bulk soil VOC concentrations under environmen-
p-Xyl are also consistent with the trends estab-
lished by the theoretical analysis of Rong (1996).
tal conditions. Additionally, these findings sup-
These laboratory findings support the assump-
port the view that the organic carbon content is
tion that linear partitioning exists between soil
the dominant variable controlling the capacity of
vapor and bulk soil VOC concentrations as in-
a soil to retain VOCs.
ferred by Conant et al. (1996) and Rong (1996).
Furthermore, that the sorption of VOCs by soil
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under conditions where mineral surfaces are
hydrated (but perhaps unsaturated with respect
Atlas, R.M. (1981) Microbial degradation of petro-
to bulk water content) is likely to be more depen-
leum hydrocarbons: An environmental perspec-
dent on the organic carbon content than moisture
tive. Microbiological Reviews, 45: 180209.
content.
Chiou C.T., P.E. Porter, and D.W . Schmedding
To further substantiate the concept that linear
(1983) Partition equilibria of nonionic organic
partitioning exists between soil vapor and bulk
compounds between soil organic matter and
soil VOC concentrations, a field study should be
water. Environmental Science and Technology, 17:
performed. Because of the potential problems
227231.
cited previously, special attention should be
Cho, H.J., P.R. Jaffe, and J.A. Smith (1993) Simulat-
given to both the collection of soil vapor and soil
ing the volatilization of solvents in unsaturated
samples. Small volume soil gas probes (Conant et
soils during laboratory and field infiltration exper-
al. 1996) and a soil coring device that collects and
iments. Water Resources Research, 29(10): 3329
transfers a sample with limited disruption and
3342.
exposure (Hewitt 1996) would complement this
Conant B.H., R.W . Gillham, and C.A. Mendoza
effort. In addition, a site that has VOC concentra-
(1996) Vapor transport of trichloroethylene in the
tions ranging over several orders of magnitude in
unsaturated zone: Field and numerical modeling
the near-surface unsaturated zone should be
investigations. Water Resources Research, 32: 922.
selected. The reason for initially attempting to
Dewulf, J., D. Drijvers, and H.V. Langenhove
establish this relationship with near-surface soils
(1995) Measurement of Henry's law constant as
is that collecting soil from depths greater than
functions of temperature and salinity for the low
several meters is difficult without inducing vola-
temperature range. Atmospheric Environment, 29:
tilization losses using conventional downhole
323331.
procedures (Hewitt 1996, Hewitt and Lukash
Hewitt, A.D. (1995a) Enhanced preservation of
1996).
volatile organic compounds in soil with sodium
Establishing a linear relationship between
bisulfate. USA Cold Regions Research and Engi-
vapor concentrations and soil concentrations
neering Laboratory, Special Report 95-26.
could have a profound effect on future site char-
Hewitt, A.D. (1995b) Evaluation of methanol and
acterization activities. The development of a soil
NaHSO4 for preservation of volatile organic com-
gas measurement procedure that would allow
pounds in soil samples. American Environmental
computation of soil concentrations to within an
Laboratory, 7: 1618.
order of magnitude of the actual concentration
Hewitt, A.D. (1996) Establishing a relationship
would expedite site characterization and signifi-
between soil vapor and grab sample techniques
cantly reduce the cost of site characterization. Soil
for determining volatile organic compounds.
gas probes can be rapidly installed and sampled,
USA Cold Regions Research and Engineering
which coupled with on-site analysis techniques,
Laboratory, Special Report 96-14.
allows for near-real-time vertical and horizontal
Hewitt, A.D., and C.L. Grant (1995) Round robin
profiling. Furthermore, because most subsurface
study of performance evaluation soils vapor-for-
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tified with volatile organic compounds. Environ-
(<0.20%), CO values may have a broad range of
mental Science and Technology, 29: 769774.
applications with regard to soil type.
Hewitt, A.D., and N.J.E. Lukash (1996) Sampling
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in soil. USA Cold Regions Research and Engi-
SUMMARY
neering Laboratory, Special Report 96-5.
The findings of this laboratory experiment
Hewitt, A.D., T.F. Jenkins, and C.L. Grant (1995)
provide preliminary support for the theory that
Collection, handling, and storage: Keys to im-
linear partitioning exists between soil vapor and
proved data quality for volatile organic com-
10
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