ANAEROBIC ORTHO DECHLORINATION OF POLYCHLORINATED-BIPHENYLS BY ESTUARINE SEDIMENTS FROM BALTIMORE HARBOR

Reductive dechlorination of the ortho moiety of polychlorinated biphen yls (PCBs) as well as of meta and para moieties is shown to occur in a naerobic enrichments of Baltimore Harbor sediments, These estuarine se diments ortho dechlorinated 2,3,5,6-chlorinated biphenyl (CB), 2,3,5-C B, and 2,3,6-CB in freshwater or estuarine media within a relatively s hort period of 25 to 44 days, ortho dechlorination developed within 77 days in marine medium. High levels of ortho dechlorination (>90%) occ urred when harbor sediments were supplied with only 2,3,5-CB, Incubati on with 2,3,4,5,6-CB or 2,3,4,5-CB resulted in the formation of the or tho dechlorination product 3,5-CB; however, para dechlorination of the se congeners always preceded ortho chlorine removal, ortho dechlorinat ion of PCBs is an exceedingly rare event that has not been reported pr eviously for marine or estuarine conditions, The activity was reproduc ible and could be sustained through sequential transfers, In contrast, freshwater sediments incubated under the same conditions exhibited on ly meta and pam dechlorinations, The results indicate that unique anae robic dechlorinating activity is catalyzed by microorganisms in the es tuarine sediments from Baltimore Harbor.