PM05 Bioaccumulation and Kinetics of POPs
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(PM040) Bioaccumulation factors for PCBs revisited.

Borgå, K.1, Muir, D.2, Whittle, D.3, Swackhamer, D.4, 1 Norwegian Polar Institute, Tromso, Norway2 National Water Research Institute, Burlington, ON, Canada3 Fisheries and Ocean Canada, Burlington, ON, Canada4 University of Minnesota, Minneapolis, MN, Canada

ABSTRACT- Recent PCB analyses in European Arctic seawater have revealed concentrations in the fg/L range. The resulting log bioaccumulation factors (BAF) for individual PCB congeners in calanoid copepods were 7.3-9.0, which is 2 orders of magnitude higher than BAFs recently reported for congeners in the same KOW range in Canadian and Alaskan Arctic marine calanoid copepods(log BAFs 5.5-6.5). They are also higher than reported in freshwater zooplankton (150-500 um) and Mysis (Lake Ontario) from the mid- to early 1980s (log BAF 4.5-7). If the recent high BAFs are realistic, it means that earlier reported BAFs for Arctic marine copepods are too low probably due to erroneously high water concentrations, and that bioaccumulation in Arctic zooplankton is more efficient than previously assumed. Likewise, it suggests that BAFs previously reported from some other systems may be too low by a factor of 10 or more. Determination of the dissolved fraction of PCBs in water is challenging and early work may not have thoroughly accounted for shipboard and laboratory contamination. Several methodological advances during the 1990s including use of clean rooms on ships, solid phase extraction, and in situ samplers have led to significantly lower dissolved PCBs reported both in the Arctic and in the Great Lakes. However, PCB concentrations have also declined in surface waters due to reduced local and atmospheric inputs and this needs factored in when comparing older and recent BAFs. Species composition of the zooplankton also needs to be considered. The present study investigates various hypotheses to explain the observed differences in BAFs: are these real differences or artifacts due to compromised PCB concentrations quantified in either water or biota?

Key words: PCBs, bioaccumulation, zooplankton, copepods

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