Consumption of atmospheric methane in a limestone cave in Indiana, USA

Webster, Kevin D.; Mirza, Anmar; Deli, Jessica M.; Sauer, Peter E.; Schimmelmann, Arndt

doi:10.1016/j.chemgeo.2016.09.020

Cited by 23 publications

(36 citation statements)

References 50 publications

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“…We suggest that the sources include CH4 produced from acetate fermentation and from CO2 reduction. These data corroborate recent findings of partially oxidized CH4 entering cave air from acetate fermentation and CO2 reduction in Indiana (Webster et al, 2016). These observations of CH4 production by acetate fermentation and carbonate reduction suggest that both processes happen over a wide scale in the environment.…”

Section: Discussionsupporting

confidence: 81%

“…Consideration of an additional source of thermogenic CH4 (natural gas) from deep geologic sources enlarges the plausibility fields of both prior scenarios to encompass all of the data. Our δ 13 CCH 4 and δ 2 HCH 4 data also agree with observations of δ 13 CCH 4 and δ 2 HCH 4 from a cave in Indiana where it appeared that CH4 from both acetate fermentation and carbonate reduction influenced cave air geochemistry (Webster et al, 2016). Additionally our data resemble an arctic system characterized by acetoclastic and hydrogenotrophic CH4 sources and methanotrophy (McCalley et al, 2014).…”

Section: Methane Oxidation Mechanismssupporting

confidence: 81%

“…Other studies have also shown microbially produced CH4 entering caves (Mattey et al, 2013;Webster et al, 2016). Our data point to the methanogenic sources of acetate fermentation and carbonate reduction (Fig.…”

Section: Subsurface-surface Atmospheric Exchangesupporting

confidence: 51%

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Subterranean Karst Environments as a Global Sink for Atmospheric Methane

Webster¹,

Drobniak²,

Etiope³

et al. 2017

Preprint

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Abstract:The air in subterranean karst cavities is often depleted in methane (CH4) relative to the atmosphere. Karst is considered a potential sink for the atmospheric greenhouse gas CH4 because its subsurface drainage networks and solution-enlarged fractures facilitate atmospheric exchange. Karst landscapes cover about 14 % of earth's continental surface, but observations of CH4 concentrations in cave air are limited to localized studies in Gibraltar, Spain, Indiana (USA), Vietnam, Australia, and by incomplete isotopic data. To test if karst is systematically acting as a global CH4 sink, we measured the CH4 concentrations, δ 13 CCH 4 , and δ 2 HCH 4 values of cave air from 33 caves in the USA and three caves in New Zealand. We also measured CO2 concentrations, δ 13 CCO 2 , and radon (Rn) concentrations to support CH4 data interpretation by assessing cave air residence times and mixing processes. Among these caves, 35 exhibited subatmospheric CH4 concentrations in at least one location compared to their local atmospheric backgrounds. CH4 concentrations and δ 13 CCH 4 and δ 2 HCH 4 values suggest that microbial methanotrophy within caves is the primary CH4 consumption mechanism as the atmosphere exchanges with subsurface air. The pattern of δ 13 CCH 4 and δ 2 HCH 4 values along CH4 concentration gradients in cave air provides evidence for incomplete oxidation by methanotrophy. Only 5 locations from 3 caves showed elevated CH4 concentrations compared to the atmospheric background and could be ascribed to local CH4 sources from sewage and outgassing swamp water. Several associated δ 13 CCH 4 and δ 2 HCH 4 values point to carbonate reduction and acetate fermentation as biochemical pathways of limited methanogenesis in karst environments and suggest that these pathways occur in the environment over large spatial scales. Our data show that karst environments function as a global CH4 sink. Estimates of CH4 flux in karst landscapes are needed in order to include the subterranean CH4 sink in climate models.

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Section: Discussionsupporting

confidence: 81%

Section: Methane Oxidation Mechanismssupporting

confidence: 81%

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Subterranean Karst Environments as a Global Sink for Atmospheric Methane

Webster¹,

Drobniak²,

Etiope³

et al. 2017

Preprint

Self Cite

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show abstract

“…We 392 suggest that the sources include CH4 produced from acetate fermentation and from CO2 393 reduction. These data corroborate recent findings of partially oxidized CH4 entering cave 394 air from acetate fermentation and CO2 reduction in Indiana (Webster et al, 2016). These 395 observations of CH4 production by acetate fermentation and carbonate reduction suggest 396 that both processes happen over a wide scale in the environment.…”

Section: Subsurface-surface Atmospheric Exchange 253supporting

confidence: 81%

Subterranean Karst Environments as a Global Sink for Atmospheric Methane

Webster¹,

Drobniak²,

Etiope³

et al. 2017

Preprint

Self Cite

View full text Add to dashboard Cite

21The air in subterranean karst cavities is often depleted in methane (CH4) relative to the 22 atmosphere. Karst is considered a potential sink for the atmospheric greenhouse gas CH4 because 23 its subsurface drainage networks and solution-enlarged fractures facilitate atmospheric exchange. 24Karst landscapes cover about 14% of earth's continental surface, but observations of CH4 25 concentrations in cave air are limited to localized studies in Gibraltar, Spain, Indiana (USA), 26Vietnam, Australia, and by incomplete isotopic data. To test if karst is acting as a global CH4 sink, 27we measured the CH4 concentrations, δ

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“…We measured CH 4 and CO 2 concentrations from discrete samples with a Varian 450 gas chromatograph (GC) (see Webster et al, 2016). CH 4 and CO 2 calibration curves for concentration and uncertainty estimates were calculated following the methods of Webster et al (2016).…”

Section: Laboratory Analysesmentioning

confidence: 99%

Isotopic evidence for the migration of thermogenic methane into a sulfidic cave, Cueva de Villa Luz, Tabasco, Mexico

Webster¹,

Lagarde²,

Sauer³

et al. 2017

JCKS

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Methane (CH 4 ) is an economic resource and a greenhouse gas, but its migration through rocks is not immediately associated with speleogenesis. Sulfuric-acid speleogenesis is a cave-forming mechanism that has produced a variety of economically important oil fields and aquifers, and is theorized to be related to the oxidation of CH 4 and hydrocarbons. Despite hypotheses that the oxidation of CH 4 may provide a basis for the generation of sulfides during sulfuric-acid speleogenesis, evidence from active systems has not yet been obtained.

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Consumption of atmospheric methane in a limestone cave in Indiana, USA

Cited by 23 publications

References 50 publications

Subterranean Karst Environments as a Global Sink for Atmospheric Methane

Subterranean Karst Environments as a Global Sink for Atmospheric Methane

Subterranean Karst Environments as a Global Sink for Atmospheric Methane

Isotopic evidence for the migration of thermogenic methane into a sulfidic cave, Cueva de Villa Luz, Tabasco, Mexico

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