Abstract：
Compound-specific isotope analysis (CSIA) is an established tool to track the in situ transformation of organic chemicals at contaminated sites. In this work, we evaluated the potential of multi-element CSIA to assess biodegradation of 2,3-dichloroaniline (2,3-DCA), which is a major industrial feedstock. Using controlled laboratory experiments, we determined, for the first time, negligible carbon (<0.5‰) and hydrogen (<10‰) isotope fractionation and a significant inverse nitrogen isotope fractionation (>10‰) during aerobic 2,3-DCA biodegradation by a mixed enrichment culture. The tentative identification of a glutamate conjugate of 2,3-DCA as a reaction intermediate indicates that the initial multistep enzymatic reaction may be rate-limiting. The formation of the glutamate adduct would increase the bond energy at the N atom, thus likely explaining the observed inverse N isotope fractionation. The corresponding nitrogen enrichment factor was +6.8 ± 0.6‰. This value was applied to investigate the in situ 2,3-DCA biodegradation at a contaminated site where the carbon and nitrogen isotope signatures from field samples suggested similar aerobic processes by native microorganisms. Under the assumption of the applicability of the Rayleigh model in a pilot wetland treating contaminated groundwater, the extent of biodegradation was estimated to be up to 80-90%. This study proposes multi-element CSIA as a novel application to study 2,3-DCA fate in groundwater and surface water and provides insights into biodegradation pathways.
摘要：
化合物特定同位素分析（CSIA）是跟踪受污染地点有机化学物质原位转化的既定工具。在这项工作中,我们评估了多元素CSIA评估2,3-二氯苯胺（2,3-DCA）生物降解的潜力，这是一种主要的工业原料。使用受控的实验室实验，我们决定，第一次,在混合富集培养的好氧2,3-DCA生物降解过程中，碳（<0.5‰）和氢（<10‰）的同位素分馏和显着的逆氮同位素分馏（>10‰）。2,3-DCA的谷氨酸缀合物作为反应中间体的初步鉴定表明，最初的多步酶促反应可能是限速的。谷氨酸加合物的形成会增加N原子的键能，因此可能解释了观察到的反N同位素分馏。相应的氮富集因子为+6.8±0.6‰。该值用于研究受污染地点的原位2,3-DCA生物降解，现场样品中的碳和氮同位素特征表明天然微生物的有氧过程相似。在Rayleigh模型在处理受污染地下水的试点湿地中的适用性的假设下，生物降解的程度估计高达80-90%。这项研究提出了多元素CSIA作为研究地下水和地表水中2,3-DCA命运的新应用，并提供了对生物降解途径的见解。
