Measurement of particle phase dry deposition fluxes of polychlorinated biphenyls (PCBs) with a water surface sampler

It has been shown that the atmospheric pathways including dry deposition are an important source of polychlorinated biphenyls (PCBs) entering surface waters in many locations. To assess how important this pathway is, accurate measurements or modeled estimates of dry deposition are needed. However, dry deposition is not well quantified because the direct measurement of dry deposition is difficult and indirect estimation techniques have substantial uncertainties associated with them. In this study, PCB dry deposition fluxes were directly measured with a water surface sampler (WSS) simultaneously with measurements of airborne concentrations in the Chicago urban area. The average particulate phase PCB flux to the WSS was 240±160 ng/m2-d, and the particulate phase airborne concentrations was 0.08±0.05 ng/m3. Average overall dry deposition velocities, calculated by dividing the fluxes by total particle phase PCB concentrations were 4.2±2.7 cm/s. This number is consistent with values determined using similar experimental techniques and higher than the values typically used to model PCB dry deposition. This difference may be due, in part, to the influence of PCBs associated with large particles being deposited onto the WSS.