standard solution is not an explanation for the missing
under refrigeration. In contrast, both nitramines and
TNT.
nitroaromatics were quite stable under refrigeration in
TNT does not bind directly to soil. Therefore, the
four field-contaminated soils. When three of these field-
contaminated soils were fortified with TNT, rapid deg-
disappearance of TNT implies degradation or transfor-
radation of TNT occurred under refrigeration. Our
mation. The design of our experiment allows us to con-
experiments demonstrated that fresh additions of TNT
clude only that the TNT was rapidly degraded or trans-
to soils were more subject to being degraded, being
formed to products unanalyzed for by Method 8330,
transformed, being rendered unextractable, or some
perhaps coupled with the binding of the products in the
combination of these processes than were field-aged,
soil. There is abundant evidence in the literature for the
contaminated soils. We found no immediate degrada-
irreversible binding of TNT products in soil (Comfort
tion products of TNT (2 amino-DNT, 4 amino-DNT).
et al. 1995, Grant et al. 1995, McGrath 1995, Brannon
This was true for both aqueous and soil extracts in both
et al. 1997, Hundal et al. 1997).
Treatments 1 and 2. Grant et al.'s (1995) paper is espe-
cially relevant to our study as their refrigeration temper-
LITERATURE CITED
ature (4C) is similar to our unfrozen layer temperature
(08C) (Fig. 2). However, one potentially significant
Ayorinde, O.A., L.B. Perry, and I.K. Iskandar (1989)
difference between the studies is that their study was
Use of innovative freezing technique for in-situ treat-
done under aerobic conditions while our study was done
ment of contaminated soils. In Proceedings of the Third
under anaerobic (moisture-saturated) conditions. In one
International Conference on New Frontiers for Haz-
soil, they found the complete loss of TNT within six
ardous Waste Management, Pittsburgh, Pennsylvania,
days; however, amino-DNT was easily detected in this
September 1013, 1989, p. 489498.
soil across the 56 days of the experiment. The total soil
Boitnott, G.E., I.K. Iskandar, and S.A. Grant (1997)
TNT concentration in the Grant study was 1.0 mg/kg,
The use of frozen-ground barriers for containment and
which is much lower than our total addition of 25 mg/
in-situ remediation of heavy-metal-contaminated soil.
kg in five additions of 5 mg/kg (see below). If TNT
In Proceedings of the International Symposium on Phys-
were degrading in our studies with five times more TNT
ics, Chemistry, and Ecology of Seasonally Frozen Soils,
than the Grant study, then we should have seen degra-
Fairbanks, Alaska, June 1012, 1997 (I.K. Iskandar et
dation products; or, the degradation process was so rap-
al., Ed.), p. 409416. USA Cold Regions Research and
id, perhaps in combination with soil binding, as to be
Engineering Laboratory, Special Report 97-10.
undetectable.
Bradley, P.M., F.H. Chapelle, J.E. Landmeyer, and
Another possible explanation for the missing TNT
J.G. Schumacher (1994) Microbial transformation of
is that the quantities in the aqueous additions were
nitroaromatics in surface soils and aquifer materials. Ap-
diluted to below the detection limits when combined
plied and Environmental Microbiology, 60: 21702175.
with the soil. In Chambers 1 and 3, a total of 14.0 and
Brannon, J.M., C.B. Price, and C.A. Hayes (1997)
12.8 mg of TNT was added in five additions to the unfro-
Abiotic and biotic TNT transformations. USA Engineer
zen soil layers that contained 520 g soil; the overall
Waterways Experiment Station, Vicksburg, Mississip-
soil concentrations of TNT in Chambers 1 and 3 were
pi, Miscellaneous Paper IRRP-97-3.
therefore, respectively, 26.9 and 24.7 mg/kg (assuming
Comfort, S.D., P.J. Shea, L.S. Hundal, Z. Li, B.L.
a uniform distribution). The Method 8330 quantitation
Woodbury, J.L. Martin, and W.L. Powers (1995)
limit is 0.25 mg/kg (USEPA 1994), so we should have
TNT transport and fate in contaminated soil. Journal
easily seen the TNT if present. In a few cases, we did
of Environmental Quality, 24: 11741182.
detect barely measurable soil TNT concentrations in
Grant, C.L., T.F. Jenkins, K.F. Myers, and E.F. Mc-
Chambers 1 and 3. However, the amounts detected were
Cormick (1995) Holding-time estimates for soils con-
minor compared to the amount added (Fig. 5c).
taining explosives residues: Comparison of fortifica-
tion vs. field contamination. Environmental and Toxic
Another possible explanation for the missing TNT
Chemicals, 14: 18651874.
could be a decreasing TNT concentration of the stan-
dard solution added to the columns. What we think we
Hundal, L.S., P.J. Shea, S.D. Comfort, W.L. Pow-
ers, and J. Singh (1997) Long-term TNT sorption and
added in Treatment 1 may not be what we actually
added. However, eight determinations (four days two
bound residue formation in soil. Journal of Environ-
replicates) of the aqueous solution TNT concentration
mental Quality, 26(3): 896904.
on Days 38, 66, 80, and 95 (Fig. 2, 3) showed no de-
Iskandar, I.K., and F.H. Sayles (1997) Ground freez-
tectable trends in the TNT concentrations (data not pre-
ing for containment of hazardous waste: Engineering
sented) and a relatively low coefficient of variability of
aspects. In Proceedings of the International Symposium
on Physics, Chemistry, and Ecology of Seasonally Fro-
8
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