Subterranean atmospheres may act as daily methane sinks.
In recent years, methane (CH4) has received increasing scientific attention because it is the most abundant non-CO2 atmospheric greenhouse gas (GHG) and controls numerous chemical reactions in the troposphere and stratosphere. However, there is much that is unknown about CH4 sources and sinks and their evolution over time. Here we show that near-surface cavities in the uppermost vadose zone are now actively removing atmospheric CH4. Through seasonal geochemical tracing of air in the atmosphere, soil and underground at diverse geographic and climatic locations in Spain, our results show that complete consumption of CH4 is favoured in the subsurface atmosphere under near vapour-saturation conditions and without significant intervention of methanotrophic bacteria. Overall, our results indicate that subterranean atmospheres may be acting as sinks for atmospheric CH4 on a daily scale. However, this terrestrial sink has not yet been considered in CH4 budget balances.
Department of Geology, National Museum of Natural Sciences (MNCN-CSIC), 28006 Madrid, Spain.|Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK.|Geomnia Natural Resources SLNE, 28003 Madrid, Spain.
Angel
A
Fernandez-Cortes
Department of Geology, National Museum of Natural Sciences (MNCN-CSIC), 28006 Madrid, Spain.|Geomnia Natural Resources SLNE, 28003 Madrid, Spain.
Soledad
S
Cuezva
Department of Geology, National Museum of Natural Sciences (MNCN-CSIC), 28006 Madrid, Spain.
Miriam
M
Alvarez-Gallego
Department of Geology, National Museum of Natural Sciences (MNCN-CSIC), 28006 Madrid, Spain.
Elena
E
Garcia-Anton
Department of Environment and Earth Sciences, University of Alicante, San Vicente del Raspeig, 03690 Alicante, Spain.
Concepcion
C
Pla
Department of Environment and Earth Sciences, University of Alicante, San Vicente del Raspeig, 03690 Alicante, Spain.
David
D
Benavente
Department of Agrochemistry, Environmental Microbiology and Soil Conservation, Institute of Natural Resources and Agricultural Biology (IRNAS-CSIC), 41012 Seville, Spain.
Valme
V
Jurado
Department of Agrochemistry, Environmental Microbiology and Soil Conservation, Institute of Natural Resources and Agricultural Biology (IRNAS-CSIC), 41012 Seville, Spain.
Cesareo
C
Saiz-Jimenez
Department of Geology, National Museum of Natural Sciences (MNCN-CSIC), 28006 Madrid, Spain.
Sergio
S
Sanchez-Moral