## 6 Discussion
### Natural CO\({}_{2}\) Flux
The biological contribution was estimated as 5,217 t/d and the deep contribution was estimated as 11,037 t/d based on the mean of the partitioned populations A and C.  
Given the survey area of 280 km\({}^{2}\), a mean emission rate of 58 t/d km\({}^{2}\) was estimated based on the total natural soil CO\({}_{2}\) output. An emission rate of 115 t/d km\({}^{2}\) was estimated for the Bagni San Filippo high soil CO\({}_{2}\) flux area (A in Figure 5), while emission rates ranging from 154-200 t/d km\({}^{2}\)[15; 35; 36] were estimated from localized high soil CO  
Figure 5: Soil CO\({}_{2}\) flux map with areas of Bagnore, Piancastagnaio (geothermal fields in operation, brownfields), Bagni San Filippo (geothermal greenfield), and Paglia River high emission areas. Red stars are the concentrated gas emissions and gas vents considered in the CO\({}_{2}\) total emissions budget in the atmosphere. The geothermal wells in operation used to define B and C areas are also reported (Enel Green Power data). degassing areas only. The lower emission soil CO\({}_{2}\) flux area coincides with the upper slopes of the volcanic edifice, characterized by the presence of a climate forested zone, where an emission rate of 27 t/d km\({}^{2}\) was computed [16]. [PERSON] et al. [16] explained this very low soil flux on the dome complex volcano as being due to the lamination of the shallow geothermal reservoir to the presence of a phreatic aquifer grading upward in thick water unsaturated fractured lavas of the dome complex. In this framework, the increase of deep CO\({}_{2}\) appears to be slowed down. For more details on the subsoil geology of AVGA, see the paper by [PERSON] et al. [16], which reports a reconstruction of the buried structures. Soil CO\({}_{2}\) flux profiles in relation to simplified geological sections help to visualize the main degassing structures. In Figures 6 and 7a, the geochemically anomalous soil CO\({}_{2}\) flux areas (where fluxes are higher than the background threshold, 10.4 umol m\({}^{-2}\) s\({}^{-1}\)) of Piancastagnaio and Bagnore geothermal fields are well evidenced south of the volcano. These wide degassing areas span from about 25 km\({}^{2}\) for Bagnore and about 35 km\({}^{2}\) for Piancastagnaio. These two areas were computed considering only the geothermal wells in operation (Enel Green Power data) as the surface projection of the interference area of the wells in the geothermal reservoir. In the northern AVGA, high emission areas are delimited. The most intense and wide are the greenfield areas of Bagni San Filippo and Seggiano. The soil flux profiles (Figure 7b) describe the degassing areas well. In profile AA', the maximum gas flow rate occurs in the Piancastagnaio field, reflecting the presence of the relatively shallow and thick carbonate-evaporitic reservoir. At the top of this reservoir, a CO\({}_{2}\) vapor gas cap in the upflow zone of a robust convection system has developed. Furthermore, the K-horizon is relatively shallow at a depth of approximately 4.5 km. The K-horizon is the proxy of the granitic intrusion. In the thermometamorphic aureole of granites, CO\({}_{2}\) is produced by thermometamorphic reactions feeding the geothermal reservoirs, and finally, the diffuse soil degassing is observed. In the same profile, an area of anomalous flux was observed in the Seggiano area. Figure 6: Probability map of occurrence of soil CO\({}_{2}\) flux higher than the background threshold. In profile BB', an increase of flux between 15 to 20 \(\upmu\)mol m\({}^{-2}\) s\({}^{-1}\) was shown in correspondence with the Bagnore field, while the strongest values occur in the greenfield areas of Bagni San Filippo and Mt. Labro.