Combining different tracers (CFC-12, 3H, 3He, 4He) to understand the hydrogeological functioning of a semiconfined aquifer.

Abstract

The hydrochemical results obtained in a semiconfined aquifer called Niebla-Posadas aquifer (S of Spain) show an increase in mineralisation and δ13C in the flow direction, suggesting increasing residence time in the aquifer. However, different agricultural contaminants associated with recently infiltrated waters appear in the confined section. The combination of different groundwater-age tracers (CFC-12, 3H, 3He, 4He) provides valuable information to understand the hydrogeological processes and water quality intending to achieve proper water supply management. The preliminary result of tracers suggests that samples may be a mixture of a majority of tritium-free old groundwater and a minor fraction of recently infiltrated water.