Paul H. Miyares

Chemical signatures of TNT-filled land mines.

The equilibrium headspace above several military-grade explosives was sampled using solid phase microextraction fibers and the sorbed analytes determined using gas chromatography with an electron capture detector (GC-ECD). The major vapors detected were the various isomers of dinitrotoluene (DNTs), dinitrobenzene (DNBs), and trinitrotoluene (TNTs), with 2,4-DNT and 1,3-DNB often predominating. Although 2,4,6-TNT made up from 50 to 99% of the solid explosive, it was only a minor component of the equilibrium vapor. The flux of chemical signatures from intact land mines is thought to originate from surface contamination and evolution of vapors via cracks in the casing and permeation through polymeric materials. The levels of external contamination were determined on a series of four types of Yugoslavian land mines (PMA-1A, PMA2, TMA5 and TMM1). The flux into air as a function of temperature was determined by placing several of these mines in Tedlar bags and measuring the mass accumulation on the walls of the bags after equilibrating the mine at one of five temperatures. TNT was a major component of the surface contamination on these mines, yet it accounted for less than 10% of the flux for the three plastic-cased mines, and about 33% from the metal antitank mine (TMM1). Either 2,4-DNT or 1,3-DNB produced the largest vapor flux from these four types of land mines. The environmental stability of the most important land mine signature chemicals was determined as a function of temperature by fortifying soils with low aqueous concentrations of a suite of these compounds and analyzing the remaining concentrations after various exposure times. The kinetics of loss was not of first order in analyte concentration, indicating that half-life is concentration dependent. At 23 degrees C, the half life of 2,4,6-TNT, with an initial concentration of about 0.5 mg kg(-1), was found to be only about 1 day. Under identical conditions, the half-life of 2,4-DNT was about 25 days. A research minefield was established and a number of these same four mine types were buried. Soil samples were collected around several of these mines at several time periods after burial and the concentration of signature chemicals determined by acetonitrile extraction and GC-ECD analysis. Relatively high concentrations of 2,4,6-TNT and 2,4-DNT were found to have accumulated beneath a TMA5 antitank mine, with lower concentrations in the soil layers between the mine and the surface. Signatures were distributed very heterogeneously in surface soils, and concentrations were very low (low mug kg(-1) range). Lower, but detectable, concentrations of signatures were detectable irregularly in soils near the PMA-1A mines in contrast to the TMA5 mines. Concentrations of signature chemicals were generally below detection limits (<1 mug kg(-1)) near the TMM1 and PMA-2 mines, even 8 months after burial.

Comparison of solid phase extraction with salting-out solvent extraction for preconcentration of nitroaromatic and nitramine explosives from water

Abstract Residues of high explosives are a significant pollution problem at U.S. military facilities. Because TNT, RDX and HMX, as well as several manufacturing impurities and environmental transformation products, are mobile in the soil and have caused groundwater pollution, there is an increasing demand for low-concentration analysis of these compounds in water from installation boundary wells. Because RDX and HMX are polar, conventional liquid-liquid extraction with nonpolar solvents yields poor recovery. Two techniques have been reported that appear to offer improved recovery and adequate preconcentration: solid phase extraction (SPE) and salting-out solvent extraction (SOE). This paper compares resin based cartridge-SPE, membrane-SPE, and SOE using fortified reagent grade water samples and a set of 58 groundwater samples from an explosives-contaminated military facility. The three methods were comparable with respect to low-concentration detection capability, which ranged from 0.05 to 0.30 μg/l. Percent recoveries generally exceeded 80%, except for HMX and RDX by membrane-SPE. Interferences were found in extracts from half of the groundwater samples preconcentrated using the two SPE procedures, but were not found in any of the extracts from the SOE. These interferences were traced to matrix interaction of the polymeric resins with low-pH groundwater containing high levels of dissolved solids.

Monitored Natural Attenuation of Explosives

Explosives are subject to several attenuation processes that potentially reduce concentrations in groundwater over time. Some of these processes are well defined, while others are poorly understood. The objective of the project was to optimize data collection and processing procedures for evaluation and implementation of monitored natural attenuation of explosives. After conducting experiments to optimize data quality, a protocol was established for quarterly monitoring of thirty wells over a 2-year period at a former waste disposal site. Microbial biomarkers and stable isotopes of nitrogen and carbon were explored as additional approaches to tracking attenuation processes. The project included a cone penetrometry sampling event to characterize site lithology and to obtain sample material for biomarker studies. A three-dimensional groundwater model was applied to conceptualize and predict future behavior of the contaminant plume. The groundwater monitoring data demonstrated declining concentrations of explosives over the 2 years. Biomarker data showed the potential for microbial degradation and provided an estimate of the degradation rate. Measuring stable isotopic fractions of nitrogen in TNT was a promising method of monitoring TNT attenuation. Overall, results of the demonstration suggest that monitored natural attenuation is a viable option that should be among the options considered for remediation of explosives-contaminated sites.

Use of Snow-Covered Ranges to Estimate Explosives Residues from High-Order Detonations of Army Munitions

Estimation of the amounts of residues resulting from high-order detonation of munitions is complicated by the presence of residues from previous detonations and the inability to easily obtain adequately-sized samples to overcome spatial heterogeneity in residue deposition. This study was conducted to assess the use of snow-covered ranges to provide these types of estimates. Specifically, snow-covered ranges were used to estimate the amount of explosives residues that resulted from detonation of individual mortar rounds and a small antipersonnel land mine. At Fort Drum, NY, 60 mm mortars were fired and at Camp Ethan Allen, VT, 81 mm mortars and a Yugolavian PMA2 land mine were detonated by EOD (explosives ordnance disposal) personnel after attaching C4 (RDX) and/or a blasting cap. The locations where residues were deposited were identified by the presence of soot from the detonation of TNT on the surface of the otherwise clean snow. Large surface snow samples were collected with a snow shovel and the melted snow was extracted and analyzed by gas chromatography with an electron capture detector (GC-ECD) and reversed-phase high performance liquid chromatography (RP-HPLC). For both types of mortars the main charge was composition B (60% RDX and 39% TNT); for the land mine, the main charge was TNT with an RDX booster. The major residues produced for the mortars were RDX and nitroglycerine (NG), with lesser amounts of HMX, and TNT. Surface concentrations ranged from as high as 4430 mg/m 2 for RDX to <0.05 mg/m 2 for TNT, both at Camp Ethan Allen. For the land mine, the major residues were TNT and RDX with surface concentrations of 20.8 and 1.8 mg/m 2 , respectively. Published by Elsevier Science B.V.

Apparent donor-acceptor interaction between nitroaromatics and acetonitrile

The partitioning behavior of nitro-aromatics in octanol-water and acetonitrile/NaCl-saturated water was examined. The nitro group contribution is opposite in the two systems, from which two different bonding mechanisms were inferred. In addition to cavity effects the octanol-water system is characterized by H-bonding of water to the nitro groups, while in the acetonitrile/NaCl-saturated water system electron donor-acceptor complexation predominates. A linear free energy relationship which relates the partition coefficients in the two systems was logPaw=0.727 logPow+0.395 n+0.742 where n is the number of nitro groups per ring.