Fluxes of deep CO2 in the volcanic areas of central-southern Italy

Both the shallow (organic-derived) and deep (mantellic–magmatic–metamorphic) fluxes of CO2 [Flux CO2, mass time^(-1)] and specific fluxes of CO2 [Flux CO2 mass time^(-1) surface^(-1)] dissolving in the shallow groundwaters of the volcanic areas of Amiata, Vulsini-Vico-Sabatini, Albani, Roccamonfina, Vesuvio, Vulture, and Etna were evaluated by partitioning the composed population of total dissolved inorganic carbon in two individual populations and subsequent subtraction of local background population. The flux of deep CO2 released from the geothermal fields of Piancastagnaio (Amiata), Torre Alfina, Latera, Marta, Bracciano south, Cesano, and Mofete and from the Overall Northern Latium Hydrothermal Reservoir were also evaluated by means of the total surface heat flux and the enthalpy and CO2 molality of the single liquid phase circulating in each geothermal reservoir. These data suggest that the Flux CO2 released to the atmosphere varies from 9.5 x 10^6 to 3.0 x 10^6 mol x year^(-1) x km^(-2), over the geothermal fields of Bracciano south and Cesano, respectively, and that a total Flux CO2 of 3.8 x 10^8 mol x year^(-1) is cumulatively released from the geothermal fields of Torre Alfina, Latera and Cesano extending over an area of only 66 km^2. In addition, a flux of about 2.2 x 10^11 to 3.8 x 10^11 mol x year^(-1) of gaseous CO2 entering the atmosphere is obtained for the entire anomalous area of central Italy, extending from the Tyrrhenian coastline to the Apennine chain (45,000 km^2). Thus terrestrial CO2 emission in central-southern Italy appears to be a significant carbon source