Recent studies have shown that the insensitive nitoaromatic explosive 2,4,-dinitroanisole (DNAN) and the insensitive nitramine explosive 3-nitro-1,2,4-triazol-5-one (NTO) are each susceptible to biotic and abiotic transformation by various mechanisms. In many instances, the degradation of these compounds in soils, groundwaters, and marine environments is difficult to assess because the degradation products produced are either unknown, common in nature (e.g., NO2-, N2O, NO3-), or are labile and/or difficult to measure. Moreover, abiotic and biotic processes may occur simultaneously, making them difficult to distinguish or apportion based solely on analyses of concentrations. The development and application of compound-specific stable isotope (CSIA) methods for DNAN and NTO is therefore a necessary step to allow the extent of in situ degradation to be quantified and to potentially provide insights into degradation mechanisms.
The key objectives of this project are (1) to develop and validate CSIA methods for analysis of carbon and nitrogen in DNAN and NTO; and (2) to quantify kinetic isotope effects in carbon and nitrogen during the biotic and abiotic degradation of these insensitive munitions constituents by various mechanisms, thereby providing new diagnostic measurement tools that may allow these mechanisms to be more clearly assessed and quantified in natural environments.
The overall technical approach is to first develop and validate CSIA methods for DNAN and NTO and then perform a series of laboratory experiments to assess the ε13C and ε15N values for DNAN and NTO during abiotic and biotic degradation. These studies will be performed in simple laboratory systems and utilize pure bacterial cultures, environmental samples prepared as microcosms, and minerals and photolytic equipment to promote abiotic degradation of DNAN and/or NTO.
This work will provide isotopic enrichment factors and enrichment factor ratios of C and N for different biotic and abiotic transformation pathways of NTO and DNAN, potentially allowing their degradation mechanisms to be more clearly evaluated in groundwater and other environments. This work is expected to provide DoD with an important CSIA tool and useful dataset with which to determine the importance of biotic and abiotic transformation of DNAN and NTO on ranges and other contaminated sites. (Anticipated Project Completion - 12/2019)
Fuller, M., R. Rezes, P. Hedman, J. Jones, N.C. Sturchio, and P. Hatzinger. 2020. Biotransformation of the insensitive munition constituents 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4-dinitroanisole (DNAN) by Aerobic Methane-Oxidizing Consortia and Pure Cultures. Journal of Hazardous Materials 407:24341. doi.org/10.1016/j.hazmat.2020.124341.
Wang, C., M.E. Fuller, L.J. Heraty, P.B. Hatzinger, N.C. Sturchio. 2021. Photocatalytic mechanisms of 2,4-dinitroanisole Degradation in Water Deciphered by C and N Dual-Element Isotope Fractionation. Journal of Hazardous Materials, 411:125109. doi.org/10.1016/j.jhazmat.2021.125109.
Wang, C.L., L.J. Heraty, A.F. Wallace, C. Liu, X. Li, G.P. McGovern, J. Horita, M.E. Fuller, P.B. Hatzinger, N.C. Sturchio. 2021. Position-Specific Isotope Effects During Alkaline Hydrolysis of 2,4- Dinitroanisole Resolved by Compound-Specific Isotope Analysis, 13C NMR, and Density-Functional Theory. Chemosphere, 280:130625.
Wang, C.L., A.F. Wallace, L.J. Heraty, H. Qi, N.C. Sturchio. 2020. Alkaline Hydrolysis Pathway of 2,4-Dinitroanisole Verified by 18O Tracer Experiment. Journal of Hazardous Materials, 396:122627.