Groundwater geochemical characterization in the karst aquifer feeding the Pertuso spring (Italy)

The present study deals with the geochemical characterization of Pertuso karst spring, the main perennial outlet of the karst aquifer in the Upper Valley of Aniene River, which is an important source for drinking water in the southeast part of Latium Region, in Central Italy. This paper deals with the supervisory monitoring plan related to the catchment project of the Pertuso spring which is going to be exploited to supply an important water network in the south part of Roma district. In order to identify the hydrogeochemical processes governing the evolution of groundwater and its circulation patterns, a multi-tracer approach was used to describe the hydrogeology of this karst system with the aim of achieving proper management and protection of this important resource due catchment works. To investigate the evolution of groundwater compositions, groundwater from different parts of the aquifer was sampled. Groundwater samples were collected from Pertuso karst spring and from four monitoring wells between July 2014 and January 2015 and analysed for major and trace elements. Physico-chemical parameters (e.g., temperature, pH, Eh, EC etc.) were also measured. A detailed analysis provides that all of groundwater samples have the same origin, associated lithologies, and mineral-solution reactions related to hydrodynamic responses. Piper diagram reveals higher bicarbonate and calcium suggests interactions with carbonate rocks, yielding increased Ca concentrations in the groundwater. Groundwater are characterized by low mineralization and low Mg/Ca ratios and represents the flux of rapid infiltration of surface waters through sinkholes and well-developed karst conduits network. Results from geochemical interpretation of groundwater chemistry using PHREEQC and the measured pH and Eh of groundwater sampled indicate that most of the samples were saturated with respect to calcite and aragonite, however all sampled waters were undersaturated with respect to dolomite and gypsum. Geochemical modelling showed that spring water and groundwater are made of surface water, providing quantitative information on the vulnerability of groundwater to potential surface water contamination.