Controls on the carbon isotopic composition of coalbed biogenic methane and implications for biogas stimulation

大卫·文森博士获得了美国国家科学基金会地球科学博士后奖学金，将在西北大学实施一项研究和教育计划。他将研究煤在产甲烷生物降解过程中传递的稳定碳同位素特征。自然丰度碳稳定同位素（13C/12C）比值是与甲烷生成相关的特定途径和过程的有价值的标志。然而，解释上的不确定性和与微生物技术的差异使得使用碳同位素诊断感兴趣的产甲烷途径（例如丙酮裂解产甲烷和二氧化碳还原）变得复杂。其他相互竞争的生物地球化学过程——特别是硫酸盐还原——和质量平衡效应也可能影响观测到的碳同位素特征。其他特定途径的工具和技术可能会提高对甲烷前体，特别是醋酸利用的理解。本研究的主要任务是将分析醋酸盐化合物特异性和分子内碳同位素比率的方法应用于微生物气体系统中遇到的低浓度，分析天然和实验室构建的产甲烷系统水体中的这些同位素比率，以追踪产甲烷过程中醋酸盐的利用，并将包括反应输运模型在内的建模技术应用于产甲烷煤生物降解的质量平衡。天然气是一种日益重要的能源资源，其中很大一部分是生物源的。该研究的重点是来自未开采煤（煤层气）的微生物甲烷，并对来自其他碳源的自然发生和人为刺激的沼气资源具有启示意义。为了刺激本地微生物群落产生额外的甲烷，需要对自然过程和途径有详细的了解。在这项研究中，化合物特异性同位素示踪技术的使用将促进对醋酸盐在甲烷生成或不产生甲烷的竞争过程中的利用的理解。换句话说，天然或改性甲烷生产系统的效率可以通过乙酸的同位素特征，结合源有机碳和最终产物（甲烷和二氧化碳）的信息来记录。与博士后奖学金相关的教育和推广活动包括为K - 12教师开发和开展与生物燃料相关的夏季研讨会，并让本科生参与研究。

Dr. David Vinson has been awarded an NSF Earth Sciences Postdoctoral Fellowship to implement a research and education program based at Northwestern University. He will investigate stable carbon isotope signatures imparted during methanogenic biodegradation of coal. Natural abundance carbon stable isotope (13C/12C) ratios are valuable signatures of specific pathways and processes associated with methanogenesis. Yet, interpretive uncertainties and discrepancies with microbiological techniques complicate the use of carbon isotopes to diagnose methanogenic pathways of interest (e.g. acetoclastic methanogenesis and CO2 reduction). Other competing biogeochemical processes - in particular sulfate reduction - and mass balance effects may also influence observed carbon isotope signatures. Additional pathway-specific tools and techniques may improve understanding of the utilization of methane precursors, especially acetate. The primary tasks of the research are to adapt methods of analyzing compound-specific and intramolecular carbon isotope ratios of acetate to the low concentrations encountered in microbial gas systems, to analyze these isotope ratios in waters from natural and laboratory-constructed methanogenic systems in order to trace acetate utilization during methanogenesis, and to apply modeling techniques including reactive transport modeling to the mass balance of methanogenic coal biodegradation.Natural gas is an increasingly important energy resource, of which a significant portion is of biogenic origin. The research focuses on microbial methane derived from unmined coal (coalbed methane), and has implications for naturally-occurring and human-stimulated biogas resources derived from other carbon sources. In order to stimulate the native microbial community to yield additional methane, a detailed understanding of natural processes and pathways is required. In this research, the use of a compound-specific isotope tracer technique will promote understanding of the utilization of acetate in methanogenesis or in competing processes that do not yield methane. In other words, the efficiency of natural or modified methane-producing systems may be recorded by the isotope signature of acetate, combined with information on source organic carbon and end products (methane and CO2). Education and outreach activities associated with the postdoctoral fellowship include developing and conducting a biofuels-related summer workshop for K 12 teachers and involving undergraduate students in the research.