concentrations were 13.6, 69.0, and 17.5 g/kg, respec-
conducted to determine which of these possibilities is
tively. The initial contamination that was present on
correct. Nevertheless, surfaces of the TMA-5 mines
the metal-cased TMM-1 mines has been transferred to
continue to be highly contaminated with ERCs after
the surrounding environment over the 472 days of burial
368 and 472 days of burial.
and the metal case is an effective barrier to prevent fur-
Surface sampling results for the PMA-1A mines are
ther surface soil contamination. Thus, from these
less consistent (Table 21). For mines EX-011 and EX-
results, it appears unlikely that the ERC levels in soils
013, which were sampled after being buried for 368
near these mines will increase with time as the mines
days, the top and bottom have similar concentrations
remain in the ground.
of 1,3-DNB, 2,4-DNT, and 2,4,6-TNT, all of which are
Surface concentrations of 2,4-DNT on the PMA-2
about an order of magnitude lower than when the mines
mines after burial are similar to results before burial,
were buried. Results for EX-048 sampled after 472 days
but the concentration of 2,4,6-TNT has been reduced
are a little different; the top and bottom concentrations
by about 66% on mine EX-111, about 64% on mine
are within a factor of 3 of each other for all analytes,
EX-117, and to levels that were below detection on EX-
and, except for 1,3-DNB, the concentrations are com-
144. It appears that the residual surface concentration
parable to estimates made before burial. Analytical
of 2,4-DNT is higher on the top of the three PMA-2
results for EX-051 are more like those found for the
mines than on the bottom after burial. This could be
TMA-5 mines, where the bottom surface has a much
attributable to a continued flux of this signature evolv-
higher concentration than the top, and the pre-burial
ing around the fuse well that was threaded with a plas-
estimates are intermediate between the two. This vari-
tic plug instead of an actual fuse. But this flux may be
ability could be caused by differences in the local
less than from a PMA-2 with a real fuse installed. Com-
microenvironment where these mines are buried. It is
ments from one person experienced in mine detection
important to note, though, that the surfaces of the PMA-
indicate that the fuse well seal is susceptible to weath-
1A mines remain contaminated with ERCs 368 and 472
ering and has been observed to be ruptured on mines
days after they were buried. Thus, it appears that, like
that have been detected and removed from the ground.
the TMA-5 mines, ERCs will be available for detec-
Visually, the seals for these two mines were intact and,
tion for many years after burial.
hence, the flux may be atypically low compared with real
The results for the three Type 72 mines indicate that,
mines that have been buried for the same length of time.
after 97 days of burial, the surface concentrations were
For the four plastic-cased TMA-5 mines, the sur-
similar to those measured when the mines were buried.
face contamination is comparable to estimates made
After 201 days, the concentrations of the three major
before burial (Table 21). Each pre-burial value is a mean
analytes (2,4-DNT, 2,4,6-TNT, and RDX) remaining
for the mine that was determined from surface swipes
on EX-464 were lower than initially measured by about
collected from both the top and bottom surfaces. For
an order of magnitude (Table 21). Whether a steady
the samples taken after burial, the swipes from the top
state has been achieved or the surface concentration
and bottom were kept separate. For all four TMA-5
will continue to decline is uncertain.
mines, the contamination on the bottom surfaces was
Soilair partition coefficients for soils collected
generally at least an order of magnitude higher than on
at the Fort Leonard Wood research minefield
the top surfaces. This may be ascribable to downward
Soilair partition coefficients (Ks/a) for nine explo-
percolating water that washes contamination from the
sives-related chemicals on 16 Fort Leonard Wood soils
top and sides of the mine and deposits it under the mine.
are presented in Table 22. These Ks/a values were
Alternatively, it could be attributable to water leaking
determined from 14 soil samples collected near two
from the four holes present in the bottom of the TMA-
TMA-5 mines and two near PMA-1A mines in April
5 mines or moisture trapped underneath the mine,
1999. These soils were not fortified with these chemi-
resulting in a water dominated flux rate.* The holes in
cals, rather they became contaminated because of their
the bottom of the mine allow water to contact a wax-
proximity to the TMA-5 mines.
like liner within the mine that holds the explosive in
Depending on which chemicals were present in a
place. Analysis of this waxlike material at Sandia
given soil, up to 15 individual Ks/a values were obtained
National Laboratory indicated that it contained large
for a given chemical. Median Ks/a values for the most
concentrations of TNT.† Future sampling should be
commonly encountered ERC are 1.04 105 mL-air/g-
soil for 2,4-DNT, 4.48 106 mL-air/g-soil for TNT,
1.55 106 mL-air/g-soil for 4-ADNT, and 1.89 106
*Personal communication with D. Leggett, CRREL, 2000.
mL-air/g-soil for 2-ADNT.
†Personal communication with P. Rodacy, Sandia National
If we assume that there is a boundary layer of air
Laboratories, 1999.
32
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