Assessment of Natural Attenuation via in Situ Reductive Dechlorination of Polychlorinated Biphenyls in Sediments of the Twelve Mile Creek Arm of Lake Hartwell, SC

Abstract

Polychlorinated biphenyl (PCB)-contaminated sediment cores taken from five locations in Lake Hartwell, SC, with an increasing distance from the point source were evaluated for the presence of in situ reductive dechlorination of PCBs on the basis of a comparative congener-specific analysis of PCB distribution profiles between historical (1987) and current (1998) sediments from the same sites. A layer of 1998 sediment that was equivalent to 1987 sediment was determined by direct comparison of total PCB depth profiles after correction for any sedimentation that occurred at each location since 1987. Natural capping of contaminated sediments with the continued deposition of new sediments was observed in all locations except the one farthest from the source area. The residual PCB congeners accumulated in the field samples did not vary from site to site. Certain PCB congeners (e.g., 236-24 + 34-34, 245-25, and 23-4 CB) decreased with time and with depth along with an increase in lower chlorinated PCB congeners in all sampling locations. A similarity in distribution profiles between dechlorinated PCBs in laboratory microcosms and in the field samples was observed. These results provide supporting evidence that in situ reductive dechlorination has occurred in the Twelve Mile Creek arm of Lake Hartwell. Several sediment layers, particularlythe sites with highest PCB concentration, showed similar PCB distribution profiles between 1987 and 1998. An additional change in chlorine distribution between 1987 and 1998 at most "equivalent" depths was not observed. The ortho- and para-substituted congeners that accumulated during dechlorination of Aroclor 1254 after nearly 1 yr of incubation in the laboratory were the prominent residual products in all field samples. At a few locations and depths, evidence for dechlorination at surprisingly low concentrations (1-5 ppm) was observed. These results confirm that in situ reductive dechlorination of PCBs is operating at a very slow rate and may have been at a plateau since 1987 for certain depths and certain locations.

Biodiversity of Dehalorespiring Bacteria with Special Emphasis on Polychlorinated Biphenyl/Dioxin Dechlorinators

“…Microbial reductive dehalogenation of halogenated biphenyls as well as of other haloorganic compounds has been extensively studied using anaerobic sediment cultures and microcosms 17,23,28,33,74,78,94,100,101,130,134,137) . Most of the earlier reports provided little or no definitive information about dehalogenating microorganisms in the cultures in terms of quantity and quality.…”

Anaerobic degradation of Polychlorinated Biphenyls (PCBs) and Polychlorinated Biphenyls Ethers (PBDEs), and microbial community dynamics of electronic waste-contaminated soil

“…During dehalogenation process, the common electron donors include lactate, acetate and glucose (Rhee et al, 2003;Boyle et al, 1999). The metabolites are further degraded to non-toxic compounds by aerobic microorganisms (Bedard, 2003;Bedard et al, 2005;Boyle et al, 1999;Bzdusek et al, 2006a,b;Li et al, 2005Li et al, , 2012Magar et al, 2005a,b;Pakdeesusuk et al, 2005;Payne et al, 2013;Sanford et al, 1996;Yan et al, 2006). Dehalorespiration is critical for effective dehalogenation, and the effect of dissimilatory iron reduction on dehalogenation has been discussed (Li et al, 2008;Wu et al, 2010).…”

Advances and perspective in bioremediation of polychlorinated biphenyl-contaminated soils

“…Bioaugmentation of granular anaerobic methanogenic microbial consortium along with a suitable carbon source was successfully demonstrated (Nollet et al 2005). In this line, anaerobic dechlorination of PCBs has also been reported for various contaminated sites (Pakdeesusuk et al 2005). Macedo et al (2007) observed transformation of highly chlorinated PCB congeners as an effect of adaptation of microbial communities in contaminated soil.…”