Abiotic and seasonal control of soil-produced CO2 efflux in karstic ecosystems located in Oceanic and Mediterranean climates

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Título: Abiotic and seasonal control of soil-produced CO2 efflux in karstic ecosystems located in Oceanic and Mediterranean climates
Autor/es: García Antón, Elena | Cuezva Robleño, Soledad | Fernández Cortés, Ángel | Álvarez Gallego, Miriam | Pla, Concepción | Benavente, David | Cañaveras, Juan C. | Sánchez Moral, Sergio
Grupo/s de investigación o GITE: Petrología Aplicada | Ingeniería Hidráulica y Ambiental (INGHA)
Centro, Departamento o Servicio: Universidad de Alicante. Departamento de Ciencias de la Tierra y del Medio Ambiente | Universidad de Alicante. Departamento de Ingeniería Civil
Palabras clave: Vadose zone | CO2 exchange | δ13CO2 | Climatic control | Soil CO2 diffusion
Área/s de conocimiento: Petrología y Geoquímica | Ingeniería Hidráulica
Fecha de publicación: sep-2017
Editor: Elsevier
Cita bibliográfica: Atmospheric Environment. 2017, 164: 31-49. doi:10.1016/j.atmosenv.2017.05.036
Resumen: This study characterizes the processes involved in seasonal CO2 exchange between soils and shallow underground systems and explores the contribution of the different biotic and abiotic sources as a function of changing weather conditions. We spatially and temporally investigated five karstic caves across the Iberian Peninsula, which presented different microclimatic, geologic and geomorphologic features. The locations present Mediterranean and Oceanic climates. Spot air sampling of CO2 (g) and δ13CO2 in the caves, soils and outside atmospheric air was periodically conducted. The isotopic ratio of the source contribution enhancing the CO2 concentration was calculated using the Keeling model. We compared the isotopic ratio of the source in the soil (δ13Cs–soil) with that in the soil-underground system (δ13Cs–system). Although the studied field sites have different features, we found common seasonal trends in their values, which suggests a climatic control over the soil air CO2 and the δ13CO2 of the sources of CO2 in the soil (δ13Cs–soil) and the system (δ13Cs–system). The roots respiration and soil organic matter degradation are the main source of CO2 in underground environments, and the inlet of the gas is mainly driven by diffusion and advection. Drier and warmer conditions enhance soil-exterior CO2 interchange, reducing the CO2 concentration and increasing the δ13CO2 of the soil air. Moreover, the isotopic ratio of the source of CO2 in both the soil and the system tends to heavier values throughout the dry and warm season. We conclude that seasonal variations of soil CO2 concentration and its 13C/12C isotopic ratio are mainly regulated by thermo-hygrometric conditions. In cold and wet seasons, the increase of soil moisture reduces soil diffusivity and allows the storage of CO2 in the subsoil. During dry and warm seasons, the evaporation of soil water favours diffusive and advective transport of soil-derived CO2 to the atmosphere. The soil CO2 diffusion is enough important during this season to modify the isotopic ratio of soil produced CO2 (3–6‰ heavier). Drought induces release of CO2 with an isotopic ratio heavier than produced by organic sources. Consequently, climatic conditions drive abiotic processes that turn regulate a seasonal storage of soil-produced CO2 within soil and underground systems. The results here obtained imply that abiotic emissions of soil-produced CO2 must be an inherent consequence of droughts, which intensification has been forecasted at global scale in the next 100 years.
Patrocinador/es: This research was funded by the Spanish Ministry of Economy and Competitiveness projects CGL2016-78318-C2-1R and CGL2016-78318-C2-2R AEI/FEDER/UE and its programme Torres Quevedo (PTQ 13-06296). Funding was also provided by the People Programme (Marie Curie Actions-Intra-European Fellowships, call 2013) of the European Union's Seventh Framework Programme (FP7/2007-2013) under the REA grant agreement nº 624204.
URI: http://hdl.handle.net/10045/66629
ISSN: 1352-2310 (Print) | 1873-2844 (Online)
DOI: 10.1016/j.atmosenv.2017.05.036
Idioma: eng
Tipo: info:eu-repo/semantics/article
Derechos: © 2017 Elsevier Ltd.
Revisión científica: si
Versión del editor: http://dx.doi.org/10.1016/j.atmosenv.2017.05.036
Aparece en las colecciones:INV - PETRA - Artículos de Revistas
INV - IngHA - Artículos de Revistas
Investigaciones financiadas por la UE

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