Total (fumarolic + diffuse soil) CO2 output from Furnas volcano

Abstract

Furnas volcano, in São Miguel island (Azores), being the surface expression of rising hydrothermal steam, is the site of intense carbon dioxide (CO2) release by diffuse degassing and fumaroles. While the diffusive CO2 output has long (since the early 1990s) been characterized by soil CO2 surveys, no information is presently available on the fumarolic CO2 output. Here, we performed (in August 2014) a study in which soil CO2 degassing survey was combined for the first time with the measurement of the fumarolic CO2 flux. The results were achieved by using a GasFinder 2.0 tunable diode laser. Our measurements were performed in two degassing sites at Furnas volcano (Furnas Lake and Furnas Village), with the aim of quantifying the total (fumarolic + soil diffuse) CO2 output. We show that, within the main degassing (fumarolic) areas, the soil CO2 flux contribution (9.2 t day−1) represents a minor (~15 %) fraction of the total CO2 output (59 t day−1), which is dominated by the fumaroles (~50 t day−1). The same fumaroles contribute to ~0.25 t day−1 of H2S, based on a fumarole CO2/H2S ratio of 150 to 353 (measured with a portable Multi-GAS). However, we also find that the soil CO2 contribution from a more distal wider degassing structure dominates the total Furnas volcano CO2 budget, which we evaluate (summing up the CO2 flux contributions for degassing soils, fumarolic emissions and springs) at ~1030 t day−1.Electronic supplementary materialThe online version of this article (doi:10.1186/s40623-015-0345-5) contains supplementary material, which is available to authorized users.

3-D interpretation of short-period magnetotelluric data at Furnas Volcano, Azores Islands

“…This is for instance the case at Furnas, where 60-90 per cent of dwellings are built over hydrothermal CO 2 emission zones (Viveiros et al 2010). In addition, hydrothermal explosions were reported in one of the fumaroles located close to Furnas village (Pedone et al 2015, and references therein). Along The Azores islands are located at the triple junction between the North American, Eurasian and African plates.…”

Carbon Dioxide Emissions from Subaerial Volcanic Regions

“…Techniques to quantify CO 2 remotely and from smaller features have also developed in recent years. Tunable diode laser spectrometer [60][61][62] measurements have shown that the CO 2 output from fumaroles is significant (hundreds of t/d) at some volcanoes, illustrating a nontrivial contribution to the volcanic CO 2 flux from this largely unquantified source at a global scale. In addition, LIDAR, specifically differential absorption LIDAR, 38,63 the smaller CO 2 differential absorption LIDAR, 39 and miniaturized light laser sensing spectrometers, 64 have been used to determine path-integrated CO 2 concentrations over kilometer scales.…”

Volcanic Gas Hazard Assessment in the Baia di Levante Area (Vulcano Island, Italy) Inferred by Geochemical Investigation of Passive Fluid Degassing

“…The Multi-GAS sensors were calibrated before the field surveys in the laboratory by using standard gas cylinders (all in nitrogen matrixes) at different concentrations within the sensor ranges. Laboratory tests indicated a typical measurement error in the CO 2 /H 2 S ratios ≤20% [67]. The Multi-GAS instrumentation was equipped with a GPS to have continuous time and space coordinates during acquisition.…”