(HMX, RDX, TNT, 4-AmDNT, and 2-AmDNT) and
RESULTS AND DISCUSSION
much better resolution for these target analytes
was obtained on the LC-CN column as compared
Analytical results for RP-HPLC analysis of all
to the LC-18.
soil samples are presented in Appendix B. Table
B1 provides the results for sampling location 1-
44. Likewise, Tables B2B5 give results for sam-
Extraction time assessment and evaluation of
pling locations R44, 148, 248, and R48, respec-
on-site methods for RDX and HMX
An initial experiment was conducted to deter-
tively. Table B6 presents the results for spiked
mine the effect of various extraction times on
samples analyzed to assess recovery of target
recovery of HMX for soil samples from Fort Ord.
analytes.
Three discrete samples from location 1-44-1 were
selected for this evaluation: one from the 0- to 15-
Overview of explosives detected
cm depth, one from the 30- to 45-cm depth, and
in the various sampling areas
one from the 105- to 120-cm depth. A 20-g portion
By far, the greatest concentration of explosives
of each was placed in individual plastic extraction
residues was detected in range 44, sampling loca-
bottles and 100 mL of acetone (3% water) was
tion 1-44. HMX was detected at the highest con-
added. The samples were shaken manually for 3
centration, with up to 587 mg/kg in the surface
minutes, and, after approximately 1 minute of set-
soil (Table 2). Concentrations of RDX, TNT,
tling, we removed a 2-mL aliquot and filtered it
4-AmDNT, and 2-AmDNT were also detected in
through a 0.5-m Millex SR filter. The bottles were
area 1-44, but the maximum values obtained for
then given an additional 7 minutes of shaking
these analytes were only 1.70, 0.59, 1.46, and 1.31
and another 2-mL aliquot was removed in
mg/kg, respectively (Table 3). No other explosives-
a similar manner. We then shook the bottles
related compounds were detected in any samples
for an additional 20 minutes, and removed a
from the inland firing ranges at Fort Ord.
2-mL aliquot, which was processed as above.
Some explosives residues were also detected at
Thus, three aliquots representing 3-, 10-, and
sampling area 1-48, although concentrations were
30-minute shaking periods were collected from
very low compared with those found in area 1-44
each soil. These samples were diluted 1:5
(Table 4). The maximum values found among the
with reagent grade water and analyzed by
80 soil samples analyzed from area 1-48 for HMX,
RP-HPLC-UV on an LC-CN column as described
RDX, TNT, 4-AmDNT, and 2-AmDNT were 1.43,
above.
0.46, 0.01, 0.08, and 0.09 mg/kg, respectively; the
In a second experiment, we selected a set of 11
latter three values are estimates that were below
soil samples to assess the usefulness of the two
method detection limits (MDLs).
commercially available on-site RDX methods for
Very low concentrations of TNT, 4-AmDNT, and
analysis of the soil samples. For each soil selected,
2-AmDNT were occasionally detected in the 80 soil
a 20-g portion of field-moist soil was placed in a
samples from sampling area 2-48, but neither RDX
plastic bottle and 100 mL of acetone (3% water)
nor HMX was detected. Maximum values were
was added. The bottles were shaken periodically
all below MDLs of 0.2 mg/kg, however. No
over 30 minutes and the soil particles were allowed
explosives residues were detected in any of the 40
to settle for at least 15 minutes. A 50-mL aliquot
soil samples from sampling areas R-44 or R-48.
was then withdrawn with a Plastipak syringe and
filtered through a Millex SR filter. The resulting
Depth of contamination
acetone extract was analyzed by three methods:
Since explosives residues were almost exclu-
1) RP-HPLC using the LC-CN column, 2) a colori-
sively confined to areas 1-44 and 1-48, the follow-
metric method available from EnSys (now Strate-
ing discussions concerning the depth of contami-
gic Diagnostics Corp.) (Jenkins and Walsh 1992),
nation will concentrate only on these areas.
and 3) a DTECH enzyme immunoassay method
In area 1-44, HMX concentrations were greatest
from Strategic Diagnostics.
by far in the surface 015 cm (Table 2). In grid A,
For HPLC analysis, each acetone extract was
the sampling grid nearest the tank target, the mean
diluted 1:5 with deionized water prior to injection.
concentration of HMX in the 0- to 15-cm depth was
This was done to ensure that the solvent strength
295 mg/kg, while mean concentrations in the 15-
of the injected sample was lower than the eluent
to 30-cm, 30- to 45-cm, 45- to 60-cm, and 105- to
to maintain adequate peak shape.
120-cm depth intervals were 1.65, 0.62, 0.37, and
9
Previous Page
