DEVELOPMENT OF A MASS-BALANCE MODEL FOR ESTIMATING PCB EXPORT FROM THE LOWER FOX RIVER TO GREEN BAY

A mass balance approach was used to model contaminant cycling in the l ower Fox River from the DePere Dam to Green Bay. The objectives of thi s research were 1) to estimate present contaminant export from the Fox River to Green Bay, and 2) to quantify contaminant transport and fate pathways in the lower river for the study period. Specifically, a mod el describing the transport, fate, and export of chlorides, total susp ended solids, total PCBs, and six PCB congeners for the lower Fox Rive r was developed. Field data collected as part of the U.S. Environmenta l Protection Agency's Green Bay Mass Balance Study were used to calibr ate the model. From 10 October 1988 to 31 May 1990, the estimated tota l PCB export was 423 kg; for calendar year 1989, the estimate was 280 kg. Model results suggest that the transport of in-place pollutants si gnificantly contributed to the cumulative export of total PCBs over th is period. Estimated total PCB transport in the Fox River during 1989 increased 60% between the dam and river mouth due to the resuspension of lower river sediments. Total suspended solids and PCB predictions a re most sensitive to particle transport parameters, particularly the s ettling and resuspension velocities. The significant components of the total PCB mass balance are import (loading over the DePere Dam), sett ling, resuspension, and export to Green Bay. Volatilization, porewater transport, and point source input were not significant to the mass ba lance. Present point source discharges to the river are not significan t total PCB sources, collectively contributing less than 6 kg of PCB t o the river during the mass balance period.