mixing, and careful subsampling, resulted in an
The results on field-contaminated soils did not
RSD of 11%. Because this field-mixing procedure
show the rapid degradation of TNT and TNB that
was so effective in homogenizing the sample, the
was observed in the spiked soils, and refrigera-
sampling and subsampling procedure is presented
tion appeared satisfactory. Presumably, the explo-
here (Jenkins et al. 1996a). Soil cores (0 to 15 cm in
sives still present in the field soil after many years
length and 5.6 cm in diameter) were collected into
of exposure are less biologically available than in
plastic resealable bags, and vegetation was re-
the spiked soils.
moved. The sample of dry soil, a mixture of sand
Another study (Bauer et al. 1990) has shown
and gravel, was placed into 23-cm aluminum pie
that explosives in spiked, air-dried soils are stable
pans and was broken up using gloved hands; large
for a 62-day period under refrigeration. Data from
rocks were removed (sieving may work well, too).
the Grant et al. (1993) study indicate that air dry-
A second pie pan was used to cover the sample,
ing of field-contaminated soils may not result in
which was then shaken and swirled vigorously to
significant losses of explosives contaminants. Ex-
disperse and homogenize the soil. The sample was
plosives in air-dried soils are stable at room tem-
then coned and quartered, and 5-g subsamples
perature if they are kept in the dark.
were removed from each quarter and composited
Acetonitrile extracts of soil samples are ex-
to form the 20-g sample for analysis. Splits of the
pected to be stable for at least 6 months under re-
same sample were obtained by remixing the soil
frigeration. Acetone extracts also are thought to
and repeating the coning and quartering.
be stable if the extracts are stored in the dark un-
Wilson (1992) studied sample preparation pro-
der refrigeration. (Acetone enhances photo-
cedures for homogenizing compost prior to analy-
degradation of explosives.)
sis for explosives. Wilson's (1992) method involves
macerating air-dried compost using a No. 4 Wiley
Explosion hazards and shipping limitations
mill followed by sample splitting using a Jones-
The Department of Defense Explosive Safety
type riffle splitter. The improved method de-
Board approved the two-test protocol (Zero Gap
creased the RSD from more than 200% to 3% for
and Deflagration to Detonation Transition tests)
TNT analyses.
in March 1988 for determining the explosive reac-
tivity of explosives-contaminated soil. Tests on
TNT and RDX in sands with varied water content
Sample holding times
showed that soils with 12% or more explosives are
and preservation procedures
The EPA-specified holding time for nitroaro-
susceptible to initiation by flame, and soils con-
matic compounds in soil is 7 days until extraction,
taining more than 15% explosives are subject to
and extracts must be analyzed within the follow-
initiation by shock (EPA 1993). Explosives exist as
ing 40 days (EPA 1995). The specified sample pres-
particles in soil ranging in size from crystals to
ervation procedure is cooling to 4C. This crite-
chunks, which can detonate if initiated. However,
rion was based on professional judgment rather
if the concentration of explosives is less than 12%,
than experimental data.
the reaction will not propagate. The water content
Two significant holding time studies have been
of the soil has minimal effects on reactivity. The
conducted on explosives (Maskarinec et al. 1991;
test results apply to total weight percent of sec-
Grant et al. 1993, 1995). Based on spiking clean soils
ondary explosives such as TNT, RDX, HMX, DNT,
with explosives in acetonitrile, Maskarinec recom-
TNB, and DNB. The tests do not apply to primary
mended the following holding times and condi-
or initiating explosives such as lead azide, lead
tions: for TNT, immediate freezing and 233 days
styphnate, and mercury fulminate. As a conser-
at 20C; for DNT, 107 days at 4C; for RDX, 107
vative limit, the EPA Regions and the U.S. Army
days at 4C; and for HMX, 52 days at 4C. Grant
Environmental Center consider soils containing
spiked soils with explosives dissolved in water to
more than 10% secondary explosives, on a dry
eliminate any acetonitrile effects and also used a
weight basis, to be susceptible to initiation and
field-contaminated soil. The results on spiked soils
propagation (EPA 1993). If chemical analyses in-
showed that RDX and HMX are stable for at least
dicate that a sample is below 10% explosives by
8 weeks when refrigerated (2C) or frozen (15C)
dry weight, that sample is considered to be
but that significant degradation of TNT and TNB
nonreactive. In most cases, this eliminates the re-
degradation can occur within 2 hours without
quirement to conduct the expensive two-test re-
preservation. Freezing provides adequate preser-
activity protocol.
vation of spiked 2,4-DNT for 8 weeks or longer.
In sampling to determine whether an explosion
11
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