Prominent chlorobornane residues in estuarine sediments contaminated with toxaphene

Soils and sediments contaminated with residues of technical toxaphene may r equire remedial action to reduce human health and ecological risks. Sedimen ts were collected from a coastal wetland impacted by discharge from a forme r toxaphene production facility and analyzed by gas chromatography-electron capture detection and conventional and enantioselective gas chromatography -mass spectrometry in the electron capture negative ion mode. The prominent chlorobornanes (CHBs) in all samples were 2-exo,3-endo,6-exo,8,9,10-hexach lorobornane (B6-923 or Hx-Sed) and 2-endo,3-exo,5-endo,6-exo,8,9,10-heptach lorobornane (B7-1001 or Hp-Sed), metabolites of higher chlorinated componen ts of technical toxaphene (CTTs). Pentachlorobornanes, toxaphene homologs n ot previously reported in environmental samples, and likely precursor CTTs were also detected. Several CHB congeners were enantioresolved, the majorit y of which exhibited racemic composition. These results indicate that the p rofile of CHBs persisting in estuarine sediment is highly modified relative to the technical mixture, and also provides strong evidence of in situ red uctive dechlorination, a process that if enhanced could act to reduce bioac cumulation and toxicity of sediment-bound CTTs at toxaphene-contaminated si tes.