5 to 14 different depths, ranging from 1.5 to 20.5
Table 1. Description of transects along which
m for determination of TNT concentration and
groundwater samples were collected.
stable isotope ratios for extractable TNT and soil
carbon.
Well in
Well at
Transect
source
leading
The soil samples were air dried, ground with a
number
region
edge
Aquifer
mortar and pestle, then passed through a no. 20
sieve. A 2.0-g subsample of each soil was extracted
1
141
112
Lower
with AcN. The extract was analyzed by HPLC to
2
141
110
Lower
determine the concentration of TNT and the mono-
3
140
108
Upper
4
085
108
Upper
amino-dinitrotoluenes. An additional subsample
of each soil was washed twice with 10 mL of AcN
for 18 hours with ultrasonication, air dried, then
analyzed by dual inlet IRMS to determine the δ13C
tridges with 5.0 mL of AcN and the concentrations
and δ15N values for the soil.
determined by HPLC. The extracts were then ana-
lyzed by GC-IRMS to determine the δ13C and δ15N
values for TNT.
RESULTS AND DISCUSSION
Isotope ratio in soil at LAAP
Soil core samples were collected from five loca-
Method development
tions at LAAP using the Site Characterization and
This project's initial task was to develop sample
Analysis Penetrometer System (SCAPS) (Table 2).
preparation techniques that would allow isolation
At each location, subsamples were obtained from
and preconcentration of TNT, but would not intro-
Table 2. Locations and depths from which the soil samples from LAAP were collected.
Location no.
Hole no.
Depth (m)
Location no.
Hole no.
Depth (m)
2
1
7.8
6
2
1.5
2
1
10.2
6
2
3.1
2
1
14.4
6
2
4.6
2
1
18.9
6
2
6.1
2
3
5.6
6
2
7.6
2
3
13.4
6
2
8.2
2
3
17.4
6
2
9.1
6
2
10.4
4
2
1.6
6
2
12.3
4
2
3.1
6
2
13.1
4
2
4.6
6
2
13.7
4
2
5.4
6
2
15.2
4
2
7.7
6
2
17.5
4
2
9.1
6
2
18.3
4
2
10.7
4
2
12.2
6
3
6.3
4
2
13.8
6
3
10.6
6
3
13.1
4
2
15.2
6
3
15.9
4
5
1.5
6
3
17.9
4
5
3.1
4
5
4.6
4
5
6.1
4
5
7.6
4
5
9.4
4
5
10.7
4
5
12.2
4
5
14.2
4
5
15.2
4
5
16.8
4
5
18.3
4
5
20.5
7
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