MICROBIAL REDUCTIVE DECHLORINATION OF TRICHLOROBIPHENYLS IN ANAEROBIC SEDIMENT SLURRIES

To understand how the number and arrangement of chlorines on a phenyl ring affect polychlorinated biphenyl (PCB) dechlorination, anaerobic microbial reductive dechlorination of six trichlorobiphenyls is characterized by the acclimation time before dechlorination and the sequence of chlorine removal. Each of the six trichlorobiphenyls with all chlorines on one phenyl ring was incubated at 22-25 degrees C in slurries of PCB-contaminated sediment from the Hudson River (NY), Silver Lake (MA), and Woods Pond (MA). In each slurry, the chlorine between the other two chlorines on the phenyl ring Was usually removed from the trichlorobiphenyl first. Approximately the same acclimation time (3 weeks) and dechlorination sequences were observed in every slurry for trichlorobiphenyls with adjacent meta and para chlorines. All meta and para but no ortho chlorines were removed in Hudson River sediment slurries. Generally only one meta or para chlorine was removed in Silver Lake and Woods Pond sediment slurries, leaving a terminal, dichlorobiphenyl dechlorination product. However, ortho-dechlorination of 2,4,6-trichlorobiphenyl occurred in the Woods Pond and Silver Lake samples. The results indicate that the sediments share some microbial PCB dechlorination characteristics, but the differences probably indicate several, distinct, microbial populations.