Characterization and fate of polychlorinated biphenyl contaminants in Kernaalanjärvi sediments

Polychlorinated biphenyl (PCB) content and distribution of individual PCB congeners in sediment samples from Kernaalanjärvi, a lake in Finland, were determined with a gas chromatography-electron/capture detection (GC-ECD) technique. Three different extraction methods with hexane–acetone mixture were tested. Neither extended extraction time (1 day vs. 10 days) nor sonication increased the recovery of PCBs from the aged sediments. For freshly spiked PCBs the extraction efficiency was 93% ± 2% (w/w). Total PCB concentrations ranging from 0.5 to 10.7 mg kg–1 d.w. were measured in Kernaalanjärvi sediment samples from the 2–15 cm depth. Comparison of PCB discharge documentation to congener distribution patterns in sediments suggested selective removal of lower chlorinated PCBs by physical processes. There was no evidence of in situ biotransformations of PCBs by indigenous sediment microorganisms. Presence of potentially toxic mono- and di-ortho chlorinated coplanar PCBs in sediments resulted in estimated 2,3,7,8-TCDD (tetrachlorodibenzo-p-dioxin) toxic equivalents between 15 and 301 ng kg–1 d.w.