Hydrothermal gases in a shallow aquifer at Mt. Amiata, Italy: Insights from stable isotopes and geochemical modeling.

We investigate the interaction between hydrothermal gases and groundwater in a major aquifer exploited for potable supply in the geothermal-volcanic area of Mt. Amiata, Central Italy. The chemical and isotope composition of more than 80 water samples from two springs emerging on the southwestern side of the volcanic edifice has been processed with geochemical modelling techniques. Best fitting conditions between analytical data and model outputs have been achieved by numerical optimization, allowing for a quantitative description of gas-water-rock interactions occurring in this aquifer.