Table 3a presents kinetic results for TNT from seven archived soil samples from five installations.
Extracted concentrations generally increase with extraction time for both acetone and methanol,
indicating that extraction is not complete in three minutes; however, the additional increase is gen-
erally small. The concentration obtained for the three-minute extraction time was always at least
75% of the value obtained after shaking for 18 hours for both solvents. Thus for these high concen-
tration samples, the extraction rate is relatively fast for both acetone and methanol compared to that
observed for air-dried, lower concentration field-contaminated soils using acetonitrile and ultra-
sonic extraction (Jenkins et al. 1989).
Similar kinetic results were obtained for the extraction of RDX from these archived soils (Table
3b). For one soil (Iowa SS-8-005), only 6667% of the RDX extractable at 18 hours was extracted in
the first three minutes. For the other three soils, at least 85% of the concentration found after 18
hours of extraction was attained after only three minutes of shaking for both methanol and acetone.
Comparison of the extraction efficiencies of acetone versus methanol cannot be made because ex-
tractions were performed on separate subsamples and the analytes were heterogeneously distrib-
uted between subsamples. This heterogeneity is evident in both samples from Iowa AAP (Table 3a).
2,4-DNT is a propellant rather than a secondary explosive and its sensitivity to shock and flame
in soil was not evaluated by Kristoff et al. (1987). Nevertheless, an on-site method for 2,4-DNT in
soil is available (Jenkins and Walsh 1991) and two samples of soil contaminated with high levels of
2,4-DNT were available. Therefore, we decided to determine the extraction rate for this compound
when present at high concentrations in soil. Kinetic extraction results for 2,4-DNT in archived soils
are presented in Table 3c. Here again, the rate of extraction was rapid with extracted concentrations
after only three minutes of shaking, at least 70% of that attained after 18 hours with either acetone or
methanol.
Additional kinetic extraction studies were conducted with four field-moist soil samples from
Volunteer AAP that contained high levels of TNT (Table 4). The rate of extraction for these samples
was quite rapid. At least 88% of the TNT concentration obtained after 18 hours of shaking was
attained after only a three-minute extraction time using either acetone or methanol. Concentrations
extracted after the three-minute acetone or methanol extraction were at least 70% of the values
obtained using the standard laboratory extraction procedure of 18 hours of ultrasonic extraction
Table 4. Extraction rate data for TNT from field-moist soils.
TNT concentration (g/g)
Volunteer AAP
Volunteer AAP
Volunteer AAP
Volunteer AAP
(7R-1)
(7R-4)
(7R-6)
(8-3)
Time
Acetone Methanol
Acetone Methanol Acetone Methanol
Acetone Methanol
3 min
85300
84000
88800
83500
101000
102000
24600
26700
10 min
88400
85000
91300
82500
97500
102000
28700
26700
30 min
90900
85000
94300
83000
118000
101000
27100
26400
60 min
87700
85500
94800
82500
101000
102000
26900
26300
18 hrs
85800
85500
96300
85500
102000
104000
28000
27000
Ratio:
3 min/18 hr
0.99
0.98
0.92
0.98
0.99
0.98
0.88
0.99
Method
109000
119000
100000
21300
8330*
(ACN)
(ACN)
(ACN)
(ACN)
Ratio:
3 min/8330
0.78
0.77
0.75
0.70
1.01
1.02
1.15
1.25
EnSys†
82000
76200
78200
23200
Ratio:
EnSys/8330
0.75
0.64
0.78
1.09
* Method 8330 results from acetonitrile ultrasonic extraction for 18 hr followed by RP-HPLC
determination.
† EnSys results determined in the field prior to laboratory sample homogenization using acetone
extraction and colorimetric determination.
8
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