FACTORS INFLUENCING THE RATE OF POLYCHLORINATED BIPHENYL DECHLORINATION IN HUDSON RIVER SEDIMENTS

The altered distribution of polychlorinated biphenyls (PCBs) observed in aquatic sediments due to anaerobic microbial activity displays a depletion of highly chlorinated PCB congeners with corresponding increases in the lower chlorinated PCBs. Laboratory experiments demonstrated PCB dechlorination over a broad range of PCB concentrations (20-1500 ppm) and conditions. The observed rate of anaerobic PCB dechlorination in Hudson River, NY, sediments was most significantly affected by PCB sediment concentrations in both laboratory experiments and in the environment. Therefore, these laboratory observations are consistent with the extent of PCB dechlorination occurring naturally in Hudson River sediments and other aquatic sediments. Additions of various nutrients and surfactants resulted in inhibition or only minor (2-fold) rate accelerations compared to unamended sediments. The addition of vitamin B-12 inhibited PCB dechlorination rates 3-fold with an apparent K(i) of 100 mug/L. Dechlorination of aged PCBs occurred at rates comparable (80%) to that of freshly spiked material.