Vulnerability assessment of mazzoccolo spring aquifer (Central italy), combined with geo-chemical and isotope modeling

The present study deals with the characterization of Mazzoccolo karst spring which feeds the most important water supply network in southern part of Latium region, in Central Italy. During sample collections from 2006 to 2008, a series of in situ measurements were conducted for pH, electrical conductivity (EC), total dissolved solids (TDS) and temperature. The environmental isotopic and hydrochemical measurements were carried out for the vulnerability assessment and geochemical modeling with the aim of achieving (i) proper management and protection of this important resource, (ii) hydrochemical processes controlling the evolution of groundwater and (iii) identification of recharge areas. All sampled spring waters are characterized as Ca-HCO3 type waters reflecting the main rock types in the area investigated, where limestones and Pliocene conglomerates are the most dominant formations. The electrical conductivity (EC) and TDS values of water samples from springs varies from with a maximum value of 341 mu S/cm and 268 mg/l and minimum value of 28 mu S/cm and 104 mg/l, respectively. The pH values of spring samples range from 7.4 to 9 indicating alkaline nature. The anion composition is quite stable showing HCO3->Cl->SO42- (in mg/l), while calcium is the dominant cation, followed by magnesium, sodium and potassium. The comparison of delta O-18 and delta H-2 values of spring water samples with meteoric water lines shows that most of the samples fall to the Local Meteoric Water Line suggesting input to local rain-fall derives from the Mediterranean Sea. The elevation of the recharge areas range between 600 and 800 m a.s.l confirming the Aurunci karst aquifer is feeding Mazzoccolo spring.