Speciation of Heavy Metals in the Soil and the Tailings, in the Zinc-Lead Sidi Bou Othmane Abandoned Mine

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 tailings abandoned for ten to twenty years. 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 Tailings, ii)-To carry out the chemical speciation, of heavy metals in the Tailing 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 Tailings) were measured using the standards methods, heavy metals concentration was determined by ICP-MS. Therefore, a sequential extraction scheme according to the BCR’s (Community Bureau of Reference) guidelines and total acid digestion were applied to soil and Tailings samples.  The results obtained showed that the abandoned mine of Sidi Bou Othmane still containing very important quantities of solid waste, these site can become potential source 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 mine, probably linked to weathering effect, the wind and the topography.

Keywords: Soil, tailings, heavy metals, sequential extraction, speciation.