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Munitions Constituents – Photolysis
Munitions compounds (MCs), including 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ), absorb light in the UV range and are therefore susceptible to photolysis on soil surfaces and in surface water. Photochemical reactions are important to consider when assessing the environmental impact of MCs since they can yield products that differ from their parent compounds in both toxicity and transport behavior. Quantum yield calculations can aid in predicting the photolysis rates and half-lives of MCs. The photolysis of MCs may be enhanced or inhibited in the presence of compounds that are also excited by UV irradiation. Munitions compounds (MCs), including 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ), absorb light in the UV range and are therefore susceptible to photolysis on soil surfaces and in surface water. Photochemical reactions are important to consider when assessing the environmental impact of MCs since they can yield products that differ from their parent compounds in both toxicity and transport behavior. Quantum yield calculations can aid in predicting the photolysis rates and half-lives of MCs. The photolysis of MCs may be enhanced or inhibited in the presence of compounds that are also excited by UV irradiation.
Related Article(s):
Contributor(s): Dr. Warren Kadoya
Key Resource(s):
- Environmental Organic Chemistry, Chapter 15: Direct Photolysis[1]
- Photochemical Degradation of Composition B and Its Components[2]
- Verification of RDX Photolysis Mechanism[3]
- Photochemical transformation of the insensitive munitions compound 2,4-dinitroanisole[4]
- Photo-transformation of aqueous nitroguanidine and 3-nitro-1,2,4-triazol-5-one: Emerging munitions compounds[5]
Introduction
Insensitive munitions, including IMX-101 and IMX-104, are replacing traditional explosives because they are less prone to accidental detonation and therefore safer for military personnel to handle. IMX-101, composed of 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ), will replace 2,4,6-trinitrotoluene (TNT) in artillery; IMX-104, composed of DNAN, NTO, and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), will replace Composition B (Comp B) in mortars[6]. As both traditional munitions compounds and these insensitive munitions compounds (collectively referred to as MCs) may be deposited onto firing ranges via incomplete detonation, understanding their environmental fate is of concern7. Phototransformation due to sunlight exposure is an important fate-controlling parameter for MCs and can occur on the surfaces of solid explosive particles, as shown in Figure 1, as well as in the aqueous phase following MC dissolution by rainwater. Furthermore, MC photolysis can be affected by the presence of natural organic matter and other compounds that are excited by sunlight.
- ^ Schwarzenbach R.P., Gschwend P.M., and Imboden D.M., 2002. Chapter 15, Direct Photolysis. In: Schwarzenbach R.P., Gschwend P.M., and Imboden D.M. (eds). Environmental Organic Chemistry. 2nd ed. Hoboken, NJ: John Wiley & Sons, Inc, pp. 611-654. doi:10.1002/0471649643.ch15
- ^ Pennington J.C., Thorn K.A., Cox L.G., MacMillan D.K., Yost S., and Laubscher R.D., 2007. Photochemical Degradation of Composition B and Its Components. U.S. Army Engineer Research and Development Center (ERDC)/ Environmental Laboratory (EL) TR-07-16. Report
- ^ Peyton G.R., LeFaivre M.H., and Maloney S.W., 1999. Verification of RDX photolysis mechanism. U.S. Army Engineer Research and Development Center (ERDC)/ Construction Engineering Research Laboratory (CERL) TR 99/93. Report
- ^ Rao B., Wang W., Cai Q., Anderson T., and Gu B., 2013. Photochemical Transformation of The Insensitive Munitions Compound 2,4-Dinitroanisole. Science of The Total Environment, 443, pp. 692-699. doi: 10.1016/j.scitotenv.2012.11.033
- ^ Becher J.B., Beal S.A., Taylor S., Dontsova K., Wilcox D.E., 2019. Photo-transformation of aqueous nitroguanidine and 3-nitro-1,2,4-triazol-5-one: Emerging munitions compounds. Chemosphere, 228, pp. 418-426. doi:10.1016/j.chemosphere.2019.04.131
- ^ BAE Systems, 2021. Making explosives safer
