Acute and chronic toxicity of the new explosive CL‐20 to the earthworm (<i>Eisenia andrei</i>) exposed to amended natural soils

Robidoux, Pierre Yves; Sunahara, Geoffrey I.; Savard, Kathleen; Berthelot, Yann; Dodard, Sabine; Martel, Majorie; Gong, Ping; Hawari, Jalal

doi:10.1897/03-308

Cited by 65 publications

(34 citation statements)

References 13 publications

(25 reference statements)

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4,6,8,10,4,6,8,10, or HNIW) is a high-energy nitramine explosive. To improve atomistic understanding of the thermal decomposition of CL-20 gas and solid phases, we performed a series of ab initio molecular dynamics simulations.

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confidence: 99%

Ab Initio Molecular Dynamics Study on the Initial Chemical Events in Nitramines: Thermal Decomposition of CL-20

et al. 2008

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CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane or HNIW) is a high-energy nitramine explosive. To improve atomistic understanding of the thermal decomposition of CL-20 gas and solid phases, we performed a series of ab initio molecular dynamics simulations. We found that during unimolecular decomposition, unlike other nitramines (e.g., RDX, HMX), CL-20 has only one distinct initial reaction channelhomolysis of the N-NO2 bond. We did not observe any HONO elimination reaction during unimolecular decomposition, whereas the ring-breaking reaction was followed by NO 2 fission. Therefore, in spite of limited sampling, that provides a mostly qualitative picture, we proposed here a scheme of unimolecular decomposition of CL-20. The averaged product population over all trajectories was estimated at four HCN, two to four NO2, two to four NO, one CO, and one OH molecule per one CL-20 molecule. Our simulations provide a detailed description of the chemical processes in the initial stages of thermal decomposition of condensed CL-20, allowing elucidation of key features of such processes as composition of primary reaction products, reaction timing, and Arrhenius behavior of the system. The primary reactions leading to NO2, NO, N 2O, and N2 occur at very early stages. We also estimated potential activation barriers for the formation of NO2, which essentially determines overall decomposition kinetics and effective rate constants for NO2 and N2. The calculated solid-phase decomposition pathways correlate with available condensed-phase experimental data.

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Ab Initio Molecular Dynamics Study on the Initial Chemical Events in Nitramines: Thermal Decomposition of CL-20

et al. 2008

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“…The following eight controls were prepared as described above: (1) Fe 0 , CL-20, water, in air; (2) Analytical Techniques. A gastight syringe was used to sample gaseous products from the headspace for subsequent analysis of nitrous oxide by GC-ECD as described by Sheremata and Hawari (23).…”

Section: Methodsmentioning

confidence: 99%

“…CL-20 has been found to be toxic (2,3), thereby necessitating its removal from contaminated environments. Several abiotic or biotic reactions have recently been shown to degrade CL-20.…”

Section: Introductionmentioning

confidence: 99%

Decomposition of the Polycyclic Nitramine Explosive, CL-20, by Fe⁰

Balakrishnan

Monteil-Rivera

Halasz

et al. 2004

Environ. Sci. Technol.

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CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), C6H6N12O12, is an emerging energetic chemical that may replace RDX, but its degradation pathways are not well-known. In the present study, zerovalent iron was used to degrade CL-20 with the aim of determining its products and degradation pathways. In the absence of O2, CL-20 underwent a rapid decomposition with the concurrent formation of nitrite to ultimately produce nitrous oxide, ammonium, formate, glyoxal, and glycolate. LC/MS (ES-) showed the presence of several key products carrying important information on the initial reactions involved in the degradation of CL-20. For instance, a doubly denitrated intermediate of CL-20 was detected together with the mono- and dinitroso derivatives of the energetic chemical. Two other intermediates with [M-H]- at 392 and 376 Da, matching empirical formulas of C6H7N11O10 and C6H7N11O9, respectively, were detected. Using 15N-labeled CL-20, the two intermediates were tentatively identified as the denitrohydrogenated products of CL-20 and its mononitroso derivative, respectively. The present experimental findings suggest that CL-20 degraded via at least two initial routes: one involving denitration and the second involving sequential reduction of the N-NO2 to the corresponding nitroso (N-NO) derivatives prior to denitration and ring cleavage.

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“…Initial reports on biological toxicity of CL-20 Robidoux et al 2004) have prompted the research in the area of determining its environmental fate and impacts. It is quite likely that extensive use of CL-20 in the near future (Giles 2004) may also raise similar environmental, biological, and health concerns as those previously experienced with structurally similar cyclic nitramines such as RDX and HMX (Etnier and Hartley 1990;Hoek 2004;McLellan et al 1988;Talmage et al 1999;Woody et al 1986;Yinon 1990).…”

Section: Introductionmentioning

confidence: 99%

Biotransformation of CL-20 by a dehydrogenase enzyme from Clostridium sp. EDB2

Bhushan

Halasz

Hawari

2005

Appl Microbiol Biotechnol

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In a previous study, a marine isolate Clostridium sp. EDB2 degraded 2, 4,6,8,10,4,6,8,10, under anaerobic conditions (Bhushan B, Halasz A, Thiboutot S, Ampleman G, Hawari J (2004c) Chemotaxis-mediated biodegradation of cyclic nitramine explosives RDX, HMX, and CL-20 by Clostridium sp. EDB2. Biochem Biophys Res Commun 316:816-821); however, the enzyme responsible for CL-20 degradation was not known. In the present study, we isolated and purified an enzyme, from strain EDB2, responsible for CL-20 degradation. The enzyme was membrane-associated and NADH-dependent and had a molecular weight of 56 kDa (with SDS-PAGE). N-terminal amino acid sequence of enzyme revealed that it belonged to dehydrogenase class of enzymes. The purified enzyme degraded CL-20 at a rate of 18.5 nmol/h mg protein under anaerobic conditions. Carbon and nitrogen mass balance of the products were 100 and 64%, respectively. In LC-MS-MS studies, we detected three different initial metabolites from CL-20, i.e., mononitroso derivative, denitrohydrogenated product, and double-denitrated isomers with molecular weight of 422, 393, and 346 Da, corresponding to presumed empirical formulas of C 6 H 6 N 12 O 11 , C 6 H 7 N 11 O 10 , and C 6 H 6 N 10 O 8 , respectively. Identity of all the three metabolites were confirmed by using ring-labeled [ 15 N]CL-20 and the nitro-group-labeled [ 15 NO 2 ]CL-20. Taken together, the above data suggested that the enzyme degraded CL-20 via three different routes: Route A, via two single electron transfers necessary to release two nitro-groups from CL-20 to produce two doubledenitrated isomers; Route B, via a hydride transfer necessary to produce a denitrohydrogenated product; and Route C, via transfer of two redox equivalents to CL-20 necessary to produce a mono-nitroso derivative of CL-20. This is the first biochemical study which showed that CL-20 degradation can be initiated via more than one pathway.

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Acute and chronic toxicity of the new explosive CL‐20 to the earthworm (Eisenia andrei) exposed to amended natural soils

Cited by 65 publications

References 13 publications

Ab Initio Molecular Dynamics Study on the Initial Chemical Events in Nitramines: Thermal Decomposition of CL-20

Ab Initio Molecular Dynamics Study on the Initial Chemical Events in Nitramines: Thermal Decomposition of CL-20

Decomposition of the Polycyclic Nitramine Explosive, CL-20, by Fe⁰

Biotransformation of CL-20 by a dehydrogenase enzyme from Clostridium sp. EDB2

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Acute and chronic toxicity of the new explosive CL‐20 to the earthworm (Eisenia andrei) exposed to amended natural soils

Cited by 65 publications

References 13 publications

Ab Initio Molecular Dynamics Study on the Initial Chemical Events in Nitramines: Thermal Decomposition of CL-20

Ab Initio Molecular Dynamics Study on the Initial Chemical Events in Nitramines: Thermal Decomposition of CL-20

Decomposition of the Polycyclic Nitramine Explosive, CL-20, by Fe0

Biotransformation of CL-20 by a dehydrogenase enzyme from Clostridium sp. EDB2

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Decomposition of the Polycyclic Nitramine Explosive, CL-20, by Fe⁰