ATMOSPHERIC INPUTS OF SELECTED POLYCYCLIC AROMATIC-HYDROCARBONS AND POLYCHLORINATED-BIPHENYLS TO SOUTHERN CHESAPEAKE BAY

Atmospheric and precipitation levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were measured at a rural site in southern Chesapeake Bay throughout 1991. Wet depositional inputs of PAHs and PCBs to the lower Bay were directly determined from the data; dry deposition and gas exchange fluxes were also estimated for PAHs. Notable seasonal variability in the atmospheric concentrations of aerosol-associated PAHs and gaseous PCBs was observed. Conversely, wet deposition concentrations and fluxes exhibited little temporal variability. Annual wet deposition fluxes of PAHs and PCBs were determined to vary spatially in Chesapeake Bay, presumably due to the influence of temperature on the efficiency of washout. The uncertainty in measured wet deposition and ambient atmospheric concentrations is 25-50%, however, there is currently large uncertainty associated with estimates of dry deposition and gas exchange fluxes of semivolatile organic contaminants (SOCs). Nonetheless, atmospheric fluxes of SOCs are predicted to be both into and out of lower Chesapeake Bay.