Accumulation of polychlorinated biphenyls (PCBs) in surficial Lake Superior sediments. Atmospheric deposition

Maximum PCB concentrations in sediment core samples from lake Superior were found in surficial sediments in a location in the prevailing downwind direction of Thunder Bay, Ontario. Depth-fractionated sediments yielded no detectable PCB at depths greater than 3 cm below the sediment/water interface and they were often not detected below a burial depth of 1 cm. Atmospheric input of PCB is estimated as 3-8x10 6 g per year and their sedimentation rate as 03-04 g/m 2 per year. It is suggested that atmospheric transport and deposition may dominate PCB input into the lake Superior ecosystem.