Seasonal variations of CO₂ and ²²²Rn in a mediterranean sinkhole - spring (Causse d’Aumelas, SE France)

Authors

Christelle Batiot-Guilhe, Université Montpellier II
Jean-Luc Seidel, Université Montpellier IIFollow
Hervé Jourde, Université Montpellier II
Olivier Hébrard, Université Montpellier II
Vincent Bailly-Comte, Université Montpellier II

Abstract

Carbon dioxide and ²²²Rn monitoring of the atmosphere of a Mediterranean sink hole - spring (SE France) during two hydrological cycles (from September 2004 to September 2006) showed seasonal variations with very high concentrations during summer (greater than 6% and 20 000 Bq/m³, respectively). Gas dynamics in caves often show seasonal variations. Meteorological parameters (barometric pressure and temperature mainly), cave geometry and fracture networks control exchanges between the cavity and outside atmosphere. Carbon dioxide and ²²²Rn may have different sources (atmosphere, soil, bedrock, deep gas diffusion, in situ oxidation of organic matter and, in some caves, the key role of swift underground streams). For a CO₂ origin, ¹³C measurements on water and gas samples taken into the cavity suggest a superficial origin. Radon-222 appears to be locally produced and transported by biogenic CO₂. Further investigations will be carried out in order to study the relationship of gas-level variations with barometric pressure variations and piezometric level fluctuations within the aquifer.

DOI

http://dx.doi.org/10.5038/1827-806X.36.1.5

Recommended Citation

Batiot-Guilhe, Christelle; Jean-Luc Seidel; Hervé Jourde; Olivier Hébrard; and Vincent Bailly-Comte. 2007. Seasonal variations of CO₂ and ²²²Rn in a mediterranean sinkhole - spring (Causse d’Aumelas, SE France). International Journal of Speleology, 36: 51-56.
Available at: https://digitalcommons.usf.edu/ijs/vol36/iss1/5