Fischer Anko, Bauer Jana, Meckenstock Rainer U, Stichler Willibald, Griebler Christian, Maloszewski Piotr, Kästner Matthias, Richnow Hans H
UFZ-Center for Environmental Research Leipzig-Halle, Department of Isotope Biogeochemistry, Permoserstrasse 15, D-04318 Leipzig, Germany.
Environ Sci Technol. 2006 Jul 1;40(13):4245-52. doi: 10.1021/es052466t.
Compound-specific stable isotope analysis (CSIA) is one of the most important methods for assessing biodegradation activities in contaminated aquifers. Although the concept is straightforward, the proof that the method cannot be only used for a qualitative analysis but also to quantify biodegradation in the subsurface was missing. We therefore performed a multitracer test in the field with ring-deuterated (d5) and completely (d8) deuterium-labeled toluene isotopologues (400 g) as reactive tracers as well as bromide as a conservative tracer. The compounds were injected into the anoxic zone of a BTEX plume located down-gradient of the contaminant source. Over a period of 4.5 months the tracer concentrations were analyzed at two control planes located 24 and 35 m downgradient of the injection well. Deuterium-labeled benzylsuccinate was found in the aquifer, indicating the anaerobic biodegradation of deuterated toluene via the benzylsuccinate synthase pathway. Three independent methods were applied to quantify biodegradation of deuterated toluene. First, fractionation of toluene-d8 and toluene-d5 using the Rayleigh equation and an appropriate laboratory-derived isotope fractionation factor was used for the calculation of the microbial decomposition of deuterated toluene isotopologues (CSIA-method). Second, the biodegradation was quantified by the changes of the concentrations of deuterated toluene relative to bromide. Both methods gave similar results, implying that the CSIA-method is a reliable tool to quantify biodegradation in contaminated aquifers. The results of both methods yielded a biodegradation of deuterated toluene isotopologues of approximately 23-29% for the first and 44-51% for the second control plane. Third, the mineralization of deuterated toluene isotopologues was verified by determination of the enrichment of deuterium in the groundwater. This method indicated that parts of deuterium were assimilated into the biomass of toluene degrading microorganisms.
化合物特异性稳定同位素分析（CSIA）是评估受污染含水层中生物降解活动的最重要方法之一。尽管该概念很简单，但此前缺少证据证明该方法不仅可用于定性分析，还能定量分析地下的生物降解情况。因此，我们在现场进行了一项多示踪剂测试，使用环氘代（d5）和完全氘代（d8）的甲苯同位素异构体（400克）作为反应性示踪剂，以及溴化物作为保守示踪剂。这些化合物被注入到位于污染源下游的BTEX羽流的缺氧区。在4.5个月的时间里，在位于注入井下游24米和35米处的两个控制平面分析示踪剂浓度。在含水层中发现了氘代苄基琥珀酸酯，表明氘代甲苯通过苄基琥珀酸合酶途径进行厌氧生物降解。应用了三种独立方法来定量氘代甲苯的生物降解。首先，使用瑞利方程和适当的实验室得出的同位素分馏系数对甲苯-d8和甲苯-d5进行分馏，用于计算氘代甲苯同位素异构体的微生物分解（CSIA方法）。其次，通过氘代甲苯相对于溴化物浓度的变化来定量生物降解。两种方法得出了相似的结果，这意味着CSIA方法是定量受污染含水层中生物降解的可靠工具。两种方法的结果显示，第一个控制平面中氘代甲苯同位素异构体的生物降解率约为23 - 29%，第二个控制平面为44 - 51%。第三，通过测定地下水中氘的富集情况来验证氘代甲苯同位素异构体的矿化作用。该方法表明部分氘被同化到甲苯降解微生物的生物量中。
