Ecological risk assessment using trace elements from surface sediments of _ Izmit Bay (Northeastern Marmara Sea) Turkey Hakan Pekey a, * , Duran Karakas ß b , Savas ß Ayberk c , Leyla Tolun b , Mithat Bako glu c a Department of Environmental Protection, University of Kocaeli, P.O. Box 318, 41275 _ I zmit, Kocaeli, Turkey b T € U B _ I TAK-MRC, Earth and Marine Sciences Research Institute, P.O. Box 21, 41470 Gebze, Kocaeli, Turkey c Environmental Engineering Department, University of Kocaeli, P.O. Box 318, 41300 _ I zmit, Kocaeli, Turkey Abstract The aim of this study was to study ecological risk assessment of trace elements (As, Cd, Cr, Cu, Ni, Pb and Zn) in _ Izmit Bay surface sediments in the <63 lm fraction. Sediment samples were collected from 8 sites along the north coastline of the bay. Samples were subjected to a total digestion technique and analyzed for major (organic carbon) and minor (As, Cd, Cr, Cu, Ni, Pb and Zn) elements. Sediments heavily contaminated are evaluated by the Sediment Quality Guidelines (SQG) of US EPA. The degree of contamination ðC d Þ is estimated as very high at each site. Two sets of SQGs, effect range-low/effect range median values and TEL/ probable effect level (PEL) values were used in our study. Sediments from the each site are judged toxic when two or more of the PEL values exceed EPA guidelines. Our results are in agreement with previously reported sediment toxicity test results. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Trace elements; Total organic carbon; Sediment quality guidelines; Degree of contamination; Surface sediments; ICP/AES 1. Introduction Marine sediments can be sensitive indicators for monitoring contaminants in aquatic environments (Ergin et al., 1991; Balls et al., 1997; Atgın et al., 2000). They have been found polluted with various kinds of hazardous and toxic substances (Fukue et al., 1999; Zabetoglou et al., 2002), including trace elements which accumulate in sediments via several pathways, including disposal of liquid effluents, terrestrial runoff, and leachates carrying chemicals originating from numerous urban, industrial, and agricultural activities, as well as atmospheric deposition (Salomons and F€ orstner, 1984; Rivail Da Silva et al., 1996; Karageorgis et al., 2002; Mucha et al., 2003). Such accumulation is enhanced in enclosed and semi-enclosed areas where exchange of water with the open sea is limited (Okay et al., 1996; Karageorgis et al., 2002). Grain size plays a significant role in determining elemental concentrations in sediments (Szefer et al., 1996). Sediments are very heterogeneous in their textural characteristics and the first issue is the different grain size fractions selected for analysis: <63 lm fraction, <150 lm fraction, <2 mm fraction, or total metal content (Ruiz, 2001). Salomons and F€ orstner (1984) recommended a particle size fraction of <63 lm for analysis because they thought it was most nearly equivalent to materials carried in suspension, the most important system for transport of sediments. Certain trace elements, Cu and Zn, are essential micronutrients required for normal growth and function of organisms. Other trace elements, i.e., As, Cd, Hg, Pb and Sn, are considered to be toxic with respect to human health and aquatic life (Libes, 1992; Ouyang et al., 2002). With its east-west elongated shape, _ Izmit Bay is located in Northeastern Marmara Sea latitudes 40°41 0 – 40°47 0 N, longitudes 29°21 0 –29°57 0 E (Fig. 1). It is an important semi-enclosed embayment situated close to the Bosphorus and _ Istanbul, and has been strongly affected by growing populations and industrialization (Okay et al., 1998; Balkıs, 2003). The bay is about 45 km long, varies 1.8–9 km in width, and has an area of 261 km 2 . It consists of three sections (western, central and eastern) connected to each other by narrow openings. The eastern section is 15 km in length, with an average depth of 30 m. The largest sub-region of the bay is the * Corresponding author. Fax: +90-262-341-33-75. E-mail address: hpekey@lycos.com (H. Pekey). 0025-326X/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2003.11.023 www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 48 (2004) 946–953