Impacts of mining activities on soil properties: case studies from Morocco mine sites

Due to its very rich and varied geological heritage, the Moroccan subsoil contains many mining deposits that are subject to large-scale exploitation and extraction (mainly phosphates, base metals and precious metals) assigning to this sector an important role in the country's economic development. However, the exploitation of these mineral resources can present serious negative influence on the environment. Indeed, mining activities can disrupt natural environments in several ways, e.g. by altering landscapes, depositing large amounts of hazardous tailings and discharging polluted liquid and atmospheric effluents. Thus, it causes significant environmental damage with negative impacts on air, water and soil quality as well as the loss of biodiversity. Growing concerns about the consequences of mining activities, particularly mining waste, have led many researchers to assess the extent of the environmental damage they have caused. This review summarizes the most important research finding published on the environmental impact assessment of mining industries. Particular attention is paid to some metal ore mines, mainly abandoned ones, occurring across Morocco. The results of the environmental assessments have shown that the abandoned tailings dumps have caused severe contamination of the environment and its compartments. However, the major impact was observed in soils around the mining zones. Thus, particularly in sulphide-rich mines, such as Kettara, Draa Lasfar, Ouixane, Axara and Setolazar mines, the tailings with high acid-generating potential have led to a significant pH level decrease (down to pH 2) and to a severe metal contamination of soils. In many affected areas, toxic metal concentrations exceed standard levels admitted for agricultural soils (1.5 mg of Cd kg(-1), 300 mg of Cu kg(-1), 150 mg of Pb kg(-1) and 300 mg of Zn kg(-1)). Currently, this pollution continues to spread through these sites to the environment due to the lack of proper remediation of these mining lands. The persistence of this situation, therefore, poses a risk not only to the environment but also to the health and safety of the local population living near these sites.