Speciation of Heavy Metals in the Soil and the Mining Residues, in the Zinclead Sidi Bou Othmane Abandoned Mine in Marrakech Area

Abstract

Mining activity is one of the most important sources of Heavy metals in the environment. In Marrakech region, functioning or abandoned mines represent a great hazard due to huge amounts of waste deposited in waste dumps and tailings often with high concentration of heavy metals pollution. These mining sites located near Marrakesh contain mining residues abandoned for ten to twenty years. They are presently in an agricultural region of the Haouz district (Jbilets- Centrales). The present study was realized for the abandoned mine of Sidi Bou Othmane in order: i) -To determine the total content of heavy metal in soil and mining residues, ii)-To carry out the chemical speciation, of heavy metals in the mining residues and in the samples of soil collected in the vicinity of the mine. The pH, the electrical conductivity, Organic matter content and Total carbonate content in all the samples (soil and mining residues) were measured using the standards methods, heavy metals concentration was determined by atomic spectrophotometery. Therefore, a sequential extraction scheme according to the BCR’s (Community Bureau of Reference) guidelines and total acid digestion were applied to soil and mining residues samples. The results obtained showed that all the abandoned mines still containing very important quantities of solid waste, these sites can thus become potential sources of pollution by releasing heavy metals. In this concern, 4 polluting heavy metals (Cd, Cu, Pb and Zn) were detected with concentrations exceeding those admitted for agricultural soil. For all heavy metals, the most contaminated sites were found in the vicinity of the mines, probably linked to weathering effect, the wind and the topography.