Vapor Signatures from Military Explosives. Part 1. Vapor Transport from Buried Military-Grade TNT
[report]
Thomas F. Jenkins, Daniel C. Leggett, Thomas A. Ranney
1999
unpublished
Crystals of military-grade TNT were placed Both the qualitative and quantitative nature of the beneath 2.5 cm of soil in enclosed 40-mL amber vials chemical signature above buried TNT is strongly a and the accumulation of signature vapors in the head-function of temperature. At 23 and 4 0 C, 2,4-DNT was space above the soil was determined as a function of present at the highest concentration in the headspace time. Three different soils-sand, silt, and clay-were vapor, 2,4,6-TNT being only a
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... r component. At investigated at three different moisture contents: air -12 0 C, the more volatile 1,3-DNB predominated. dry, low moisture, and high moisture. Two replicates of Vapors penetrate the soils in the order sand > silt > each combination of soil type and soil moisture were clay, with vapor concentrations in the same order. Dry equilibrated at three temperatures (23, 4 and -1 2 0 C) soils are very retentive of TNT vapors, while soil moisover periods ranging from 63 to 173 days. ture facilitates movement of vapors to the headspace. The headspace was sampled by a polyacrylate Soil-air partition coefficients, computed for these solid phase microextraction (SPME) fiber for periods three soils at 23 and 4 0 C for 2,4,6-TNT, ranged from ranging from 5 to 20 minutes, and analytes were 1.6 x 104 mL-air/g-soil for moist sand at 23 0 C to 3.0 desorbed in the injection port of a gas chromatograph x 107 for moist clay at 4 0 C. Partition coefficients for equipped with an electron capture detector, Mass 2,4-DNT were about an order of magnitude lower. detection limits using this method were below 1 pg (1 x Vapor concentrations for several of the air-dried soils 10-12 g) for the major signature chemicals-2,4-diniwere too low to measure and hence the partition coeftrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), ficients for dry soils could not be estimated, but were and 2,4,6-trinitrotoluene (2,4,6-TNT). At the end of the much higher than for the same soil with higher moisexperiment, the top 5 mm of soil was carefully ture. These results indicate that for detection of buried removed, extracted with acetonitrile, and the extracts mines, the largest mass of signature chemicals will be were analyzed using RP-HPLC-UV according to present in the surface soil rather than the overlying air. SW846 Method 8330.
doi:10.21236/ada373402
fatcat:e2j5vegg5nehbfubmdkyl7re4q