Reductive Dechlorination of Preexisting Sediment Polychlorinated Biphenyls With Long-Term Laboratory Incubation

Abstract

Abstract—The dechlorination potential of polychlorinated biphenyl (PCB)‐contaminated sediments from the St. Lawrence River was investigated in laboratory incubations over a 39‐month period. During the first 4 months, dechlorination reduced the average total chlorines in the General Motors 001 sediments from 3.2 to 2.5 per biphenyl, an additional 22% beyond the in situ level, for an overall 36% reduction from the original Aroclor 1248 contaminant. With continued incubation, however, an additional dechlorination of a single peak 2,4′,5+2,4,4′‐chlorobiphenyl ensued after a lag that reduced the average chlorines from 2.5 to 2.4. After this, there was no further transformation until the end of incubation. The extent of dechlorination and congener pattern of Aroclor 1248‐spiked sediments were similar to those of the native sediments after a comparable period of time despite differences in sediment sources and starting congener composition. The results indicate that most dechlorination occurs during a relatively short period of the initial rapid phase and any further transformation, if it occurs, would be extremely slow, and its contribution to the total dechlorination may not be significant.

Modeling polychlorinated biphenyl congener patterns and dechlorination in dated sediments from the Ashtabula River, Ohio, USA

“…Laboratory studies conducted on the reductive dechlorination of preexisting sediment PCBs (Aroclor 1248) [34] and Aroclor 1248 in spiked sediments [35] indicate that the dechlorination activity occurs in a relatively short period of time (four months [34] and 15 weeks [35]), after which very small or no change in congeners was observed. A similar situation could be possible in Ashtabula sediments, where a rapid dechlorination activity after PCB contamination may have helped create a certain dechlorination pattern, as observed in loading 2 of 2 (Fig.…”

Kinetics of polychlorinated biphenyl dechlorination and growth of dechlorinating microorganism

“…Although there is extensive evidence that PCBs in anaerobic sediments are reductively dechlorinated by microorganisms [2–8,12–14,17,18], information on these microorganisms themselves is scarce, mainly because they have not been isolated or characterized so far. In the absence of biochemical markers or molecular probes, the MPN technique is presently the only method available to investigate these populations.…”

“…The PCB congeners in the extract were identified and quantitated using a calibration standard containing a 1:1:1:1 mixture of Aroclors 1016, 1221, 1254, and 1260 (0.2 μg/ml of each in hexane). Peaks were identified and calibrated as previously described [4–6,8,12–14]. The analysis resolves 98 peaks representing 127 congeners.…”

Effect of aroclor 1248 concentration on the rate and extent of polychlorinated biphenyl dechlorination

“…The hexane extracts were treated with a tetrabutylammonium sulfite reagent to remove elemental sulfur [15] and cleaned up on a 4% deactivated Florisil column [2]. Congener‐specific PCB analysis was performed on a Hewlett‐Packard 5890 (Hewlett‐Packard, Avondale, PA, USA) gas chromatograph (GC) equipped with an electron‐capture detector, autosampler, splitless injector, 60‐m Rtx®‐5 capillary column (Restek, Bellefonte, PA, USA), and a computerized data acquisition system (Chrom Perfect, Justice Innovation, Mountain View, CA, USA), as previously described [2,10,16]. The PCB congeners in the extract were identified and quantitated using a calibrations standard containing a 1:1:1:1 mixture of Aroclors 1016, 1221, 1254, and 1260 (0.2 μg/ml in hexane).…”