Evaluation of Passive Diffusion Bag Samplers,
Dialysis, Samplers, and Nylon-Screen Samplers
in Selected Wells at Andersen Air Force Base, Guam, March-April 2002
By Don A. Vroblesky, Manish Joshi, Jeff Morrell, and J E. Peterson
Water-Resources Investigation Report 03-4157
By
Don A. Vroblesky1, Manish Joshi2, Jeff Morrell3, and J E. Peterson4
Prepared in cooperation with the
AIR FORCE CENTER FOR ENVIRONMENTAL EXCELLENCE
1U.S. Geological Survey, Columbia, South Carolina 2Earth Tech, San Antonio, Texas 3EA Engineering, Science, and Technology, Inc, Yigo, Guam 4Earth Tech, Alexandria, Virginia
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.
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.
2-6. Graphs showing borehole-flowneter data under nonpumped and pumped conditions, approximate water-yielding
zones during pumping, and trichloroethene concentrations in dialysis samples, passive diffusion bag samples,
and pumped samples at:
2. Well IRP-3, Main Base, Andersen Air Force Base, Guam, April 2002
3. Well IRP-39, Main Base, Andersen Air Force Base, Guam, April 2002
4. Well IRP-51, Main Base, Andersen Air Force Base, Guam, April 2002
5. Well IRP-29, MARBO Annex, Andersen Air Force Base, Guam, April 2002
6. Well IRP-31, MARBO Annex, Andersen Air Force Base, Guam, April 2002
7-9. Graphs showing:
7. Comparison of trichloroethene concentrations in passive diffusion bag and dialysis samples to
trichloroethene concentrations in pumped samples, Main Base and MARBO Annex, Andersen
Air Force Base, Guam, April 2002
8. Comparison of tetrachloroethene concentrations in passive diffusion bag and dialysis samples to
tetrachloroethene concentrations in pumped samples, Main Base and MARBO Annex, Andersen
Air Force Base, Guam, April 2002
9. Chloride concentrations in nylon-screen, dialysis, and pumped samples at well IRP-29, MARBO Annex,
Andersen Air Force Base, Guam, April 2002
