A Diffusive Sampler for Passive Monitoring of Underground Storage Tanks |
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| Authors: | Kenneth E. Karp |
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| Affiliation: | As a project manager for Chem-Nuclear Geotech Inc., at the U.S. Department of Energy (DOE) Grand Junction Projects Office, Kenneth Karp (Chem-Nuclear Geotech Inc., U.S. Department of Energy, Grand Junction Projects Office, P.O. Box 14000, Grand Junction, CO 81502) is responsible for managing all resources and activities associated with hazardous waste site investigations. He has developed new analytical methods to monitor and characterize hazardous waste in the vadose zone and ground water at U.S. Air Force and DOE sites. Prior to his current position, Karp worked at the GJPO as a geologist for the National Uranium Resource Evaluation program and the Technical Measurements Center. |
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| Abstract: | Passive measurements of volatile organic compounds (VOCs) provide a method for early detection and long-term monitoring of potential leaks from underground storage tanks (USTs) and associated fuel service lines. A diffusive sampler was constructed of a sorbent tube that fits inside a specially designed sampling chamber. VOCs in the soil enter the chamber by molecular diffusion and are collected by the sorbent. The sorbent is easily retrieved for laboratory analyses by thermally desorbing into a gas chromatograph/mass spectrometer (GC/MS), or qualitative concentrations can be determined directly in the field with specific-indicator detectors.
The diffusive samplers were evaluated in an exposure chamber under controlled conditions. Laboratory measurements of the sorbed mass of organic vapor were found to be in close agreement with theoretical values and indicate the passive sampling approach is viable for detecting relatively low concentrations of organic vapors in the vadose zone over a one-day sampling period, as well as providing relatively long-term monitoring periods up to 58 days. A field test found the sampling approach successful in identifying an area where the vadose zone was contaminated by leaking petroleum USTs. |
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