
0.03
0.127.8
12.8
13.4
10.61
1.1
EBC
283503325
1.9
1356814
8740927
1194606
0.7
23214626
2508.5
4615
1.5
14825
6399
Station 124969450
4.1
1225411
6660032
958722
1.4
19217210
1346.5
5683
1.0
17923
17177
230329558
4.8
1671212
4959820
917072
1.5
19224613
1244.8
6327
<DL17623
11091
320681427
8.1
2672212
3949827
949048
1.4
19210118
1542.6
5350
0.1
16924
135112
419517411
6.2
1926513
10844429
897707
0.9
12277935
1846.0
4302
2.5
12221
10772
517158999
7.2
1170715
7835522
1068041
1.0
12279826
2268.1
4349
3.3
10723
7580
617089421
8.1
9993712
4652843
1118375
1.8
16172541
1760.9
4872
0.8
18531
15977
713469562
8.5
5701413
6576242
1116254
0.9
16153599
1734.9
4812
4.3
16248
13981
818337893
8.9
6041712
4743141
1089415
0.8
14159822
1910.2
4467
1.2
18422
15872
914285766
5.3
9307312
4740643
1096693
0.8
16164914
1722.0
4795
1.8
17021
16376
1018792591
4.6
7584212
4241031
1036398
0.8
15179249
2032.7
4647
2.1
15919
14778
1124726999
2.8
2636712
4344835
1087611
1.1
15204464
1542.0
4892
1.2
15321
12481
1214501435
3.8
5218713
3640136
1057143
1.8
15159179
1722.0
4699
1.5
15024
13380
1317820507
5.2
1964110
5861943
774926
0.9
9255901
2313.2
3420
2.7
11714
15656
1419481450
2.7
201918
6444721
663878
0.6
9238320
5045.5
3343
0.1
9015
7952
1519371474
1.5
5433012
5145326
903558
0.7
16207449
1805.1
5134
0.4
15020
11283
1625806500
<DL1822912
4653531
953607
0.9
15232452
1973.3
5186
1.9
15320
11473
1720650427
<DL2371510
2452530
782843
0.7
10232238
3135.1
3943
2.4
10517
9954
1815467228
3.3
1653921
2565861
1027417
0.8
10221406
40310.5
5088
3.0
11625
24078
1915087438
<DL3668314
3741939
1022683
1.1
15167256
2185.5
4714
1.0
13420
2576
2028436622
<DL1807713
5852136
1063026
1.1
15228587
2124.5
4924
1.2
15219
11769
2112187468
1.8
9016612
4534828
892137
1.1
15162113
1822.9
5141
1.6
15320
9872
2222033525
<DL1616910
4449227
702214
0.9
13259116
1817.6
4963
0.6
12818
8270
2321065342
1.1
147678
4438821
622785
1.0
8234571
2333.4
3249
0.4
9113
5936
2414757514
<DL8734813
3640428
962219
1.3
16176525
1845.0
5061
0.4
14529
11276
305
-
YAŞAR, AKSU, USLU
between its detection limit and 0.2 ppm, with an av-erage
concentration of 0.1 ppm (Table 1). These datasuggest that the
central and inner bay surface sedi-ments are considerably enriched
in cadmium. Cobaltvalues are generally low (10-25 ppm) in outer
andcentral İzmit Bay, but notably increase to 40-60 ppmin the
northeastern outer bay and the inner bay (Fig.5; Table 1). The
background level of this metal inthe deep Marmara Sea core is 28
ppm, which indi-cates that only surface sediments from the inner
andnortheastern segment of the central İzmit Bay are
slightly enriched in cobalt. Copper values are moder-ate in the
study area, with the highest values occur-ring in inner İzmit Bay
surface sediments and at sta-tion 18 offshore of Tuzla (Fig. 5).
Its abundance inthe uncontaminated Marmara Sea sediments
rangesbetween 22 and 59 ppm, with an average of 34 ppm(Table 1),
which is nearly identical to the averagecopper concentration of 35
ppm in shales (Adriano,1986). These data show that copper is only
slightlyenriched in central and inner İzmit Bay sediments(Fig. 5;
Table 1).
(%)
3.00
2.40
1.80
1.20
0.60
0.00
1.0
0.8
0.6
0.4
0.2
0
(%)
Figure 3. Bar graphs showing the distribution and abundance (%)
of total sulphur (top) and total organic carbon(bottom) in İzmit
Bay surface sediments.
(ppm)
1.00
0.80
0.60
0.40
0.20
0.00
0.70
0.56
0.42
0.28
0.14
0.00
(ppm)
Figure 4. Bar graphs showing the distribution and abundance
(ppm) of total concentrations of silver (top) and cadmium(bottom)
in İzmit Bay surface sediments. Arrows indicate background
concentrations.
(ppm)
80
64
48
32
16
0
60
48
36
24
12
0
(ppm)
Figure 5. Bar graphs showing the distribution and abundance
(ppm) of total concentrations of cobalt (top) and copper(bottom) in
İzmit Bay surface sediments. Arrows indicate background
concentrations.
Mercury concentrations are highest (1.2-1.5 ppm)in inner and
eastern central İzmit Bay surface sedi-ments and show a dramatic
decline to 0.5 ppm at the
Dil Burnu Entrance (Fig. 2), west of which the Hgvalues are
below the detection limit in all samples(Fig. 6; Table 1). The
background level of mer-
306
-
YAŞAR, AKSU, USLU
cury in Marmara Sea core MAR97-25 is calculatedto be 0.07 ppm,
which indicates that all samples fromthe inner and central İzmit
Bay are considerably en-riched in mercury. The distribution of
molybdenumconcentrations in surface sediments is similar to thatof
mercury, with the highest values of 7.0-9.0 ppmoccurring in inner
and central İzmit Bay (Fig. 6).West of the Dil Burnu Entrance, Mo
concentrationsare generally less than 3 ppm; for 6 samples
valueswere below the detection limit. The pre-industrialbackground
level of 1.9 ppm for this metal in coreMAR97-25 shows that it is
enriched by 5-7 ppm inthe inner and central İzmit Bay surface
sediments(Table 1).Nickel concentrations range between 30 and
110
ppm in İzmit Bay surface sediments, with the high-est values
occurring in the eastern central bay andthe entrance to the inner
bay (Table 1). Ergin etal. (1991) reports nickel values ∼15-20%
higher thanthose in this study. The background level for nickel
is87 ppm in the Marmara Sea core MAR97-25 (Table1), so that except
for one sample (station 4) none ofthe surface sediments in İzmit
Bay show enrichmentin nickel. Lead concentrations range between 21
and61 ppm in İzmit Bay, with the highest values occur-ring in the
central bay (30-50 ppm) and at station 18,
offshore of Tuzla (Fig. 7; Table 1). These values arenearly
identical to previously reported lead valuesfrom İzmit Bay (Ergin
et al., 1991). A backgroundlevel of 27 ppm suggests that the
surface sedimentsthroughout the study area are slightly enriched
inlead.
Arsenic concentrations range between 6 and 30ppm in İzmit Bay
surface sediments (Fig. 7; Table1). The background level of 15 ppm
suggests thatsediments from the inner, central and eastern
seg-ments of outer İzmit Bay are moderately enriched inarsenic.
Antimony concentrations are variable buthigh in the study area,
ranging between 0.5 and 1.8ppm, with the highest values occurring
in the in-ner bay and along the northern shores of the centralbay
(Fig. 8). Antimony is rare in the uncontam-inated Marmara Sea
sediments (Table 1), with anaverage value of 0.7 ppm in core
MAR97-25. Thisindicates that most of the inner and central bay
sur-face sediments are moderately enriched in this metal(Table 1).
Zinc values are moderate in İzmit Baywith slightly higher values
in the central bay, andthe highest value at station 18 (Fig. 8;
Table 1). Er-gin et al. (1991) reported zinc values 40-50%
lowerthan in this study.
(ppm)
9.00
7.20
5.40
3.60
1.80
0.00
1.50
1.20
0.90
0.60
0.30
0.00
(ppm)
Figure 6. Bar graphs showing the distribution and abundance
(ppm) of total concentrations of mercury (top) andmolybdenum
(bottom) in İzmit Bay surface sediments. Arrows indicate
background concentrations.
(ppm)
60
48
36
24
12
0
30
24
18
12
6
0
(ppm)
Figure 7. Bar graphs showing the distribution and abundance
(ppm) of total concentrations of arsenic (top) and lead(bottom) in
İzmit Bay surface sediments. Arrows indicate background
concentrations.
307
-
YAŞAR, AKSU, USLU
(ppm)
240
192
144
96
48
0
1.80
1.44
1.08
0.72
0.36
0.00
(ppm)
Figure 8. Bar graphs showing the distribution and abundance
(ppm) of total concentrations of antimony (top) and zinc(bottom) in
İzmit Bay surface sediments. Arrows indicate background
concentrations.
Degree of sediment contamination
Figure 9 shows the geographical distribution ofthe normalized
varimax components of factor 2 inİzmit Bay, where zones A to F
correspond respec-tively to factor loadings of 0.75. The
highestconcentrations of heavy metals associated with fac-tor 2
occur in inner İzmit Bay (Zone F), east ofthe İpraş-Gölcük
line (Fig.9). The geo-accumulationindices show that this zone is
strongly to verystrongly polluted in Hg (25x1.5=48-fold
enrichments;Igeo=5), strongly polluted in Cd (24x1.5=24-fold
en-richments; Igeo=4), and moderately polluted in Ag,Mo and Sb
(23x1.5=6-fold enrichments; Igeo=3).However, the zone is either
unpolluted (Igeo=0) orunpolluted to moderately polluted with
respect toAs, Cr, Co, Cu, P, Pb, Ti, V and Zn, despite thefact that
these elements display concentrations abovetheir background levels
(Fig. 9).Zone E is located along the northeast segment of
central İzmit Bay and displays strong to very strongpollution
in Cd and Hg (Igeo=5), moderate to strongpollution in Ag (Igeo=3)
and moderate pollution inMo and Sb (Igeo=2; Fig. 9). A trend of
decreasingIgeo values is clearly visible across central İzmit
baytowards the outer bay (Zones D through A). Zone Dextends from
Diliskelesi to Hereke along the northernshores of central İzmit
Bay, encircling Zone E, and inthe northwestern portion of the study
area offshoreTuzla (Fig. 9). It shows strong to very strong
pollu-tion in Cd (Igeo=5), strong pollution in Hg (Igeo=4),moderate
to strong pollution in Ag (Igeo=3) andmoderate pollution in Mo
(Igeo=2). Zone C formsa narrow band at the western margin of Zone D
incentral İzmit Bay and encircles the small zone off-shore of
Tuzla. The zone displays strong pollutionin Cd (Igeo=4), moderate
to strong pollution in Hg(Igeo=3) and moderate pollution in Ag
(Igeo=2; Fig.
9). Zone B mainly occurs in shallower shelf depths ofouter
İzmit Bay, as well as the southwestern segmentof the central bay.
These sediments are largely un-polluted except for moderate to
strong pollution inCd (Igeo=3), and moderate pollution in Ag and
Sb(Igeo=2; Fig. 9). Zone A is situated along the deeperaxis of
outer İzmit Bay and shows only moderate pol-lution in Cd and Sb
(Igeo=2; Fig. 9). Despite no-table total sedimentary concentrations
of Cr, Ti andV, the geo-accumulation index shows that
surfacesediments in İzmit Bay are unpolluted (Igeo=0) withrespect
to these elements. Similarly, these sedimentsare unpolluted to
moderately polluted (Igeo=1) withrespect to As, Co, Cu, P, Pb and
Zn.
Discussion
The following general sources can be identifiedfor the pollution
observed in the İzmit Bay surfacesediments:
1) Domestic pollution: untreated liquid and solidwaste produced
by the inhabitants of the cities,supplied to the bay by the sewage
network andsmall creeks;
2) Industrial pollution: untreated liquid and solidwaste
produced by over 120 industrial centres,also supplied to the bay by
the sewage networkand small creeks;
3) Atmospheric pollution: particulate emissionproduced by
vehicles, trains and vessels; fly ashemission from coal- and
fuel-oil-burning plants,by-products of open-air burning of
municipaland industrial solid waste and garbage, all ofwhich are
eventually transported into the in-ner and central Izmir Bay by
precipitation anddrainage.
308
-
YAŞAR, AKSU, USLU
29°50’N—
—
—
— — — —
— — — —
—
—
—
29°45’N
29°40’N
29°50’E29°40’E29°30’E29°20’E
‹prafl‹zmit
HerekeDiliskelesiDar›ca
Tuzla
Gölcük
KaramürselDil
Burnu
Yalova
A
D
B
B
C
BD
E
F
0 3 6
Scale (km)
Figure 9. Map of the study area showing the degree of sediment
contamination by Ag, As, Cd, Co, Cu, Hg, Mo, Pb,Sb and Zn,
discussed in text (top) and the index of geo-accumulation, Igeo
(bottom) in İzmit Bay surfacesediments.
There are numerous raw sewage outlets in the pe-riphery of
İzmit Bay, actively discharging ∼370,000m3 day−1 of waste water
into the bay, includ-ing untreated sewage (TÇV, 1998).
Approximately∼51.4% (190,000 m3 day−1) of this discharge is
do-mestic waste, 79% of which is discharged along thenorthern
shores of İzmit Bay. Nearly all indus-trial waste is also
untreated and is either dischargedthrough the domestic sewage
network or via a fewsmall rivers and creeks. There are no data on
thechemical composition of the sewage discharge intoİzmit Bay.
However, high total organic carbon in thesurface sediments can be
correlated with the organicwaste input into the bay. For example,
there arereports of periods of an intense foul smell emanat-ing
from the inner bay, particularly during the hotsummer months.
During these months, the dissolved
oxygen levels in inner İzmit Bay decrease dramati-cally to
values close to zero (TÇV, 1998), reflect-ing partial
decomposition of organic waste in shal-low waters, and suggesting
that the bottom waters inthis region must periodically become
anoxic. Similarfoul odours are reported along the shoreline
seawardof the major sewage outfalls of smaller communitiesand
industrial centres, particularly along the north-ern shores of the
bay.The high concentrations of total organic carbon
in surface sediments (Fig. 3) reflect organic matterinflux via
effluent input, as well as input through therelatively high primary
productivity in the water col-umn (10-170 g C m2 year−1; TÇV,
1998). High phos-phorus may be related to the use of detergents
andthe discharge of phosphate through the sewage sys-tem,
particularly in central İzmit Bay (Table 1). Fly
309
-
YAŞAR, AKSU, USLU
ash from coal- and petroleum-burning plants, as wellas the
İpraş Refinery, is probably the major sourceof sulphur in İzmit
Bay surface sediments (Fig. 3).Oxidation of the organic waste
probably accounts forthe low dissolved oxygen levels observed
within theentire İzmit Bay water column.There are over 120 major
industrial centres along
İzmit Bay, largely concentrated along the north-ern shores
(Fig. 10). Many of these industriesempty their untreated effluent
into İzmit Bay; how-ever, there are no data available on the types
andrates of heavy metal discharges from these indus-tries. Fifteen
major industries discharge their wastewaters into the inner bay,
including 3 large pulpmills and chlor-alkali plants, 4
pharmaceutical andchemical plants, 4 petrochemical plants, 3 steel
fac-tories/smelters, and a leather factory (TÇV, 1998).SEKA (Fig.
10) is the largest of the pulp mills/chlor-
alkali plants and provides over 50% of the anthro-pogenic
organic matter influx into İzmit Bay (TÇV,1998). A major
proportion of the industrial effluentis supplied into the inner
İzmit Bay via the KumlaRiver and its tributaries, including the
dischargesfrom a large slaughter house, a number of
leather-processing plants and small smelters. Central İzmitBay
receives the effluent from 10 large industrial cen-tres, including
4 chemical plants, 2 petroleum re-fineries, a chlor-alkali plant, a
paper mill, a ceramicfactory and two large textile factories (Fig.
10). Ex-cept for one large textile factory in Karamürsel, allthese
industries are concentrated along the northernshores of central
İzmit Bay (Fig. 10). Three majorindustries discharge their waste
into the outer bay,including a chemical plant, an automobile plant,
andan appliance factory.
Figure 10. Map of İzmit Bay, showing the distribution of major
industrial centres (data from TÇV, 1998).
Fly ash constitutes a major pollutant from coal-burning and is
known to contribute notable quan-tities of As, Cd, Cu, Mo, Pb, Sb,
and Zn to theenvironment (Natusch et al., 1975). Nearly all
thesmelters in the region use coal as their primary fuel.The fly
ash emanating from these plants initially set-tles over the greater
city of İzmit and it is probablyquickly washed by rain into the
inner bay via thesewage network and the Kumla River. Leather
tan-ning plants which employ large quantities of arsenicand
chromium salts in the tanning procedure dis-charge their untreated
waste products directly intoinner İzmit Bay. Nearly all
antifouling paints appliedto commercial, naval and recreational
vessels at thelarge military shipyard at Gölcük and the
civilianshipyards and docks at Tuzla and Dil Iskelesi (Fig.
2) contain significant quantities of copper and lesserquantities
of antimony, lead and mercury, probablycontributing the high total
sedimentary concentra-tions of these heavy metals in inner İzmit
Bay aswell as offshore of Tuzla (Figs. 5-8).
The main source of lead in the study area is prob-ably
automobile traffic. Until recently, the great ma-jority of the cars
in Turkey had no catalytic convert-ers and burned leaded petrol.
Lead sulphide ore hasalso been used since antiquity for the
extraction ofsilver impurities (Patterson, 1971). The effluent
fromlarge chlor-alkali plants as well as industries whichuse bleach
probably supply most of the mercury andmercury salts found in the
İzmit Bay surface sedi-ments. The correlation between the highest
mercuryvalues in inner İzmit Bay and the SEKA complex
310
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YAŞAR, AKSU, USLU
is noteworthy (Fig. 10). Until recently, mercury-bearing
compounds have been used in the preventionand control of industrial
slime, and these compoundseventually ended up in inner İzmit Bay.
Large bat-tery recycling plants are known for their potential
fordelivering mercury and lead compounds into the en-vironment.
Therefore, some mercury compounds areprobably also supplied by the
Kumla River. In theprocess of chromium- and nickel-plating and
galva-nizing, the surfaces to be plated are often cleanedusing
strong acids. This process leaches a num-ber of heavy metals, which
are released into İzmitBay via the sewage network. Furthermore,
variouschromium, nickel and zinc pigments and compoundsare used in
metal plating, probably contributingsome undeterminable quantities
of these heavy met-als into the bay via the Kumla River.
In the greater İzmit Bay region, cadmium is ex-tensively used
by various industries in the produc-tion of copper, lead, silver
and aluminium alloys,and in various pigments. Some of the finest
Turk-ish rugs are woven in Hereke, where cadmium, an-timony,
copper, cobalt and zinc salts are commonlyused in the process of
wool-dyeing. Cadmium saltsare also widely used by the ceramic
industries, andmay also be contributed as wastes from zinc, lead
andcopper smelters. High cadmium abundances in cen-tral İzmit Bay,
particularly along the northern shore(Fig. 4), appear to reflect
the contributions frommainly the large ceramic plants and textile
indus-tries (Fig. 10). Silver in İzmit Bay surface sedimentsis
probably largely supplied by photographic indus-tries, with lesser
contributions from the disposal ofsilver-zinc and silver-cadmium
batteries.
Molybdenum is frequently found in municipalsludges at levels
that are above the background con-centrations (Adriano, 1986). In
industrial regions itis mainly supplied by fly ash resulting from
powergeneration using coal combustion, with estimates of15 tonnes
of Mo per year for every 1000 MW of powergenerated (Adriano, 1986).
Molybdenum salts arealso commonly used in fertilizers. The highest
Moconcentrations in inner and central İzmit Bay, wellabove
background levels, clearly suggest an indus-trial anthropogenic
influx (Figs. 6, 10). The pri-mary sources of vanadium in the study
area are prob-ably combustion byproducts of coal-burning plantsand
the fly ash from petroleum-fired plants in theform of vanadium
pentoxide. Antimony is used inpaints, lacquers, ceramic enamels and
glass and pot-tery industries. It is also commonly used,
alloyed
with lead, by manufacturing industries. The notableabundance of
antimony in the inner and central İzmitBay surface sediments,
above background levels, sug-gests contamination mainly from
shipyards, and ce-ramic factories.
Ergin et al. (1991) concluded that the surfacesediments in
İzmit Bay are basically uncontaminatedby anthropogenic pollution.
This study was primar-ily based on the evaluation of the total
sedimentaryconcentrations of a limited number of heavy metals:Cu,
Co, Cr, Fe, Mn, Ni, Pb and Zn. The inorganicgeochemical data
presented in this paper stronglycontradicts the conclusions of
Ergin et al. (1991)and clearly show that the surface sediments in
İzmitBay are moderately to very strongly polluted withrespect to
Ag, Cd, Hg, Mo and Sb, with Igeo valuesbetween 2 and 5, and
unpolluted to moderately pol-luted with respect to As, Co, Cu, Pb,
and Zn, withIgeo values between 0 and 1. These data indicatethat
anthropogenic pollution must be viewed seri-ously within this
embayment. The heaviest contam-ination is observed along the
northeastern segmentof the central bay offshore of Hereke and
İpraş (ZoneE) and the entire inner bay (Zone F; Fig. 9),
reflect-ing the high concentrations of chemical,
petroleum,chlor-alkali and pharmaceutical industries (Fig. 10).The
data conclusively show that the anthropogenicpollution observed in
inner and central İzmit Bay isalmost exclusively confined to these
regions by theshallow sill at the Dil Burnu Entrance (Fig. 9).
Thelow tidal range and restricted water circulation be-tween the
central and outer parts of İzmit Bay con-trol this
confinement.
Most previous studies along the coastal watersof Turkey focussed
on the surficial sedimentary con-centrations of only a limited
numbers of elements;thus, the distinction between the natural and
anthro-pogenic elemental associations was not always pos-sible
(e.g., Ergin et al., 1991). In many instances,the sedimentary
concentration of an element is as-sumed to be anthropogenic,
because of the involve-ment of that element in polluted sediments
else-where. The present study highlights the importanceof a broader
elemental data set in the assessmentof anthropogenic pollution in
small coastal embay-ments.
Increased concentrations of heavy metals in ma-rine sediments
enhance the importance of sedimentsas a direct source of potential
toxins in nearshoreenvironments. However, sedimentary
geochemistrydata, such as those presented here, provide no ev-
311
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YAŞAR, AKSU, USLU
idence for biological damage in a marine environ-ment.
Therefore, a comprehensive assessment of ma-rine pollution should
ideally include coupled studieslinking the levels of pollutants in
the seawater withthose in the surface sediments, and the seawater
andsediment with tissues in various biota. Furthermore,the
bio-availability of a heavy metal is critical in theassessment of
its damage in the ecosystem. Thus,studies determining the chemical
speciation of heavymetals are important.
Conclusions
1. Inorganic geochemical data show that innerand central İzmit
Bay surface sediments display highabundances of total organic
carbon, S and P, asso-ciated with enrichments in Ag, As, Cd, Cr,
Co, Cu,Hg, Mo, P, Pb, Sb, Ti, V, and Zn, which are abovetheir
pre-industrial background levels. Distributionmaps illustrate that
heavy metal concentrations arehighest in central and inner İzmit
Bay, dramaticallydecreasing near Dil Burnu Entrance.2. The
geo-accumulation indices show that the
surface sediments of central and inner İzmit Bayare moderately
to very strongly polluted with re-spect to Ag, Cd, Hg, Mo and Sb,
and unpollutedto moderately polluted with respect to As, Co, Cu,Pb,
and Zn. Despite total sedimentary concentra-
tions above their pre-industrial background
levels,geo-accumulation indices show that the surface sed-iments in
İzmit Bay are unpolluted with respect toCr, Ti and V.3. Except for
a localized area offshore of Tuzla,
outer İzmit Bay is generally unpolluted with respectto heavy
metals.
Acknowledgments
We thank Prof. Dr. Erol Izdar, the Directorof the Piri Reis
Foundation for Maritime and Ma-rine Resources Development and
Education, for hiscontinual support and encouragement. We extendour
special thanks to the officers and crew of theRV KocaP iriReis for
their assistance in data ac-quisition, in particular Captain Mehmet
Özsaygılıand Chief Engineer Ömer Çubuk. We acknowledgeresearch
funds from the Natural Sciences and En-gineering Research Council
of Canada (NSERC) toAksu (OGP0042760) and special grants from the
PiriReis Foundation for Maritime and Marine ResourcesDevelopment
and Education. Hüseyin Avni Benli(Efe) of the Institute of Marine
Sciences and Tech-nology and Richard Hiscott of Memorial
Universityof Newfoundland critically read the manuscript
andprovided many valuable comments.
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