Brusca, Lorenzo

Gas and water samples were collected at CO2-rich wells in the plain of Florina (N. Greece). Chemical and isotopic composition of the analysed gases reveals their main crustal origin even if a small but significant contribution of mantle derived gases can be recognized. As a consequence of CO2 dissolution, HCO3- is always the main dissolved anion while cationic composition allows us to distinguish at least two main groups characterized by Na or Ca as dominant dissolved cations. The water-rock interaction is strongly enhanced by the dissolution of CO2 and the consequent lowering of pH. Such a process increases the mobility of some trace elements whose concentrations very often exceed UE drinking water limits. This study confirms that the Florina basin represents a good natural analogue of carbon storage systems and underscores the fact that possible deterioration of water quality due to CO2 leaks of the reservoirs must be carefully taken in account.