Fluxes of deep CO 2 in the volcanic areas of central-southern Italy

Abstract

Both the shallow (organic-derived) and deep (mantellic–magmatic–metamorphic) fluxes of CO 2 [ Φ CO 2 , mass time −1] and specific fluxes of CO 2 [ ϕ CO 2 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 CO 2 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 CO 2 molality of the single liquid phase circulating in each geothermal reservoir. These data suggest that the ϕ CO 2 released to the atmosphere varies from 9.5×10 6 to 3.0×10 6 mol year −1 km −2, over the geothermal fields of Bracciano south and Cesano, respectively, and that a total Φ CO 2 of 3.8×10 8 mol 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 ∼2.2×10 11 to 3.8×10 11 mol year −1 of gaseous CO 2 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 CO 2 emission in central-southern Italy appears to be a significant carbon source.