Mohammed A. Khairy 1,2 Marit Kolb 1 Christiane Schmidt 1 Dieter W. Zachmann 1 Alaa R. Mostafa 2 Anwar A. EL-Fiky 2 Mu ¨ fit Bahadir 1 1 Institute of Environmental and Sustainable Chemistry, Technische Universita ¨ t Braunschweig, Braunschweig, Germany 2 Department of Environmental Sciences, Faculty of Science, Alexandria University, Alexandria, Egypt Research Article Trace Elements in Sediments and Mussels – Spatial Distribution, Chemical Partitioning, and Risk Assessment Sediment samples were collected from 30 different locations in Abu Qir Bay (Mediterranean Sea), East Alexandria, Egypt and analyzed for trace elements. The highest concentrations of most of the elements were observed in the nearshore stations in the vicinity of the major anthropogenic activities as industrial settlements, waste- water discharges, and agricultural drainage. In addition, mussel samples of Mactra corallina and Tapes decussata were collected corresponding to the sediment samples. Concentrations of As, Cd, Cr, Mn, and Zn in the mussel tissues were higher than concentrations in sediments, thus indicating their relatively high bioavailability. Sequential extraction procedure was performed on selected sediment samples. Significant correlations were observed between the concentrations of Cu, Mn, Pb, and Zn in the exchangeable fraction of the sediments and the corresponding tissues of M. corallina. The output of the risk assessment applied on the sediments revealed that adverse ecological effects to benthic species could occur and that a higher level of risk is expected from the exposure to Cd, Cr, Hg, and Zn. No adverse carcinogenic or non- carcinogenic human health effects are expected from the consumption of the two mussel species from Abu Qir Bay. Keywords: Abu Qir Bay; Mussels; Risk assessment; Sediments; Sequential extraction Received: April 20, 2010; revised: September 3, 2010; accepted: September 13, 2010 DOI: 10.1002/clen.201000145 1 Introduction The accumulation of persistent and partly toxic substances (metals, chlorinated organic compounds, polycyclic aromatic hydrocarbons) in the environment continuously increases owing to anthropogenic activities [1]. In estuarine ecosystems, sediments are recognized as the most important pollutant sinks and as a carrier and possible future sources of contaminants. The accumulation of contaminants in sediments can thus pose serious environmental problems in surrounding areas [2]. Such accumulation is enhanced in enclosed and semi-enclosed areas where exchange of water with the open sea is limited [3]. In sediments, heavy metals and metalloids can be present in various chemical forms, and generally exhibit different physical and chemical behavior in terms of chemical interactions, mobility, biological availability, and potential toxicity [4–7]. Information obtained from the total element analysis is not satisfactory for a complete view about the mobility and bioavailability of these pollu- tants in sediments, and thus it is necessary to determine the differ- ent chemically bonded element fractions (exchangeable, carbonatic, reducible, oxidizable, residual) [8, 9]. Limited data are available on the concentration of trace elements in sediments and mussels of Abu Qir Bay (Mediterranean Sea), Egypt. Studies on chemical partitioning of element concentrations in the bay sediments are lacking until now. Most of the studies conducted on the bay sediments concentrated only on few trace elements [10– 16] and no published data are available for Se, As, Co, and Hg. The most comprehensive study on the trace element pollution in sedi- ments of the bay was performed by EL-Sokkary, [14] more than a decade ago. Previous studies on trace metal contamination in mussel species concentrated on Mactra corallina and Donax trunculus [17–21]. In these studies, only Cd, Pb, and Zn concentrations were determined. Industrial and human activities in and around Abu Qir Bay have increased dramatically in the last 20 years. Consequently, updated information is needed as basis for decision makers to establish effective management plans. Thus, the purpose of this study was to evaluate the levels and the spatial distribution of trace metals in the surfacial sediments and mussel samples and to investigate the factors regulating the pattern of spatial distribution of trace metals in the bay sediments and mussels. In addition, a sequential extrac- tion procedure of trace elements in Abu Qir Bay sediments was performed to provide a better understanding of the mobility and bioavailability of the elements. Finally, this study aimed to evaluate Correspondence: Dr. Mohammed A. Khairy, Institute of Environmental and Sustainable Chemistry, Technische Universita ¨t Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany E-mail: mohammed_khairy77@yahoo.com Abbreviations: AQD, Abu Qir Drain; CDI, chronic daily intake; HHRA, human health risk assessment; HQ, hazard quotient; OSF, oral slope factor; PEC, probable effect concentration; RfD, reference dose; SLERA, screening level ecological risk assessment; SQG, sediment quality guideline; TEC, threshold effect concentration; TOC, total organic carbon. 1184 Clean – Soil, Air, Water 2010, 38 (12), 1184–1193 ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com