Availability and uptake of metals in the accumulated sediments in stormwater treatment facilities was assessed by the metal accumulation patterns observed in freshwater mussels, as the first step in an Environmental Risk Assessment (ERA). Freshwater mussels, Elliptio complanata, were caged in various locations in several stormwater treatment facilities and control sites in southeastern Ontario. Mussels were sampled at 2, 5.5, 8, 11 and 14 weeks, and Ni, Cr, Cu, Cd and Pb concentrations in soft tissues were determined by ICP-MS. Selection of these metals was based on previous studies which had identified them in substantial quantities in stormwater pond sediments. A significant decrease in Ni concentrations and an increase in Pb concentrations relative to background levels were observed. Concentrations of Cu, Cd and Cr were generally not significantly different from background.

Total metal concentrations in sediments were also determined, and compared with the observed mussel metal concentrations. No correlations were observed between total metals in sediment and the accumulated burden in the mussels. The results suggest that Pb is a possible concern in these stormwater facilities due to its availability. Ni, Cr and Cd did not appear to be in bioavailable forms and Cu had limited availability. The study was complementary to other work examining trace metals in stormwater management facilities, and provides further useful information about the habitat quality of these facilities, and the ecotoxicological risks that might be posed to resident species.

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