Accumulation of polychlorinated biphenyls (PCB) associated with bottom sediments in larvae of Chironomus riparius Meigen

Patterns of bioaccumulation of polychlorinated biphenyls (PCBs) by chironomid larvae (Chironomus riparius Meigen) were studied under laboratory conditions. Larvae were maintained for 20 days, separately in two batches of natural bottom sediments sampled from Rybinsk Reservoir (Russia), each differing in PCB content (425.6 mu g / kg or 24.8 mu g / kg dry weight, respectively). The study revealed that chironomid larvae accumulated PCBs at levels comparable to the PCB content measured in sediments from each exposure. The bioaccumulation coefficient (1.11 and 1.59, respectively, as per dry weight for compared sediment batches) depended directly on the sum PCB content in sediments. At high sediment PCB content, the ratios of homologous groups of PCBs in larvae and sediment were identical and corresponded to the Aroclor 1254 congeners profile; at lower PCB content, pronounced differences were revealed. In larvae, the ratios of 3, 4, 5, and 6CB homologues were evenly distributed at levels of 20-34 %, while the 4CB homologues prevailed (47 %) in sediments. The content of the latter compounds in larvae was lower than in sediments, and higher for the other homologous groups. The study indicates selective bioaccumulation of various homologous groups of PCBs under conditions of low sediment PCB content.