EGU2020-11762, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-11762
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Soil carbon dioxide efflux weekly monitoring network for the volcanic surveillance of Tenerife, Canary Islands

Violeta T. Albertos1, Conor M. Graham2, Leopoldo Cabassa3, Teresa Borges da Cruz4, Gladys V. Melián1,5,6, Nemesio M. Pérez1,5,6, María Cordero-Vaca1, Cecilia Amonte1, María Asensio-Ramos1, and Pedro A. Hernández1,5,6
Violeta T. Albertos et al.
  • 1Instituto Volcanológico de Canarias (INVOLCAN), 38240 La Laguna, Tenerife, Canary Islands, Spain (valbertos@iter.es)
  • 2Department of Earth Sciences, Royal Holloway University of London, Egham, TW20 0EX, U.K.
  • 3Department of earth and atmospheric sciences, Saint Louis University, St. Louis MO 63108, U.S.A.
  • 4School of Energy, Construction and Environment, Coventry University, Coventry CV1 5FB, U.K.
  • 5Instituto Tecnológico y de Energías Renovables (ITER), 38611 Granadilla de Abona, Tenerife, Canary Islands, Spain
  • 6Agencia Insular de la Energía de Tenerife (AIET), 38611 Granadilla de Abona, Tenerife, Canary Islands, Spain

Carbon dioxide (CO2) is one of the first gases to escape from the magmatic environment due to its low solubility in basaltic magmas at low pressures. Monitoring of volcanic gases in Tenerife Island (2,304 km2) has been focused mainly on diffuse CO2 degassing and other volatiles due to the absence of visible gas manifestations except fumaroles at the summit of Teide volcano. An inexpensive method to determine CO2 fluxes based in the absorption of CO2 through an alkaline medium followed by titration analysis has been used with the aim of contributing to the volcanic surveillance of Tenerife. During summer 2016, a network of 31 closed alkaline traps was deployed along the three volcanic rifts of Tenerife (NE, NW and NS) and at Cañadas Caldera. To do so, an aliquot of 50 mL of 0.1N KOH solution is placed inside the chamber at each station to absorb the CO2 released from the soil. The solution is replaced in a weekly basis and the trapped CO2 is later analyzed at the laboratory by titration. Values are expressed as weekly integrated CO2 efflux. We present herein the results of one year CO2 efflux estimated by closed alkaline traps. The CO2 efflux values ranged from 1.0 to 14.5 g·m-2·d-1, with average values of 8.5 g·m-2·d-1 for the NE rift-zone, 5.2 g·m-2·d-1 for Cañadas Caldera, 6.4 g·m-2·d-1 for NW rift-zone and 6.1 g·m-2·d-1 for NS rift-zone. The estimated CO2 efflux values were of the same order than the observed ones in 2016. Relatively high CO2 efflux values were observed at the NE rift-zone, where maximum values were measured. The temporal evolution of CO2 efflux estimated by closed alkaline traps did not show significant variations during 2019. However, small seasonal variations are observed during the period 2016 – 2019. To investigate the origin of the soil CO2, soil gas samples were weekly sampled on the head space of the closed chambers. Chemical and isotopic composition of C in the CO2 were analysed in the gas samples. The concentration of CO2 on the head space of the closed chambers showed a range of 355-50,464 ppm, with an average value of 1,850 ppmV, while the isotopic composition expressed as d13C-CO2 showed a range from -5.03 to -30.44 ‰, with an average value of -15.9 ‰. The heaviest values of d13C-CO2 are in the NW rift-zone. The systematics of closed static chambers alkaline traps can be a simple and economical tool with volcanic surveillance purposes in system where visible volcanic gases manifestations are absence.

How to cite: Albertos, V. T., Graham, C. M., Cabassa, L., Borges da Cruz, T., Melián, G. V., Pérez, N. M., Cordero-Vaca, M., Amonte, C., Asensio-Ramos, M., and Hernández, P. A.: Soil carbon dioxide efflux weekly monitoring network for the volcanic surveillance of Tenerife, Canary Islands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11762, https://doi.org/10.5194/egusphere-egu2020-11762, 2020