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==Introduction==
 
==Introduction==
 
[[wikipedia:Insensitive_munition|Insensitive munitions]], including [[wikipedia:IMX-101|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. [[wikipedia:IMX-101|IMX-101]], composed of [[wikipedia:2,4-Dinitroanisole|2,4-dinitroanisole]] (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and [[wikipedia:Nitroguanidine|nitroguanidine]] (NQ), will replace [[wikipedia:TNT|2,4,6-trinitrotoluene]] (TNT) in artillery; IMX-104, composed of DNAN, NTO, and [[wikipedia:RDX|hexahydro-1,3,5-trinitro-1,3,5-triazine]] (RDX), will replace [[wikipedia:Composition_B|Composition B]] (Comp B) in mortars<ref>BAE Systems, 2021. [https://www.baesystems.com/en-us/feature/making-explosives-safer. Making explosives safer]</ref>. 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 concern<ref>Pennington, J.C., Silverblatt, B., Poe, K., Hayes, C.A., and Yost, S, 2008. Explosive residues from low-order detonations of heavy artillery and mortar rounds. Soil and Sediment Contamination: An International Journal, 17(5), pp. 533-546. [https://doi.org/10.1080/15320380802306669 doi: 10.1080/15320380802306669]</ref>. 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.  
 
[[wikipedia:Insensitive_munition|Insensitive munitions]], including [[wikipedia:IMX-101|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. [[wikipedia:IMX-101|IMX-101]], composed of [[wikipedia:2,4-Dinitroanisole|2,4-dinitroanisole]] (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and [[wikipedia:Nitroguanidine|nitroguanidine]] (NQ), will replace [[wikipedia:TNT|2,4,6-trinitrotoluene]] (TNT) in artillery; IMX-104, composed of DNAN, NTO, and [[wikipedia:RDX|hexahydro-1,3,5-trinitro-1,3,5-triazine]] (RDX), will replace [[wikipedia:Composition_B|Composition B]] (Comp B) in mortars<ref>BAE Systems, 2021. [https://www.baesystems.com/en-us/feature/making-explosives-safer. Making explosives safer]</ref>. 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 concern<ref>Pennington, J.C., Silverblatt, B., Poe, K., Hayes, C.A., and Yost, S, 2008. Explosive residues from low-order detonations of heavy artillery and mortar rounds. Soil and Sediment Contamination: An International Journal, 17(5), pp. 533-546. [https://doi.org/10.1080/15320380802306669 doi: 10.1080/15320380802306669]</ref>. 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.  
[[File: PhotolysisFig1.png | thumb | 650px | left | Figure 1. Color change over time as particles of IMX-101 and IMX-104 were exposed to sunlight and rainfall, suggesting phototransformation. Image courtesy of the U.S. Army Engineer Research and Development Center<ref>Dontsova, K., Taylor S., Pesce-Rodriguez, R., Brusseau, M., Arthur, J., Mark, N., Walsh, M., Lever, J.,    and Simunek, J., 2014. Dissolution of NTO, DNAN, and insensitive munitions formulations and their fates in soils. U.S. Army Engineer Research and Development Center (ERDC)/ Cold Region Research and Engineering Laboratory (CRREL) TR-14-23. [[Media: ERDC2014.pdf | Report]]
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[[File: PhotolysisFig1.png | thumb | 650px | left | Figure 1. Color change over time as particles of IMX-101 and IMX-104 were exposed to sunlight and rainfall, suggesting phototransformation. Image courtesy of the U.S. Army Engineer Research and Development Center<ref>Dontsova, K., Taylor S., Pesce-Rodriguez, R., Brusseau, M., Arthur, J., Mark, N., Walsh, M., Lever, J.,    and Simunek, J., 2014. Dissolution of NTO, DNAN, and insensitive munitions formulations and their fates in soils. U.S. Army Engineer Research and Development Center (ERDC)/ Cold Region Research and Engineering Laboratory (CRREL) TR-14-23. [[Special:FilePath/ERDC2014.pdf| Report]]
</ref>.]]  
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== Direct photolysis ==
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Compounds that absorb [[wikipedia:Ultraviolet|ultraviolet]] (UV, 100-400 nm) and/or [[wikipedia:Visible_spectrum|visible]] (Vis, 400-800 nm) light can undergo direct photolysis from sunlight. Light is absorbed in discrete units, or [[wikipedia:Photon|photons]], and the energy of these photons is indirectly proportional to the wavelength of the light. When a chemical molecule absorbs a photon, its ground state electrons may become excited. As the excited electrons return to the ground state, they may undergo a chemical reaction that results in transformation. Figure 2 shows that the UV range is further divided into UV-A (315-400 nm), UV-B (280-315 nm), and UV-C (100-280 nm). Because most of UV-C is filtered out by the Earth’s atmosphere, direct photolysis of compounds at the surface primarily involves UV-A and UV-B<ref>Brennan, P., and Fedor, C., 1994. Sunlight, UV, & accelerated weathering. Q-Lab Corporation, Technical Bulletin LU-0822. [[Media: Brennan1994.pdf | Paper]]</ref>. <references />

Revision as of 19:49, 14 December 2021

I have installed SandboxLink extension that provides each user their own sandbox accessible through their personal menu bar (top right)

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):

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 concern[7]. 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.

Figure 1. Color change over time as particles of IMX-101 and IMX-104 were exposed to sunlight and rainfall, suggesting phototransformation. Image courtesy of the U.S. Army Engineer Research and Development Center[8].

Direct photolysis

Compounds that absorb ultraviolet (UV, 100-400 nm) and/or visible (Vis, 400-800 nm) light can undergo direct photolysis from sunlight. Light is absorbed in discrete units, or photons, and the energy of these photons is indirectly proportional to the wavelength of the light. When a chemical molecule absorbs a photon, its ground state electrons may become excited. As the excited electrons return to the ground state, they may undergo a chemical reaction that results in transformation. Figure 2 shows that the UV range is further divided into UV-A (315-400 nm), UV-B (280-315 nm), and UV-C (100-280 nm). Because most of UV-C is filtered out by the Earth’s atmosphere, direct photolysis of compounds at the surface primarily involves UV-A and UV-B[9].

  1. ^ 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
  2. ^ Pennington, J.C., Thorn, K.A., Co, 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
  3. ^ 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
  4. ^ 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
  5. ^ 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
  6. ^ BAE Systems, 2021. Making explosives safer
  7. ^ Pennington, J.C., Silverblatt, B., Poe, K., Hayes, C.A., and Yost, S, 2008. Explosive residues from low-order detonations of heavy artillery and mortar rounds. Soil and Sediment Contamination: An International Journal, 17(5), pp. 533-546. doi: 10.1080/15320380802306669
  8. ^ Dontsova, K., Taylor S., Pesce-Rodriguez, R., Brusseau, M., Arthur, J., Mark, N., Walsh, M., Lever, J., and Simunek, J., 2014. Dissolution of NTO, DNAN, and insensitive munitions formulations and their fates in soils. U.S. Army Engineer Research and Development Center (ERDC)/ Cold Region Research and Engineering Laboratory (CRREL) TR-14-23. Report
  9. ^ Brennan, P., and Fedor, C., 1994. Sunlight, UV, & accelerated weathering. Q-Lab Corporation, Technical Bulletin LU-0822. Paper