Geochemical And Isotopic Evolution Of Mazzoccolo Karst Spring, In Southern Latium Region, Central Italy

The present study deals with isotopic and geochemical evolution of Mazzoccolo karst spring which is the most important water supply network in southern Latium region, Central Italy. The environmental isotopic and physico-chemical measurements were carried out from 2006 to 2008. The electrical conductivity (EC) and TDS values of water samples varies from 28 to 341 μS/ cm and 103 to 265.8 mg/l with minimum and maximum values, respectively. All sampled spring waters are characterized as Ca-HCO3 type recharge water and can be considered as fresh water with alkaline nature (TDS ˂ 500 mg/l). Calcium is the dominant cation followed by mag-nesium, sodium and potassium, while HCO3 is the dominant anion. Geochemical modeling re-sults show that few samples are saturated with respect to calcite and aragonite and all sampled waters are undersaturated with respect to dolomite and gypsum suggesting Mazzocolo spring is discharged by a conduit flow, characterized by short residence times and low electrical conduc-tivity. Evaluation of isotopic data (i.e. comparison of δ18O and δ2H) show that most of the sam-ples fall to the Local Meteoric Water Line suggesting input to local rain-fall derives from the Mediterranean Sea. The water samples show high deuterium excess values (above + 24‰), which suggests eastern Mediterranean area is the source of moisture. Considering the identified mean elevation of recharge areas, ranging between 748 and 949 m a.s.l., and low mineralization, it can be assumed that Mazzocolo spring is discharged by a perched aquifer with a conduit flow.