Enhanced airborne polychlorinated biphenyl (PCB) concentrations and chlorination downwind of Lake Ontario

Air samples were collected simultaneously at three sites downwind of Lake O ntario and at a control site near Lake Erie from March to July of 1999. The Lake Erie site (Stockton, NY) had PCB concentrations similar to rural Inte grated Atmospheric Deposition Network(IADN) sampling sites across the Great Lakes, exhibited limited seasonal variation, and approximates regional bac kground. Samples taken along Lake Ontario's southeastern shore (Rice Creek and Sterling, NY) had elevated PCB concentrations averaging similar to1 ng/ m(3) and were more chlorinated than air collected at IADN sites and at Stoc kton. Air samples from Potsdam (similar to 75 km inland) had similar concen trations but were less chlorinated. Clausius-Clapeyron plots revealed a str ong correlation between PCB fugacity and temperature near Lake Ontario; how ever, the extent of chlorination of the air samples rules out volatilizatio n from the lake as a major source. It is hypothesized that volatilization f rom local surfaces, enriched in higher chlorinated congeners by meteorologi cal or geographic factors, drives both the concentration and composition of airborne PCBs along Lake Ontario's southeastern shore.