RESUSPENSION OF BOTTOM SEDIMENTS IN LAKE-ONTARIO DURING THE UNSTRATIFIED PERIOD, 1992-1993

Time-series measurements of current velocity and water temperature mad e at a station in southwestern Lake Ontario between October 1992 and J une 1993 are combined with analyses of material collected in a sequenc ing sediment trap moored at the same location. The results show that l ocal resuspension of bottom material occurred several times during Nov ember and December. Analyses of total PCBs and Mirex concentrations we re used to infer the origins of the material collected in the traps. M aterial collected during the fall has multiples sources; in addition t o material already in suspension and bottom material resuspended from the immediate area, some material appears to be derived from the Niaga ra River delta. This is the first reported instance of bottom resuspen sion in the Great Lakes at depths below wave base during the unstratif ied period that has been confirmed by current velocity measurements.