New explosive compounds that are less sensitive to shock and high temperatures are being used as replacements for TNT and RDX. Two of these explosives, 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO), were shown to have good detonation characteristics and were used as the main ingredients in several new explosive formulations. Both compounds, however, were more soluble than either TNT or RDX and have been shown to have some human and environmental toxicity. Data on their fate and transport is needed to determine if DNAN and NTO have the potential to reach groundwater and be transported off military training bases. The objective of this project was to measure the dissolution, photodegradation, and soil adsorption properties of DNAN, NTO, and insensitive munitions formulations that contain them (Insensitive Munitions eXplosive-101 [IMX], IMX-104, and Picatinny Arsenal eXplosive-21 [PAX]).

Detonation residues of insensitive munitions (IM) formulations, IMX-101, IMX-104, and PAX-21 were characterized using light and electron microscopy, as well as X-ray tomography and Raman spectroscopy and exposed to either simulated rainfall in the lab or to natural rainfall and sunshine outside on a location in New Hampshire. Indoor particles were again examined using X-ray tomography following exposure to water to quantify changes to their 3-D structure as they dissolve. Solution concentrations of NTO, nitroguanidine (NQ), DNAN, RDX, HMX (an impurity in RDX), and ammonium perchlorate (AP) were also measured to calculate the amount of IM constituents dissolved into solution. The photo-degradation of DNAN and NTO in solid (outdoors) and aqueous (in the lab) form was measured to determine if these compounds degrade in sunlight either before or after dissolution. Adsorption and transport behavior of IM compounds in a range of soils collected on training facilities was also studied. Results were used to determine how DNAN and NTO interact with the soils and to correlate transport and fate parameters to soil properties. Obtained dissolution and transport parameters were used together in HYDRUS-1D, a software package for simulating water, heat and solute movement in one-dimensional variably-saturated media, to predict the environmental fate of IM explosives for several locations.

Both outdoor and indoor dissolution experiments indicated that IM constituents dissolve sequentially as predicted by solubility, NTO, followed by NQ and DNAN in IMX-101 and DNAN and RDX in IMX-104. Fast dissolution of most soluble components resulted in porous particles that broke easily. High initial concentrations of NTO caused significant decrease of pH for rainwater in contact with IM formulations. Photo-transformation of outdoor IM was evident; but its relative contribution is smaller than for traditional explosives due to faster dissolution of IM compounds. Solution-phase NTO photo-transformation was influenced by pH and enhanced in the presence of dissolved organic matter, while DNAN photo-transformation rates increased with temperature.

NTO adsorption in soils was very low and further decreased with increasing soil pH, while DNAN was adsorbed and its adsorption positively correlated with soil organic matter and clay. Both NTO and DNAN were transformed in soils and products of DNAN transformation, 2-amino-4-nitroanisole (2-ANAN) and 4-amino-2-nitroanisole (4-ANAN) were observed. Exposing explosive residues to water resulted in initial high peak in concentration for NTO and NQ followed by lower concentrations, and lower concentration of DNAN. High release of NTO and its low adsorption in soils indicate higher risk of its transport to the ground and surface waters, while DNAN with slower dissolution and TNT-like behavior in soils indicates lower potential for off-site transport. However, numerical simulations indicate that both NTO and DNAN would be transformed in soils preventing them from reaching groundwater.

The U.S. military is interested in replacing TNT and RDX with DNAN and NTO, which have similar explosive characteristics but are less likely to detonate unintentionally. Although these replacements are good explosives, basic information about their fate and transport was needed to evaluate their environmental impact and life-cycle management. This project measured their dissolution, photo-degradation, and how aqueous solutions interact with soils, data critical to determining exposure potential and, consequently, risk.

Arthur, J.D., N.W. Mark, S. Taylor, J. Šimunek, M.L. Brusseau, and K.M. Dontsova. 2017. Batch Soil Adsorption and Column Transport Studies of 2,4-Dinitroanisole (DNAN) in Soils. Journal of Contaminant Hydrology, 199:14-23.

Arthur, J.D., N.W. Mark, S. Taylor, J. Šimůnek, M.L. Brusseau, and K.D. Dontsova. 2018. Dissolution and Transport of Insensitive Munitions Formulations IMX-101 and IMX-104 in Saturated Soil Columns. Science of the Total Environment, 624:758-768.

Dontsova, K., S. Taylor, R. Pesce-Rodriguez, M. Brusseau, J. Arthur, N. Mark, M. Walsh, J. Lever, and J. Šimůnek. 2014. Dissolution of NTO, DNAN, and Insensitive Munitions Formulations and Their Fates in Soils. Cold Regions Research and Engineering Laboratory, Hanover, NH, p. 92. http://www.dtic.mil/dtic/tr/fulltext/u2/a609594.pdf

Mark, N., J. Arthur, K. Dontsova, M. Brusseau, and S. Taylor. 2016. Adsorption and Attenuation Behavior of 3-Nitro-1,2,4-Triazol-5-One (NTO) in Eleven Soils. Chemosphere, 144:1249-1255.

Mark, N., J. Arthur, K. Dontsova, M. Brusseau, S. Taylor, and J. Šimůnek. 2017. Column Transport Studies of 3-Nitro-1,2,4-triazol-5-one (NTO) in Soils. Chemosphere, 171:427-434.

Taylor, S., D.B. Ringelberg, K. Dontsova, C.P. Daghlian, M.E. Walsh, and M.R. Walsh. 2013. Insights into the Dissolution and the Three-dimensional Structure of Insensitive Munitions Formulations. Chemosphere, 93:1782-1788.

Taylor, S., K. Dontsova, M.E. Walsh, and M.R. Walsh. 2015. Outdoor Dissolution of Detonation Residues of Three Insensitive Munitions (IM) Formulations. Chemosphere, 134:250-256.

Taylor, S., Park, E., Bullion, K., Dontsova, K., 2015. Dissolution of three insensitive munitions formulations. Chemosphere, 119:342-348.

Taylor, S., K. Dontsova, and M. Walsh. 2017. Insensitive Munitions Formulations: Their Dissolution and Fate in Soils. in: Shukla, M., V. Boddu, J. Steevens, D. Reddy, J. Leszczynski (Eds.). Energetic Materials: From Cradle to Grave. Springer. pp. 407-443.

Taylor, S., M.E. Walsh, J.B. Becher, D.B. Ringelberg, P.Z. Mannes, and G.W. Gribble. 2017. Photo-degradation of 2,4-Dinitroanisole (DNAN): An Emerging Munitions Compound. Chemosphere, 167:193-203.