The ERCs that accumulate under the mine could
ber samples compared to the August samples is the
serve as the source of signature found around the
higher frequency of detection of ERCs in surface soil
perimeter of the mine to form a discontinuous halo of
samples and the detection of 3-NA in some of the sur-
ERCs at the surface. Furthermore, the water that col-
face soils near the TMA-5, PMA-1A, and PMA-2
lects under the mine will become contaminated with
mines. The enhanced volatility of 3-NA, relative to
explosives compounds at a rate dependent on the
2,4,6-TNT, makes it a compound that may be a useful
water-based flux rate from the mine (Leggett et al., in
target analyte for detection of mines, but the stability of
prep.). In the case of TMA-5 mines, it is our experi-
this compound in soil has not been investigated. We didn't
ence from the field sampling events that the
specifically analyze the August 1998 samples for 3-NA.
underside of the mine remains wet even in the driest
Soil samples collected in April 1999
soil conditions.
ERCs were also detected in 8 of the 25 soil samples
On the basis of the results of analysis of soils col-
collected near PMA-1A mines. For the surface soils,
lected near EX-268 during the November sampling, we
ERCs were detected in 5 of the 10 samples analyzed.
decided to reduce the number of mines to be sampled
The most frequently detected analytes in the surface
in April 1999, but to increase the number of samples
were 2-ADNT, 4-ADNT, 3-NA, and 2,4-DNT; 2,4,6-
collected near each mine selected. We collected 220
TNT was not detected in any surface soil sample. Con-
soil samples (App. C), 40 for two PMA-1A mines, 40
centrations in the surface were as high as 51 g/kg for
for two PMA-2 mines, and 70 each for two TMA-5,
2,4-DNT, 56 g/kg for 2-ADNT, 33 g/kg for 4-ADNT,
and two TMM-1 mines (Table 18).
and 125 g/kg for 3-NA.
Analysis of the April 1999 samples indicated that
ERCs were detected in three of the nine soil samples
the detection frequency of ERCs remained the highest
collected near PMA-2 mines. The analytes detected
for TMA-5 mines. For 2,4,6-TNT, detection increased
were 2-ADNT, 4-ADNT, 3-NA, and 3,4-DNT; the high-
substantially to 47 out of 70 samples, compared to only
est concentration found was 14 g/kg for 3-NA in a
37 out of 143 for the November 1998 samples. We
surface soil sample collected directly above the PMA-
attribute this increase to the improved stability of 2,4,6-
2 mine. Neither 2,4-DNT, 1,3-DNB, nor 2,4,6-TNT
TNT in soil during the colder months, prior to the April
were detectable in any of the nine samples analyzed.
sampling. Increased stability of 2,4,6-TNT at lower tem-
For the samples collected near the TMM-1 mines,
peratures has been observed by Grant et al. (1993) and
only trace levels of 2-ADNT and 4-ADNT were found
Miyares and Jenkins (in press). That's why we use rapid
in 3 of the 26 samples analyzed. Apparently, the metal
cooling of soil samples in our sampling methodology
casing is a much better seal than the plastic casing,
to help preserve 2,4,6-TNT. For the April sampling,
inhibiting leakage of signatures from the mine. The
there was also an increase in the percentage of samples
inhibitory nature of metallic cases has also been sug-
in which 1,3-DNB was detected, but the increase was
gested to explain external contamination data collected
less than that observed for 2,4,6-TNT, and was not found
from U.S. M16 mines (Leggett et al., 2000).
for surface samples. A separate analysis of surface
The major difference in the results for the Novem-
samples by RP-HPLC was not conducted for the April
Table 18. Frequency of detection of ERCs in soil samples collected near buried mines in April 1999.
Number of detections
Total soil samples (surface samples**)
Mine
Soil samples
type
collected*
2,4-DNT
2,4,6-TNT
1,3-DNB
2-ADNT
4-ADNT
3,5-DNT
2,5-DNT
PMA-1A
40 (20)
14 (3)
11 (3)
7(0)
19 (7)
18 (6)
5 (0)
3 (0)
PMA-2
40 (18)
2 (1)
2 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
TMA-5
70 (34)
33 (6)
47 (15)
9 (1)
38 (10)
37 (11)
0 (2)
18 (1)
TMM-1
70 (34)
1 (0)
2 (0)
0 (0)
1 (0)
0 (0)
0 (0)
0 (0)
*Numbers inside parenthesis in the Soil samples collected column refer to the number of surface soil samples that were
collected for a given mine type.
**Numbers inside parenthesis in the Number of detections columns refer to the number of surface soil samples in which
ERCs were detected for a given mine type.
18
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