CONCENTRATION AND DISTRIBUTION OF PCB CONGENERS IN ISOLATED ONTARIO LAKES CONTAMINATED BY ATMOSPHERIC DEPOSITION

The concentration of 19 PCB congeners was analysed in biota, sediments, water, and suspended solids in four central Ontario lakes in which atmospheric deposition was the major source of PCB contamination. Input from the atmosphere resulted in total congener concentrations of 1-2 ng.L-1 dissolved in water, 10-50-mu-g.kg-1 (dry weight) in sediment, 5-10-mu-g.kg-1 (wet weight) in biota from lower trophic levels (i.e. zooplankton, golden shiner (Notemigonus crysoleucas)), and 10-30-mu-g.kg-1 (wet weight) in fish from upper trophic levels (yellow perch (Perca flavescens), smallmouth bass (Micropterus dolomieui)). The dominant PCB congeners in the lakes were the trichlorobiphenyl congeners 31 (28) and the hexachlorobiphenyl congeners 153 and 138, consistent with congener distributions reported for vapour- and particulate-bound PCBs in the atmosphere. Discriminant analysis indicated slight differences in congener patterns between the study lakes, but the general pattern for isolated lakes was substantially different from point-source contaminated lakes, primarily due to the high proportion of congeners 31 (28). There was no significant difference in the total PCB concentrations in biota (lipid basis) between lakes, but within the lakes, total PCB concentrations were significantly higher in yellow perch than in biota from lower trophic levels.