Long-Term Recovery of PCB-Contaminated Sediments at the Lake Hartwell Superfund Site: PCB Dechlorination. 2. Rates and Extent
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- 作者：Victor S. Magar ; Richard C. Brenner ; Glenn W. Johnson ; and John F. Quensen ; III
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：May 15, 2005
- 年：2005
- 卷：39
- 期：10
- 页码：3548 - 3554
- 全文大小：541K
- 年卷期：v.39,no.10(May 15, 2005)
- ISSN：1520-5851
文摘
This paper reports on extensive polychlorinated biphenyl(PCB) dechlorination measured in Lake Hartwell (PickensCounty, SC) sediments. Vertical sediment cores were collectedfrom 18 locations in Lake Hartwell (Pickens County, SC)and analyzed in 5-cm increments for PCB congeners. Thepreferential loss of meta and para chlorines with sedimentdepth demonstrated that PCBs in the sediments underwentreductive dechlorination after burial. Notably, orthochlorines were highly conserved for more than 5 decades;since the first appearance of PCBs, ca. 1950-1955.These dechlorination characteristics resulted in theaccumulation of lower chlorinated congeners dominatedby ortho chlorine substituents. Dechlorination rates weredetermined by plotting the numbers of meta plus para chlorinesper biphenyl molecule (mol of chlorine/mol of PCB) withsediment age. Regression analyses showed linear correlationsbetween meta plus para chlorine concentrations withtime. The average dechlorination rate was 0.094 ± 0.063mol of Cl/mol of PCB/yr. The rates measured using the 2001cores were approximately twice those measured usingthe 2000 cores, most likely because the 2001 cores werecollected only at transects O, L, and I, which had the highestrates measured in 2000. An inverse of the dechlorinationrates indicated that 16.4 ± 11.6 yr was required per meta pluspara chlorine removal (ranging from 4.3 to 43.5 yr perchlorine removal). The rates determined from this studywere 1-2 orders of magnitude lower than rates reportedfrom laboratory microcosm studies using Hudson Riverand St. Lawrence River sediments, suggesting thatdechlorination rates reported for laboratory experimentsare much higher than those occurring in situ.