Risk assessment of metals and organic pollutants for herbivorous and carnivorous small mammal food chains in a polluted floodplain (Biesbosch, The Netherlands) Timo Hamers a, * , Johannes H.J. van den Berg a , Cornelis A.M. van Gestel b , Frederik-Jan van Schooten c , Albertinka J. Murk a a Wageningen University, Toxicology Group, PO Box 8000, 6700 EA Wageningen, The Netherlands b Vrije Universiteit, Department of Animal Ecology, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands c Maastricht University, Department of Health Risk Analysis and Toxicology, PO Box 616, 6200 MD Maastricht, The Netherlands Received 1 June 2005; received in revised form 4 January 2006; accepted 11 January 2006 In polluted floodplain areas, dietary exposure to metals poses a larger risk for small mammals in a carnivorous than in a herbivorous food chain. Abstract A risk assessment was made for a carnivorous and a herbivorous food chain in a heavily polluted natural estuary (Biesbosch), by determining the most critical pollutants and the food chain most at risk. Exposure of food chains to metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) was assessed by analyzing dietary concentrations, internal concentrations, and biomarkers of exposure. Com- mon shrew (Sorex araneus) and bank vole (Clethrionomys glareolus) were selected as representative small mammal species for the carnivorous and herbivorous food chain, respectively, and earthworms (Lumbricus rubellus) and snails (Cepaea nemoralis) as representative prey species for the carnivorous food chain. Metals contributed most to the total risk for small mammals and earthworms. PCBs, but not PAHs, contributed to the overall risk for S. araneus at regularly flooded locations. The carnivorous food chain appeared most at risk given the higher exposure levels and bioaccumulating potency found for contaminants in S. araneus. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Sorex araneus; Clethrionomys glareolus; Biomarker; Bioassay; Diffuse pollution 1. Introduction In the Netherlands, floodplains of the main rivers are con- sidered to be valuable nature conservation and nature develop- ment areas. Located in the estuary of rivers Rhine and Meuse, National Park the Biesbosch is one of such areas, which is characterized by creeks, islands, and willow bushes. In the sec- ond half of the last century, floodplains in The Netherlands became moderately to heavily polluted with metals and or- ganic contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and polyhalogenated aromatic hydrocarbons (PHAHs) including polychlorinated biphenyls (PCBs) due to the deposi- tion of polluted sediments. For the Biesbosch area, this was es- pecially the case after completion of the Delta works. This dam construction was built to protect the Southwestern part of The Netherlands from flooding, but as a consequence of the absent tidal influences, polluted clay particles could more easily precipitate in the floodplains (Van der Scheer and Gerritsen, 1998). Although water quality has considerably improved over the last decades, development of natural ecosystems in the * Corresponding author. Institute for Environmental Studies (IVM), Vrije Universiteit Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands. Tel.: þ31 20 598 9529; fax: þ31 20 598 9553. E-mail address: timo.hamers@ivm.falw.vu.nl (T. Hamers). 0269-7491/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2006.01.020 Environmental Pollution 144 (2006) 581e595 www.elsevier.com/locate/envpol