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Water-Resources Investigation Report 03-4157

Evaluation of Passive Diffusion Bag Samplers, Dialysis, Samplers, and Nylon-Screen Samplers in Selected Wells at Andersen Air Force Base, Guam, March-April 2002

U.S. Geological Survey Water-Resources Investigation Report 03-4157, 29 pages (Published 2003)

By Don A. Vroblesky1, Manish Joshi2, Jeffrey Morrell3, and J E. Peterson4


1U.S. Geological Survey, Columbia, South Carolina
2Earth Tech, San Antonio, Texas
3EA Engineering, Science, and Technology, Inc, Yigo, Guam
4Earth Tech, Alexandria, Virginia

This report is available online in pdf format (1 MB): USGS WRIR 03-4157


Cover of WRIR 03-4157.

During March-April 2002, the U.S. Geological Survey, Earth Tech, and EA Engineering, Science, and Technology, Inc., in cooperation with the Air Force Center for Environmental Excellence, tested diffusion samplers at Andersen Air Force Base, Guam. Samplers were deployed in three wells at the Main Base and two wells at Marianas Bonins (MARBO) Annex as potential ground-water monitoring alternatives. Prior to sampler deployment, the wells were tested using a borehole flowmeter to characterize vertical flow within each well. Three types of diffusion samplers were tested: passive diffusion bag (PDB) samplers, dialysis samplers, and nylon-screen samplers. The primary volatile organic compounds (VOCs) tested in ground water at Andersen Air Force Base were trichloroethene and tetrachloroethene. In most comparisons, trichloroethene and tetrachloroethene concentrations in PDB samples closely matched concentrations in pumped samples. Exceptions were in wells where the pumping or ambient flow produced vertical translocation of water in a chemically stratified aquifer. In these wells, PDB samplers probably would be a viable alternative sampling method if they were placed at appropriate depths. In the remaining three test wells, the trichloroethene or tetrachloroethene concentrations obtained with the diffusion samplers closely matched the result from pumped sampling.

In all of the tests, the regenerated cellulose dialysis samplers produced lower VOC concentrations than the passive diffusion bag samplers and most of the pumped results. The source of the difference is unknown, but a possible explanation may be the biodegradation of the dialysis membrane during the 22 to 23 days of deployment.

Chloride concentrations in nylon-screen samplers were compared with chloride concentrations in dialysis and pumped samples to test inorganic-solute diffusion into the samplers across a range of concentrations. The test showed that the results from nylon-screen samplers might have underestimated chloride concentrations at depths with elevated chloride concentrations. The reason for the discrepancy in this investigation is unknown, but may be related to nylon-screen-mesh size, which was smaller than that used in previous investigations.




Site Description



Borehole-Flowmeter Surveys

Diffusion Sampler Construction and Deployment

Water-Sample Collection and Diffusion-Sampler Recovery

Results and Discussion

Distribution of Ground-Water Flow in Wells

Comparison of Trichloroethene and Tetrachloroethene Concentrations in Passive Diffusion Bag Samples and Pumped Samples

Comparison of Passive Diffusion Bag Samples to Dialysis Samples

Comparison of Chloride in Nylon-Screen Samples, Dialysis Samples, and Pumped Samples

Practical Considerations for the Use of Passive Diffusion Bag Samplers in Wells at Andersen Air Force Base

Summary and Conclusions



This report is available online in pdf format (1 MB): USGS WRIR 03-4157
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