Table 16. Concentrations of metals in discrete samples collected
at 50-m intervals parallel to eastwest road.
Concentration (g/g)
Node
(m)
Fe*
Zn
Pb
Ni
Cr
Cu
Ba*
Sb
Cd
0
31,000
61
11
27
22
29
500
<4.0
<0.5
50
30,000
67
11
28
22
32
420
<4.0
<0.5
100
29,000
63
10
27
22
31
640
<4.0
<0.5
150
30,000
87
7.4
21
18
440
460
<4.0
<0.5
200
24,000
48
7.5
19
16
25
510
<4.0
<0.5
250
26,000
70
9.4
24
20
36
440
<4.0
<0.5
300
27,000
58
8.0
25
20
34
470
<4.0
<0.5
350
32,000
52
7.4
28
25
38
590
<4.0
<0.5
400
29,000
65
10
27
22
38
440
<4.0
<0.5
450
27,000
63
9.6
25
21
35
500
<4.0
<0.5
500
32,000
58
8.7
20
19
77
600
<4.0
<0.5
550
32,000
55
9.1
25
19
35
640
<4.0
<0.5
600
28,000
53
9.5
21
17
33
670
<4.0
<0.5
650
29,000
60
9.6
26
22
34
590
<4.0
<0.5
700
30,000
56
11
23
18
29
490
<4.0
<0.5
750
29,000
61
11
27
21
34
680
<4.0
<0.5
*Iron and barium were determined by XRF. The remaining metals were determined
by atomic absorption.
Metals
DISCUSSION
Unlike the explosives, metals have natural
Explosives residues
background concentrations. Probability plots help to
show which samples contain abnormally high
We detected explosives residues in 48% of the 107
concentrations for a particular set of samples. For
soil samples we collected. RDX was the most frequently
example, the 40-mm firing test resulted in increased
detected explosive (39%) (Table 17). Of the samples
levels of copper (Fig. 24). The TOW test increased
above the detection limit, median RDX concentration
was only 0.021 g/g (Fig. 23a). Soil samples collected
under low-order detonations accounted for four of the
five highest RDX concentrations. TNT was the second
Table 17. Summary of explosives found in
most frequently detected explosive (21%) (Table 17);
soil samples.
concentrations were lower than RDX. Median TNT
concentration in samples where TNT was detected was
Median conc.
only 0.004 g/g. Similar to RDX, soil samples collected
of samples
above
beneath low-order detonations produced the highest
Percent of detection Maximum
TNT concentration observed (Fig. 23b). TNT is more
Number of sample
limit concentration
readily biotransformed than RDX, and the
(g/g)
(g/g)
Analyte
detections collected
transformation products of TNT were detected in about
RDX
42
39
0.021
340
10% of the samples. HMX was found in 11% of the
TNT
23
21
0.004
130
samples. HMX is the least water-soluble of the
HMX
12
11
0.12
40
explosives and is likely to persist in surface soils.
2-Am-DNT
12
11
0.006
0.84
However, its toxicity is low.
4-Am-DNT
10
9
0.005
1.0
The analytes 2,4-DNT and NG were detected at the
2,4-DNT
6
6
NG
4
4
Lampkin Range firing point and in a few samples on
2,6-DNT
2
2
the Washington Range. The highest concentration of
PETN
2
2
2,4-DNT we found was in a sample not associated with
TNB
1
1
a known event. The likely source of the contamination
Tetryl
0
0
was either firing using single-base propellant or burning
DNB
0
0
of excess propellant.
27
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