Enantiomeric composition of chiral polychlorinated biphenyl atropisomers in aquatic and riparian biota

The enantiomeric composition of polychlorinated biphenyl (PCB) atropisomers was measured in river and riparian biota (fish, bivalves, crayfish, water snakes, barn swallows) from selected sites throughout the United States by using chiral gas chromatography/mass spectrometry. Nonracemic enantiomeric fractions (EFs) were observed for PCBs 91, 95, 136, and 149 for aquatic and riparian biota from Lake Hartwell, SC, a reservoir heavily contaminated wi th PCBs, and for these congeners and PCBs 132, 174, 176, and 183 in river f ish and bivalves nationwide. Fish and bivalves showed marked differences in EFs as compared to sediment found at the same sampling sites, thus suggest ing that PCBs are bioprocessed in biota in a different manner from those fo und in sediment (e.g., reductive dechlorination). Species-dependent pattern s in PCB EFs were observed, which suggest differences in the ability of dif ferent species to bioprocess PCBs enantioselectively, most likely by metabo lism. The presence of nonracemic PCBs in fish and bivalves suggests greater metabolic degradation of PCBs in these organisms than indicated from previ ous achiral studies and underscores the powerful potential of chiral analys is as a tracer of environmental bioprocesses.