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PERFORMANCE OF A NEW PASSIVE DIFFUSION SAMPLER FOR MONITORING BENZENE IN EITHER SOIL GAS OR GROUND WATER
Citation:
PAUL, C. J., K. P. JEWELL, J. T. WILSON, AND R. SHARMA. PERFORMANCE OF A NEW PASSIVE DIFFUSION SAMPLER FOR MONITORING BENZENE IN EITHER SOIL GAS OR GROUND WATER. Presented at The 19th Annual National Tanks Conference and Expo, San Antonio, TX, March 05 - 07, 2007.
Impact/Purpose:
To inform the public.
Description:
Understanding transport of volatile contaminants in soil gas and ground water, particularly those associated with underground storage tanks, requires a detailed knowledge about the depth-dependent distribution of chemical species in the subsurface. A risk assessment of the movement of vapors of volatile organic contaminants from ground water through the unsaturated zone and into living spaces usually involves a transport and fate model such as the Johnson and Ettinger model. The concentration of volatile organic contaminants in groundwater is needed to calibrate these models. EPA recommends that ground water samples should be obtained from the uppermost portions of the ground water and/or capillary fringe (Appendix G of EPA OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway, November, 2002). Historically, samples have not been obtained from these zones. Generally, water samples have been acquired from conventional wells screened across the water table. A conventional well produces a composite sample. The average concentration across the screened interval may not be representative of the concentration at the top of the aquifer or in the capillary fringe. The passive diffusion sampler (PDS) is an alternative to conventional wells. PDS were used at a field site in Madison, WI to evaluate their effectiveness outside the laboratory.