Movilidad de metales en residuos mineros y valoración del impacto ambiental del distrito minero de São Domingos (Faja Pirítica Ibérica), SW de la Península Ibérica

Abstract

São Domingos is one of the most emblematic Portuguese mining districts in the Iberian Pyrite Belt (IPB). The beginning of mining exploitation in the area has been dated back to pre-Roman times, remaining in activity until 1966 when it was definitely halted. The intense mining labours are reflected in the presence of a huge amount of sulphide-mining wastes and downstream production of acid mine drainage (AMD). The chemical speciation of potentially toxic elements (As, Cd, Cr, Cu, Fe, Mn, Pb, S, Sb and Zn) in the highly heterogeneous mine wastes from São Domingos was performed by modified BCR-sequential extraction. The oxidizable fraction is the most pollutant fraction for the environment in this type of residues. Part of this fraction is retained by precipitation of soluble secondary minerals in warm periods, moving to the bio-available fraction that is dissolved in rainy periods. Just considering the bio-available fraction, all mine wastes from São Domingos may leach up to 207031 tons of Fe, 14859 t of S, 6305 t of Pb, 3259 t of Zn, 1316 t of Mn, 1143 t of Cu, 219 t of Cr, 163 t of As, 40 t of Sb and 1.7 t of Cd. As a function of the seasonal variation, this fraction is self-fed every year by oxidation of the oxidizable fraction. Thus, the present study shows the pollutant potential of this IPB mining district and justifies the spoiled state of the fluvial courses in the region