found in samples collected under the mine. For the sur-
not considered any long-term trend in these data. To
face soils, only 3 of the 21 surface soil samples had
look at this question, we prepared bar graphs of the
detectable ERCs. The most often detected analytes for
detection frequency of 2,4-DNT, 2-ADNT,* and 2,4,6-
the Type 72 mine were 4-ADNT and RDX. Except for
TNT in soils near the TMA-5 (Fig. 11) and PMA-1A
one surface soil, RDX was only present in four samples
mines (Fig. 12), as a function of time after burial.
collected under the mines. Finding RDX in soils near
For the soils near the TMA-5 mines, the detection
the Type 72 mines is, however, consistent with the type
frequencies for 2,4-DNT (Fig. 11b) and 2-ADNT (Fig.
of high explosive present in this mine (50%TNT, 50%
11b) appear to be increasing with time, although the
RDX) and the very high concentration of RDX present
results from November 1998 were high for both signa-
on the surfaces (74 ng/cm2) of Type 72 mines (Table 2)
ture chemicals, particularly in the surface soils. The
when they were buried.
detection frequency for 2,4,6-TNT (Fig. 11c) shows a
similar trend, with a noticeable spike in April 1999 for
Detection frequency for major signature
both total soils and surface soils. With only five data
chemicals in soils near TMA-5 and PMA-1A
points, our conclusions in this regard must be guarded,
mines as a function of time after burial
but clearly there is no evidence to suggest that the
If vapor sensing is a viable concept for detection of
buried land mines, the ERCs must persist in the vicin-
ity of these mines for long periods. Thus far, we have
*4-ADNT was not plotted because whenever 2-ADNT was
presented the frequency of detection of individual ERCs
present, 4-ADNT was also present at very similar concentra-
tions.
in soils for each sampling time (Tables 1620), but have
100
2,4-DNT
All Soils
TMA-5
Surface Soils
90
80
70
60
50
40
30
20
10
0
Aug 98
Nov 98
Apr 99
Jul 99
Nov 99
a. 2,4-dinitrotoluene.
Figure 11. Detection frequency for ERCs in soil samples
collected near buried TMA-5 land mines.
27
to contents
Previous Page
