Distribution of PCB Congeners in Sheboygan River (Wisconsin) Sediments

2005

Environ. Sci. Technol.

Nine sediment cores were collected from the Sheboygan River Inner Harbor, WI, and analyzed for polychlorinated biphenyl (PCB) congeners. Total PCBs ranged from approximately 0 to 161 mg/g. Positive matrix factorization (PMF) was applied to the PCB data setto determine source profiles. Two factors were determined to be significant. One factor resembled the original approximated PCB mixture of 50% Aroclor 1248 and 50% Aroclor 1254 and the other factor was a dechlorinated version of the mixture. An anaerobic dechlorination model was applied to the dechlorinated source profiles to quantify possible dechlorination pathways. It was found that dechlorination process H' provided the best fit for an individual process, and H' + M provides the best fit for combined processes. PMF source contributions, and plots of PCB concentration versus congener for individual samples, provide evidence of enhanced dechlorination at high concentrations (>40 ppm) and small amounts of dechlorination at low concentrations (<3 ppm). In addition, downward migration of lower chlorinated PCBs in core SR1a has occurred. Remediation dredging in the Upper Sheboygan River in 1989 and 1990 reintroduced PCBs to the water column and selective transport of PCB 18 is observed in core SR7.

Section: Introductionmentioning

confidence: 99%

PCB Congeners and Dechlorination in Sediments of Sheboygan River, Wisconsin, Determined by Matrix Factorization

2005

Environ. Sci. Technol.

“…This monitored natural attenuation can benefit from weathering of the PCBs through biological and phys icochemical processes. Modeling of key weathering processes such as anaerobic dechlorination of PCBs, which has been documented for several contaminated sites, such as the Sheboygan River, Fox River, Hudson River, Ashtabula River, Silver Lake, and Woods Pond ( − ), can improve our understanding of the critical mechanisms for decreasing risk. Anaerobic dechlorination is an important process for removing predominantly meta or para chlorines from higher chlorinated congeners to create more di-, tri-, and tetrachlorobiphenyls, which are generally less toxic and aerobically degradable ( − ).…”

Section: Introductionmentioning

confidence: 99%

PCB Congeners and Dechlorination in Sediments of Lake Hartwell, South Carolina, Determined from Cores Collected in 1987 and 1998

Lee

et al. 2005

Environ. Sci. Technol.

Four sediment cores were collected from Lake Hartwell, SC, in 1987 and 1998 and analyzed for polychlorinated biphenyl (PCB) congeners. Total PCBs ranged from -0 to 58 microg/ g. Positive matrix factorization (PMF) was applied to the data sets to determine PCB source profiles. Two factors were determined for each data set. One factor resembled the original estimated PCB mixture of 80% Aroclor 1016 and 20% Aroclor 1254 and the other factor was a dechlorinated version of the mixture. Evidence of a dechlorination plateau is apparent from the PMF loading solutions because the dechlorinated congener profiles do not change from 1987 to 1998, butthe contribution to the profile from the dechlorinated factor increases from 73% (1987) to 87% (1998). PMF source contributions and plots of PCB concentration versus congener for individual samples provide evidence of enhanced dechlorination at high concentrations. After source apportionment an anaerobic dechlorination model was applied to the dechlorinated source profiles to quantify possible dechlorination pathways. It was found that dechlorination process M, extended to target biphenyl rings with up to six chlorines, provided the best fit for an individual process, and M + Q provides the best fit for combined processes, although M + LP also provides a similarfit. Process LP targets the higher chlorinated congeners and appears to dechlorinate PCBs in the sediments initially.

“…Tecumseh is believed to be a primary source of PCB contamination. Tecumseh used hydraulic fluids containing PCBs from 1959 to 1971 and only Aroclors 1248 and 1254 were used [ David et al , 1994].…”

Section: Study Areamentioning

confidence: 99%

Evidence of fine‐grained sediment transport and deposition in Sheboygan River, Wisconsin, based on sediment core chemical tracer profiles

Water Resources Research

2005

Fine‐grained sediment transport and deposition is observed in nine dated sediment cores obtained from the Sheboygan River. The sediment cores were dated by 137Cs and 210Pb methods. Sediment dating was supported by a polychlorinated biphenyl (PCB) analysis and U.S. Army Corps of Engineers (USACE) hydrographic surveys from 1976 to 2002. Plots of 137Cs activity versus depth show distinct peaks related to peak Sheboygan River discharges in the years 1966, 1975, 1979, and 1989. These peaks result from the scouring of sediments during storm discharges and the increased deposition of the fine‐grained fraction of particles, including colloidal clay particles (associated with 137Cs and, to some extent, PCBs), in place of the scoured sediments. Core SR1a, upstream of the Pennsylvania Avenue Bridge, and cores SR5‐SR8, farther downstream, show continuous sedimentation (1.2–11.8 cm/yr) since the late 1950s, whereas net sediment accumulation virtually ceased after 1988 at the intermediate sites of cores SR1–SR4. The maximum PCB concentration (161 ppm) occurs in 1969 in core SR4.