Mine Tailings Impact on the Physico-Chemical and Biological Characteristics of Underground Waters in Marrakech Mining Area (Morocco)

Metal sulphide tailings present a potential risk basically for environment and particularly for water resources, because of their natural oxidability which leads to the production of acid/neutral mine drainage. The prospected site close to Marrakech includes zinc, lead and copper sulphide deposits. This site is located in an agricultural area where groundwater is used both for irrigation and drinking. Eco-toxicological investigations have been undertaken in order to assess the tailings impact on water quality in nearby wells. These investigations include physicochemical characterization of underground waters as well as faunistic population determination. As compared to a standard well, waters from the wells located downstream of the mining site, have high electrical conductivities and high major ions contents, which can reach 755 mg l -1 in SO 4 2- , 2224 mg l -1 in Ca 2+ , 551 mg l -1 in Mg 2+ , 2290 mg l -1 in Na + and 14981 mg l -1 in CI. The fauna distribution analysis carried out around the studied wells shows qualitative and quantitative differences according to the flow gradient of the underground waters. Areas located upstream of the mine tailings site are richer in stygobite species (type and quantity) than those located downstream or close to it. It is likely that these biological differences are due to water quality alteration induced by the mining activity.