Development and Application of Tools to Measure PCB Microbial Dechlorination and Flux into water During In-situ Treatment of Sediments
Investigators: Joel Baker, Kevin Sowers, Upal Ghosh
Duration: 2006-2009
Funding agency: Strategic Environmental Research and Developmental Program (DoD)

Summary. This research is quantifying the two most important long-term loss processes of PCBs in sediments: 1) microbial degradation and 2) diffusive and resuspension-related losses to the water column. These main PCB loss mechanisms from sediments depend upon the ease with which PCBs can partition between solid and porewater phases and may be impacted by in-situ remediation. Recent laboratory tests demonstrated that amendment of sediment with activated carbon results in large reductions in the bioaccumulation of PCBs by clams, worms, and amphipods. Two important question that are being addressed in this research are (1) how is natural PCB microbial dechlorination activity in sediment affected by the addition of activated carbon and (2) how is PCB mobility altered by the addition of activated carbon?

Competitive PCR and denaturing HPLC analyses together with an assay detecting potential PCB dechlorinating activities were combined with physical-chemical characterizations to identify factors affecting the reductive dechlorination of PCBs in the three historically impacted sediments: Grasse and Buffalo Rivers, NY and Anacostia River, DC. In Grasse River sediment an in situ enriched population consisting of Dehalococcoides phylotypes was abundant in high numbers together with a high dechlorination potential and a high concentration of congeners containing unflanked chlorine substitutions. In contrast microbial communities in Anacostia and Buffalo River sediments consisted of similar total numbers of dechlorinating bacteria, but the populations consisted of more diverse dechlorinating phylotypes and were associated with low dechlorination potentials and high concentrations of flanked congeners. Ongoing experiments are also evaluating the effects of activated carbon addition on the aerobic degradation of PCBs in the Grasse River sediment.

Publications:

Site specific microbial communities in three PCB-impacted sediments are associated with different in situ dechlorinating activities. B.V. Kjellerup, X. Sun, U. Ghosh, H.D. May, K.R. Sowers. Environ. Microbiol., 10, 1296-1309, 2008.