PCBS IN LAKE-MICHIGAN WATER REVISITED

PCBs were determined in water samples from 11 open water sites in Lake Michigan and compared to data from 1980. PCB concentrations declined from 1980 to 1991 with a first-order rate constant calculated to be -0 .078 yr(-1). The most southern and southwesterly sites sampled were hi gher in concentration and exhibited different homolog profiles and par titioning behavior than samples from other sites, The organic carbon-n ormalized partition coefficients were not correlated to K-ow. A simple mass budget about the water column for 1991 using current measurement s of PCB inputs and outputs shows a significant imbalance of PCBs and indicates the need for further study of the roles that subregional atm ospheric deposition and sediment-water interactions play as sources to the lake.