Biogeochemical constraints on the origin of methane in an alluvial aquifer: evidence for the upward migration of methane from underlying coal measures
Biogeochemical constraints on the origin of methane in an alluvial aquifer: evidence for the upward migration of methane from underlying coal measures
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DOI：
10.5194/bg-14-215-2017
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发表时间：
2017-01
期刊：
影响因子：
4.9
通讯作者：
C. P. Iverach;S. Beckmann;D. Cendón;M. Manefield;B. Kelly
中科院分区：
文献类型：
--
作者：
C. P. Iverach;S. Beckmann;D. Cendón;M. Manefield;B. Kelly
摘要。地下水中甲烷（CH4）生成、氧化和迁移过程的地球化学和微生物指标对于确定气源具有重要意义。必须了解控制地下水中CH4自然赋存的过程，特别是考虑到煤层气（CSG）生产的全球扩张对地下水质量和数量的潜在影响。我们使用地球化学和微生物学数据，以及CH4同位素组成（δ13C-CH4）的测量，来确定在澳大利亚煤炭生产目标煤上直接覆盖的淡水冲积含水层中作用于CH4的过程。CH4测量表明，含水层中存在生物成因CH4；然而，微生物数据表明，地下水中没有产甲烷的古细菌。此外，地球化学数据，特别是溶解无机碳（DIC）和溶解有机碳（DOC）的同位素，以及SO42−的浓度，表明原位甲烷生成的潜力有限。微生物群落分析也表明，CH4在冲积含水层中发生好氧氧化。微生物学指标和地球化学指标的结合表明，CH4最可能的来源是来自下伏煤系的向上运移，而CH4存在于淡水含水层中。
Abstract. Geochemical and microbiological indicators of methane (CH4) production, oxidation and migration processes in groundwater are important to understand when attributing sources of gas. The processes controlling the natural occurrence of CH4 in groundwater must be understood, especially when considering the potential impacts of the global expansion of coal seam gas (CSG) production on groundwater quality and quantity. We use geochemical and microbiological data, along with measurements of CH4 isotopic composition (δ13C-CH4), to determine the processes acting upon CH4 in a freshwater alluvial aquifer that directly overlies coal measures targeted for CSG production in Australia. Measurements of CH4 indicate that there is biogenic CH4 in the aquifer; however, microbial data indicate that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), as well as the concentration of SO42−, indicate limited potential for methanogenesis in situ. Microbial community analysis also shows that aerobic oxidation of CH4 occurs in the alluvial aquifer. The combination of microbiological and geochemical indicators suggests that the most likely source of CH4, where it was present in the freshwater aquifer, is the upward migration of CH4 from the underlying coal measures.