Dry Deposition of Particulate Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons to Lake Michigan

Abstract

Dry deposition was collected from November 1993 to October 1995 at multiple sites within the Lake Michigan basin to estimate fluxes of particulate polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) as part of the Lake Michigan Mass Balance Study (LMMBS). Samples were also collected during the Atmospheric Exchange over Lakes and Oceans (AEOLOS) project to estimate fluxes to coastal waters adjacent to the Chicago urban area. Fluxes of particulate PCBs and PAHs were higher in Chicago than <15 km offshore and at rural sites. Geometric mean dry deposition fluxes across the Lake Michigan basin ranged from 3.6 to 65 mg/m2-day for particle mass, 0.06 to 0.21 μg/m2-day for Σ-PCBs, and 0.25 to 18 μg/m2-day for Σ-PAHs. Similarities in both the distribution pattern of PCB congeners and PAHs and the magnitude of their fluxes between dry deposition and surficial sediment suggest that dry deposition may dominate loadings to the lake. Conservative estimates of loadings to Lake Michigan through particle dry deposition are estimated to be 1100 kg/yr for PCBs and 5000 kg/yr for PAHs. These loadings are more than 3× greater than loadings by wet deposition and, for PCBs, are similar to inputs by air/water exchange.