Impact of mine tailings on surrounding soils and ground water: Case of Kettara old mine, Morocco

摘要

The old ochre-pyrrhotite mine of Kettara, near Marrakech (Morocco) ceased operating some 30 years ago but its excavations, plants, and tailings have been totally abandoned since then. Geochemical analyses of the soils, stream sediments and waters of the surrounding area were carried out to assess the pollution impact of this mining site. Tailing characterization showed the presence of sulphide primary minerals, as well as secondary ones containing among others (Fe, S, Cu, Pb, Zn, Cd, Ni, Cr, Co, As, Se). In spite of the presence of theses pollutants in the Acid Mine Drainage (AMD) of Kettara, groundwater did not show significant levels of these metals probably related to the low ion circulation under the local dry climate with low annual rainfall that prevents metal ion circulation. The chemical analyses of soil and stream sediment samples included elements most of which are internationally considered as dangerous for human health (As, Cd, Co, Cr, Cu, Fe, Ni, Pb, S, Se and Zn). Geochemical maps of these elements showed that Cr and Ni were linked to mafic intrusions of Kettara sector. Sulphur is linked to the mining activity and the others are related both to lithological outcrops and mining activity. However, the levels of these contaminants did not exceed Italian Standards of soil pollution.