Mapping of potentially hazardous elements in the Cambrian Vendian aquifer system, northern Estonia

Communities and towns in northern Estonia rely upon either surface waters or groundwater from Cambrian-Vendian aquifer system with limited fresh water resources. The composition of groundwater is controlled, among other factors, by the lithologic composition of water bearing rocks and sediments. The peculiarities of the rock matrix may locally restrict the use of groundwater as a source of water supply. The distribution of fluorine, barium and arsenic has been studied in northern Estonian water supply wells. The results of the hydrogeochemical mapping enable to delimit the barium anomaly in the Cambrian-Vendian aquifer system. Vertical distribution of studied compounds and hydraulic connection between water-bearing Vendian sediments with underlying crystalline basement refers the weathered basement rocks as the plausible source of barium and fluorine in groundwater. The elevated concentrations of barium and fluorine detected in groundwater from North Estonian wells may become a source of growing concern in Estonia. The results of hydrochemical research should be transformed to instructions how to avoid or eliminate the quality problems in the risk areas