Analyse et spéciation des métaux dans un Oued en zone minière

Abstract

The abandonment of the Sidi Kamber mine has led to a gradual submergence and a degradation of the water quality of Oued Essouk. In this context, the objective of this study is to characterize the evolution of water and sediment qualities of the river by combining physico-chemical and mineralogical approaches. Water and sediments Samples were taken during 2008. The samples were characterized by the analysis of various physico-chemical parameters. Metals Fe, Zn, Cu, Pb, Cd were analyzed in filtered water, suspended matter and sediments. The distribution of metals in sediments was assessed by sequential extraction tests. The identification of the mineralogical composition of sediments was evaluated by SEM-EDS, XRD and IR. The obtained results show that the mine waters are more acidic in low flow periods. Metals are mainly in the dissolved phase. Their concentrations are highest in June. Along the river, the pH values of water were higher in winter. Mineralization and sulphate concentrations are more important in November. Metals are mostly in the dissolved phase. The majority of the studied metals are trapped in sediments. Their concentrations are high in particular iron, zinc and lead. Speciation of metals in sediments of mining effluent shows the predominance of the reducible fraction for lead, the exchangeable fraction for cadmium and zinc. Copper is bound to oxidizable.fraction. In the river sediments, the fractions sensitive to physico-chemical conditions changes have higher.rates.of.metals.uptake. Sediments of the mining effluents are mainly jarosite and schwertmannite. The sediments of the river contain lepidocrocite and amorphous oxyhydroxides witch are effective adsorbents for metals.