and mixing with brine waters

ABSTRACT: This paper describes the chemical and isotopic characterization of H2S-bearing groundwaters of the Fontevivo area, northern Italy. Groundwaters from Fontevivo (Parma Province) contain dissolved H2S and minor hydrocarbons, which are released from the truncated front of a buried geological structure (Calabrian– Miocene terrains) and through abandoned unsealed oil wells. H2S concentration is up to 5.54 mg/l in groundwaters from the topographical high of the village and its distribution in the investigated area is inversely related with those of NH4 + and SO4 2. Groundwaters are dominantly Ca-HCO3 type with lesser Ca-SO4 and Na-Cl types and display two compositional trends: group A, waters from Ca-HCO3 to Ca-SO4; group B, waters from Ca-HCO3 to Na-Cl. Group A water compositions are influenced by redox processes including the oxidation of H2S to SO4 2. Primary sulphate from dissolution of Messinian evaporite is rare. Group B waters represen