Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, MN 55455-0116, USA.
Environ Sci Process Impacts. 2019 Jan 23;21(1):51-62. doi: 10.1039/c8em00381e.
The recent development of insensitive munitions, such as 2,4-dinitroanisole (DNAN), as components of military explosives has generated concern for potential subsurface contamination and created a need to fully characterize their transformation processes. Compound specific isotope analysis (CSIA) has proven to be a useful means of assessing transformation pathways according to characteristic stable isotope fractionation patterns. The C and N isotope fractionation of DNAN associated with abiotic and enzymatic hydrolysis was recently assessed. The extent to which DNAN isotope fractionation will be affected by other potentially competing transformation pathways known for nitroaromatic compounds (e.g., reduction) and if previous knowledge can be extrapolated to other environmental matrices remains to be understood. Here, we investigated the C and N isotope fractionation and reaction rate constants of DNAN during abiotic reduction mediated by mineral-associated Fe(ii) species as a function of mineral type, natural organic matter presence, and repeated exposures to DNAN. Though rate constants varied, N and C apparent kinetic isotope effects (AKIEs) remained consistent across all experiments (averaged values of 15N-AKIE = 1.0317 ± 0.0064 and 13C-AKIE = 1.0008 ± 0.0005) and revealed significant 15N- and minimal 13C-enrichment in agreement with previous work on nitroaromatic compounds. Moreover, the observed fractionation was clearly distinct from trends for abiotic and enzymatic hydrolysis. This study provides a strengthened basis for the use of CSIA as a robust tool for monitoring DNAN degradation in complex environmental matrices as a component of future remediation efforts.
最近，2,4-二硝基苯甲醚（DNAN）等钝感弹药作为军用炸药的组成部分得到了发展，这引起了人们对潜在的地下污染的关注，并需要对其转化过程进行全面的特征描述。化合物特异性同位素分析（CSIA）已被证明是一种根据特征稳定同位素分馏模式评估转化途径的有用方法。最近评估了与非生物和酶水解相关的 DNAN 的 C 和 N 同位素分馏。DNAN 的同位素分馏将在多大程度上受到其他潜在的竞争转化途径（例如还原）的影响，以及以前的知识是否可以外推到其他环境基质中，这仍有待了解。在这里，我们研究了矿物相关 Fe(ii)物种介导的非生物还原过程中 DNAN 的 C 和 N 同位素分馏和反应速率常数，作为矿物类型、天然有机物存在和反复暴露于 DNAN 的函数。尽管速率常数有所不同，但 N 和 C 的表观动力学同位素效应（AKIE）在所有实验中保持一致（平均 15N-AKIE 值为 1.0317 ± 0.0064，13C-AKIE 值为 1.0008 ± 0.0005），并与先前关于硝基芳烃化合物的工作一致，表明存在显著的 15N 和最小的 13C 富集。此外，观察到的分馏明显不同于非生物和酶水解的趋势。这项研究为 CSIA 作为一种监测复杂环境基质中 DNAN 降解的有力工具提供了更坚实的基础，这是未来修复工作的一部分。
