Chemical and Environmental Engineering
Insensitive munition compounds (IMCs) are a new class of chemicals being considered by the United States Army as replacements for conventional explosives due to their improved ability to withstand unintended detonations. The compound 3-nitro-1,2,4-triazol-5-one (NTO) is one of the constituents of the insensitive munitions formulations, and emissions of NTO to the environment are expected to increase as its use becomes widespread. However, the fate of NTO in the environment is not well understood. My research is examining the transformation of NTO in soil in batch bioassays under different redox conditions (i.e., anaerobic, aerobic and sequential anaerobic-aerobic). Under anaerobic conditions, NTO undergoes a microbial reduction to 3-amino-1,2,4-triazol-5-one (ATO) when utilizing pyruvate as an electron donor. However, ATO biodegradation was only observed after the redox condition was switched to aerobic. Abiotic controls using sterilized soil demonstrated that NTO persisted in the environment in the absence of microorganisms, indicating that biological activity plays an important role in NTO transformation in soil. ATO-degrading enrichment cultures were derived from an initial culture containing soil, mineral medium, and ATO. After multiple transfers (10% vol/vol), ATO mineralization was achieved. The results indicate extensive mineralization of ATO since approximately 95% of ATO-carbon was recovered as carbon dioxide and 100% of ATO-nitrogen was recovered as inorganic ionic nitrogen species and dinitrogen gas. The results obtained in this research suggest that NTO mineralization can be achieved through a sequential anaerobic-aerobic approach, decreasing the risks of this compound to the ecosystem and to public health.