Seasonal air–water exchange fluxes of polychlorinated biphenyls in the Hudson River Estuary

Polychlorinated biphenyls (PCBs) were measured in the air and water over the Hudson River Estuary during six intensive field campaigns from December 1999 to April 2001. Over-water gas-phase ∑PCB concentrations averaged 1100 pg/m3 and varied with temperature. Dissolved-phase ∑PCB concentrations averaged 1100 pg/L and displayed no seasonal trend. Uncertainty analysis of the results suggests that PCBs with 5 or fewer chlorines exhibited net volatilization. The direction of net air/water exchange could not be determined for PCBs with 6 or more chlorines. Instantaneous net fluxes of ∑PCBs ranged from +0.2 to +630 ng m−2 d−1. Annual fluxes of ∑PCBs were predicted from modeled gas-phase concentrations, measured dissolved-phase concentrations, daily surface water temperatures and wind speeds. The net volatilization flux was +62 μg m−2 yr−1, corresponding to an annual loss of +28 kg/yr of ∑PCBs from the Hudson River Estuary for the year of 2000.