WET DEPOSITION OF POLYCHLORINATED-BIPHENYLS TO GREEN BAY, LAKE-MICHIGAN

Precipitation was sampled at three sites along the eastern shore of Green Bay, Lake Michigan from April 18, 1989 through May 15, 1990 and analyzed for 86 PCB congeners. The objective was to estimate the wet flux of PCBs to Green Bay as part of the Green Bay Mass Balance Study. The arithmetic mean concentration of SIGMA-PCBs in precipitation was 2.7 +/- 2.1 ng/L and the volume-weighted mean concentration was 2.2 ng/L. No spatial or temporal trends in PCB concentrations were observed among the sites distributed over about 170 km. Assuming 80 cm/yr precipitation to the bay and a surface area of 4200 km2, the wet flux of PCBs to Green Bay is 2.2 +/- 1.7 mug/m2-yr or 2 to 16 kg/yr. Mass of PCBs detected in laboratory XAD resin blanks was approximately half of that in the rain samples. When blank corrected, both the rain concentrations and wet flux estimates are reduced to approximately 1 ng/l, and 4 kg/yr, respectively.