Assessing Radon in the karst spring waters: the case-study of the Capodifiume spring mixed waters, National Park of the Cilento, Vallo di Diano and Alburni-European Geopark (Southern Italy)

Based on the results of previous geological, hydrogeological and geomorphological surveys, hydrochemical and isotopic tracer techniques have been applied for investigating the origin of significantly elevated Radon (222Rn) activity concentrations detected at the highly NaCl / CaCO3 mineralized Capodifiume karst spring group, located near the archaeological site of Poseidon-Paestum, Southern Italy. Compared to other karst springs in the Cilento and Vallo di Diano Geopark both Radon concentration and salinity show remarkably high values as well as a good correlation. Latest Trends in Energy, Environment and Development ISBN: 978-960-474-375-9 50 Radon concentrations range between 367±20 and 111±8 Bq/l with an average of 230 Bq/l. The high Radon levels of the spring water can neither be explained by the composition of the karst aquifer rocks or the attached travertine deposits (limestone and dolomite), which both show low Radium (226Ra) concentrations, nor by the dissolved Radium content of the spring water. In order to explain the contemporary high levels both of Radon and salinity, several measurement campaigns were carried out and collected data were analyzed, considering the Radon and Electrical Conductivity and Temperature, as useful parameters to differentiate between groundwater of different origin. Results suggest the presence of two different groundwater fluxes at Capodifiume springs originating from different karst aquifer. In fact the similar behavior of the three parameters in the area can be explained by the mixing of different kinds of groundwater. Considering the correlation and the similar behavior of Radon activity concentration, electrical conductivity and temperature, two different groundwater fluxes have been individuated. A different hydro-geological origin and pathway could be assumed to explain their characteristics. This is a first step of a future investigation that will focus on a quantitative analysis and assessment of the groundwater mixing at Capodifiume springs