GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 GNGTS 2023 Possible influence of local tectonic stress on gas emissions from Santa Venera al Pozzo thermal area (Mt. Etna, Italy) F. Sortino 1 , S. Alparone 2 , P. Bonfanti 2 , C. Bottari 2 , L. Calderone 1 , S. Giammanco 2 1 INGV sez.Palermo 2 OE-INGV sez.Catania The Santa Venera al Pozzo thermal spring (TSVP) is located on the SE foot of Mt. Etna volcano (Sicily, Italy), in an area crossed by some of the most important and seismically active tectonic faults of southern Italy (Bottari et al., 2020). A first near-continuous geochemical monitoring both of gas emissions (CO 2 , CH 4 and H 2 S) and of water temperature was conducted from December 2017 to April 2019 (Sortino et al., 2022). Acquired data highlighted the presence of methane as predominant gas as well as temporal changes in gas concentrations, in part due to daily fluctuations (which caused small amplitude variations), and in part due to non-environmental causes. These latter were temporally correlated with the occurrence of earthquakes and magmatic intrusions at Mt. Etna, considering however that no input of magmatic gases into the thermal aquifer occurred, given the non-magmatic origin of all monitored gases. Sortino et al. (2022) actually modelled the geothermal system feeding the TSVP as a reservoir of purely geothermal fluids almost saturated in reduced gases (CH 4 and H 2 S) and very sensitive to tectonic stresses acting on it. With the aim to continuously monitor the natural gases emissions at TSVP, a low-cost GMS (Gas Monitoring Station) equipped with an automatic data transmission module was developed and assembled since March 2022. This GMS is powered by an external battery, recharging itself with a 12V solar panel, and it samples the gaseous species every 5 minutes. Acquired measurements are both stored into a local SD-card and transmitted to a database with an internet connection. Currently, the GMS at TSVP allows to simultaneously analyze CO 2 , CH 4 (using IR sensors), while sampling of H 2 S and other species is planned for the next future by adding appropriate electrochemical sensors. During the March-November 2022 period, some significant variations of methane concentration were observed, with peaks on 24 March, 5 April and 17 June and a marked long-term increase in the baseline concentration values between the two peaks in March and June. Similar to what already observed in the previous work, the concentrations of CO 2 showed no significant change. In the same period, seismic activity near the thermal baths showed no significant event and the