Temporal and Spatial Trends in a Long-Term Study of Gas-Phase PCB Concentrations near the Great Lakes

Atmospheric concentrations of gas-phase polychlorinated biphenyls (PCBs) were measured at three sites near the Great Lakes as part of the Integrated Atmospheric Deposition Network (IADN). Air samples were collected every 12 days beginning in November 1990. Mean yearly values ranged from 89 to 370 pg/m3. Concentrations at the more urban site near Lake Erie (Sturgeon Point) were about two times higher than concentrations at the two more remote sites near Lake Superior (Eagle Harbor) and Lake Michigan (Sleeping Bear Dunes). Multiple regression analysis was used to relate atmospheric PCB concentrations to meteorological conditions. As expected, atmospheric temperature had a very significant effect on gas-phase PCB concentrations. Including wind speed and wind direction in the regression analysis improved the predicted values only slightly. Atmospheric levels of PCBs have remained unchanged as a function of time near Lake Superior but have declined slightly over time near Lakes Michigan and Erie. The rate constants at the latter two sites indicate an environmental half-life in the atmosphere of approximately 6 yr, which agrees well with PCB half-lives in other environmental compart ments.