Comparison of Vapor Concentrations of Volatile Organic Compounds with Ground-Water Concentrations of Selected Contaminants in Sediments beneath the Sudbury River, Ashland, Massachusetts, 2000
Open-File Report 02-143
By Jean P. Campbell, Forest P. Lyford, and Richard E. Willey
A mixed plume of contaminants in ground water, including volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), and metals, near the former Nyanza property in Ashland, Massachusetts, discharges to the Sudbury River upstream and downstream of Mill Pond and a former mill raceway. Polyethylene-membrane vapor-diffusion (PVD) samplers were installed in river-bottom sediments to determine if PVD samplers provide an alternative to ground-water sampling from well points for identifying areas of detectable concentrations of contaminants in sediment pore water near the ground-water and surface-water interface. In August and September 2000, the PVD samplers were installed near well points at depths of 8 to 12 inches in both fine and coarse sediments, whereas the well points were installed at depths of 1 to 5 feet in coarse sediments only.
Comparison between vapor and water samples at 29 locations upstream from Mill Pond show that VOC vapor concentrations from PVD samplers in coarse river-bottom sediments are more likely to correspond to ground-water concentrations from well points than PVD samplers installed in fine sediments. Significant correlations based on Kendall's Tau were shown between vapor and ground-water concentrations for trichloroethylene and chlorobenzene for PVD samplers installed in coarse sediments where the fine organic layer that separated the two sampling depths was 1 foot or less in thickness.
VOC concentrations from vapor samples also were compared to VOC, SVOC, and metals concentrations from ground-water samples at 10 well points installed upstream and downstream from Mill Pond, and in the former mill raceway. Chlorobenzene vapor concentrations correlated significantly with ground-water concentrations for 5 VOCs, 2 SVOCs, and 10 metals. Trichloroethylene vapor concentrations did not correlate with any of the other ground-water constituents analyzed at the 10 well points. Chlorobenzene detected by use of PVD samplers appears to be a strong indicator of the presence of VOCs, SVOCs, and metals in ground water sampled from well points at this site.
Results from PVD samplers indicate that contaminant concentrations
in water from well points installed 1 to 5 ft below fine sediments
may not reflect concentrations in pore water less than 1 foot
below the river bottom. There is insufficient information available
to determine if VOC concentrations detected in PVD samplers are
useful for identifying detectable aqueous concentrations of SVOCs
and metals in sediment pore water at this site. Samples of pore
water from a similar depth as PVD samplers are needed for confirmation
of this objective.
Description of Study Area
Polyethylene-Membrane Vapor-Diffusion Samplers
Construction of Samplers
Installation and Retrieval of Samplers
Analysis of Vapor Samples
Quality Assurance and Quality Control
Collection and Analysis of Ground-Water Samples
Quality-Assurance Results for Vapor Samples
Compounds Detected in Vapor Samples Upstream from Mill Pond
Comparison of Volatile Organic Compounds in Vapor and Ground-Water Samples
Comparison of Chemicals in Vapor and Ground-Water Samples
Assessment of Sampling Methods
Summary and Conclusions
1 through 3. Maps showing:
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Outside Cover--1 page (21 KB)
Inside Cover--2 pages (43 KB)
Contents--2 pages (62 KB)
Body of Report--33 pages (802 KB)
Whole Report--37 pages (774 KB)
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