Geochemical and isotopic characteristics of karstic springs in coastal mountains

article i nfo Seventeen gravity springs from the slopes of the Biokovo, Sutvid and Rilic Mountains at the Adriatic coast of Croatia were investigated. Five of them are included in the regional and three of them are included in the local water supply system. Other springs are used by local inhabitants and tourists for drinking. The aim of this study was to determine the underground karst connections, source and type of the groundwater defining different hydrochemical facies, the aquifer behavior and the impact of the rehabilitated landfill Donja Gora on karstic springs due to the detected anomalous concentrations of lead in sediments. Hydrochemical facies was determined using a Piper diagram. It was shown that groundwater belongs to the Ca-HCO3 type of water. Concentrations of 17 dissolved and total trace elements, organic compounds, organic carbon, nutrients and ions, phenols, PCBs and mineral oil microbiological properties, physical and chemical indicators were determined in groundwater samples. Their concentrations were extremely low, more than 3 orders of magnitude less than allowed by the Croatian regulations for the first category of groundwater and drinking water, so the quality of water is excellent. Origin of some elements is discussed and complex statistical analysis is performed, using log-probability plots and partitioning of distributions following the Sinclair graphical procedure. Majority of minor and trace element concentrations show unimodal distribution of the data. Only five elements (Al, Mn, Ni, Pb and Zn) show the combinations of 2 or 3 log-normal distributed populations, probably reflecting the presence of different sources and/or processes. For the first time, isotopic investigations were performed in any karst region of Croatia, measuring the concentra- tion of dissolved radon in the groundwater. The measured values of radon concentrations for spring water ranged from 0.45 Bq L �1