Polychlorinated biphenyls in the Great Lakes: 1990`s concentrations

Concentrations of polychlorinated biphenyls (PCBs) in the water column of the Laurentian Great Lakes have declined over the last decade. The measurement of current concentrations of these hydrophobic organic contaminants (HOCS) requires the sampling of large sample volumes, typically 100--400 liters. This paper will present results from the water column HOC trend program, begun by GLNPO in 1991. Water samples were filtered with a 0.7{mu}M glass fiber filter, and the filtrate was collected and extracted using the Goulden Large Sample Extractor (GLSE). PCBs were extracted from the filters with Soxhlet extraction, and the resulting operationally-defined particulate and dissolved phases were analyzed by gas chromatography with electron capture detection. Results indicate concentrations in the 100s of picograms/liter for total PCBs. Spatial differences within and between Lakes, and temporal differences will be presented.