THE EFFECT OF UNCONFINED MINE TAILINGS ON THE GEOCHEMISTRY OF SOILS, SEDIMENTS AND SURFACE WATERS OF THE LOUSAL AREA (IBERIAN PYRITE BELT, SOUTHERN PORTUGAL)

The former Lousal mine, situated on the SW limb of the Lousal anticline, has left a significant environmental and landscape disturbance due to mining activities and tailings disposed around the site, leading to soil contamination and acid mine drainage. This study investigates the geochemical impacts of unconfined mine tailings on surrounding soils, sediments, and surface waters, particularly focusing on the metal concentrations in these environments. The investigation reveals that, despite the area's semiarid climate, substantial water erosion of tailings is evident, particularly during heavy rainfall events. Elevated concentrations of metals such as Cu, Pb, Zn, As, Cd, and Hg were detected in soil samples taken from tailing deposits, with values far exceeding permissible levels. The acid mine drainage associated with pyritic material shows extremely low pH levels and high concentrations of sulfates, iron, and aluminum, extending to mixed stream waters. This elevated metal content poses significant environmental and public health concerns, necessitating attention and remedial action by the Portuguese government regarding abandoned mine sites across the country.