Browsing by Author "Beckmann, S"

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    Biogeochemical constraints on the origin of methane in an alluvial aquifer: evidence for the upward migration of methane from underlying coal measures
    (European Geosciences Union, 2017-04-26) Iverach, CP; Beckmann, S; Cendón, DI; Manefield, M; Kelly, BFJ
    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 characterised, especially when considering the potential impacts of the global expansion of unconventional gas production on groundwater quality and quantity. We use geochemical and microbiological data, along with measurements of CH4 isotopic composition ( 13C-CH4), to determine the processes acting upon CH4 in a freshwater alluvial aquifer that directly overlies coal measures targeted for unconventional gas production in Australia. A combination of geochemical and microbiological groundwater samples were collected from private irrigation boreholes. The groundwater was analysed for the major ions, water stable isotopes ( 2H and 18O), the isotopic composition of dissolved organic carbon ( 13CDOC) and dissolved inorganic carbon ( 13CDIC). Quantitative realtime PCR was used to determine abundances of bacterial and archaeal 16S rRNA gene targets and functional gene targets in the groundwater. Measurements of CH4 indicate that there is biogenic CH4 in the aquifer, however microbial community analysis indicates that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of DIC and, as well as the concentration of SO2-4 , indicate limited potential for methanogenesis insitu. Microbial community analysis also showed that aerobic oxidation of CH4 is occurring in the alluvial aquifer despite the absence of a microbial pathway to produce the CH4. 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. © Author(s) 2016. CC Attribution 3.0 License.
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    Biogeochemical constraints on the origin of methane in an alluvial aquifer: evidence for the upward migration of methane from underlying coal measures
    (European Geosciences Union, 2017-01-17) Iverach, CP; Beckmann, S; Cendón, DI; Manefield, M; Kelly, BFJ
    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. © Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 Licence.
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    Constraining source attribution of methane in an alluvial aquifer with multiple recharge pathways
    (Elsevier B. V., 2020-02-10) Iverach, CP; Cendón, DI; Beckmann, S; Hankin, SI; Manefield, M; Kelly, BFJ
    Identifying the source of methane (CH4) in groundwater is often complicated due to various production, degradation and migration pathways, particularly in settings where there are multiple groundwater recharge pathways. This study demonstrates the ability to constrain the origin of CH4 within an alluvial aquifer that could be sourced from in situ microbiological production or underlying formations at depth. To characterise the hydrochemical and microbiological processes active within the alluvium, previously reported hydrochemical data (major ion chemistry and isotopic tracers (3H, 14C, 36Cl)) were interpreted in the context of CH4 and carbon dioxide (CO2) isotopic chemistry, and the microbial community composition in the groundwater. The rate of observed oxidation of CH4 within the aquifer was then characterised using a Rayleigh fractionation model. The stratification of the hydrochemical facies and microbiological community populations is interpreted to be a result of the gradational mixing of water from river leakage and floodwater recharge with water from basal artesian inflow. Within the aquifer there is a low abundance of methanogenic archaea indicating that there is limited biological potential for microbial CH4 production. Our results show that the resulting interconnection between hydrochemistry and microbial community composition affects the occurrence and oxidation of CH4 within the alluvial aquifer, constraining the source of CH4 in the groundwater to the geological formations beneath the alluvium. © 2019 The Author(s). Published by Elsevier B.V. Open Access - CC BY licence
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    Where do the methanogens live? New insights into the origin of methane in the Condamine River alluvial aquifer
    (National Centre for Groundwater Research And Training, 2017-07-11) Iverach, CP; Beckmann, S; Cendón, DI; Manefield, M; Kelly, BFJ
    There is considerable debate about the origin of methane (CH4) in aquifers surrounding coal seam and shale gas exploration and production. Numerous processes control the natural occurrence of CH4 in groundwater. To determine the origins of CH4 in an aquifer both the geochemical and microbial community need to be characterised, however this is rarely done. We use geochemical and microbiological data, along with measurements of CH4 isotopic composition (δ13C-CH4), to determine the processes acting upon CH4 in the Condamine River Alluvial Aquifer, a freshwater aquifer that directly overlies coal measures targeted for coal seam gas production in Australia. Groundwater samples for geochemical and microbiological analyses were collected from private irrigation boreholes in the Condamine Catchment. The groundwater was analysed for the major ions, water stable isotopes (δ2H and δ18O), the isotopic composition of dissolved organic carbon (δ13CDOC) and dissolved inorganic carbon (δ13CDIC). Quantitative real-time PCR was used to determine abundances of bacterial and archaeal 16S rRNA gene targets and functional gene targets in the groundwater. Measurements of CH4 concentration and isotopic composition suggest that there is biogenic CH4 in the aquifer, however microbial community analysis indicates that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of DIC and, as well as the concentration of SO42-, indicate limited potential for methanogenesis in situ. Microbial community analysis also showed that aerobic oxidation of CH4 is occurring in the alluvial aquifer despite the absence of a microbial pathway to produce the CH4. The combination of microbiological and geochemical indicators suggests that the most likely source of CH4, where it was present in the deeper freshwater aquifer, is the upward migration of CH4 from the underlying coal measures.