Table 5. δ13C and δ15N values for different
days. After day 14, the concentrations of all of the
analytes decreased with time. These concentration
sources of TNT.
changes agree with previous results from the
monitoring of TNT spiked onto wetted soils (Grant
Standard
Standard
δ13C
δ 15N
deviation
deviation
et al. 1993). The mass balance calculations indi-
cated that recoverable TNT and transformation
SARM
26.42
0.47
3.41
0.84
products decreased by 70% from the original mass
SNL
22.21
0.21
9.64
0.89
of TNT in just 21 days (Fig. 4). A much smaller
PA
23.36
0.14
3.58
0.57
decrease in concentration of TNT and a small
Kodak
22.69
0.30
2.58
0.54
Croatian
23.04
0.22
5.38
1.15
increase in the concentration of the amino-
dinitrotoluenes was observed in the LAAP soil.
SARM = Standard Analytical Reference Material; SNL = U.S.
The total loss of extractable TNT and transforma-
military grade obtained from Sandia National Laboratory; PA
tion products was 37% over 77 days (Fig. 5). No
= U.S. military grade obtained from Picatinny Arsenal; Kodak
significant change in the δ13C value for the extract-
= technical laboratory grade from Eastman Kodak; Croatian =
able TNT (Fig. 6 and 7) or for the δ13C of the soil
military grade from Croatia taken from a PMA1A antiperson-
nel land mine.
carbon was observed (Fig. 8).
The data above (Fig. 6 and 7) showed that,
range for the δ13C values is small, 23.0‰
although the concentration of extractable TNT
(Croatian) to 22.2‰ (SNL). The range for the δ15N
decreased during incubation, no changes could be
detected in the δ13C value for TNT. This was con-
values is much broader, 5.38‰ (Croatian) to
9.64‰ (SNL).
sistent with predicted results. A measurable
change in the δ13C value for the soil was sought
Laboratory studies
as the TNT became irreversibly bound to the soil
Incubation study 1: Isotope ratio of TNT-amended soil
organic matter. Figure 8 showed that no change
the in δ13C value for the soil could be measured
over time
For the Charlton soil, the concentration of TNT
over the length of the experiment. Thorne (Thorne
decreased rapidly over the first 7 days (Fig. 3). The
and Leggett 1998) reported that the highest per-
concentration of the 2-amino- and 4-amino-
centage of TNT bound to organic matter that he
dinitrotoluene (2-Am-DNT and 4-Am-DNT)
had measured in finished compost was 0.2%
reduction products increased during the first 7
(w/w). The total percent carbon in the soils used
12
10
8
SNL
6
SARM
PA
4
2
Kodak
0
2
Croatian
4
6
8
28
21
27
26
25
24
23
22
13
δ C for TNT
Figure 2. Plot of δ15N vs. δ13C for TNT from several different sources.
9
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