## 6 Discussion  
### Natural CO\({}_{2}\) Flux  
The whole dataset of 3208 measurements available for the Mt. Amiata region was used to compute the soil CO\({}_{2}\) flux maps and the total CO\({}_{2}\) release from diffuse soil degassing using the sGs technique [49]. There were 100 equiprobable realizations of the soil CO\({}_{2}\) flux produced over a 50 \(\times\) 50 m simulation grid. The resulting map of Mt. Amiata soil CO\({}_{2}\) flux, representing the average of the 100 realizations is presented in Figure 5.  
The highest slopes of the volcanic massif (with the highest peak of 1730 m) are characterized by low CO\({}_{2}\) flux values near the biological background (Figure 5). Similar low soil CO\({}_{2}\) flux values are also found in a broad area in the western sector of the area. The lowest slopes of the volcanic edifice are instead characterized by soil CO\({}_{2}\) flux values higher than the biological background threshold (10.41 umol m\({}^{-2}\) s\({}^{-1}\) or 39.6 g m\({}^{-2}\) d\({}^{-1}\)). High soil CO\({}_{2}\) flux anomalies (higher than the background threshold) characterize the geothermal fields of Bagnore (B area) and Piancastagnaio (C area), where steam and gases accumulate in a dome-shaped structure (i.e., gas caps) present at the top of the shallow carbonate-evaporitic geothermal reservoir. These geothermal areas are delimited using the influence radius in reservoirs of the geothermal deep production wells. Other important high soil CO\({}_{2}\) fluxes are found in the Bagni San Filippo area and in the river Paglia valley. These greenfield and high emission areas are delimited by the 20 umol m\({}^{-2}\) s\({}^{-1}\) isoflux line on the sGs map. In the Bagni San Filippo area, the highest soil CO\({}_{2}\) fluxes are recorded in correspondence with the western border of the Radicofani basin and its master faults system, and in the Inferno area, CO\({}_{2}\)-focused emissions are also present and in correspondence with the Campiglia d'Orcia NE-SW fault system (north of the volcanic massif). A structural control on the Paglia River Valley is inferred by looking at Figure 1,  
Figure 4: Log-normal probability plot of soil CO\({}_{2}\) flux measurements. The partitioned populations [48] and the inflection points are shown. A dashed straight line traced through the central part of the plot helps visualize the chosen inflection points. where buried normal faults related to the graben structure could have driven the NW-SE valley incision. In the AVGA, high soil CO\({}_{2}\) fluxes are found in correspondence with the infrastructures, tunnels, and mine shafts of Hg mines, where Quaternary faults and fractures are widespread, in correspondence with the Pietrineri, Bagnore, Mt. Labro, and Senna Morita mining areas (the latter is located between Piancastagnaio and Poggio Nibbio) (Figure 1). Using the background threshold (Table 2) as the cutoff value, the probability that soil CO\({}_{2}\) flux exceeds this value highlights the diffuse degassing structures [49]. The probability map (Figure 6) emphasizes areas where the biological background prevails in addition to areas of diffuse anomalous degassing (deep carbon populations B and C), highlighting the strong soil CO\({}_{2}\) diffuse degassing that affects the whole Mt. Amiata volcano geothermal area, with many areas showing anomalous fluxes. The total soil CO\({}_{2}\) degassing over the whole Mt. Amiata area and its uncertainty was calculated with the sGs technique. The total natural CO\({}_{2}\) output, computed as the sum of the product of simulated values of each cell in the simulation grid by the value of the simulation grid area, represents the average of the 100 equiprobable realizations. The total natural soil CO\({}_{2}\) degassing was estimated as 16,254 t/d, with a 95% confidence interval of 15,800-16,642 t/d.