are 0.001 g/g for the di- and trinitroaromatics, 0.003
81-mm HE projectiles. We marked a 3-m 3-m area
g/g for RDX, 0.025 g/g for HMX, 0.01 g/g for NG,
encompassing the densest concentration of fins (Area
and 0.02 g/g for PETN. In this report, we report
Blue) and another 3-m 3-m area nearby that contained
concentrations below the computed method detection
no fins (Area Yellow) (Fig. 3). We also located a low-
limits if the concentrations were confirmed using a
order detonation next to Area Blue (Fig. 3a). We
second GC column or using HPLC for HMX. We used
sampled the explosive composition and the soil directly
Method 8330 (Nitroaromatics and Nitramines by High-
under the low-order detonation to a depth of 22 cm, the
Performance Liquid Chromatography [HPLC])
deepest we could reasonably dig through the cobbly
(USEPA 1994) when we found higher concentration
substrate with a small shovel.
samples (>0.2 g/g) and to quantify the explosives
From each of these areas, we used a small shovel to
components in low-order detonations.
collect soil at the nodes of a 1-m-square grid (Fig. 3b)
to form a composite soil sample. We excluded rocks
White phosphorus
(particles >2 mm) from the samples by either sampling
A limited number of samples were analyzed for white
around them or picking them out. Three 120-mL
phosphorus using Method 7580 (White Phosphorus [P ]
subsamples were obtained by taking 30 random
4
by Solvent Extraction and Gas Chromatography)
increments from the composite for subsequent
(USEPA 1996b).
laboratory analysis for explosives residues. The
remainder of the sample was placed in a plastic bag for
Metals
other analyses (XRF and field colorimetric methods).
Metals were determined in the field using a field-
In the field lab, we used colorimetric methods to
portable Niton Model XL-722S X-Ray Fluorescence
test acetone extracts of the soil samples for
Multi-Element Analyzer. Confirmatory analysis for
nitroaromatics (Method 8515) and nitramines/nitrate
antimony, cadmium, chromium, copper, lead, nickel,
esters (Method 8510). Method 8515 appeared to
barium, and zinc was conducted on 50 samples at the
indicate the presence of nitroaromatic compounds. The
Environmental Lab (Vicksburg, Mississippi) using
initial background color of the acetone extract was
Method 3050 (Acid Digestion of Sediments, Sludges,
yellow, and addition of the EnSys reagent (tetrabutyl
and Soils) and atomic absorption.
ammonium hydroxide) resulted in an amber color. The
color was more intense in the sample collected from
the area without projectile fins. (Subsequent laboratory
RESULTS
analysis showed that this color formation was due to
the presence of elemental sulfur and sulfur compounds.)
Known events
The following day, we marked out two additional 3-m
3-m areas (labeled Areas Red and Pink) on either side
Mortar projectile impact zone
of the two areas previously sampled in line with the
The first area we sampled was used in February 1992
firing point.
Using gas chromatography-ECD (Method 8095),
to test the reliability of the M734 multi-option fuse.
we detected low (<1 g/g) concentrations of RDX and
Forty-five 81-mm mortar projectiles were fired with
their fuses set to proximity into a limited (100-m2) target
HMX in the soil samples from the grid (Area Yellow)
area. The projectile was an 81-mm M821E1, which is
with no projectile fins (Fig. 4) that was located 6.5 m
a U.S. version of the United Kingdom's M821 HE (high-
from the grid (Area Blue) with several projectile fins
explosive) cartridge (U.S. Army 1977). The complete
(Table 3). Some explosives residues were detected in
round is made up of a fuse, four increment propellant
each of the other three grids, but concentrations were
charges, a fin assembly, ignition cartridge, and shell
much lower than in the Area Yellow and near the method
body. Unfortunately some of the information about this
detection limits.
projectile is proprietary, but what we do know is given
The explosive composition from the low-order
in Table 2.
detonation was 66% RDX, 9% HMX, and 25% TNT
We were able to locate the target area from the
(Table 4). This composition is more consistent with
description of the firing point in the test report and the
cyclotol (75% RDX and 25% TNT) rather than
cluster of mortar projectile fins in a relatively small
Composition B (60% RDX and 40% TNT). HMX is
area (Fig. 2). We found 47 projectile fins, most of which
always present as an impurity in military-grade RDX;
were from 81-mm projectiles, and the remainder were
however, the proportion of HMX we found in this round
from 60-mm projectiles. We don't know the source of
is high. HMX is the least soluble of these three
the 60-mm projectile fins, but range records indicate
explosives, and preferential dissolution of RDX and
that 60-mm smoke projectiles were frequently fired with
TNT may account for the enrichment of HMX. The soil
8
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