PCBs in sediments of the Great Lakes - Distribution and trends, homolog and chlorine patterns, and in situ degradation
2009
Li, An | Rockne, Karl J. | Sturchio, Neil | Song, Wenlu | Ford, Justin C. | Wei, Hua
A region-wide data analysis on polychlorinated biphenyls (PCBs) in the sediment of the Great Lakes reveals a total accumulation of approximately 300 ± 50 tonnes, representing a >30% reduction from the 1980s. Evidence of in situ degradation of sediment PCB was found, with estimated t1/2 of 11 and 17 years, at two open water locations in Lake Ontario. The relative abundance of heavy homologs as well as para-chlorines decreases with increasing depth, while the opposite is true for medium and light homologs and ortho-chlorines. In Lake Michigan, the vertical pattern features enrichment of heavier congeners and reduction of ortho-chlorines in deeper sediment layers, opposite to the trend in Lake Ontario. PCBs decrease log-linearly with increasing latitude and longitude. Air deposition of PCBs to lake sediment decreases at about 0.077 ng cm-2 yr-1 per degree latitude (N) for the geographic region extending from the Great Lakes to within the Arctic Circle. Data analysis on PCBs in the Great Lakes sediments reveals decline of overall burden, occurrence of in situ degradation, and the geographic gradient in the region and beyond.
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