The “breathing spots” in karst areas—the sites of advective exchange of gases between soils and adjacent underground cavities

Faimon, Jiřı́; Lang, Marek; Geršl, Milan; Šráček, Ondra; Bábek, Ondřej

doi:10.1007/s00704-020-03280-7

Cited by 11 publications

(14 citation statements)

References 62 publications

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“…It has already been shown that the updraft in PP during cold periods contributes significantly to the soil CO 2 , thus obviously requiring the existence of an underground CO 2 reservoir (Krajnc et al 2017). Similarly, Faimon et al (2020) found a clear relationship between updraft (UAF) and downdraft (DAF) modes of subsurface ventilation and the CO 2 concentration and δ 13 C isotopic composition of soil air fluxes at the breathing spot above the probable cavity in Hranice Karst (Czech Republic). The concepts presented in that paper agree well with the concept presented here.…”

Section: The Conceptual Model Of Co 2 Transportmentioning

confidence: 68%

CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

Kukuljan

Gabrovšek

Covington

et al. 2021

Theor Appl Climatol

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Understanding the dynamics and distribution of CO2 in the subsurface atmosphere of carbonate karst massifs provides important insights into dissolution and precipitation processes, the role of karst systems in the global carbon cycle, and the use of speleothems for paleoclimate reconstructions. We discuss long-term microclimatic observations in a passage of Postojna Cave, Slovenia, focusing on high spatial and temporal variations of pCO2. We show (1) that the airflow through the massif is determined by the combined action of the chimney effect and external winds and (2) that the relationship between the direction of the airflow, the geometry of the airflow pathways, and the position of the observation point explains the observed variations of pCO2. Namely, in the terminal chamber of the passage, the pCO2 is low and uniform during updraft, when outside air flows to the site through a system of large open galleries. When the airflow reverses direction to downdraft, the chamber is fed by inlets with diverse flow rates and pCO2, which enter via small conduits and fractures embedded in a CO2-rich vadose zone. If the spatial distribution of inlets and outlets produces minimal mixing between low and high pCO2 inflows, high and persistent gradients in pCO2 are formed. Such is the case in the chamber, where vertical gradients of up to 1000 ppm/m are observed during downdraft. The results presented in this work provide new insights into the dynamics and composition of the subsurface atmosphere and demonstrate the importance of long-term and spatially distributed observations.

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Section: The Conceptual Model Of Co 2 Transportmentioning

confidence: 68%

CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

Kukuljan

Gabrovšek

Covington

et al. 2021

Theor Appl Climatol

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“…However, karstic areas deserve special attention given their great capacity to temporally store large amounts of gaseous CO 2 belowground (Decarlo & Caylor, 2020; Emmerich, 2003; Serrano‐Ortiz et al, 2010) within their carbonate vadose zone, which usually contains an interconnected system of caves, macropores, and fissures. According to Faimon et al (2020), these places can be considered as “breathing spots” that may be relevant in the carbon cycle at basin scale. Finally, another non‐biological process that might be involved in vadose zone CO 2 production is related to deep‐seated CO 2 seepage from porous reservoirs usually related to volcanic or hydrothermal activity (Burton et al, 2013; Chiodini et al, 2008; Lewicki et al, 2003; Mörner & Etiope, 2002; Rey et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

“…Subterranean ventilation is a non‐diffusive transport process that provokes the abrupt transfer of CO 2 ‐rich air from the vadose zone to the atmosphere under drought and high‐turbulence conditions (Kowalski et al, 2008). Recent studies developed in drylands have pointed out the importance of the vadose zone as a significant temporary CO 2 pool, given its capacity to store vast amounts of gaseous CO 2 in interconnected cracks, pores, and cavities belowground where volumetric CO 2 fractions can rise to two orders of magnitude greater than in the atmosphere (Benavente et al, 2010; Faimon et al, 2020; Fernandez‐Cortes et al, 2015; Sánchez‐Cañete et al, 2016). Regardless of its originating process, the enhanced density of CO 2 ‐rich air (Kowalski & Sánchez‐Cañete, 2010)—due to its large molecular mass—may enable it to descend from shallow soil layers, where most root and microbial respiration takes place (Buchmann, 2000; Coleman & Crossley, 2004, down to the water table level, creating a concentration gradient that increases with depth.…”

Section: Introductionmentioning

confidence: 99%

“…Recent research has demonstrated that subterranean ventilation can temporarily dominate land–atmosphere CO 2 exchange in some Mediterranean ecosystems (Faimon et al, 2020; López‐Ballesteros et al, 2017; Pérez‐Priego et al, 2013; Sanchez‐Cañete et al, 2011). These studies were mainly developed in Southwestern Europe and utilized specific experimental setups designed to carefully monitor the influencing factors mentioned above.…”

Section: Introductionmentioning

confidence: 99%

“…Recent research has demonstrated that subterranean ventilation can temporarily dominate land-atmosphere CO 2 exchange in some Mediterranean ecosystems (Faimon et al, 2020;López-Ballesteros et al, 2017;Pérez-Priego et al, 2013;Sanchez-Cañete et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ecosystem CO₂ release driven by wind occurs in drylands at global scale

Moya

López‐Ballesteros

Sánchez-Cañete

et al. 2022

Global Change Biology

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Subterranean ventilation is a non-diffusive transport process that provokes the abrupt transfer of CO 2 -rich air (previously stored) through water-free soil pores and cracks from the vadose zone to the atmosphere, under high-turbulence conditions. In dryland ecosystems, whose biological carbon exchanges are poorly characterized, it can strongly determine eddy-covariance CO 2 fluxes that are used to validate remote sensing products and constrain models of gross primary productivity. Although subterranean ventilation episodes (VE) may occur in arid and semi-arid regions, which are unsung players in the global carbon cycle, little research has focused on the role of VE CO 2 emissions in land-atmosphere CO 2 exchange. This study shows clear empirical evidence of globally occurring VE. To identify VE, we used in situ qualitycontrolled eddy-covariance open data of carbon fluxes and ancillary variables from 145 sites in different open land covers (grassland, cropland, shrubland, savanna, andbarren) across the globe. We selected the analyzed database from the FLUXNET2015, AmeriFlux, OzFlux, and AsiaFlux networks. To standardize the analysis, we designed an algorithm to detect CO 2 emissions produced by VE at all sites considered in this study. Its main requirement is the presence of considerable and non-spurious correlation between the friction velocity (i.e., turbulence) and CO 2 emissions. Of the sites analyzed, 34% exhibited the occurrence of VE. This vented CO 2 emerged mainly from arid ecosystems (84%) and sites with hot and dry periods. Despite some limitations in data availability, this research demonstrates that VE-driven CO 2 emissions occur globally. Future research should seek a better understanding of its drivers and the improvement of partitioning models, to reduce uncertainties in estimated biological CO 2 exchanges and infer their contribution to the global net ecosystem carbon balance.

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Karst cave, a seasonal carbon dioxide exchanger: an example of Sloup-Šošůvka Caves (Moravian Karst)

Faimon,

Lang,

Štelcl

et al. 2024

Theor Appl Climatol

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Part of the gaseous carbon dioxide (CO2) produced in karst soils / epikarst is transported into underground cavities / caves during the growing season by advective flux, diffusive flux, and flux associated with degassing of seeping water. In dynamic caves, accumulated CO2 is released into the outside atmosphere during the autumn-winter period through advective flux associated with ventilation of the cave in the upward airflow mode. This case study from the Moravian Karst (MK) showed that the net weight of CO2 released annually from the Sloup-Šošůvka Caves (total volume of 131,580 m3 and a total area of 17,950 m2) into the external atmosphere was 348 kg. Extrapolating this value to all known MK caves (area about 352,080 m2) yielded a total of CO2 flux of 6820 kg yr−1. This flux is representing only 0.024‰ of the annual soil respiration from entire MK area (about 2.81 × 108 kg CO2 yr−1).

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The “breathing spots” in karst areas—the sites of advective exchange of gases between soils and adjacent underground cavities

Cited by 11 publications

References 62 publications

CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

Ecosystem CO₂ release driven by wind occurs in drylands at global scale

Karst cave, a seasonal carbon dioxide exchanger: an example of Sloup-Šošůvka Caves (Moravian Karst)

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The “breathing spots” in karst areas—the sites of advective exchange of gases between soils and adjacent underground cavities

Cited by 11 publications

References 62 publications

CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

Ecosystem CO2 release driven by wind occurs in drylands at global scale

Karst cave, a seasonal carbon dioxide exchanger: an example of Sloup-Šošůvka Caves (Moravian Karst)

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Ecosystem CO₂ release driven by wind occurs in drylands at global scale