RT Conference Proceedings
T1 Methane concentration and isotopic composition (d13C-CH4) in the Nerja Cave system (South Spain)
A1 Vadillo-Pérez, Iñaki
A1 Etiope, Giuseppe
A1 Benavente Herrera, José
A1 Ojeda, Lucía
A1 Liñán-Baena, Cristina
A1 Carrasco-Cantos, Francisco
K1 Metano
AB Air in underground caves often has methane (CH4) concentrations below the atmospheric level, due to methanotrophic or other unkown CH4 consuming processes. Caves are thus considered a potential sink for atmospheric methane. If globally important, this underground CH4 oxidation should be taken into account in the atmospheric methane budget, in addition to the known soil methanotrophy and tropospheric/stratospheric sinks. A large set of data is however necessary to understand how and how much methane from external atmospheric air is consumed in the caves. While methane concentration data are available for several caves worldwide, its isotopic composition and variations in space and time are poorly documented.We measured methane concentration and stable C isotope composition (d13C) in the Nerja cave (Southern Spain) air during two surveys in March and April 2015. CH4 concentration decreases progressively from the more external cave rooms, with atmospheric levels of 1.9 ppmv, to the more internal and isolated rooms down to 0.5 ppmv.d13C increases correspondingly from -47 h to -41 h (VPDB). CH4 is systematically 13C-enriched (d13C > -45 permil) in areas of the cave where the concentration is below 1.4 ppmv. This combination of concentration decrease and 13C-enrichment towards the more internal and isolated zones of the cave confirms the importance of CH4 oxidation, likely driven by methanotrophic bacteria. Further data, including stable H isotope composition of subatmosphericCH4 concentrations, CO2 and microbial analyses, shall be acquired over time to assess the actual role of methanotrophic bacteria and seasonal controls in the CH4 consumption process.
YR 2016
FD 2016-04-26
LK http://hdl.handle.net/10630/11246
UL http://hdl.handle.net/10630/11246
LA eng
NO Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.
DS RIUMA. Repositorio Institucional de la Universidad de Málaga
RD 20 ene 2026