ANAEROBIC DECHLORINATION OF PCBs IN SEDIMENTS OF KINNICKINNIC RIVER, WISCONSIN

1 INTRODUCTION Polychlorinated biphenyls (PCBs) have been used for several decades in a variety of industrial applications such as for transformers, capacitors, and hydraulic fluids (Rachdawong and Christensen, 1997). Because of their stability and desirable hydraulic and dielectric properties, PCBs were used extensively. However, later it became clear that they can be toxic and can have deleterious reproductive effects on biota and humans. They may also display dioxin-like toxicity…

ANAEROBIC DECHLORINATION OF PCBs IN SEDIMENTS OF KINNICKINNIC RIVER, WISCONSIN

Six vibra cores of 1.80 3.15 m length, collected in 1994 from the Kinnickinnic River, Wisconsin, were examined for indications of anaerobic PolyChlorinated Biphenyl (PCB) dechlorination. The cores were previously dated using 210Pb and 137Cs and analyzed for several PCB congeners. The PCB analysis was carried out after Soxhlet extraction, Kuderna-Danish (K-D) volume reduction and silica gel chromatographic cleanup. Purified extracts were injected into a DB-5 column of a Hewlett-Packard (HP) 5890 gas chromatograph with electron capture detector. Overall PCB concentrations were 0.15 45 ppm (dry weight basis). Measured values of congeners with International Union of Pure and Applied Chemistry (IUPAC) numbers 5, 29, 44, 52, 87, 101, 118, 138, 153, and 180 (marker congeners) were used in the dechlorination analysis. Modeling of dechlorination involves the following steps. First, an overall average congener profile (nmoles/g) is generated based on all samples. This profile is then subjected to chemical mass balance modeling to estimate the contribution of Aroclors 1242, 1254, and 1260, and a calculated congener profile (mole %) is created by adding the contributions of each. Simulation of dechlorination reactions that involve at least one of the above marker congeners is then carried out on the calculated profile until the fit between calculated and measured concentrations of marker congeners is optimal as indicated by a least-squares criterion. Overall, mild dechlorination of the PCBs was found, by reactions such as #138(234-245)#87(234-25), #180(2345-245) #153(245-245), #44(23-25)#18(25-2), and #22(23-4)#5(23), where # signs indicate congener numbers. The significance of the dechlorination products #87 and #5 is confirmed by factor analysis.