| Abstract
| - PCB-contaminated sediments from the HousatonicRiver have accumulated in Woods Pond, a shallowimpoundment on the river located in Lenox, MA. Weused GC/ECD analysis to determine the PCB congenerdistributions in 181 sediment samples from 94 locationsin Woods Pond in order to learn which Aroclorswere originally present and whether there was evidenceof dechlorination. The congener distributions of allsamples showed the hexa-, hepta-, and octachloro-biphenyls (octa-CB) characteristic of Aroclor 1260,but key hexa- and hepta-CBs were decreased by asmuch as 45% relative to Aroclor 1260, and the tri-,tetra-, and penta-CBs were increased. GC/MSanalysisrevealed unusual tetra-, penta-, and hexa-CBs, manycontaining 2,4- and 2,4,6-chlorophenyl rings, whichare uncommon in higher Aroclors, and provided strongevidence of dechlorination. A quantitative mother−daughter analysis of key hexa- and hepta-CBs thatwere decreased relative to Aroclor 1260 and theirputative dechlorination products yielded mass balancesranging from 90 to 108%. The data indicate that thePCBs consist of partially dechlorinated Aroclors 1260and 1254 (∼95:5). Relative to Aroclor 1260, themostextensively dechlorinated samples had lost 11−19% ofthe meta chlorines and 2−7% of the parachlorines.This modest dechlorination caused a 20−28%decrease in the concentrations of the PCB congenersreported to be most persistent in humans.
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