MOBILITY OF METALS IN EGYPTIAN DESERT SOILS SUBJECT TO INUNDATION BY LAKE NASSER

Extraction and adsorption techniques were used to study the behaviour of Al, Fe, Mn, Co, Ni, Cu and Zn in soils from around Lake Nasser in t he Eastern Desert of Egypt, to assess the potential of such areas for agricultural development and the risks of pollution of the lake. Soil metal contents were very variable, either because of particle size sor ting by flowing water or through changes in redox resulting from flood ing by lake water. Metal availability was low. Extraction using EDTA a nd oxalate suggested that mobility of copper was controlled by carbona te, whereas Co, Ni and Zn were controlled by Fe and Mn oxides. Adsorpt ion studies confirmed the strong ability of these soils to remove Cu a nd Zn from solution, and suggested that Cu and Zn concentrations in so lution were controlled bg carbonate. Some trace metal fertilizers will probably be required for certain crops, but pollution of the lake by leaching oi metals from soil is unlikely. The main process by which me tals could be lost from the soil to lake water is a lowering of soil r edox potential as a result of flooding by lake water.