Monitoring of a public water supply system: a case of groundwater contamination by acid rock drainage

Abstract

The present study shows hydrochemistry of shallow groundwater from two wells planned to supply public fountains in the north of Portugal. One of the wells suffers higher impact by acid rock drainage due to mineral-water interaction in a host lithology richer in sulfides. Dissolution of sulfate efflorescences, infiltration and recharge, structural faults, and high porosity of the terrain control the evolution trends of water chemistry. The study concludes by noting the strong contamination, including by toxic elements (Al, Mn, Cd), making impossible to use the water for public supply as planned.