Sources of polychlorinated biphenyls to Upper Hudson River sediment post-dredging

The Upper Hudson River (UHR) has been contaminated with polychlorinated biphenyls (PCBs) since the 1940s due to the manufacture of capacitors at two plants near Hudson Falls and Fort Edward, NY by General Electric (GE). Dredging of portions of the UHR was conducted from 2009 to 2015 as a partial remedy for this contamination. In 2017, the New York State Department of Environmental Conservation undertook a comprehensive post-dredging survey of sediment contamination in the UHR. Thousands of samples were collected, and 130 of these were analyzed for PCBs using EPA method 1668A. This data set was analyzed using Positive Matrix Factorization. Six factors were observed. One factor resembled the dominant Aroclors used by GE with little alteration. Three factors represented different pathways and/or extents of microbial dechlorination. One factor resembled a mixture of microbial dechlorination products and a higher molecular weight Aroclor used by GE. The congener patterns of the dechlorination factors suggest that removal of chlorines at the ortho position does occur in the UHR sediment, in agreement with several laboratory studies showing that such ortho dechlorination is possible. This ortho dechlorination could theoretically lead to complete dechlorination of PCBs to biphenyl in UHR sediment. Only one factor was not attributable to GE. It represents inputs of PCBs from tributaries and urban areas and explains 1.7% of the PCB mass in the sediments. The small contribution from the non-GE PCB source suggests that recontamination of the sediment after dredging was minor.