are transport within water solution through evapotrans-
1,4-), two additional isomers of TNT (2,3,4-, 2,4,5), 2-
piration and capillary rise, and vapor diffusion through
ANT, 4-ANT, TNB, and 3,5-dinitroaniline (3,5-DNA).
soil pore space. Partition coefficients quantify the equi-
We specifically analyzed for 3-NA in the Novem-
librium distribution of analytes between phases under
ber samples because of the very low concentrations of
a specific condition. Soilair partition coefficients have
1,3-DNB detected in the August samples. Likewise, we
been found to depend highly on soil moisture content;
targeted 2-ANT and 4-ANT, environmental reduction
the drier the soils are, the more strongly are explosives-
products of 2,4-DNT (Miyares and Jenkins, in press).
related compounds bound to the soil (Jenkins et al. 1999,
We speculated that 3-NA might form from environmen-
George et al. 1999, Webb et al. 1998). When soils are
tal transformation of 1,3-DNB, and 2-ANT and 4-ANT
moist, i.e., there are more than four monomolecular
might form from 2,4-DNT in a manner analogous to
layers of water covering the soil particles, transport is
the accumulation of 2-ADNT and 4-ADNT from trans-
dominated by vapor diffusion (Webb, in press). How-
formation of 2,4,6-TNT. Because 3-NA, 2-ANT, and
ever, under drying conditions, explosives partition in
4-ANT only have one nitro group on their aromatic
the water to the degree determined by the combination
rings, the response factors for these ERCs on the GC-
of the waterair, airsoil, and watersoil partition
ECD are very low compared with the other target
coefficients. The ERCs that have partitioned into the
analytes that contain two or more nitro groups. Thus,
soil water are subsequently carried toward the soil sur-
we analyzed the extracts using RP-HPLC in an attempt
face with capillary water, but at a rate that is slower
to obtain quantitative information for these analytes.
than that of water, owing to sorptiondesorption effects.
We did find 3-NA to be present in soils when
Once at the soil surface, ERCs with low vapor pres-
2,4-DNT concentrations were high, and also in some
surface samples. The vapor pressure of 3-NA is 3.75
sures will be deposited on surface particles as the
105 torr, so it appears that 3-NA could be an important
water evaporates. When there is little subsurface
signature for mine detection methods based on vapor
water, explosives are bound to soil and migration is lim-
detection.
ited to the very slow rate dominated by vapor diffusion
The results for 2-ANT and 4-ANT were quite dif-
under a condition in which the soilair partition coeffi-
ferent from those for 3-NA. These analytes were only
cient is large. Such was the case prior to the August
detected in a few samples and never in surface soils in
1998 soil sampling event.
the November samples. This is probably because of their
Soil samples collected in November 1998
slower rate of formation from transformation of 2,4-
DNT (Miyares and Jenkins, in press). Thus, it doesn't
The second set of soil samples was collected at Fort
appear that these two compounds are important for mine
Leonard Wood in November 1998: 235 were taken near
detection.
17 buried mines (six PMA-1A mines, three PMA-2
As in August 1998, soils collected near TMA-5
mines, six TMA-5 mines, and two TMM-1 mines). For
mines gave the highest frequency of detection of ERCs
all but one of these mines, samples were collected in
(67 out of 143, or 47% of the samples) (Table 17). The
the same manner as described above. The soil near one
most frequently detected ERC analytes for this type of
TMA-5 mine (EX-268) was more extensively sampled;
mine (in the order of frequency of detection) were 2-
97 samples were collected near this mine alone. Dur-
ADNT, 4-ADNT, 2,4-DNT, 2,4,6-TNT, 3-NA, and 1,3-
ing sampling, this mine was removed from the ground
DNB.
and samples were collected under it as well. Unfortu-
In the subsurface soil collected under TMA-5 EX-
nately, during shipment to CRREL, 32 of the 235 soil
268, concentrations of individual ERCs ranged from
samples were in a cooler that was lost and never
less than detection to as high as 9870 and 6930 g/kg
located by the overnight carrier. Thus, only 203 samples
for 2,4-DNT and 2,4,6-TNT, respectively. Generally,
were analyzed (App. B). In addition to GC-ECD analy-
the three analytes present at the highest concentrations
sis, the extracts from these soils were all analyzed by
were 2,4-DNT and the two transformation products of
RP-HPLC as well, to allow measurement of 3-NA,
2,4,6-TNT (2-ADNT and 4-ADNT). The concentrations
2-ANT, and 4-ANT, which all have low response fac-
of 2,4,6-TNT were generally an order of magnitude
tors on the GC-ECD.
lower. For surface soils, ERCs were detected in 16 out
We observed 19 different ERCs in at least one of
of 31 samples analyzed. Here, too, the most frequently
the soil samples (but not all in the same sample). The
detected analytes were 2,4-DNT, 2-ADNT, and
most commonly found analytes (in order of frequency
4-ADNT, with one measured concentration as high as
of detection) were 2-ADNT, 4-ADNT, 2,4-DNT, 2,4,6-
1620 g/kg for 2,4-DNT. Only two samples contained
TNT, 3-NA, and 1,3-DNB. Other compounds identi-
2,4,6-TNT, with a maximum concentration of 6.9
fied included several other isomers of DNT (2,6-, 2,5-,
g/kg. Figure 4 presents the ERCs detected in surface
3,5-, 3,4-, 2,3-), other isomers of DNB (1,2-, and
16
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