MICROBIAL REDUCTIVE DECHLORINATION OF AROCLOR-1260 IN ANAEROBIC SLURRIES OF ESTUARINE SEDIMENTS

Reductive dechlorination of Aroclor 1260 was investigated in anaerobic slurries of estuarine sediments from Baltimore Harbor (Baltimore, Md. ). The sediment slurries were amended with 800 ppm Aroclor 1260 with a nd without the addition of 350 mu M 2,3,4,5-tetrachlorobiphenyl (2,3,4 ,5-CB) or 2,3,5,6-tetrachlorobiphenyl (2,3,5,6-CB) and incubated in tr iplicate at 30 degrees C under methanogenic conditions in an artificia l estuarine medium. After 6 months, extensive meta dechlorination and moderate ortho dechlorination of Aroclor 1260 occurred in all incubate d cultures except for sterilized controls. Overall, total chlorines pe r biphenyl decreased by up to 34%. meta chlorines per biphenyl decreas ed by 65, 55, and 45% and ortho chlorines declined by 18, 12, and 9%, respectively, when 2,3,4,5-CB, 2,3,5,6-CB, or no additional congener w as supplied. This is the first confirmed report of microbial ortho dec hlorination of a commercial polychlorinated biphenyl mixture. In addit ion, compared with incubated cultures supplied with Aroclor 1260 alone , the dechlorination of Aroclor 1260 plus 2,3,4,5-CB or 2,3,5,6-CB occ urred with shorter lag times (31 to 60 days versus 90 days) and was mo re extensive, indicating that the addition of a single congener stimul ated the dechlorination of Aroclor 1260.