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WHFC Cooperative Dives in Snake Pond
Dann Blackwood, Barry Irwin, Rick Rendigs, and Mike Casso, members of the USGS WHFC dive team, were involved in a cooperative project with Denis Leblanc of USGS Water Resources Division (WRD), Northborough, MA, for determining the presence of ethylene dibromide (EDB) in sediments from Snake Pond in Sandwich, MA. This cooperative is part of a larger multi-year project, involving many agencies and organizations, to understand the geology, hydrology, and contamination of a major superfund site on Cape Cod. EDB, which is considered a carcinogen at low levels, has been detected in several well points below the pond bottom in an area where there should be no contaminants. Although the well is screened more than 40 ft below the pond bottom, ground water is discharging into the pond in the area and EDB could be entering the pond water. The concern is that the well where the chemical has been detected is near the swimming beach of the Camp Good News children's camp. The diffusion-sampling method was used to determine if EDB was discharging into the northern cove of the pond just off Camp Good News in Forestdale. The water-diffusion samplers were water-filled 4-mil polyethylene tubes enclosed in small wire cages. Volatile organic compounds (VOCs) dissolved in pore water diffuse through the polyethylene into the water in the sampler until equilibrium is reached. USGS divers buried 50 samplers about 0.5 ft into pond sediments on May 16th and 17th. These included column samplers installed at the water/sediment interface along with blanks and duplicate samplers at specific sites for determining any potential within-station variability. The samplers were set along nine lines that extended from 25 to 300 ft offshore. The lines were spaced about 150 ft apart and the ends of the lines were demarcated with GPS. The samplers were allowed to equilibrate and were retrieved on May 30th. The water samples were decanted into septum vials, chilled for preservation, and analyzed for EDB within 48 hrs at the Severn Trent on-site laboratory at the Massachusetts Military Reservation. The lab analysis indicated that EDB was not detected in any of the water-diffusion samplers, including the column samplers and the quality-assurance blanks.
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in this issue:
Southern California Academy of Sciences  |
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U. S. Department of the Interior | U.S. Geological Survey
cover story:
