Tr. J. of Engineering and Environmental Science 23 (1999) , 39 – 48. c TUB¨ ITAK˙ Pollution Monitoring Using Marine Sediments: A Case Study on the Istanbul Metropolitan Area A.O. ALGAN, M.N. C¸AGATAY,˘ H.Z. SARIKAYA, N. BALKIS, E. SARI Institute of Marine Sciences and Management, University of Istanbul, M¨u¸sk¨ule Sokak, Vefa, 34470, Istanbul-TURKEY Received 21.07.1998 Abstract Heavy metal concentrations of surfical sediments around the Istanbul metropolitan area are generally higher than the average shale values, with the highest contents occurring near the confluence of the Istanbul Strait (Bosphorus) with the Sea of Marmara. The metal distribution, together with that of organic carbon, suggests a significant contribution from munipical wastewater discharges. A total of 28 sites were sampled twice, with a 10-month interval (February and December 1996) to assess changes in the sediment composition. Analyses of the two batches of sediment samples suggest no significant changes in Cu, Pb and Zn; increases in Fe and Mn, and decreases in Hg and Ni contents over this time interval. Despite the high population density and industrialization in the area, these sediments have not been significantly contaminated in comparison with similar marine areas elsewhere in the world. This is mainly due to the dynamic two-layer circulation system of the area. Key Words: Pollution, Marine Sediments Denizel Sedimentler ile Kirlenme Izlenmesi:˙ Istanbul˙ Metropolitan Alan C¸alı¸sması Ozet¨ Istanbul˙ metropolitanın civarındaki denizel y¨uzey sedimanlarının a˘gır metal i¸cerikleri ¸seyl ortalaması ile kar¸sıla¸stırıldı˘gında genellikle y¨uksektirler. En y¨uksek de˘gerler Istanbul˙ Bo˘gazı’nın Marmara Denizi giri¸sinde bulunmaktadır. Metal ve organik karbon de˘gerlerinin da˘gılım paternleri atık su de¸sarjlarınınonemli ¨ ¨ol¸c¨ude etkisi oldu˘gunu g¨ostermektedir. 28 istasyondan 10 ay aralıkla iki kez (S¸ubat 1996 ve Aralık 1996) sed- iment ¨orneklemesi yapılmı¸stır. Bu iki setorne˘ ¨ gin analiz edilmesi sonucunda Cu, Pb ve Zn i¸ceriklerinde zaman i¸cerisinde ¨onemli bir de˘gi¸siklik g¨ozlenmezken, Fe ve Mn’ın arttı˘gı,HgveNii¸ceriklerinin de azaldı˘gı saptanmı¸stır. Istanbul’un˙ yo˘gun n¨ufusu ve end¨ustriyel faaliyetleri g¨oz¨on¨une alındı˘gında, denizel sediment- lerinin, d¨unyanın benzer di˘ger b¨olgelerindekiler kadar kirlenmedi˘gi ortaya ¸cıkmaktadır. Bu durum b¨uy¨uk ¨ol¸c¨ude b¨olgenin iki tabakalı y¨uksek enerjili dinami˘ginden kaynaklanmaktadır. Anahtar S¨ozc¨ukler: Kirlenme, Deniz Ust¨¨ u Sedimanları, 39 ALGAN, C¸AGATAY,˘ SARIKAYA, BALKIS SARI Introduction Surfical sediments are a feeding source for biologi- work in the area includes studies on the chemical cal life, a transporting agent for pollutants and an ul- and physical oceanography of the Strait and the Sea timate sink for settling organic and inorganic matter. of Marmara (Ba¸st¨urk et al., 1988; DAMOC, 1971; Their composition constitutes an important criterion Ozs¨¨ oy et al., 1986; Ozsoy¨ et al., 1988), and a few for the assessment of long-term water quality. The investigations on the metal concentrations of bot- metal content of sediments has natural and anthro- tom sediments (Ergin et al., 1991; Bodur and Er- pogenic components. In heavily polluted sediments, gin, 1994). The Strait of Istanbul˙ is characterized the anthropogenically introduced components by far by a two-layer flow system, with less saline Black exceed the natural component, and because of their Sea water entering the Sea of Marmara as the sur- bio-availability constitute a hazard to the marine face current, and more saline Mediterranean water ecosystem. Interactions between solid sedimentary flowing to the Black Sea as the under current. The matter and dissolved metals play an important role velocity of the surface currents is between 0.20 and 5 in the regulation of dissolved metal concentrations m/sec, and that of the under current between 0.05 to (which are the most bioavailable) in the water. 2.50 m/sec (Ozsoy,¨ 1986). As a consequence of such Istanbul˙ is the most heavily populated and in- strong current activity, coarse-grained sediments of dustrialized metropolitan area of Turkey, situated on mainly sand and gravel composition cover the floor both sides of the Strait of Istanbul (Bosphorus) (Fig- of the Strait. Fine-graind (silt and clay) sediments ure 1). The Istanbul˙ Metropolitan area, with about with varying proportions of sand occur near the con- 15% of the population of Turkey and 40% of the in- fluence of the Strait and the Sea of Marmara. A dustrial activity, is the major source of pollution for mixture of coarse- and fine-grained material is found the Sea of Marmara (Orhon et al., 1994). Previous at the Black Sea entrance of the Strait. K7 K1 K5 _ BLACK SEA K6 K3 K0 _ + Core samples surface (grab) samples effluent discharge _ Golden Horn 41 _ M96 M98 M1 M2 M3 M99 M97 M6 M7 M8 M4 M5 M14 M78 _ M15 M9 M16 M79 M11 M19 M80 SEA OF MARMARA _ M20 _ _ _ _ _ _ _ _ _ 29 Figure 1. Sampling locations 40 ALGAN, C¸AGATAY,˘ SARIKAYA, BALKIS SARI Sampling and Analytical Methods Dried samples were ground for homogenization in a pre-cleaned agate mortar. Surface sediment samples were collected from 28 sites Organic carbon (C ) content was determined by Van veen grab on the board of R. V. Arar of org by the Walkey-Blake method by oxidation via IMSM (Institute of Marine Sciences and Manage- sulphochromic acid and back titraiton of the excess ment, Istanbul University) (Figure 1). Each site dichromate (Gaudette, 1974; Loring and Rantala, was sampled twice, during February and December, 1992). All metals were determined by flame atomic 1996, to monitor possible temporal changes in the absorption spectrophotometer (AAS) after a total metal concentrations of the sediments. Surface sedi- digestion, involving HF+HCIO +HNO acid mix- ment samples were taken from the uppermost part of 4 3 ture, except for Hg, which was analyzed by Hydride the sediment with spoons and spatulas and deposited ◦ Generator-AAS. The precision of the total digestion into plastic bags which were kept in a room at 4 C was 2-14% (Table 1) as determined from five repli- until granulometric and chemical investigations were cates. The precision for all the metals was better carried out in the laboratory. Gravity core samples than 10% at, 95% significance level, except for Ni, were also obtained from seven sites. Each core was which was 14%. The accuracy of the analyses was sliced into 2 cm sections with a plastic spatula for checked against the International Standards (BCR metal analysis. Reference Material CRM 142; and AQCS Reference Materials SL-1 and SL-7) (Table 2). The difference Pretreatment of the samples between measured and reference concentrations were The entire apparatus was pre-cleaned by soaking in generally small, except for Fe and Ni in CRM 142 50% HNO3 for 24 hrs. Samples were extruded from and Zn in SL-1. The metal data were normalized the plastic bags and mixed by plastic spatula in a to Al (weight ratios) to minimize the grain-size and ◦ glass mortar before drying at 110 Cintheoven. CaCO3-dilution effects. Table 1. Precision of the metal analysis from five replicate samples. Element Mean Precision (%) Pb (ppm) 30 2 Cu (ppm) 20 8 Zn (ppm) 104 4 Hg (ppb) 2946 2 Fe (%) 4.6 8 Mn (ppm) 257 4 Al (%) 6.6 8 Ni (ppm) 15 14 Cr (ppm) 63 4 Precision at 95 % significance level %P=((2σ)/Conc.)× 100 Results The Corg contents of the sediment samples col- lected in February and December, 1996, were found Organic Carbon (Corg ) Distribution in general to be generally similar (Table 3). Despite this similarity, the Corg contents at some sites lo- The Corg contents of the surficial sediments collected in February and December, 1996, were found to have cated in the area close to the Strait/Marmara Sea the same range (0.2-2.35 %) and similar distributions confluence (sites M3 and M1) and Prince’s Islands (Figure 2). High (>1.5 %) values were found along (sites M78 and M79) appear to have increased by as the coast near the confluence of the Istanbul Strait much as 110% during the ten-month period. Some with the Marmara Sea. The Black Sea sediments decreases (<50%) in Corg at three sites K6, M6 and (K0 to K7) are characterized by intermediate values M4) may indicate the dynamic circulation and pol- lution of this marine environment. of (0.71-1.34%) Corg . 41 ALGAN, C¸AGATAY,˘ SARIKAYA, BALKIS SARI Table 2. The accuracy of metal analysis. Int.St.Reference Material Element Reference Conc. (ppm) Measured (matrix) Confidence interval CRM 142 (Light sandy soil) Mn 569 574 Fe 19600 25800 Pb 37.8 35 Cu 27.5 25 Zn 92.4 92 Ni 29.2 14 Cr 74.9 85 SL-7 (Soil) Mn 604-650 634 Pb 55-71 60 Zn 110-113 91 SL-1 (Lake sediment) Fe 65700-69100 61400 Pb 30-45 41 Cu 24-36 28 Zn 213-233 147 Ni 36.9-52.9 39 Cr 95-113 98 Corg (%) 0.20 to 1.00 1.00 to 1.50 1.50 to 2.00 2.00 to 2.40 Figure 2. Distribution of corg content of the sediment samples collected in December, 1996. 42 ALGAN, C¸AGATAY,˘ SARIKAYA, BALKIS SARI Table 3. Basic statistical parameters and results of F-Test performed on analyses of two batches of 28 sediment samples collected during February 1996 and December 1996. Corg & February 1996 December 1996 F-Test Metals Mean Variance Mean Variance F-calculated F-Critical Corg % 1.31 0.24 1.26 0.34 1.41 1.92 Cu (ppm) 37.48 179.8 32.44 320.5 1.78 1.92 Pb (ppm) 34.7 138.0 32.35 178.8 1.29 1.92 Zn (ppm) 95.51 723.8 89.2 1332.8 1.84 1.92 Hg (ppb) 360.7 107441.3 251.8 25256.0 4.25 1.94 Al(%) 5.80 3.63 5.29 2.44 1.48 1.92 Cr (ppm) 131.93 15116.1 104.13 7996.2 1.89 1.91 Fe (%) 2.35 0.94 2.92 0.44 2.13 1.91 Mn (ppm) 204.6 4130.2 253.2 9159.8 2.21 1.92 Ni (ppm) 37.04 233.3 27.00 79.69 2.92 1.91 The highest annual primary productivity was de- ranean waters.