Insensitive munition compounds (IMC) are an emerging class of explosives that are less susceptible to accidental explosions compared to the conventional explosives they will be replacing. An IMC that has been incorporated in several explosives formulations is 2,4-dinitroanisole (DNAN). As the manufacture, storage, and use of these compounds increases, the expected releases in natural and engineered systems might pose an environmental hazard to public health and ecosystems. To date there is little information on the environmental fate and toxicology of DNAN. However, nitroaromatic compounds are known to be toxic, mutagenic and difficult to completely biodegrade. In order to study the fate and (bio)transformation of DNAN, microcosm studies with soils and anaerobic wastewater sludge were performed to determine (bio)transformation pathways and key factors influencing (bio)conversion. Transformation was enhanced in anaerobic conditions, in particular when exogenous electron donor was added. Abiotic transformation (in heat-killed soil) was also significant and dominated transformation reactions in soils that were not amended with exogenous electron donor. The organic carbon content of soils was a key factor that correlated to the anaerobic biotransformation rate. Having identified (bio)transformation products using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry, an overall pathway of (bio)transformation was devised and consistent with nitro-group reduction to form aromatic amines. During the nitro-group reduction, reactive products (e.g. nitroso-intermediates) coupled with amines to form azo-dimers and oligomers. Subsequent transformation pathways included N-alkylation, N-acetylation, and stepwise demethoxylation of these oligomers. The assessment of the toxicity of DNAN and its (bio)transformation products was performed utilizing microbial toxicity assays and ecotoxicity evaluation with zebrafish (Danio rerio) embryos. Overall DNAN severely inhibited methanogens (IC₅₀ = 41 μM ), the bioluminescent marine bacterium Aliivibrio fischeri utilized in the Microtox test (IC₅₀ = 57 μM), and nitrifiers (IC₅₀ = 49 μM). Reduced aromatic amine products in general were less toxic than DNAN with the exception of 2-methoxy-5-nitroaniline and 3-nitro-4-methoxyaniline, which were similar in toxicity to some of the test organisms as DNAN. Azo-oligomer surrogates were as toxic or more toxic than DNAN, although at trace levels they significantly stimulated activity. N-acetylated amines were found to have by far the lowest toxicity to microorganisms. In zebrafish embryos, the (bio)transformation product or surrogates 3-nitro-4-methoxyaniline and 2,2'-dimethoxy-4,4'-azodianiline caused developmental abnormalities (each with lowest observable effect level of 6.4 μM). An integrated approach which monitored (bio)transformation product mixture profile in parallel with their toxicity to microbial and zebrafish toxicity was used to characterize toxicity during the time course of the anaerobic (bio)transformation of DNAN. Enhanced inhibition of methanogenic activity and zebrafish mortality were associated with the onset of dimer formation indicating they were being mostly impacted by reactive intermediates formed early in the biotransformation of DNAN. Further accumulation of oligomers was associated with a decrease toxicity. On the other hand, A. fischeri bioluminescence became more and more inhibited as the oligomers formed, indicating different responses depending on target organism. Taken globally, the results indicate that DNAN can be readily transformed in soils and wastewater sludge forming both highly toxic (e.g. azo-oligomers) and non-toxic intermediates (e.g. N-acetylated 2,4-diaminoanisole). Depending on target organism, the prolonged formation of oligomer mixtures either resulted in detoxification or recovery of activity.

New explosive compounds that are less sensitive to shock and high temperatures are being tested on military ranges as replacements for 2, 4, 6-trinitrotoluene (TNT) and hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine (RDX). One of the two compounds being tested is 2, 4-dinitroanisole (DNAN), which has good detonation characteristics and is one of the main ingredients in a suite of explosive formulations being tested. Data on the fate and transport of DNAN is needed to determine its potential to reach groundwater and be transported off base, a result which could create future contamination problems on military training ranges and trigger regulatory action. In this study, I measured how DNAN in solution interacts with different types of soils from across the United States. I conducted kinetic and equilibrium batch soil adsorption experiments, saturated column experiments with DNAN and dissolution and transport studies of insensitive munitions (IMX-101, IMX -104), which include DNAN, 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), under steady state and transient conditions. In the rate studies, change in DNAN concentration with time was evaluated using the first order kinetic equation. Solution mass-loss rate coefficients ranged between 0.0002 h-1 and 0.0068 h-1. DNAN was strongly adsorbed by soils with linear adsorption coefficients ranging between 0.6 and 6.3 L kg-1, and Freundlich coefficients between 1.3 and 34 mg1-n Ln kg-1. Both linear and Freundlich adsorption coefficients were positively correlated with the amount of organic carbon and cation exchange capacity of the soil. In saturated miscible-displacement experiments, it was shown that under flow conditions DNAN transforms readily with formation of amino transformation products, 2-amino-4-nitroanisole (2-ANAN) and 4-amino-2-nitroanisole (4-ANAN). Dissolution miscible-displacement experiments demonstrated that insensitive munition compounds dissolved in order of aqueous solubility as indicated by earlier lab and outdoor dissolution studies. The sorption of NTO and NQ was low, while RDX, HMX, and DNAN all adsorbed to the soils. DNAN transformed in soils with formation of amino-reduction products, 2- ANAN and 4-ANAN. Adsorption parameters determined by HYDRUS-1D generally agreed with batch and column study adsorption coefficients for pure NTO and DNAN. The magnitudes of retardation and transformation observed in these studies result in significant attenuation potential for DNAN in soils, which would reduce risk of groundwater contamination.