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

Tectonically active regions are often characterized by a 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 (~2.1×1011 mol yr^-1) is the major component of the geological CO₂ budget of Italy, definitely prevailing over the CO₂ discharged by Italian active volcanoes and volcanoes in hydrothermal activity. Furthermore, the positive correlation between geothermal heat and deep CO₂ dissolved in the groundwater of central Italy suggests that (i) the geothermal heat is transported into the aquifers by the same hot CO₂ rich fluids causing the Italian CO₂ anomaly and (ii) the advective heat flow is the dominant form of heat transfer of the region.