Articles | Volume 5, issue 2
Research article
02 Dec 2014
Research article |  | 02 Dec 2014

Tunable diode laser measurements of hydrothermal/volcanic CO2 and implications for the global CO2 budget

M. Pedone, A. Aiuppa, G. Giudice, F. Grassa, V. Francofonte, B. Bergsson, and E. Ilyinskaya

Abstract. Quantifying the CO2 flux sustained by low-temperature fumarolic fields in hydrothermal/volcanic environments has remained a challenge, to date. Here, we explored the potential of a commercial infrared tunable laser unit for quantifying such fumarolic volcanic/hydrothermal CO2 fluxes. Our field tests were conducted between April 2013 and March 2014 at Nea Kameni (Santorini, Greece), Hekla and Krýsuvík (Iceland) and Vulcano (Aeolian Islands, Italy). At these sites, the tunable laser was used to measure the path-integrated CO2 mixing ratios along cross sections of the fumaroles' atmospheric plumes. By using a tomographic post-processing routine, we then obtained, for each manifestation, the contour maps of CO2 mixing ratios in the plumes and, from their integration, the CO2 fluxes. The calculated CO2 fluxes range from low (5.7 ± 0.9 t d−1; Krýsuvík) to moderate (524 ± 108 t d−1; La Fossa crater, Vulcano). Overall, we suggest that the cumulative CO2 contribution from weakly degassing volcanoes in the hydrothermal stage of activity may be significant at the global scale.

Short summary
Here, we present the results of tunable diode laser observations at four quiescent volcanoes: Nea Kameni, Hekla, Krýsuvík, and Vulcano Island, which display a range of fumarolic activity from weak to moderate. This study contributes to better characterising the typical levels of CO2 emission from such feeble volcanic point sources, suggesting that the cumulative contribution from weakly degassing volcanoes may be significant at global scale.