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Trophic Magnification of PCBs and Its Relationship to the Octanol−Water Partition Coefficient
Walters, D. M., M. A. MILLS, B. S. Cade, AND L. P. Burkard. Trophic Magnification of PCBs and Its Relationship to the Octanol−Water Partition Coefficient. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 45(9):3917-3924, (2011).
(1) To characterize biomagnification and patterns in PCB congener composition within the Lake Hartwell food web; (2) To quantify the effect of KOW of FWMFs for individual congeners and the ability of TP to predict these congener concentrations; and (3) To use an innovative approach to analyze or interpret KOW-FWMF relationships from Lake Hartwell and other published studies to describe the generality of KOW effects on PCB biomagnification.
We investigated polychlorinated biphenyl (PCB) bioaccumulation relative to octanol-water partition coefficient (KOW) and organism trophic position (TP) at the Lake Hartwell Superfund (South Carolina, USA). We measured PCBs (127 congeners) and stable isotopes (δ15N) in sediment, organic matter, phytoplankton, zooplankton, macroinvertebrates, and fish. TP, as calculated from δ15N, was strongly, linearly related to ΣPCBs, and the food web magnification factor (FWMF) for Lake Hartwell was 3.09. Highly chlorinated congeners were enriched through the food web, and congener composition suggested alternate benthic and pelagic pathways of PCB accumulation at lower trophic levels. FWMFs of individual congeners increased strongly with log KOW, as did the predictive power (r2) of individual TP-CB regression models used to calculate FWMFs. We developed log KOW-FWMF models for eight food webs with vastly different environments (freshwater, marine, arctic, temperate) and species composition (cold- vs. warmblooded species). The effect of KOW on congener FWMFs varied strongly across food webs (model slopes 0.0-15.0), because the range of FWMFs among studies was also highly variable. We standardized FWMFs within studies to mean = 0, standard deviation (SD) = 1 to normalize for scale differences and found a remarkably consistent KOW effect on FWMFs (no difference in model slopes among food webs). Our findings underscore the importance of hydrophobicity (as characterized by KOW) in regulating bioaccumulation of recalcitrant compounds, and demonstrate the KOW effects on bioaccumulation are more generalized than previously recognized.
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