Impact/Purpose:

Complete Superfund NPL and removal cleanups using efficient cost effective monitoring and assesssment tools.

Description:

Many water bodies in New England are impacted by volatile organic contaminated groundwater intrusions. To determine the health and ecological impacts of these intrusions, it is important to locate fracture zones that transport groundwater contaminated with volatile organic compounds into surface water, delineate the extent of contamination, and define concentration gradients within the contamination plume. To help define these transport zones, EPA-NE and USGS have developed and employed passive vapor diffusion samplers. Passive vapor diffusion monitors provide a low cost simple technique to locate volatile organic plume discharges into rivers, lakes, water supplies, and tidal areas in New England. Passive vapor diffusion samplers consist of an uncapped VOA vial located inside a polyethylene bag, and operate on the principal that volatile organic compounds (VOCs) in the groundwater/surface water interface will partition and diffuse through the semipermeable membrane (polyethylene bag) until concentrations in the air inside the vapor diffusion samplers reach equilibrium with concentrations of VOCs in the environment outside the sampler. Samplers are placed into the water body bottom sediment about 6-12 inches deep, with the VOA vial mouth pointed down, and left to equilibrate over a one to two week time period. Samplers can then be retrieved, capped, and rapidly analyzed using gas chromatography. Typically 100B200 diffusion samplers are placed in the study area to get a clear picture of where contamination plumes are located. Placement can be done by statistically gridding the area or by probing the sediments to find temperature variation that indicate ground water up-we

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