R.C. Sokol, C.M. Bethoney and G-Y. Rhee

School of Public Health, State University of New York at Albany and Wadsworth Center, NYS Department of Health, Albany, NY, 12201-0509, E-MAIL


Our previous study of St. Lawrence River sediments showed evidence for a varying degree of in situ dechlorination at all sites except the Reynolds 001 site. The absence of dechlorination at this site seemed due mainly to the presence of a "tar-like" non-aqueous phase liquid (NAPL) associated with PAH co-contamination, since PAHs themselves, at concentrations comparable to ambient levels, did not inhibit dechlorination in laboratory experiments. When river sediments were anaerobically incubated in the laboratory for 17 months, dechlorination continued in sediments from the General Motors (GM) site; it was rapid during the first 4 months, but leveled off with little further dechlorination up to 17 months. The average number of Cl's per biphenyl decreased approximately 14% from 3.0 before incubation to 2.6, (or an overall 32% reduction from the original Aroclor 1248). When GM sediment microorganisms were inoculated into PCB-free Grasse River sediments spiked with Aroclor 1248, dechlorination was similar. Thus, the residual PCB level in these sediments may represent the potential limit of in situ dechlorination. The dechlorination products were comprised mostly of dichloro- (66 mol%), trichloro- (24%) and tetrachloro- (10%) congeners. In contrast, river sediments from the Reynolds site did not show any further dechlorination under laboratory incubation. However, the Aroclor-1248-spiked sediments inoculated with Reynolds-site microorganisms showed dechlorination similar to that found with GM microorganisms in the same sediments. These results demonstrated that despite little in situ dechlorination, Reynolds sediments contained competent microorganisms and their overall dechlorination competence seemed to be similar to that of GM populations when compared in the same type of sediments. Taken together, however, the present study shows that in situ can vary widely depending on the prevailing sediment conditions.


polychlorinated biphenyls (PCBs), reductive dechlorination, bioremediation

This paper is from the Proceedings of the 10th Annual Conference on Hazardous Waste Research 1995, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.