TNT-based Explosives Research Articles

The Escherichia coli azoR gene promoter: A new sensing element for microbial biodetection of trace explosives

Abstract DNT (2,4-dinitrotoluene), a volatile impurity in military grade TNT-based explosives, is a potential tracer for the detection of buried landmines and other explosive devices. We have previously described DNT bioreporter strains, based on a fusion between the Escherichia coli yqjF gene promoter to either a bacterial luxCDABE luminescence gene cassette or to the green fluorescent protein gene gfp. We now present the azoR gene promoter, demonstrated to be strongly induced by DNT, as an alternative sensing element for this compound. An E. coli bioreporter strain harboring a plasmid-borne fusion of the azoR promoter region to Photorhabdus luminescens luxCDABE displayed stronger bioluminescent responses to DNT than the yqjF-based bioreporter. The azoR promoter was induced not directly by DNT but by its degradation products; the most potent inducer was 2,4,5-trihydroxytoluene (THT). This reaction was positively regulated by YhaJ, a member of the LysR family of transcriptional regulators, and was significantly amplified in a yhaK mutant. We also show that DNT degradation in E. coli involves glutathione, which plays a vital role in azoR gene promoter activation.

Outdoor weathering and dissolution of TNT and Tritonal

Low-order detonations of military munitions scatter cm-sized chunks of high-explosives onto military range soils, where rainfall can dissolve and then transport the explosives to groundwater. We present 1 year of mass-loss data obtained from cm-sized chunks of the frequently used explosives TNT (2,4,6-trinitrotoluene) and Tritonal (an 80:20 mixture of TNT and aluminum flakes) exposed outdoors to weather and dissolve under natural conditions. The explosive chunks rested on glass frits in individual funnels and all precipitation interacting with them was collected and analyzed. Mass balance data reveal that TNT in the water samples accounts for only about one-third of the TNT lost from the chunks. The creation of photo-transformation products on the solid chunks, and their subsequent dissolution or sublimation, probably accounts for the other two-thirds. Although these products cannot, as yet, be quantified they are intrinsic to the outdoor weathering and fate of TNT-based explosives. TNT in our water samples was not photo-transformed. Thus, we used the yearlong, dissolved-mass time-series to validate a drop-impingement dissolution model for TNT. The model used measured rainfall and air temperature data as input, and the results agreed remarkably well with TNT dissolved-mass time-series measured for the year. This model can estimate annual TNT influx into range soils using annual rainfall and particle-size distributions. Nevertheless, large uncertainties remain in the numbers and sizes of TNT particles scattered on military ranges and the identities and fates of the photo-transformation products.

Increasing Selectivity for TNT-Based Explosive Detection by Synchronous Luminescence and Derivative Spectroscopy with Quantum Yields of Selected Aromatic Amines

The detection of explosive material is at the forefront of current analytical problems. A detection method is desired that is not restricted to detecting only explosive materials, but is also capable of identifying the origin and type of explosive. It is essential that a detection method have the selectivity to distinguish among compounds in a mixture of explosives. The nitro compounds found in explosives have low fluorescent yields or are considered to be non-fluorescent; however, after reduction, the amino compounds exhibit relatively high fluorescence. We discuss how to increase selectivity of explosive detection using fluorescence; this includes synchronous luminescence and derivative spectroscopy with appropriate smoothing. By implementing synchronous luminescence and derivative spectroscopy, we were able to resolve the reduction products of one major TNT-based explosive compound, 2,4-diaminotoluene, and the reduction products of other minor TNT-based explosives in a mixture. We also report for the first time the quantum yields of these important compounds. Relative quantum yields are useful in establishing relative fluorescence intensities and are an important spectroscopic measurement of molecules. Our approach allows for rapid, sensitive, and selective detection with the discrimination necessary to distinguish among various explosives.

Monte Carlo simulations as a feasibility tool for non-metallic land-mine detection by thermal-neutron backscattering

The use of Monte Carlo simulations is presented for modelling a simplified land-mine detector system with thermal neutron backscattering (TNB) analysis based on a 252Cf-neutron source. Different aspects and a variety of external conditions, related to localisation and identification of a buried object have been investigated. In particular, the influence of moisture in a formation has been assessed, as moisture can be a serious interference for hydrogen as an indicator for explosives. The results of sensitivity calculations confirm that land-mine detection methods, based on an analysis of TNB may be applicable in homogeneous formations with low porosity provided that pore-water remains <5% by weight. In dry limestone, the TNT-based explosives can be well distinguished from other hydrogen-rich materials, except wood. However, in dry siliciclastic sands TNT explosives and wood are distinguishable.

Base hydrolysis of TNT-Based explosives

Four TNT explosive formulations were treated with 1.5 M and 3 M solutions of sodium hydroxide (NaOH) at temperatures between 90°C and 150°C. The reaction time needed for over 99% conversion of the explosive compound was less than 5 minutes at 150°C for both Octol and Comp B, and less than 30 minutes at 90°C for Tritonal and Tetrytol. The TNT and Tetryl fractions of the explosive produced negligible gas and liquid products were ammonia, sodium acetate, sodium formate, and sodium nitrite. The RDX and HMX fractions produced a substantial amount of gas and the major products were nitrous oxide, nitrogen, and ammonia. The aluminum used in Tritonal was converted to aluminum hydroxide and hydrogen gas.

Direct Observation of Detonation in Compressed Nitromethane

Johansson and Sternhoff1 have shown that the detonation light from some TNT-based explosives is suppressed under pressure from an externally produced shock wave. We have observed similar behaviour in nitromethane where, in this case, the homogeneous liquid can be considered to be free of voids which may influence the emitted light. A somewhat more indirect experiment has been described2 wherein a detonating nitromethane charge was observed normal to the open end. With proper under-boostering, weak light was observed which, after a time, suddenly changed to the normal detonation intensity. The weak light was attributed to detonation of material compressed by the initiating shock wave.