Loadings of Organochlorine Contaminants and Trace Elements to Two Ontario Lake Systems and Their Concentrations in Fish

Direct precipitation contributed > 90% of organochlorine (OC) loadings to Emmett and Bartley lakes and three Turkey Lakes. The OCs with highest lake loadings were PCBs, αBHC, γBHC, methoxychlor, HCB, and dieldrin with means of 31.6, 26.9, 7.2, 1.4, 1.0, and 1.0 μg∙m−2∙yr−1, respectively. Heptachlor epoxide, α- and γ-chlordane, α- and β-endosulfan, endrin, and total DDT had mean loadings of 0.1–0.9 μg∙m−2∙yr−2 mostly from direct precipitation. Heptachlor, aldrin, and mirex were not detected in precipitation, runoff, or fish samples. γBHC, methoxychlor, α- and β-endosulfan, and endrin were not detected in any fish of five species from the five fakes but they had significant lake loadings, in multiple regression analysis, 42–68% of the variability in residues of OCs in fish was accounted for by lake loading and octanol:water partition coefficient (to quantify lipophilicity). Relatively high concentrations of total DDT occurred in fish because of high lipophilicity, high concentrations of αBHC occurred because of high loading, and high concentrations of PCB were attributable to both factors. Trace element loadings in runoff were generally higher than in precipitation to the softwater lakes and lower in the hardwater system. Pb concentrations in fish were proportional to loadings, but Cu and Ni residues in fish were less variable than their loadings, and Zn loadings and residues were relatively uniform. Hg showed highest biomagnification (residue in relation to loading), and the larger piscivorous fish had the highest residues.