Measuring and interpreting CO2 fluxes at regional scale: the case of the Apennines, Italy

Tectonically active regions are often characterized by large amounts of carbon dioxide degassing, and estimation of the total CO2 discharged to the atmosphere from tectonic structures, hydrothermal systems and inactive volcanic areas is crucial for the definition of present-day global Earth degassing. The carbon balance of regional aquifers is a powerful tool to quantify the diffuse degassing of deep inorganic carbon sources because the method integrates the CO2 flux over large areas. Its application to peninsular Italy shows that the region is characterized by specific CO2 fluxes higher than the baseline determined for the geothermal regions of the world, and that the amount of endogenous CO2 discharged through diffuse regional degassing (c. 2.1 × 1011 mol a−1) is the major component of the geological CO2 budget of Italy, definitely prevailing over the CO2 discharged by Italian active volcanoes and volcanoes with hydrothermal activity. Furthermore, the positive correlation between geothermal heat and deep CO2 dissolved in the groundwater of central Italy suggests that (1) the geothermal heat is transported into the aquifers by the same hot CO2-rich fluids causing the Italian CO2 anomaly and (2) the advective heat flow is the dominant form of heat transfer of the region. Supplementary material: The location, flow rate, extent of the hydrogeological basin, chemical and isotopic analyses of the 160 springs considered in this study, and the results of the carbon mass balance are reported in a table available at https://doi.org/10.6084/m9.figshare.c.423702

Triponzo: a thermal system in a cold area of the Apennines (Italy)

Bagni di Triponzo thermal springs, characterised by a Ca-SO4 composition and temperatures up to 30°C, are located in the eastern sector of Umbria region in the Umbria-Marche Apennine (central Italy). The region is characterised by a low geothermal gradient and low conductive heat flux and the composition of Triponzo thermal waters significantly differs with respect to the cold waters circulating in the surrounding areas. The origin of the heat transported by the waters of the Triponzo springs is mainly due to a deep component, characterised by high CO2 and He contents, coming from a deeper reservoir, rising along normal faults and mixing with infiltrating waters of meteoric origin. The total amount of thermal water discharged by the system is about 34 L s-1. According to the ternary SO4-2-F--HCO3- geoindicator for carbonate-evaporite reservoirs, the fluids at reservoir condition are charcterised by a partial pressure of CO2 about 0.5 bar and a temperature between 70-75°C whereas the Silica geothermometers give a temperature about 62°C. The computed thermal energy transported by advection and discharged at the surface by Triponzo springs is about 3.71×1011 ± 0.56×1011 J/day.Published62-721TR. Georisorse2TR. Ricostruzione e modellazione della struttura crostaleJCR Journa

Measuring and interpreting CO2 fluxes at regional scale: the case of the Apennines, Italy

Tectonically active regions are often characterized by large amounts of carbon dioxide degassing, and estimation of the total CO2 discharged to the atmosphere from tectonic structures, hydrothermal systems and inactive volcanic areas is crucial for the definition of present-day global Earth degassing. The carbon balance of regional aquifers is a powerful tool to quantify the diffuse degassing of deep inorganic carbon sources because the method integrates the CO2 flux over large areas. Its application to peninsular Italy shows that the region is characterized by specific CO2 fluxes higher than the baseline determined for the geothermal regions of the world, and that the amount of endogenous CO2 discharged through diffuse regional degassing (c. 2.1 × 1011 mol a−1) is the major component of the geological CO2 budget of Italy, definitely prevailing over the CO2 discharged by Italian active volcanoes and volcanoes with hydrothermal activity. Furthermore, the positive correlation between geothermal heat and deep CO2 dissolved in the groundwater of central Italy suggests that (1) the geothermal heat is transported into the aquifers by the same hot CO2-rich fluids causing the Italian CO2 anomaly and (2) the advective heat flow is the dominant form of heat transfer of the region.Published408–4161TR. GeorisorseJCR Journa

Earthquake-Induced Spring Discharge Modifications: The Pescara di Arquata Spring Reaction to the August–October 2016 Central Italy Earthquakes

Co-seismic changes in groundwater regime are often observed after moderate to strong earthquakes. The 24 August 2016 Mw 6.0 extensional Amatrice earthquake, which was the first event of a long-lasting seismic sequence, including the 30 October 2016 Mw 6.5 Norcia event, triggered a significant discharge alteration to the Pescara di Arquata spring, located in the Umbria-Marche Apennines (Northern Apennines, Central Italy) and exploited for drinking purposes. During the first five months after the first mainshock, an extra flow of about 30% was recorded, while both water chemistry and temperature did not show significant changes. Thereafter, the spring discharge decreased significantly, and at the end of 2019 it was still lower than normal. The Standardized Precipitation Index (SPI) indicates that these low mean monthly discharge values are not related to particularly dry conditions. The increase in post-seismic depletion coefficients indicates that the aquifer empties faster than it did during the inter-seismic period. The observed transient increase and subsequent decrease of discharge are consistent with a transient, earthquake-related increase in hydraulic conductivity