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

Abstract

Tectonically active regions are often characterized by a large amounts of carbon dioxide degassing, and estimation of the total CO 2 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 CO 2 flux over large areas. Its application to peninsular Italy shows that the region is characterized by specific CO 2 fluxes higher than the baseline determined for the geothermal regions of the world, and that the amount of endogenous CO 2 discharged through diffuse regional degassing (∼2.1×1011 mol yr −1 ) is the major component of the geological CO 2 budget of Italy, definitely prevailing over the CO 2 discharged by Italian active volcanoes and volcanoes in hydrothermal activity. Furthermore, the positive correlation between geothermal heat and deep CO 2 dissolved in the groundwater of central Italy suggests that (i) the geothermal heat is transported into the aquifers by the same hot CO 2 rich fluids causing the Italian CO 2 anomaly and (ii) the advective heat flow is the dominant form of heat transfer of the region. Supplementary material: https://doi.org/10.6084/m9.figshare.c.4237025