Volatilization of extensively dechlorinated polychlorinated biphenyls from historically contaminated sediments

A study was conducted as a preliminary characterization of the ability of Aroclor(R) 1248 polychlorinated biphenyl (PCB)-contaminated sediments to volatilize PCBs into the air upon drying under conditions meant to be environmentally relevant. Sediments collected from the St. Lawrence River contained high levels (similar to 600 ppm) of PCBs. The PCB contamination consisted of high levels of mainly ortho-substituted mono- and dichlorobiphenyls, suggesting that the original contamination had been transformed by microbial reductive dechlorination. These sediments lost 0.07 to 1.7% of their total PCB content to the air during a 24-h drying cycle. Sediments with varying amounts of overlying water (40 g of sediment with 25-100 ml of water) lost significantly less PCB to the air within the first few cycles than native sediments with no overlying water. Losses due to PCB volatilization were well correlated to sediment PCB concentration and water loss but not to drying temperatures (4-43 degrees C) within 24-h drying cycles. The PCB congeners (mostly ortho-substituted mono-, di-, and trichlorobiphenyls) representing >90% of those volatilized within the first 24 h of drying were those produced in the sediment samples as a result of microbial reductive dechlorination of the original Aroclor 1248 contamination. The presence of these congeners in volatilized air samples was positively confirmed by gas chromatography-mass spectrometry with Fourier transform infrared detection (FTIR). These results strongly suggest that significant amounts of mono-, di-, and trichlorobiphenyls may be volatilized from Aroclor 1248-contaminated sediments at ambient environmental conditions and that this PCB volatilization may be enhanced by microbial reductive dechlorination.