Many nation's armed forces are undertaking efforts to minimize the environmental impacts of live-fire military training. Based on this, the Canadian Department of National Defence has undertaken a project to examine potential alternatives to the use of Composition C4, an RDX-based plastic explosive. Plastic explosives are widely used by all armed forces for both military engineering tasks and explosive ordnance disposal and their use may lead to the deposition of explosives in the environment, namely RDX, in the case of C4. RDX is very stable in the environment, water soluble, and moves relatively rapidly towards surface and groundwater bodies. One option identified as a potential RDX-free formulation is a pentaerythritol tetranitrate (PETN) based plastic explosive, commercially available in Germany and referred to as Seismoplast. In order to measure the environmental impacts of this formulation, a deposition rate study was conducted. These tests consist of evaluating the detonation efficiencies of munitions during detonation scenarios representative of military training. Data generated from these tests are the deposition masses of the energetic components in the explosive filler, which in this case is PETN. To achieve this objective, seven blocks of Seismoplast were open detonated over a surface of pristine snow, and post-detonation surface samples were collected to measure residual PETN. The trial demonstrated that less than 1 x 10(-7)% of PETN is deposited upon detonation of Seismoplast. The energetic material deposition rates obtained in this trial are much lower than rates obtained for the RDX-based C4 currently in-service within Canada. Switching from a RDX-based plastic explosive to one based on PETN may be an interesting option through which the Department of National Defence can reduce the environmental impact of its activities.

Training with large caliber weapon systems will result in the deposition of energetic materials on military training ranges. Deposition can occur at several locations. These include firing points, impact points, propellant disposal areas, demolitions training ranges, and munitions disposal areas. The potential quantity, composition, and concentration of energetics in each of these areas is directly linked to the activities that occur there. During live-fire training, propellant residues are generated at firing points and propellant disposal locations. Explosives residues will be found down range in the impact area. Activities by engineers and explosive ordnance disposal units in demolitions training ranges will involve expedient demilitarization of munitions and practice conducting blow-in-place (BIP) of munitions. BIP operations may also occur on impact ranges with rounds that fail to detonate properly or do not detonate at all (dudded rounds). Munitions disposal areas are locations where damaged or outdated munitions may be destroyed on a military base. The mass of residues associated with these activities is contingent upon the efficiency of each operation. The US Army Cold Regions Research and Engineering Laboratory has developed methods to determine residues mass deposition rates on a per-round basis for most heavy weapon systems and activities associated with training with large caliber rounds. Research conducted since 2002 on various heavy weapon systems has given us useful insights into sources of contamination, efficiency of munitions and weapon systems, and munitions constituents that will be problematic on training ranges. This paper presents results of research for standard US weapon systems from 60-mm to 204-cm. Energetics residues deposition rates vary from 72% at the firing point for the 84mm AT-4 shoulder-fired weapon system to non-detectable residues mass at 155-mm howitzer impact points. Examples are given for various weapon systems and an example of a residues database for military training ranges is presented. This database is being used in the US to determine impacts on various training ranges and was instrumental in having one family of munitions reclassified and restricted from training range use.

Several defense departments intend to replace 2,4,6-trinitrotoluene (TNT) in munitions formulations by the less sensitive 2,4-dinitroanisole (DNAN). To help understand environmental behavior and ecological risk associated with DNAN we investigated its key initial abiotic and biotic reaction routes and determined relevant physicochemical parameters (pKa, logKow, aqueous solubility (Sw), partition coefficient (Kd)) for the chemical and its products. Reduction of DNAN with either zero valent iron or bacteria regioselectively produced 2-amino-4-nitroanisole (2-ANAN) which, under strict anaerobic conditions, gave 2,4-diaminoanisole (DAAN). Hydrolysis under environmental conditions was insignificant whereas photolysis gave photodegradable intermediates 2-hydroxy-4-nitroanisole and 2,4-dinitrophenol. Physicochemical properties of DNAN and its amino products drastically depended on the type and position of substituent(s) on the aromatic ring. Sw followed the order (TNT<DNAN<2-ANAN<4-ANAN<DAAN) whereas logKow followed the order (DAAN<4-ANAN<2-ANAN<DNAN<TNT). In soil, successive replacement of NO2 by NH2 in DNAN enhanced irreversible sorption and reduced bioavailability under oxic conditions. Although DNAN is more soluble than TNT, its lower hydrophobicity and its tendency to form aminoderivatives that sorb irreversibly to soil contribute to make it less toxic than the traditional explosive TNT.

The presence of nitroglycerin (NG) has been reported in shallow soils and pore water of several military training ranges. In this context, NG concentrations can be reduced through various natural attenuation processes, but these have not been thoroughly documented. This study aimed at investigating the role of soil organic matter (SOM) in the natural attenuation of NG, under aerobic conditions typical of shallow soils. The role of SOM in NG degradation has already been documented under anoxic conditions, and was attributed to SOM-mediated electron transfer involving different reducing agents. However, unsaturated soils are usually well-oxygenated, and it was not clear whether SOM could participate in NG degradation under these conditions. Our results from batch- and column-type experiments clearly demonstrate that in presence of dissolved organic matter (DOM) leached from a natural soil, partial NG degradation can be achieved. In presence of particulate organic matter (POM) from the same soil, complete NG degradation was achieved. Furthermore, POM caused rapid sorption of NG, which should result in NG retention in the organic matter-rich shallow horizons of the soil profile, thus promoting degradation. Based on degradation products, the reaction pathway appears to be reductive, in spite of the aerobic conditions. The relatively rapid reaction rates suggest that this process could significantly participate in the natural attenuation of NG, both on military training ranges and in contaminated soil at production facilities.

Nitroglycerin (NG) is often present in soils and sometimes in pore water at antitank firing positions due to incomplete combustion of propellants. Various degradation processes can contribute to the natural attenuation of NG in soils and pore water, thus reducing the risks of groundwater contamination. However, until now these processes have been sparsely documented. This study aimed at evaluating the ability of microorganisms from a legacy firing position to degrade dissolved NG, as well as NG trapped within propellant particles. Results from the shake-flask experiments showed that the isolated culture is capable of degrading dissolved NG but not the nitrocellulose matrix of propellant particles, so that the deeply embedded NG molecules cannot be degraded. Furthermore, the results from column experiments showed that in a nutrient-poor sand, degradation of dissolved NG may not be sufficiently rapid to prevent groundwater contamination. Therefore, the results from this study indicate that, under favorable soil conditions, biodegradation can be an important natural attenuation process for NG dissolving out of fresh propellant residues. In contrast, biodegradation does not contribute to the long-term attenuation of NG within old, weathered propellant residues. Although NG in these old residues no longer poses a threat to groundwater quality, if soil clean-up of a legacy site is required, active remediation approaches should be sought.

For the last two decades, DRDC Valcartier has been involved in the synthesis of energetic thermoplastic elastomers (ETPEs) based on Glycidyl Azide Polymers (GAPs). These ETPEs are copolyurethane thermoplastic elastomers, physically crosslinked rubbery materials that can be dissolved in organic solvent and recycled or can be used as the binder for insensitive melt cast explosives. The mechanical properties of these ETPEs were adjusted to serve as binders in melt cast explosive formulations and give the insensitive character to the formulations. An insensitive explosive named "XRT" for "eXperimental Rubbery TNT" was developed and led directly to the development of a new insensitive recyclable green explosive (GIM). A major project named "RIGHTTRAC" for "Revolutionary Insensitive Green and Healthier Training Technology with Reduced Adverse Contamination" was initiated two years ago and aims at producing a greener weapon. Work was conducted on XRT and GIM explosives to test their performance and sensitivity, their fate and behaviour into the environment, their recycling and value as ingredients to produce a greener munitions based on these concepts. Since ETPEs are recyclable, the ease of recycling and reuse of the ingredients of the new formulations at the end of their life cycle was studied. This paper will describe the syntheses of the ETPEs, the preparation of the XRT and GIM explosives and the results obtained so far describing their properties, insensitive character, recycling, fate and behaviour of formulations and ageing testing.

The revolutionary insensitive, green, and healthier training technology with reduced adverse contamination (RIGHTTRAC) program is a 5-year technology demonstration program (TDP) aimed at showing that green and insensitive munitions have better properties than current munitions, and that it is feasible to implement safer weapon solutions that would ease the environmental pressure on ranges and training areas and decrease the health hazards for the users. The goals of this TDP are to reach a near-zero dud rate and to eliminate the potential for research development explosive (RDX) contamination as well as the use of toxic and carcinogenic compounds. This will be done by performing significant improvements to the fuzing system, the main explosive charge and the gun propellant. The vehicle used for this demonstration is a 105-mm army artillery munition (high-explosive M1), currently filled with Composition B (a 60:40 RDX:TNT mix) and using a single-base gun propellant (M1 formulation). The aim of this communication is to provide an overview of the project and to describe the steps taken to evaluate the environmental properties of the chosen propellant and explosive formulations. At its completion, it is believed that this project will have provided the required data to assess the long-term effects of the munitions on the environment right at an early stage of the weapon development cycle, and that this can be cost effective in the long run. This will help sustain military training while preserving our resources, as well as shaping the future of weapon system development.

The development of insensitive munitions by NATO countries is an ongoing effort. Less-sensitive ingredients in both explosives and propellants will ensure the protection of deployed troops against an unwanted reaction to an external stimulus on the munitions stockpile. In the US Army, current efforts are directed towards the development of melt cast insensitive explosive formulations. Various formulations, mainly based on DNAN and NTO, have been developed and are now being fielded. Our research goal is to measure the deposition rate of energetics compounds from various insensitive munitions detonation scenarios. Our hypothesis is that the relative insensitiveness of these formulations leads to slightly higher deposition rates than conventional explosive formulations. This paper describes detonation residues research on mortar rounds containing IMX-104 explosive. Analyses indicate that high-order detonation residues are slightly greater for this formulation than for conventional munitions. However, blow-in-place detonations (BIPs) resulted in much higher residues deposition, indicating that a larger donor charge is required for efficient detonation. The highly soluble compound NTO was particularly problematic, with BIP deposition approaching 95% of the original load. Toxicological studies of NTO are not finalized, leaving considerable uncertainty regarding the feasibility of approving these rounds for distribution.

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and nitroglycerin (NG) are two energetic materials commonly found in the environment on military training ranges. They are deposited on the ground in the form of solid particles, which can then dissolve in infiltration water or in surface water bodies. The objective of this study was to evaluate whether photolysis by sunlight can significantly contribute to the natural attenuation of RDX and NG (as solid particles or dissolved in surface water) at mid-northern latitudes, where training ranges of Canada and many European countries are located. Experiments conducted at 46.9°N show that both compounds are degraded by sunlight when dissolved in water, with half-lives between 1 and 120d, depending on the compound and time of year. Numerical models may be useful in predicting such photolysis rates, but the models should take into account current ozone levels, as older radiation datasets, collected before the ozone depletion observed since the late 1970s, underestimate the RDX/NG photolysis rate. For solid RDX or NG-bearing particles, photolysis is slower (half-lives of 2–4months), but the degradation rate is still rapid enough to make this process significant in a natural attenuation context. However, photolysis of NG embedded within solid propellant particles cannot proceed to completion, due to the stable nitrocellulose matrix of the propellant. Nonetheless, photolysis clearly constitutes an important attenuation mechanism that should be considered in conceptual models and included in numerical modeling efforts.

N-Guanylurea-dinitramide (FOX-12) is a very insensitive energetic material intended to be used in the composition of next-generation insensitive munitions. To help predict the environmental behavior and fate of FOX-12, we conducted a study to determine its photodegradability and biodegradability. When dissolved in water, FOX-12, a guanylurea-dinitramide salt, also named GUDN, dissociated instantly to produce the dinitramide moiety and guanylurea, as demonstrated by high-performance liquid chromatography (HPLC) analysis. When an aqueous solution of FOX-12 was subjected to photolysis using a solar-simulated photoreactor, we found a rapid removal of the dinitramide with concurrent formation of N₂O, NO₂(-), and NO₃(-). The second component, guanylurea, was photostable. However, when FOX-12 was incubated aerobically with the soil isolate Variovorax strain VC1 and protected from light, the dinitramide component of FOX-12 was recalcitrant but guanylurea degraded effectively to ammonia, guanidine, and presumably CO₂. When FOX-12 was incubated with strain VC1 in the presence of light, both components of FOX-12 degraded, giving similar products to those described above. We concluded that the new insensitive explosive FOX-12 can be effectively degraded by a joint photomicrobial process and, therefore, should not cause persistent contamination of surface waters.

Insensitive high explosives are being used in military munitions to counteract unintended detonations during storage and transportation. These formulations contain compounds such as 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO), which are less sensitive to shock and heat than conventional explosives. We conducted a series of four tests on snow-covered ice utilizing 60-mm mortar cartridges filled with 358g of PAX-21, a mixture of RDX, DNAN, and ammonium perchlorate. Rounds were detonated high- and low-order using a fuze simulator to initiate detonation. Blow-in-place (BIP) operations were conducted on fuzed rounds using an external donor charge or a shaped-charge initiator. Results indicate that 0.001% of the original mass of RDX and DNAN were deposited during high-order detonations, but up to 28% of the perchlorate remained. For the donor block BIPs, 1% of the RDX and DNAN remained. Residues masses for these operations were significantly higher than for conventional munitions. Low-order detonations deposited 10-15% of their original explosive filler in friable chunks up to 5.2g in mass. Shaped-charge BIPs scattered 15% of the filler and produced chunks up to 15g. Ammonium perchlorate residue masses were extremely high because of the presence of large AP crystals, up to 400m in the recovered particles.

Nitroglycerin (NG) and nitrocellulose (NC) are constituents of double-base propellants used notably for firing antitank ammunitions. Nitroglycerin was detected in soil and water samples from the unsaturated zone (pore water) at an active antitank firing position, where the presence of high nitrate (NO3(-)) concentrations suggests that natural attenuation of NG is occurring. However, concentrations alone cannot assess if NG is the source of NO3(-), nor can they determine which degradation processes are involved. To address this issue, isotopic ratios (δ(15)N, δ(18)O) were measured for NO3(-) produced from NG and NC through various controlled degradation processes and compared with ratios measured in field pore water samples. Results indicate that propellant combustion and degradation mediated by soil organic carbon produced the observed NO3(-) in pore water at this site. Moreover, isotopic results are presented for NO3(-) produced through photolysis of propellant constituents, which could be a dominant process at other sites. The isotopic data presented here constitute novel information regarding a source of NO3(-) that was practically not documented before and a basis to study the contamination by energetic materials in different contexts.

The insensitive high-explosive PAX-21 was the first of its kind fielded in an artillery munition by the United States military. This formulation contains three main components: RDX, dinitroanisole, and ammonium perchlorate (AP). In March 2012, detonation tests were conducted on PAX-21 60mm mortar rounds to determine the energetic residues resulting from high-order and blow-in-place (BIP) detonations. Post-detonation residues were sampled and analyzed for the three main PAX-21 components. Concentrations of RDX and dinitroanisole in the samples were quite low, less than 0.1% of the munitions' original organic explosive filler mass, indicating high order or near high order detonations. However, disproportionately high concentrations of AP occurred in all residues. The residues averaged 15% of the original AP following high-order detonations and 38% of the original AP mass following the BIP operations. There was no correlation between AP residues and the RDX and dinitroanisole. Perchlorate readily leached from the detonation residues, with over 99% contained in the aqueous portion of the samples. Use of these rounds will result in billions of liters of water contaminated above drinking water perchlorate limits. As a result of this research, PAX-21 mortar rounds are currently restricted from use on US training ranges.

The high explosive nitroaromatic 2,4-dinitroanisole (DNAN) is less shock sensitive than 2,4,6-trinitrotoluene (TNT), and is proposed as a TNT replacement for melt-cast formulations. Before using DNAN in munitions and potentially leading to environmental impact, the present study examines the ecotoxicity of DNAN using selected organisms. In water, DNAN decreased green algae Pseudokirchneriella subcapitata growth (EC50 = 4.0mg/L), and bacteria Vibrio fischeri bioluminescence (Microtox, EC50 = 60.3mg/L). In soil, DNAN decreased perennial ryegrass Lolium perenne growth (EC50 =7 mg/kg), and is lethal to earthworms Eisenia andrei (LC50 = 47 mg/kg). At sub-lethal concentrations, DNAN caused an avoidance response (EC50 = 31 mg/kg) by earthworms. The presence of DNAN and 2-amino-4-nitroanisole in earthworms and plants suggested a role of these compounds in DNAN toxicity. Toxicity of DNAN was compared to TNT, tested under the same experimental conditions. These analyses showed that DNAN was equally, or even less deleterious to organism health than TNT, depending on the species and toxicity test. The present studies provide baseline toxicity data to increase the understanding of the environmental impact of DNAN, and assist science-based decision makers for improved management of potential DNAN contaminated sites.

Nitroguanidine (NQ) is an energetic material that is used as a key ingredient of triple-base propellants and is currently being considered as a TNT replacement in explosive formulations. NQ was efficiently degraded in aerobic microcosms when a carbon source was added. NQ persisted in unamended microcosms or under anaerobic conditions. An aerobic NQ-degrading bacterium, Variovorax strain VC1, was isolated from soil microcosms containing NQ as the sole nitrogen source. NQ degradation was inhibited in the presence of a more favorable source of nitrogen. Resting cells of VC1 degraded NQ effectively (54 μmol h(-1) g(-1) protein) giving NH(3) (50.0%), nitrous oxide (N(2)O) (48.5%) and CO(2) (100%). Disappearance of NQ was accompanied by the formation of a key intermediate product that we identified as nitrourea by comparison with a reference material. Nitrourea is unstable in water and suffered both biotic and abiotic decomposition to eventually give NH(3), N(2)O, and CO(2). However, we were unable to detect urea. Based on products distribution and reaction stoichiometry, we suggested that degradation of NQ, O(2)NN═C(NH(2))(2), might involve initial enzymatic hydroxylation of the imine, -C═N- bond, leading first to the formation of the unstable α-hydroxynitroamine intermediate, O(2)NNHC(OH)(NH(2))(2), whose decomposition in water should lead to the formation of NH(3), N(2)O, and CO(2). NQ biodegradation was induced by nitroguanidine itself, L-arginine, and creatinine, all being iminic compounds containing a guanidine group. This first description of NQ mineralization by a bacterial isolate demonstrates the potential for efficient microbial remediation of NQ in soil.

Live fire military training involves the detonation of explosive warheads on training ranges. The purpose of this experiment is to evaluate the hydrogeological changes to the vadose zone caused by military training with high explosive ammunition. In particular, this study investigates artillery ammunition which penetrates underground prior to exploding, either by design or by defective fuze mechanisms. A 105 mm artillery round was detonated 2.6 m underground, and hydraulic conductivity measurements were taken before and after the explosion. A total of 114 hydraulic conductivity measurements were obtained within a radius of 3m from the detonation point, at four different depths and at three different time periods separated by 18months. This data was used to produce a three dimensional numerical model of the soil affected by the exploding artillery round. This model was then used to investigate potential changes to aquifer recharge and contaminant transport caused by the detonating round. The results indicate that an exploding artillery round can strongly affect the hydraulic conductivity in the vadose zone, increasing it locally by over an order of magnitude. These variations, however, appear to cause relatively small changes to both local groundwater recharge and contaminant transport.

The present study describes the use of two commercially available lignins, namely, alkali and organosolv lignin, for the removal of 2,4-dinitroanisole (DNAN), a chemical widely used by the military and the dye industry, from water. Sorption of DNAN on both lignins reached equilibrium within 10 hr and followed pseudo second-order kinetics with sorption being faster with alkali than with organosolv lignin, i.e. k2 10.3 and 0.3 g/(mg·hr), respectively. In a separate study we investigated sorption of DNAN between 10 and 40C and found that the removal of DNAN by organosolv lignin increased from 0.8 to 7.5 mg/g but reduced slightly from 8.5 to 7.6 mg/g in the case of alkali lignin. Sorption isotherms for either alkali or organosolv lignin best fitted Freundlich equation with enthalpy of formation, ΔH0 equaled to 14 or 80 kJ/mol. To help understand DNAN sorption mechanisms we characterized the two lignins by elemental analysis, BET nitrogen adsorption-desorption and 31P NMR. Variations in elemental compositions between the two lignins indicated that alkali lignin should have more sites (O- and S-containing functionalities) for H-bonding. The BET surface area and calculated total pore volume of alkali lignin were almost 10 times greater than that of organosolv lignin suggesting that alkali lignin should provide more sites for sorption. 31P NMR showed that organosolv lignin contains more phenolic -OH groups than alkali lignin, i.e., 70% and 45%, respectively. The variations in the type of OH groups between the two lignins might have affected the strength of H-bonding between DNAN and the type of lignin used.

The expedient field disposal of excess gun propellants on the ground is an integral part of live-fire training in many countries. However, burning excess propellant in the field will leave significant quantities of energetic residues and heavy metals in the environment. Compounds such as dinitrotoluene and nitroglycerin and metals such as lead will leach into the soil column, eventually migrating to groundwater. Contamination of the environment will lead to high remediation costs and the possible loss of the training facility. After investigating the contamination at several propellant disposal sites, a portable propellant burn pan was developed and tested. The pan was transported to training sites where excess propellant was loaded and burned in a controlled manner. Up to 120 kg of excess single-base propellant charges have been burned during two series of tests at a consumption rate of greater than 99.9%. Less than 0.03% of the energetic material was recovered outside the burn pan. Recovered lead is largely contained within the pan. The turnover rate for burns is 15 min. The residues can be collected following cool-down for proper disposal. Published by Elsevier B.V.

The environmental fate of nitroglycerin (NG) in the unsaturated zone was evaluated in the context of double-base propellant residue deposition at anti-tank training ranges. Fresh propellant residues were collected during live anti-tank training. Surface soils, sub-surface soils and water samples from the unsaturated zone were collected at an active anti-tank range, and at a legacy site where NG-based propellants have been used. Results show that the residues are composed of intact propellant particles, as well as small quantities of NG, dinitroglycerin (DNG) and nitrate which are rapidly dissolved by precipitation, resulting in sporadic pulses of those compounds in water from the unsaturated zone after rain/snow melt events. The dissolved NG and DNG can be progressively degraded in the unsaturated zone, releasing nitrate as an end-product. Over a period of several years, small propellant particles located at the soil surface can be carried downward through the soil pore system by infiltration water, which explains the presence of NG in sub-surface soils at the legacy site, more than 35 years after site closure. NG is no longer leached from these old particles, therefore the detection of NG in sub-surface soils does not signify that groundwater is at risk of contamination by NG.