Anaerobic microbial dechlorination of polychlorinated biphenyls

Abstract

The LCP Superfund site in Brunswick, Georgia, was extensively contaminated with Aroclor 1268, a mixture of highly chlorinated polychlorinated biphenyl (PCB) congeners. This study investigates whether the indigenous anaerobic bacterial communities in PCB-contaminated salt-marsh sediment can dechlorinate weathered Aroclor 1268. Batch cultures of the contaminated estuarine sediment were separately primed for dechlorination with 2,6-dibromobiphenyl and 2,3,4,5,6-pentachlorobiphenyl under anaerobic, sulfate-reducing conditions and incubated at 28oC at different pH values (5.5-7.5) for one year. Dechlorination of primer 2,3,4,5,6-pentachlorobiphenyl occurred via two routes with the loss of (1) meta then para chlorine atoms and of (2) para, ortho, then meta chlorine atoms leading to the accumulation of mono-, di- and trichlorobiphenyls. Extensive dehalogenation of primer 2,6-dibromobiphenyl resulted in a significant accumulation of biphenyl and a small proportion of mono-bromobiphenyl. Neither of the two primers induced dechlorination of native Aroclor 1268 congeners.