onto glass is another possible explanation, but
low carbonate levels. Confinement of samples in
appears unlikely in light of the stability of this
vaportight vessels throughout handling and anal-
analyte in glass ampoules for the experiment with
ysis procedures is critical to the accurate assess-
an equilibration period (Table 6).
ment of both biological degradation and chemical
Furthermore, these losses are analyte specific
preservation of VOCs in soil. Using such proto-
and are likely to be condition dependent (i.e., stor-
cols allows investigators to determine if measures
age temperature); thus more detailed studies are
other than refrigeration are necessary or effective
warranted. Until such information is available,
in maintaining stable VOC concentrations over
we recommend that even chemically preserved
regulated holding times.
samples be stored refrigerated.
The soil in this study was obtained within 10
LITERATURE CITED
cm of the ground surface. In this horizon there is
typically more organic carbon and consequently
Atlas, R.M. (1981) Microbial degradation of pe-
more biological activity, as compared to soils ob-
troleum hydrocarbons: An environmental perspec-
tained from greater depths in the vadose zone.
tive. Microbiological Reviews, 45: 180209.
However, substantial evidence exists showing that
Barbeau, D.S., T.G. Ellis and C.P.L. Grady, Jr.
even subsurface soils with organic carbon of less
(1995) Oxygen leakage during respirometric mea-
than 0.5% become biologically active once oxy-
surement: A caution on the use of PTFE tape. Wa-
genated. Hence in-situ aeration systems are being
ter Resources, 29(4) 12111212.
developed to enhance bioremediation of subsur-
Chiou, C.T. (1989) Reactions and Movement of Or-
face oil and gasoline spills (Downey et al. 1994,
ganic Chemical in Soils (B.L. Sawhney and K. Brown,
Germann and Friesen 1994). Since all convention-
Eds.). Madison, Wisconsin: Soil Science Society of
al sampling methods expose soil samples to the
America, Special Publication 22, p. 129.
atmosphere during collection and handling opera-
Downey, C.D., P.R. Guest and J.W . Ratz (1994)
tions, previously oxygen limited biodegradation
Results of a two-year in situ bioventing demon-
reactions could be initiated. For this reason chem-
stration. In Proceedings of the 18th Annual Army
ical preservation is likely to be necessary when-
Environmental Technology Symposium, Williamsburg,
ever aromatic hydrocarbons are of concern.
Virginia, June, p. 223234.
With regard to whether a slurry condition is
Germann, G.G. and K. Friesen (1994) Pilot test
needed to evenly distribute the preservative, an
for integrated in situ and ex situ bioremediation
earlier experiment where 1 mL of water was add-
of petroleum-contaminated soil at a fuel storage
ed to preserved soil ampoules before spiking to
facility in Virginia. In Proceedings of the 18th Annu-
slurry the soil matrix (Hewitt 1995b) was not sig-
al Army Environmental Technology Symposium, Wil-
nificantly different (95% confidence level) from
liamsburg, Virginia, June, p. 215222.
those without excess water. However, laboratory-
Gilham, R.W . and S.F. O'Hannesin (1990) Sorp-
treated soil does not mimic the cohesiveness of a
tion of aromatic hydrocarbons by materials used
native soil. Until more information is available, a
in construction of ground-water sampling wells.
conservative approach should be recommended.
In Ground Water and Vadose Zone Monitoring, ASTM
Therefore, enough water should be present in the
STP 1053, p. 108122. Philadelphia, Pennsylva-
VOA vial to create a slurry condition, once the
nia: American Society for Testing and Materials.
soil sample has been introduced. Furthermore,
Hewitt, A.D. (1995a) Preservation of volatile or-
preservation methods that would not rely on acid-
ganic compounds in soil subsamples. American
ification (i.e., mercuric chloride) would be neces-
Environmental Laboratory, August.
sary when carbonates were present.
Hewitt, A.D. (1995b) Determining volatile organ-
ic compound concentration stability in soil. In Pro-
ceedings of 11th Annual Waste Testing and Quality
CONCLUSION
Assurance Symposium, July 2328, 1995, Washing-
By preserving with NaHSO4, treated soil sam-
ton, D.C., p. 173183.
ples held at 22C showed stable VOC concentra-
Hewitt, A.D. (1994) Concentration stability of four
tions for up to 28 days. This chemical preserva-
volatile organic compounds in soil subsamples.
tion method would complement collection
USA Cold Regions Research and Engineering Lab-
protocols that minimize volatilization losses dur-
oratory, Special Report 94-6.
ing collection, storage and analysis for soil with
Hewitt, A.D., T.F. Jenkins and C.L. Grant (1995)
14
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