A Multitracer Test Proving the Reliability of Rayleigh Equation-Based Approach for Assessing Biodegradation in a BTEX Contaminated Aquifer

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• 作者：Anko Fischer ; Jana Bauer ; Rainer U. Meckenstock ; Willibald Stichler ; Christian Griebler ; Piotr Maloszewski ; Matthias Kä ; stner ; and Hans H. Richnow
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：July 1, 2006
• 年：2006
• 卷：40
• 期：13
• 页码：4245 - 4252
• 全文大小：413K
• 年卷期：v.40,no.13(July 1, 2006)
• ISSN：1520-5851

文摘

Compound-specific stable isotope analysis (CSIA) is oneof the most important methods for assessing biodegradationactivities in contaminated aquifers. Although the conceptis straightforward, the proof that the method cannot be onlyused for a qualitative analysis but also to quantifybiodegradation in the subsurface was missing. We thereforeperformed a multitracer test in the field with ring-deuterated (d₅) and completely (d₈) deuterium-labeledtoluene isotopologues (400 g) as reactive tracers as wellas bromide as a conservative tracer. The compounds wereinjected into the anoxic zone of a BTEX plume located down-gradient of the contaminant source. Over a period of4.5 months the tracer concentrations were analyzed attwo control planes located 24 and 35 m downgradient ofthe injection well. Deuterium-labeled benzylsuccinate wasfound in the aquifer, indicating the anaerobic biodegradationof deuterated toluene via the benzylsuccinate synthasepathway. Three independent methods were applied to quantifybiodegradation of deuterated toluene. First, fractionationof toluene-d₈ and toluene-d₅ using the Rayleigh equation andan appropriate laboratory-derived isotope fractionationfactor was used for the calculation of the microbialdecomposition of deuterated toluene isotopologues (CSIA-method). Second, the biodegradation was quantified bythe changes of the concentrations of deuterated toluenerelative to bromide. Both methods gave similar results,implying that the CSIA-method is a reliable tool to quantifybiodegradation in contaminated aquifers. The results ofboth methods yielded a biodegradation of deuterated tolueneisotopologues of approximately 23-29% for the first and 44-51% for the second control plane. Third, the mineralizationof deuterated toluene isotopologues was verified bydetermination of the enrichment of deuterium in thegroundwater. This method indicated that parts of deuteriumwere assimilated into the biomass of toluene degradingmicroorganisms.