Characterization of groundwater recharge through tritium measurements

Abstract

After the nuclear weapons testing in the 1950s and 1960s, the atmospheric tritium levels have almost returned to natural levels (pre-1950 levels), which means that tritium is becoming more effective in determining transit times in hydrological systems. It has also been demonstrated that tritium is a non-reactive noble gas and in water is not subject to chemical reactions, absorption, or dissolution/precipitation processes, so it is conservative of the geochemical fingerprint of the source. In addition, it is used as an effective tracer of water contamination by landfill leachate, allowing to detect mixing percentages of the leachate up to levels not achievable with normal chemical analyses (less than 1 %). The purpose of the present work is to deepen the knowledge of the hydrogeochemical characteristics of the aquifers in the pedemontana area of the Venetian plain, and to formulate a conceptual framework of underground water circulation, aimed at understanding phenomena of contamination by toxic metals, harmful to human health. Tritium concentration analyses were performed on selected samples of groundwater collected in different wells in the south part of Treviso city to correlate the young age of the water recharge. The abundance of young waters, in fact, indicates a vulnerability of the aquifer to climate change with respect to possible contributions of surface waters, in particular to prolonged drought periods which could induce salinization dynamics.