Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland
Usage of thermal energy contained in abandoned, flooded, coal mines has the potential to contribute to low carbon heating or cooling supply and assist in meeting net-zero carbon emission targets. However, hazardous ground gases, such as CH4 and CO2, can be found naturally in superficial deposits, co...
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Frontiers Media S.A.
2023-12-01
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| Series: | Earth Science, Systems and Society |
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| Online Access: | https://www.lyellcollection.org/doi/10.3389/esss.2023.10073 |
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| author | Rebecca M. Chambers Gareth Johnson Adrian J. Boyce Stuart M. V. Gilfillan |
| author_facet | Rebecca M. Chambers Gareth Johnson Adrian J. Boyce Stuart M. V. Gilfillan |
| author_sort | Rebecca M. Chambers |
| collection | DOAJ |
| description | Usage of thermal energy contained in abandoned, flooded, coal mines has the potential to contribute to low carbon heating or cooling supply and assist in meeting net-zero carbon emission targets. However, hazardous ground gases, such as CH4 and CO2, can be found naturally in superficial deposits, coal bearing strata and abandoned mines. Determining the presence, magnitude, and origin of subsurface gases, and how their geochemical fingerprints evolve within the shallow subsurface is vital to developing an understanding of how to manage the risk posed by ground gases in geoenergy technology development. Here, we present the first CH4 and CO2 concentration-depth profiles and stable isotope (δ13CCH4, δ13CCO2, and δDCH4) profiles obtained from UK mine workings, through analysis of headspace gas samples degassed from cores and chippings collected during construction of the Glasgow Observatory. These are used to investigate the variability of gas fingerprints with depth within unmined Carboniferous coal measures and Glasgow coal mine workings. Stable isotope compositions of CH4 (δ13CCH4 = −73.4‰ to −14.3‰; δ13CCO2 = −29‰ to −6.1‰; δDCH4 = −277‰ to −88‰) provide evidence of a biogenic source, with carbonate reduction being the primary pathway of CH4 production. Gas samples collected at depths of 63–79 m exhibit enrichments in 13CCH4 and 2H, indicating the oxidative consumption of CH4. This correlates with their proximity to the Glasgow Ell mine workings, which will have increased exposure to O2 from the atmosphere as a result of mining activities. CO2 gas is more abundant than CH4 throughout the succession in all three boreholes, exhibiting high δ13CCO2 values relative to the CH4 present. Gases from unmined bedrock exhibit the highest δ13CCO2 values, with samples from near-surface superficial deposits having the lowest δ13CCO2 values. δ13CCO2 values become progressively lower at shallower depths (above 90 m), which can be explained by the increasing influence of shallow groundwaters containing a mixture of dissolved marine carbonate minerals (∼0‰) and soil gas CO2 (−26‰) as depth decreases. Our findings provide an insight into the variability of mine derived gases within 200 m of the surface, providing an important ‘time-zero’ record of the site, which is required in the design of monitoring approaches. |
| format | Article |
| id | doaj-art-28413178d564489ba876de6be8056656 |
| institution | Kabale University |
| issn | 2634-730X |
| language | English |
| publishDate | 2023-12-01 |
| publisher | Frontiers Media S.A. |
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| series | Earth Science, Systems and Society |
| spelling | doaj-art-28413178d564489ba876de6be80566562025-01-10T14:04:51ZengFrontiers Media S.A.Earth Science, Systems and Society2634-730X2023-12-013110.3389/esss.2023.10073Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, ScotlandRebecca M. Chambers0Gareth Johnson1Adrian J. Boyce2Stuart M. V. Gilfillan31School of GeoSciences, Grant Institute, University of Edinburgh, Edinburgh, United Kingdom2Department of Civil and Environmental Engineering, University of Strathclyde Glasgow, United Kingdom3Isotope Geosciences Unit, Scottish Universities Environmental Research Centre (SUERC), East Kilbride, United Kingdom1School of GeoSciences, Grant Institute, University of Edinburgh, Edinburgh, United KingdomUsage of thermal energy contained in abandoned, flooded, coal mines has the potential to contribute to low carbon heating or cooling supply and assist in meeting net-zero carbon emission targets. However, hazardous ground gases, such as CH4 and CO2, can be found naturally in superficial deposits, coal bearing strata and abandoned mines. Determining the presence, magnitude, and origin of subsurface gases, and how their geochemical fingerprints evolve within the shallow subsurface is vital to developing an understanding of how to manage the risk posed by ground gases in geoenergy technology development. Here, we present the first CH4 and CO2 concentration-depth profiles and stable isotope (δ13CCH4, δ13CCO2, and δDCH4) profiles obtained from UK mine workings, through analysis of headspace gas samples degassed from cores and chippings collected during construction of the Glasgow Observatory. These are used to investigate the variability of gas fingerprints with depth within unmined Carboniferous coal measures and Glasgow coal mine workings. Stable isotope compositions of CH4 (δ13CCH4 = −73.4‰ to −14.3‰; δ13CCO2 = −29‰ to −6.1‰; δDCH4 = −277‰ to −88‰) provide evidence of a biogenic source, with carbonate reduction being the primary pathway of CH4 production. Gas samples collected at depths of 63–79 m exhibit enrichments in 13CCH4 and 2H, indicating the oxidative consumption of CH4. This correlates with their proximity to the Glasgow Ell mine workings, which will have increased exposure to O2 from the atmosphere as a result of mining activities. CO2 gas is more abundant than CH4 throughout the succession in all three boreholes, exhibiting high δ13CCO2 values relative to the CH4 present. Gases from unmined bedrock exhibit the highest δ13CCO2 values, with samples from near-surface superficial deposits having the lowest δ13CCO2 values. δ13CCO2 values become progressively lower at shallower depths (above 90 m), which can be explained by the increasing influence of shallow groundwaters containing a mixture of dissolved marine carbonate minerals (∼0‰) and soil gas CO2 (−26‰) as depth decreases. Our findings provide an insight into the variability of mine derived gases within 200 m of the surface, providing an important ‘time-zero’ record of the site, which is required in the design of monitoring approaches.https://www.lyellcollection.org/doi/10.3389/esss.2023.10073geochemistrygeothermalmine waterenvironmental monitoringgeoenergy |
| spellingShingle | Rebecca M. Chambers Gareth Johnson Adrian J. Boyce Stuart M. V. Gilfillan Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland Earth Science, Systems and Society geochemistry geothermal mine water environmental monitoring geoenergy |
| title | Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland |
| title_full | Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland |
| title_fullStr | Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland |
| title_full_unstemmed | Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland |
| title_short | Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland |
| title_sort | constraining the geochemical fingerprints of gases from the uk carboniferous coal measures at the glasgow geoenergy observatories field site scotland |
| topic | geochemistry geothermal mine water environmental monitoring geoenergy |
| url | https://www.lyellcollection.org/doi/10.3389/esss.2023.10073 |
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