The explosive 2,4-dinitroanisole (DNAN) used in insensitive munitions formulations can, in principle, undergo several of biological and abiotic degradation reactions in contaminated environments. Because these processes will be difficult to quantify from measured DNAN concentration gradients, we have evaluated the isotope fractionation and the kinetic isotope effects of the currently known biodegradation route to enable one to track this process by compound-specific isotope analysis. To this end, we carried out laboratory experiments with <i>Nocardioides</i> strain JS1661, which initiates the mineralization of DNAN by a novel demethylase that produces 2,4-dinitrophenol and methanol. The observed C isotope fractionation of DNAN confirms a hydrolytic cleavage of the ether bond while only minor changes of N isotope ratios of the substrate illustrate that the aromatic nitro groups do not participate in the reaction. The C and N isotope fractionation of 2,4-dinitrophenol perfectly matches the observations made with DNAN and reveals a substantial intramolecular difference of C isotope signatures between C atoms in the aromatic ring and the methoxy substituent by more than 30%. None of the other known biodegradation reactions of nitroaromatic contaminants is initiated by a hydrolytic reaction and the combined C and N isotope fractionation trends of DNAN are thus distinctly different from any reductive and oxidative degradation pathways. Our observations made in the laboratory strongly suggest that compound-specific isotope analysis of DNAN is suitable to distinguish its biodegradation from other transformation processes in contaminated environments an to quantify the extent of the reaction.

Carbon and nitrogen isotope fractionation reveals the biodegradation of 2,4-dinitroanisole

253rd National Meeting (2017)

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