 |
| Titel |
Methane concentration and isotopic composition (δ13C-CH4) in the Nerja Cave system (South Spain) |
| VerfasserIn |
Iñaki Vadillo, Giuseppe Etiope, José Benavente, Lucía Ojeda, Cristina Liñán, Francisco Carrasco |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132253
|
| Publikation (Nr.) |
 EGU/EGU2016-12743.pdf |
|
|
|
|
|
| Zusammenfassung |
| 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 (δ13C) 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. δ13C increases
correspondingly from -47 ‰ to -41 ‰ (VPDB). CH4 is systematically 13C-enriched (δ13C
> -45 ) 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 sub-atmospheric CH4 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. |
|
|
|
|
|
|