Comparisons of PCBs dechlorination occurrences in various contaminated sediments

A comparison was made of reductive dechlorination occurrences of polychlorinated biphenyls (PCBs) by microorganisms collected from contaminated sediments including Er-Jen River (Tainan, Taiwan), Hudson River (Ft. Edward, NY), Silver Lake (Pittsfield, MA) and Puget Sound (Washington State). Comparisons was made in terms of chromatographic data (referring to the biological activity, including microbial availability) and thermodynamic data (demonstrating the selectivity of anaerobic microorganisms in the dechlorination of chlorinated compounds). Chromatographic data was established in terms of difference in relative retention time (Δln RRT) and thermodynamic data was estimated as heat of reaction (ΔHr0). Both were calculated and correlated to occurrences of dechlorination reactions. Observed dechlorination reactions for individually introducing PCB congener had Δln RRT levels measured as >0.47 (Er-Jen River), >0.29 (Hudson River), >0.36 (Silver Lake) and >0.45 (Puget Sound, for Aroclor 1254 dechlorination). Critical of ΔHr0 and Δln RRT values showed that Hudson River and Silver Lake microorganisms were capable of dechlorinating PCBs through reactions with larger Hr0 value (lower levels of released energy) and smaller Δln RRT value compared with those found in Er-Jen River and Puget Sound sediments. Differences in the critical Δln RRT values of these sediments may be due to differences in their levels of PCB contamination.