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The present study investigates the bioaccumulation of the insensitive munition compounds 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO), developed for future weapons systems to replace current munitions containing sensitive explosives. The earthworm Eisenia andrei was exposed to sublethal concentrations of DNAN or NTO amended in Sassafras sandy loam. Chemical analysis indicated that 2- and 4-amino-nitroanisole (2-ANAN and 4-ANAN, respectively) were formed in DNAN-amended soils. The SumDNAN (sum of DNAN, 2-ANAN, and 4-ANAN concentrations) in soil decreased by 40% during the 14-d exposure period. The SumDNAN in the earthworm body residue increased until day 3 and decreased thereafter. Between days 3 and 14, there was a 73% decrease in tissue uptake that was greater than the 23% decrease in the soil concentration, suggesting that the bioavailable fraction may have decreased over time. By day 14, the DNAN concentration accounted for only 45% of the SumDNAN soil concentration, indicating substantial DNAN transformation in the presence of earthworms. The highest bioaccumulation factor (BAF; the tissue-to-soil concentration ratio) was 6.2 ± 1.0 kg/kg (dry wt) on day 3 and decreased to 3.8 ± 0.8 kg/kg by day 14. Kinetic studies indicated a BAF of 2.3 kg/kg, based on the earthworm DNAN uptake rate of 2.0 ± 0.24 kg/kg/d, compared with the SumDNAN elimination rate of 0.87 d-1 (half-life = 0.79 d). The compound DNAN has a similar potential to bioaccumulate from soil compared with trinitrotoluene. The NTO concentration in amended soil decreased by 57% from the initial concentration (837 mg NTO/kg dry soil) during 14 d, likely due to the formation of unknown transformation products. The bioaccumulation of NTO was negligible (BAF ≤ 0.018 kg/kg dry wt). Environ Toxicol Chem 2021;40:1713-1725. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

The DNAN (2,4-dinitroanisole), NTO (3-nitro-1,2,4-triazol-5-one), and NQ (nitroguanidine) are important insensitive energetic materials used in military applications. They may find their way to the environment during manufacturing, transportation, storage, training, and disposal. A detailed investigation of possible mechanisms for self-degradation of radical anions formed by addition of solvated electron to DNAN, NTO, and NQ species was performed by computational study using the PCM(Pauling)/M06-2X/6-311++G(d,p) approach. Obtained results suggest that only NQ radical anion is able for self-degradation by elimination of nitrite anion. Formation of urea radical on the earlier stage of the NQ radical anion degradation was also predicted.

Insensitive munition assessments are required to carry out sympathetic detonation experiments, in which detonation of an explosive charge triggers detonation of another, and a chain reaction subsequency starts. In this paper, a numerical simulation method is developed to predict the sympathetic detonation behavior of fuze explosive trains, which includes the ignition and growth model, the Jones–Wilkins–Lee equations of state, and the constitutive relationship. The sympathetic detonation behaviors of a fuze is studied for a single donor and a single acceptor. The causes of sympathetic detonation of the fuze explosive trains are analyzed for different fragment and shock wave loading conditions. A sympathetic detonation criterion in different modes of loading is established, which provides a theoretical model for predicting the relationship between the detonation sequence and the placement distance of the fuze. The conclusions obtained in this paper can provide a reference for studying sympathetic detonation of fuze conditions.

Dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ) are constituents of insensitive munitions being developed to minimize the acute hazards associated with non-intenti...

3-Nitro-1,2,4-triazol-5-one (NTO) is an insensitive munition compound (MC) that has replaced legacy MC. NTO can be highly mobile in soil and groundwater due to its high solubility and anionic nature, yet little is known about the processes that control its environmental fate. We studied NTO reduction by the hematite-Fe

Insensitive munitions are munitions that are chemically stable enough to withstand thermal, mechanical, or electrical stimuli during storage and transportation, and can still explode as intended to defeat their targets. Extensive programmes have evolved worldwide for the development and introduction of insensitive munitions (IMs). The use of insensitive energetic materials significantly improves the protection of modern nuclear warheads and increases the survivability of conventional munitions in hustle environment. The most basic level to obtain insensitive munitions is the use of intrinsic insensitive energetic materials, either by synthesizing new, less sensitive crystalline materials or by improving the physical properties of existing sensitive materials. In light of the growing importance of insensitive munitions, this review paper brings out some potential insensitive energetic materials and plasticizers emphasizing their significant role in the development of futuristic IM formulations. This review also concisely brings out the recent work carried out globally, including India, on the development of advanced energetic materials and their insensitive energetic formulations.

Standard methods are in place for analysis of 17 legacy munitions compounds and one surrogate in water and soil matrices; however, several insensitive munition (IM) and degradation products are not part of these analytical procedures. This lack could lead to inaccurate determinations of munitions in environmental samples by either not measuring for IM compounds or using methods not designed for IM and other legacy compounds. This work seeks to continue expanding the list of target analytes currently included in the US Environmental Protection Agency (EPA) Method 8330B. This technical report presents three methods capable of detecting 29 legacy, IM, and degradation products in a single High Performance Liquid Chromatography (HPLC) method with either ultraviolet (UV)-visible absorbance detection or mass spectrometric detection. Procedures were developed from previously published works and include the addition of hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX); hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX); hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX); 2,4-diamino-6-nitrotoluene (2,4-DANT); and 2,6-diamino-4-nitrotoluene (2,6-DANT). One primary analytical method and two secondary (confirmation) methods were developed capable of detecting 29 analytes and two surrogates. Methods for high water concentrations (direct injection), low-level water concentrations (solid phase extraction), soil (solvent extraction), and tissue (solvent extraction) were tested for analyte recovery of the new compounds.

Currently, no standard method exists for analyzing insensitive munition (IM) compounds in environmental matrices, with or without concurrent legacy munition compounds, resulting in potentially inaccurate determinations. The primary objective of this work was to develop new methods of extraction, pre-concentration, and analytical separation/quantitation of 17 legacy munition compounds along with several additional IM compounds, IM breakdown products, and other munition compounds that are not currently included in U. S. Environmental Protection Agency (EPA) Method 8330B. The eight additional compounds included were nitroguanidine, 3-nitro-1,2,4-triazol-5-one, picric acid, 2,4-dinitroanisole, 2,4-dinitrophenol, 2-nitrophenol, 4-nitrophenol, and new surrogate ortho-nitrobenzoic acid (o-NBA). Analytical methods were developed to enable sensitive, simultaneous detection and quantitation of the 24 IM and legacy compounds, including two orthogonal high-performance liquid chromatography (HPLC) column separations with either ultraviolet (UV) or mass spectrometric (MS) detection. Procedures were developed for simultaneous extraction of all 24 analytes and two surrogates (1,2-dinitrobenzene, 1,2-DNB; o-NBA) from high- and low-level aqueous matrices and solid matrices, using acidification, solid phase extraction (SPE), or solvent extraction (SE), respectively. For low-level aqueous samples extracted by SPE, all compounds were recovered within current Department of Defense Quality Systems Manual (DoD QSM) Ver5.3 accepted limits for aqueous samples analyzed by EPA Method 8330B (57–135%), except NQ, which was consistently recovered at approximately 50%. Likewise, all compounds were recovered from six geographically/geochemically unique soil types within current QSM accepted limits for solid samples analyzed by EPA Method 8330B (64–135%). Further, the majority of compounds were recovered from four tissue types within current limits for solids, with generally low recovery only for Tetryl (from 4 to 62%). A preparatory chromatographic interference removal procedure was adapted for tissue extracts, as various analytical interferences were observed for all studied tissue types.

Polymer bonded explosives (PBX) have many applications in both the military and civilian sectors, making their safety and behavior predictability of the utmost importance. Most explosive devices are typically initiated by some external stimulus; however, initiations can also occur via localized mechanical conversion of energy during impact, called ‘hot spots’. These unintended loads can lead to crystal fracture and frictional heating, amongst other mechanisms, in the energetic crystals of a PBX. In order to visualize the behavior of these crystals, high-speed phase contrast imaging experiments were conducted using synchrotron X-ray radiation to observe the internal crack behavior of simplified PBXs subjected to low velocity impact. The PBX samples used in these experiments were composed of single production-grade and recrystallized octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals embedded in a Sylgard® 184 binder doped with iron (III) oxide. We observed a clear distinction in the qualitative behavior of production-grade versus recrystallized ‘low-defect’ HMX crystals which lacked significant internal voids. Production grade crystals exhibited consistent cracking behavior in the crystals, while the recrystallized crystals exhibited debonding from the surrounding binder material and cracked much less frequently. We assert that there is a clear effect of crystal quality on the behavior of PBX, which should influence future insensitive munition formulation design choices.

In order to minimize unintentional detonation, munitions researchers have focused on the development of chemical compounds that are insensitive to external stimuli while maintaining their effectiveness. Although these compounds, known as high-performance insensitive munition compounds, are promising in terms of potency and stability, their environmental impacts have either not been fully understood or are yet to be investigated. In the present research, we have performed a quantum chemical investigation on electronic structures and properties of an insensitive munition compound 4,6-bis(nitroimino)-1,3,5-triazinan-2-one (DNAM). The density functional theory using the B3LYP and M06-2X functionals and MP2 methodology were used for geometry optimization of various tautomeric forms of DNAM. The effect of bulk water solution was evaluated using the conductor-like polarizable continuum model and the density-based solvation model. Ionization potentials, electron affinities, redox properties, and p Ka values were also computed and compared with the available experimental data. These physical and chemical properties of DNAM have been discussed with regard to the varying tautomeric forms in which DNAM can exist.

The US Department of Defense (DOD) is developing insensitive munitions (IMs) that are resistant to unintended detonation to protect warfighters. To enable material life-cycle analysis for the IM, 1-methyl-3-nitro-1-nitroguanidine (MeNQ), ecotoxicological impacts assessment was required. A previous investigation of MeNQ exposures in Daphnia pulex revealed concentration-responsive decreases in reproduction relative to controls (0 mg/L) across a 174, 346, 709, 1385, and 2286 mg/L exposure range. The present study used those exposures to conduct global transcriptomic expression analyses to establish hypothetical mode(s) of action underlying inhibited reproduction. The number of significantly affected transcripts and the magnitude of fold-change differences relative to controls tended to increase with increasing MeNQ concentration where hierarchical clustering analysis identified separation among the “low” (174 and 346 mg/L) and “high” (709, 1385, and 2286 mg/L) exposures. Vitellogenin is critical to Daphnia reproductive processes and MeNQ exposures significantly decreased transcriptional expression for vitellogenin-1 precursor at the lowest exposure level (174 mg/L) with benchmark dose (BMD) levels closely tracking concentrations that caused inhibited reproduction. Additionally, juvenile hormone-inducible protein, chorion peroxidase, and high choriolytic enzyme transcriptional expression were impacted by MeNQ exposure having potential implications for egg production / maturation and overall fecundity. In concert with these effects on specific genes involved in Daphnia reproductive physiology, MeNQ exposures caused significant enrichment of several canonical-pathways responsible for metabolism of cellular energy substrates where BMD levels for transcriptional expression were observed at ≤100 mg/L. These observations imply possible effects on whole-organism energy budgets that may also incur indirect costs on reproduction.

Humic acid substances (HAs) in natural soil and sediment environments affect the retention and degradation of insensitive munition compounds and legacy high explosives (MCs): 2,4-dinitroanisole (DNAN), DNi-NH4+, N-methyl-p-nitroaniline (nMNA), 1-nitroguanidine (NQ), 3-nitro-1,2,4-triazol-5-one (NTO; neutral and anionic forms), 2,4,6-trinitrotoluene (TNT), and 1,3,5-trinitro-1,3,5-triazinane (RDX). A humic acid model compound has been considered using molecular dynamics, thermodynamic integration, and density functional theory to characterize the munition binding ability, ionization potential, and electron affinity compared to that in the water solution. Humic acids bind most compounds and act as both a sink and source for electrons. Ionization potentials suggest that HAs are more susceptible to oxidation than the MCs studied. The electron affinity of HAs is very conformation-dependent and spans the same range as the munition compounds. When HAs and MCs are complexed, the HAs tend to radicalize first, thus buffering MCs against reductive as well as oxidative attacks.

PhD (Mechanical Engineering), North-West University, Potchefstroom Campus Since the prediction of warhead performance is crucial in the early stages of design and the scaling of this procedure is complex and expensive, it is beneficial to have measurable parameters in one optimal model to improve the efficiency of prediction. In general, the type of explosive, mechanical properties and warhead geometries have been proven in previous approaches to provide critical parameters, in terms of size, spatial and velocity distribution, in warhead fragmentation. Statistical approaches have been developed to describe this fragmentation with a combination of these parameters (statistical factors with mechanical properties or explosive properties), and thus, the possibility of developing an integrated model that encompass the effect of detonation behaviour on natural fragmentation characteristics for the same casing material in one scale factor still exists. A literature review describes how the current models based on statistical factors have been investigated with only a single donor explosive is assumed (most commonly TNT or Composition B) in most of these studies. However, it is clear from the trends in munitions development that explosives with characteristics quite different from TNT and Composition B are being increasingly used. Therefore, limited research has been performed on the changes in fragmentation that occur in a specific material due to either changing the explosive type or changing the detonation characteristics of the same explosive. This study investigates the dominant explosive parameters that dictate the fragmentation process. In addition, this study pursues the possibility of developing an integrated model that includes both explosive and material parameters in one simple analytical model. Doctoral

Technologies are needed to address contamination with energetic compounds at military installations. This research developed and evaluated novel and sustainable materials that can be used to remove munition constituents (MC) from stormwater runoff. Initial work focused on 3-nitro-1,2,4-triazol-5-one (NTO), as it is both highly soluble and ionized at environmentally relevant pH values. Screening cellulosic materials indicated that cationized (CAT) versions of pine shavings (pine, henceforth) and burlap (jute) demonstrated >70% removal of NTO from artificial surface runoff. CAT materials also demonstrated >90% removal of the anionic propellant perchlorate. NTO removal (~80%) by CAT pine was similar across initial pH values from 4 to 8.5 S.U. An inverse relationship was observed between NTO removal and the concentration of the major anions chloride, nitrate, and sulfate due to competition for anion binding sites. Sorption isotherms were performed using a mixture of the three primary legacy explosives (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5-trinitro-s-triazine (RDX), 2,4,6-trinitrotoluene (TNT)), the three insensitive MC (nitroguanidine (NQ), NTO, 2,4-dinitroanisole (DNAN)), and perchlorate. Isotherm results indicated that effective removal of both legacy and insensitive MC would best be achieved using a mixture of peat moss plus one or more of the cationized cellulosic materials.

Insensitive Munition (IM) formulations contain 3-nitro-1,2,4-trizole-5-one (NTO), an energetic compound with the highest aqueous solubility (16 g L−1) among all IM explosives, including 2,4-dinitroanisole (DNAN) and 1-nitroguanidine (NQ); as a result wastewater streams from IM processing facilities can be highly contaminated and potentially toxic. The removal of energetic compounds from wastewater streams prior to their discharge in the environment is imperative, and new technology must be developed to efficiently treat high levels of NTO and other IM compounds in these streams. In this study, the treatment of NTO wastewater by a UV/H2O2 oxidation process under acidic conditions (pH = 3.0 ± 0.1) and a hydrogen peroxide concentration of at least 1500 mg L−1 resulted in successful removal of the energetic compound. The organic carbon from the NTO ring was completely converted to inorganic carbon (CO2), as confirmed through TOC measurements and GC–MS analysis on the reactor headspace. Nitrate and ammonium ions were the major nitrogen by-products, as indicated by mass spectrometry. The results obtained in this work demonstrate that the UV/H2O2 oxidation process can effectively mineralize high concentrations of NTO in wastewater streams leading to recovery of valuable nutrients that can be used for supporting algal biomass growth for biofuel/biogas generation.

The emerging use of 2,4-dinitroanisole (DNAN) in insensitive munitions formulations has caused concern about future contamination of subsurface environments, generating significant interest in understanding and identifying its transformation processes. Here we characterized the C and N isotope fractionation associated with abiotic and biological DNAN hydrolysis through alkaline hydrolysis at high pH as well as enzymatic hydrolysis by Nocardioides sp. JS1661 and partially purified DNAN O-demethylase. Whereas both reactions generated 2,4-dinitrophenol (DNP), compound-specific isotope analysis (CSIA) of DNAN and DNP revealed that these reactions occur by different mechanisms. Alkaline hydrolysis was associated with apparent 13C and 15N kinetic isotope effects (13C-AKIE and 15N-AKIE) of 1.044 ± 0.003 and 1.0027 ± 0.0004, respectively, reflecting the previously postulated nucleophilic aromatic substitution mechanism. Conversely, enzyme-catalyzed DNAN hydrolysis exhibited a 13C-AKIE of 1.027 ± 0.005 and a 15N-A...

This paper describes an offline low-temperature derivatization method combined with gas chromatography-isotope ratio mass spectrometry (GC-IRMS) to enable compound-specific isotope analysis (CSIA) of C and N in the explosive compound 3-nitro-1,2,4-triazole-5-one (NTO). NTO is being used widely as a component of insensitive munition (IM) composites such as IMX-101, a formulation that is being used to replace the more shock sensitive TNT in artillery shells. The alkylation of NTO with methyl iodide (MeI) as the derivatization reagent was performed in acetone solution at room temperature using triethylamine (Et3N) as a base catalyst. The methylated product of NTO derivatization was identified as 4-methyl-3-nitro-1,2,4-triazol-5-one (MNTO). Accurate and reproducible results were achieved by systematic optimization of MeI and Et3N concentrations and reaction time. Isotopic values of MNTO obtained by GC-IRMS were normalized against those of two 2,4-dinitroanisole (DNAN) in-house reference materials that had been calibrated with isotopic standard reference materials, USGS40 and USGS41a. The resulting method detection limit for derivatization/GC-IRMS of NTO was 788 ng of NTO, yielding a precision of ±0.3‰ for both δ13C and δ15N values in good agreement with δ13C and δ15N values for NTO determined by elemental analyzer-IRMS.

The biodegradation potential of insensitive munition melt cast formulations IMX101 and IMX104 was investigated in two unamended training range soils under aerobic and anaerobic growth conditions. Changes in community profiles in soil microcosms were monitored via high-throughput 16S rRNA sequencing over the course of the experiments to infer key microbial phylotypes that may be linked to IMX degradation. Complete anaerobic biotransformation occurred for IMX101 and IMX104 constituents 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one during the 30-day incubation period with Camp Shelby (CS) soil. By comparison, soil from Umatilla chemical depot demonstrated incomplete DNAN degradation with reduced transformation rates for both IMX101 and IMX104. Aerobic soil microcosms for both soils demonstrated reduced transformation rates compared to anaerobic degradation for all IMX constituents with DNAN the most susceptible to biotransformation by CS soil. Overall, IMX constituents hexahydro-1,3,5-trinitro-1,3,5-triazine and 1-nitroguanidine did not undergo significant transformation. In CS soil, organisms that have been associated with explosives degradation, namely members of the Burkholderiaceae, Bacillaceae, and Paenibacillaceae phylotypes increased significantly in anaerobic treatments whereas Sphingomonadaceae increased significantly in aerobic treatments. Collectively, these data may be used to populate fate and transport models to provide more accurate estimates for assessing environmental costs associated with release of IMX101 and IMX104.

Plane-wave density functional theory (DFT) level of investigation was performed on the adsorption of two insensitive munition compounds, nitroguanidine (NQ) and 1,1-diamino-2,2-dinitroethylene (FOX7), on the (0001) surfaces of (4 × 4) Al-terminated α-alumina (α-Al2O3) and its Al-hydroxylated form. Surface hydroxylation was obtained by using 16 water molecules. Full geometry optimizations were performed using the vdW-DF2 van der Waals functional. The interaction of electron with core was accounted using the Vanderbilt ultrasoft pseudopotentials. The charge-density difference maps were performed to characterize the nature of munitions adsorption on alumina surfaces. It was revealed that both of the munition compounds will be adsorbed in parallel orientations on alumina surfaces. It was found that deformation energy correction would be required for the reliable interaction energy prediction on pristine alumina surface. On the pristine surface adsorption will be characterized by the covalent type of interacti...

Insensitive munitions are desirable alternatives to historically used formulations, such as 2,4,6-trinitrotoluene (TNT), because of their so-called insensitivity to unintended detonation. The insensitive munition IMX-101 is a mixture of 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ). Environmental releases of munitions may be from production wastewaters or training; these munitions may be exposed to ultraviolet (UV) light. Therefore, it is useful to understand the relative toxicity of IMX-101 and its constituents both before and after photodegradation. The intent of the present study was to generate relative hazard information by exposing the standard ecotoxicological model Ceriodaphnia dubia to each insensitive munition constituent individually and to IMX-101 before and after the exposure solution was irradiated in a UV photoreactor. Without photodegradation, DNAN was more toxic (median lethal concentration [LC50] = 43 mg/L) than the other 2 constituents and it contributed predominantly to the toxicity of IMX-101 (LC50 = 206 mg/L) based on toxic units. Toxicity was observed only at high levels of NQ (LC50 = 1174 mg/L) and pH-adjusted NTO (LC50 = 799 mg/L). The toxicity of IMX-101 is lower than literature-reported TNT toxicity. Photodegradation efficiency was greater at lower insensitive munition concentrations. The observed degradation was greatest for NQ (42-99%), which in turn corresponded to the greatest relative increase in toxicity (100-1000-fold). Modest percent of degradation (4-18%) and increases in phototoxicity (2-100-fold) were observed for NTO and DNAN. Photodegraded NQ products were the predominant source of toxicity of photodegraded IMX-101. Future work involves research to enable analytical and computational confirmation of the specific degradation compounds inducing the observed photoenhanced toxicity. Environ Toxicol Chem 2017;36:2050-2057. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Herein, a fluorescent oxacalix[4]arene-based receptor, DAQTNOC(5,17-di(N-(9,10-dioxo-9,10-dihydroanthracen-1-yl)acetamide) tetranitrooxacalix[4]arene), was described for the specific recognition of N-methyl-p-nitroaniline (MNA). Among the array of explosives, DAQTNOC shows selective behaviour for MNA in the absorption and as well as emission spectra. The binding constants, stoichiometry, quantum yields, and fluorescence quenching were determined to elucidate the inclusion behaviour. Furthermore, computational insights were rendered for studying the stability and spectroscopic analysis of the inclusion complex using docking, molecular dynamics simulations, and density functional theory (DFT) along with time-dependent density functional theory (TD-DFT). The calculations considerably complement the findings and elucidate the structural geometry and mode of interactions in supramolecular complexation. Herein, we observed that DAQTNOC was selectively stabilized by van der Waals forces and hydrophobic contacts with MNA to generate a low-energy complex. These findings are of wide interest, especially because MNA is a well-known insensitive munition and has been detected for the first time via an oxacalixarenes platform.

The US Army is replacing traditional munitions with insensitive munitions resistant to accidental detonation. Although the parent insensitive munition compound nitroguanidine (NQ) is generally not acutely toxic at concentrations >1000 mg/L in aquatic exposures, products formed by intensive ultraviolet (UV) degradation resulted in multiple-order of magnitude increases in toxicity. A methylated congener of NQ, 1-methyl-3-nitroguanidine (MeNQ), is also being assessed for potential use in insensitive munition explosive formulations; therefore, the present study investigated the hazard of parent versus UV-degraded MeNQ using fathead minnows (Pimephales promelas). Although up to 716 mg/L parent MeNQ caused no significant mortality or effects on growth in larval P. promelas fish in 7-d exposures, a similar concentration of MeNQ subjected to UV treatment resulted in 85% mortality. The UV treatment degraded only 3.3% of the MeNQ (5800 mg/L stock, UV-treated for 6 h), indicating that MeNQ degradation products have potentially high toxicity. The parent MeNQ exposure caused significantly decreased transcriptional expression of genes within the significantly enriched insulin metabolic pathway, suggesting antagonism of bioenergetics pathways, which complements observed, although nonsignificant, decreases in body weight. Significant differential transcriptional expression in the UV-degraded MeNQ treatments resulted in significant enrichment of pathways and functions related to the cell cycle, as well as erythrocyte function involved in O2 /CO2 exchange. These functions represent potential mechanistic sources of increased toxicity observed in the UV-degraded MeNQ exposures, which are distinct from previously observed mechanisms underlying increased toxicity of UV-degraded NQ in fish. Environ Toxicol Chem 2020;39:612-622. © 2019 SETAC.

Two major components of insensitive munition formulations, nitroguanidine (NQ) and 3-nitro-1,2,4-triazol-5-one (NTO), are highly water soluble and therefore likely to photo-transform while in solution in the environment. The ecotoxicities of NQ and NTO solutions are known to increase with UV exposure, but a detailed accounting of aqueous degradation rates, products, and pathways under different exposure wavelengths is currently lacking. Here, we irradiated aqueous solutions of NQ and NTO over a 32-h period at three ultraviolet wavelengths (254 nm, 300 nm, and 350 nm) and analyzed their degradation rates and transformation products. NQ was completely degraded by 30 min at 254 nm and by 4 h at 300 nm, but it was only 10% degraded after 32 h at 350 nm. Mass recoveries of NQ and its transformation products were ≥80% for all three wavelengths, and consisted of large amounts of guanidine, nitrate, and nitrite, and smaller amounts of cyanamide, cyanoguanidine, urea, and ammonium. NTO degradation was greatest at 300 nm with 3% remaining after 32 h, followed by 254 nm (7% remaining) and 350 nm (20% remaining). Mass recoveries of NTO and its transformation products were high for the first 8 h but decreased to 22–48% by 32 h, with the major aqueous products identified as ammonium, nitrate, nitrite, and a urazole intermediate. Environmental half-lives of NQ and NTO in pure water were estimated as 4 and 6 days, respectively. We propose photo-degradation pathways for NQ and NTO supported by observed and quantified degradation products and changes in solution pH.

We present the first report of biotransformation of 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4-dinitroanisole (DNAN), replacements for the explosives 1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT), respectively, by methane-oxidizing cultures under aerobic conditions. Two consortia, dominated by Methylosinus spp., degraded both compounds with transient production of reduced NTO products, and non-stoichiometric production of reduced DNAN products. No release of inorganic nitrogen was observed with either compound, indicating that NTO and DNAN may be utilized as nitrogen sources by these consortia. The pure culture Methylosinus trichosporium OB3b also degraded both compounds. Degradation was observed in the presence of acetylene (a known inhibitor of methane monooxygenase; MMO) when methanol was supplied, indicating that MMO was not involved. Furthermore, studies with purified soluble MMO (sMMO) from OB3b indicated that neither compound was a substrate for sMMO. Degradation was inhibited by 2-iodosobenzoic acid, but not by dicoumarol, suggesting involvement of an oxygen- and dicoumarol-insensitive (nitro)reductase. These results indicate methanotrophs can aerobically degrade NTO and DNAN via one or more (nitro)reductases, with sMMO serving a supporting role deriving reducing equivalents from methane. This finding is important because methanotrophic bacteria are widely dispersed, and may represent a previously unrecognized route of NTO and DNAN biotransformation in aerobic environments.

The Department of Defense (DoD) is developing a new category of insensitive munitions (IMs) that are more resistant to detonation or promulgation from external stimuli than traditional munition formulations. The new explosive constituent compounds are 2,4-dinitroanisole (DNAN), nitroguanidine (NQ), and nitrotriazolone (NTO). The production and use of IM formulations may result in interaction of IM component compounds with soil. The chemical properties of these IM compounds present unique challenges for extraction from environmental matrices such as soil. A two-stage extraction procedure was developed and tested using several soil types amended with known concentrations of IM compounds. This procedure incorporates both an acidified phase and an organic phase to account for the chemical properties of the IM compounds. The method detection limits (MDLs) for all IM compounds in all soil types were

New insensitive munitions are being developed to minimize the acute hazards associated with non-intentional detonation of warheads. Two components often used in munition formulations have limited toxicity data, i.e., 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4-dinitroanisole (DNAN). Oral acute, subacute, and subchronic studies have recently been completed. The primary adverse effect from subchronic oral NTO exposure was hypospermia, which followed a dose-dependent trend. Effects from DNAN exposure include reduced body weight, anemia, and neurotoxicity. Occupational exposure levels (OEL) have recently been developed for NTO and DNAN. However, other concerns regarding environmental issues have been raised. Herein we present the latest toxicity data and interpretations for NTO and DNAN as well as the third component of IMX-101, nitroguanidine (NQ), and describe a process to assist with holistic environmental, safety, and occupational health assessment for sustained production and use.