Polychlorinated biphenyls (PCB) and dichlorodiphenyltrichloroethane (DDE) air concentrations in the Lake Ontario region: Trends and potential sources

Airborne particle and gas samples were collected approx every 12 days from April 2002 to June 2006 at the Sterling Nature Center located near the southeast corner of Lake Ontario. These samples were analyzed for polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDE). Clausius-Clapeyron (C-C) regression analyses of PCBs and DDE yielded moderate correlations (r² = 0.54, p < 0.001; r² = 0.74, p < 0.001, respectively) indicating that much of the variations in concentrations can be explained by temperature. Back trajectory analysis indicated that the most important factors driving unusually high PCB partial pressures relative to those predicted by the C-C regression were slow wind speeds and winds generally from the southwest. This combination, which occurred frequently in 2004, increased contact of the air with contaminated upwind surfaces with minimum dilution. Hybrid receptor modeling (Potential Source Contribution Function (PSCF)) results for the total PCBs identified the midwestern US region that contains the urban areas of southern Indiana (IN), southwestern Ohio (OH), and northern Kentucky (KY) having the highest PSCF values. In general urban areas like Chicago (IL), Detroit (MI), Cleveland (OH), St. Louis (MO), and Nashville (TN) also had significant possibilities. In contrast, the PSCF modeling for DDE identified northern Alabama as the area with the highest probability where DDT was applied to cotton fields.