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New Diffusion Samplers Track Contamination Entering Lakes and Ponds

Close up of diffusion sampler
Close-up of passive-vapor-diffusion sampler. Photo Credit: USGS

USGS scientists developed, tested, and demonstrated the effectiveness of a new passive-diffusion sampler to delineate where plumes of contaminants are discharging into ground-water-fed lakes and ponds. The diffusion samplers are composed of glass vials surrounded by a permeable membrane. They have many advantages over conventional ground-water sampling methods because they are made of readily accessible and inexpensive materials, are simple to deploy, and do not require time-consuming well purging procedures. The sampler is left in place long enough for contaminants dissolved in the ground water flowing past the sampler to diffuse through the membrane into the water enclosed in the vial; thus, concentrations inside and outside the sampler become equal. This provides a simple way to analyze ground water that is discharging to a river, lake, or other surface water body for the presence of selected contaminants.

Map of Snake Pond
Location of diffusion samplers in Snake Pond, Cape Cod, Massachusetts used to delineate contaminated ground-water discharge areas. Modified from WRIR 03-4133.

The samplers were recently deployed by USGS scientists to delineate where contaminated ground water is discharging to John's Pond and Snake Pond on Cape Cod, Massachusetts. The studies were conducted on separate plumes of solvents and explosive chemicals, demonstrating the broad applicability of the samplers. Delineating discharge areas is important for characterizing potential adverse effects on aquatic ecosystems. Organic contaminants often are biodegraded by microorganisms present in bottom sediments of lakes and ponds; delineating the discharge area enables scientists to understand and quantify these natural processes.

More Information

References

Church, P.E., Vroblesky, D.A., and Lyford, F.P., 2002, Guidance on the use of passive-vapor-diffusion samplers to detect volatile organic compounds in ground-water-discharge areas, and example applications in New England: U.S. Geological Survey Water-Resources Investigations Report 02-4186, 79 p.

Leblanc, D. R., 2003, Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, Massachusetts, 2001-02: U.S. Geological Survey Water-Resources Investigations Report 03-4133, 25 p.

Savoie, J.G., LeBlanc, D.R., Blackwood, D.S., McCobb, T.D., Rendigs, R.R., and Clifford, Scott, 2000, Delineation of discharge areas of two contaminant plumes by use of diffusion samplers, Johns Pond, Cape Cod, Massachusetts, 1998: U.S. Geological Survey Water-Resources Investigations Report 00-4017, 30 p.

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