2.0 to 1000 mg/L. Each standard was analyzed by
mg/L) solution was added to 35 of the 50 samples.
GC-IRMS and the δ13C value for TNT was deter-
A 4.0-mL aliquot of MilliQ grade water was added
to the remaining 15 samples to be used as blanks.
mined. The relationship between concentration
and the δ13C value for TNT was computed and a
The samples were returned to the dark and incu-
bation continued at room temperature (22 2C).
minimum concentration threshold was deter-
mined where reliable data could be obtained.
Sampling was done immediately after prepara-
tion (time zero), then at 1, 3, 7, 14, 21, and 28 days.
TNT solutions
For each sampling day, three replicates of each
An aqueous solution of SARM grade TNT (AEC)
spiked soil were chosen at random. Blanks were
was prepared by placing 250 mg of TNT into 4 L
sampled in triplicate on days 0, 3, 14, and 28. Each
of MilliQ grade water and stirring for 3 days. The
soil sample was quantitatively transferred from
solution was filtered to remove any undesolved
the incubation tube to an extraction thimble and
TNT then analyzed by HPLC. The resulting con-
extracted by Soxhlet for 24 hours with AcN at a
centration was determined to be 49.5 mg/L. This
rate of six cycles per hour. The final extract was
solution was used to spike the samples in incuba-
diluted volumetrically to 250 mL. The soil was
tion study 1.
allowed to air dry overnight, giving the AcN time
to evaporate, then oven-dried at 105C overnight
A second aqueous solution of TNT was prepared
by placing 3 g of technical grade TNT (Eastman
to remove any remaining water or solvent. Extracts
Kodak, Rochester, New York) into 20 L of tap
were analyzed for concentration of TNT and its
water. The solution was stirred for 10 days, then
transformation products by HPLC-UV as
described above and by GC-IRMS for δ13C and
filtered, and analyzed by HPLC. The resulting con-
δ15N values for TNT. The dried soil was analyzed
centration was determined to be 101 mg/L. This
by dual inlet IRMS for δ13C and δ15N values of
solution was used to spike samples in incubation
study 2.
the soil.
TNT source comparison
Incubation study 2: Unlimited contaminant source,
Samples of TNT were obtained from five differ-
maximum loading of soil
ent sources: SARM grade (AEC), technical grade
A soil collected at Hanover, New Hampshire,
was oven dried (105C) and sieved as described
(Eastman Kodak), and two U.S. Military grade
samples (Picatinny Arsenal, New Jersey, and
above. Each slurry sample was prepared by plac-
Sandia National Laboratory, Albuquerque, New
ing 25 g of soil into 250-mL glass jars. A total of 48
Mexico) and Croatian military grade removed
samples was prepared. To each soil, 6.0 mL of tap
water was added to rewet the soil. The samples
from a PMA1A antipersonnel landmine. Solutions
were then allowed to incubate in the dark at room
of each TNT were prepared at a concentration of 1
temperature for 3 days. A 100-mL aliquot of aque-
g/L in AcN. Each solution was analyzed by GC-
IRMS for δ13C and δ15N values for TNT.
ous TNT solution (101 mg/L) was added to 39 of
the 48 samples. To the remaining nine samples,
100 mL of tap water was added. The samples and
Laboratory studies
blanks were shaken on a wrist action shaker for
Incubation study 1: Isotope ratio of TNT-amended soil
20 minutes, then returned to the dark for incuba-
over time
tion. Also prepared at this time were three control
Two soils were chosen for the incubation study,
samples containing only 100 mL of the TNT spik-
one from Charlton, New Hampshire, and the other
ing solution plus 6 mL of tap water (no soil).
from Louisiana AAP. The Charlton soil was a
The spiked soils were sampled at days 0, 7, 14,
sandy loam with 1.3% total organic carbon. The
21, 28, and 56. Blanks were sampled at days 0, 21,
LAAP soil was primarily sand with a total organic
and 56. On each sampling day, all of the jars were
carbon of 0.012%. Both soils were oven dried at
105C then sieved through a no. 20 sieve (0.84
shaken for 20 minutes on a wrist action shaker,
then centrifuged for 45 minutes at 2000 rpm. Three
mm). Samples were prepared by placing 25 g of
samples were randomly selected and place to one
soil into a 50-mL test tube (50 samples of each soil
side for analysis. (At every third sampling, three
were prepared). A 2.0-mL aliquot of tap water was
added to each sample to rewet the soil and allow
blanks were also selected.) For the remaining
microbiological activity to restart. The samples
samples, the aqueous phase was decanted,
incubated in the dark at room temperature for 3
weighed, then discarded. A fresh 100-mL aliquot
days. A 4.0-mL aliquot of aqueous TNT (49.5-
of the technical grade TNT solution was then
5
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