PARTICLE-MEDIATED TRANSPORT AND FATE OF A HYDROPHOBIC ORGANIC CONTAMINANT IN SOUTHERN LAKE-MICHIGAN - THE ROLE OF MAJOR WATER COLUMN PARTICLE SPECIES

A seasonal model of water column abundance and vertical fluxes of major particle species in southern Lake Michigan is developed, based on information obtained through detailed water column sampling and sediment trap deployments. By coupling experimentally-measured equilibrium partition coefficients of a model HOC to the major particle species with the particle model, we predict both particle-specific phase partitioning of the HOC in the water column and fluxes to the sediments over an annual cycle. The results indicate a dynamic seasonal and spatial cycle of HOC association with particulate material, largely controlled by biological particle production events. Diatoms are the major sorptive particle type for HOCs in the water column during much of the year. Diatoms also serve as the major vector for HOC removal from the water column to the sediments. The fate of contaminants associated with autochthonous particles subject to diagenesis and dissolution near the sediment-water interface is uncertain. Significant phase redistribution of HOCs is likely in the benthic nepheloid layer and the upper few centimeters of sediments.