pound concentrations to obtain total solution phase con-
Table 7. Field sampling dates at Fort Leonard
taminant concentration. Total analyte concentration in
Wood research minefield.
the soil phase was determined by the difference between
total mass of analyte added and total solution phase
Days since
contaminant mass. For one soil (soil 4), 2,4-DNT was
burial of
partitioned alone and both soil and solution phases were
mines on
analyzed to assure that determination of soil concen-
Sampling date*
19 July 1998
tration by difference was adequate. Soil phase and so-
27 August 1998
41
lution phase concentrations were plotted and a linear
5 November 1998
111
regression analysis was conducted to determine the
13 April 1999
270
slope of the graph, which represents the partition coef-
20 July 1999
368 (97)†
ficient as described in eq 1
1 November 1999
472 (201)†
*Mine burial and soil sampling each took several days.
q = Kd C
(1)
The dates given are the first day of the referenced ac-
where
tivity.
q = soil phase concentration (mg /kg)
†The number of days after burying for the Type 72 mines
Kd = partitioning coefficient (L /kg)
was computed versus a burial date of 13 April 1999.
C = solution phase concentration (mg/ L).
Soil sample collection during August and
For chemical analyses, the aqueous samples were
November 1998
brought to room temperature, a 0.5-mL aliquot was
removed, combined with 2.0 mL of acetonitrile, and
For the initial sampling in August 1998, the loca-
shaken to ensure complete mixing. Three soil samples
tions of the buried mines were still visible, largely
from the first sampling, and five each from the second
because the drought conditions that had predominated
and third samplings, were analyzed in duplicate. The
since mine burial prevented substantial plant regrowth.
mixed samples were filtered through a Millex-SR
Soil samples were collected on several sides of the larger
(0.5-m) disposable filter, with the first five drops being
antitank mines, but generally only along one side of
discarded and the remainder being collected in a 2-mL
the smaller antipersonnel mines so that we didn't overly
amber glass autosampler vial. A control solution contain-
disturb the areas near these mines. We collected these
ing 2,4,6-TNT, 2,4-DNT, and 2,6-DNT at a concentra-
perimeter samples just off the edges of the mines, as
tion of 2.8 mg of each analyte per liter was prepared in
close to the edge as possible, without touching the mines
reagent grade water. Two 0.5-mL aliquots of the control
themselves. To collect the soils, any surface vegetation
solution were prepared as described above and analyzed
over the mine was removed using scissors to cut the
with each set of samples. An acetonitrile (ACN) blank
plant stems flush with the ground surface. The specific
was also processed with each set of samples. Using
locations to be sampled for each mine were identified
reverse phase high performance liquid chromatography
and soil samples were collected at each location as fol-
(RP-HPLC), we separated analytes on an LC-8 (150
lows. A metal paint scrapper was used to remove a thin
3.9 mm, Nova-Pak, Waters) column eluted with a water/
layer of surface soil, usually about 0.2 cm. This soil
isopropyl alcohol eluant (86/14, v/v) at a flow rate of 1.4
was placed in a pre-cleaned, 125-mL, wide-mouth glass
mL/min. Analytes were detected using a variable wave-
bottle, which was capped and stored in an ice-filled
length UV detector set to 254 nm. Data were collected on
cooler. In some locations, often over the center of the
a Hewlett-Packard digital integrator programmed in peak
mine, only a surface sample was collected. Around the
height mode. Concentrations of analytes were determined
perimeter of the mines, where deeper samples were to
against standards prepared from Standard Analytical Ref-
be collected, a 3/4-in. (1.9-cm) soil corer barrel was
erence Materials (SARM) (U.S. Army Environmental
placed on the spot where the surface layer had been
Center, Aberdeen Proving Ground, Maryland).
removed and it was carefully driven into the ground to
the appropriate depth for the type of mine being
Soil sampling for characterization of
sampled. The soil increment was removed from the core
explosives-related chemical signatures
barrel and placed in a pre-cleaned, 125-mL, wide-mouth
The soils at the research minefield were sampled
glass bottle; the corer was then wiped clean and rinsed
on the dates given in Table 7. The protocol for sam-
with acetone. The core barrel was then replaced in the
pling varied from sampling period to sampling period.
hole and the corer was advanced to the next depth
Details of the soil sampling protocol used for each
interval of interest. The soil increments collected for
period are provided in the following sections.
each mine type are described in Table 8.
8
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