BEHAVIOUR OF TRACE ELEMENTS IN ECOSYSTEM OF THE URBANISED AREA AT NE CAIRO/EGYPT

Abstract There is a widespread international concern over the lack of food in the developing countries, which suffer from deficiency of water for irrigation and land for cultivation. The overpopulation is an additional problem. The reuse of treated sewage as supplementary water resource were used in arid areas, in sandy soil around Cairo city. Cairo produces more than 4,5 mill m3/d sewage effluent. In the 85 years old Gabal el Asfar sewage farm, heavy metals like Fe, Zn, Cr, Mn, Cu and Pb have been accumulated in the upper soil. The contamination of heavy metals in soil has been reflected in the citrus plants. To assess the metal concentration in the soil, 48 soil samples have been collected from different localities in a selected sewage pilot. XRF method has applied. Citric acid leaching method has been applied to determine the plant available heavy metals in the soil. To measure concentration of heavy metals in plants, 20 citrus juice samples were collected, squeezed and acid digested using nitric acid followed by hydrogen peroxide. In both soil and plant samples, metal concentration was determined by AAS and/or IC. Results show that the heavy metal concentration in the soil has been reflected in the plants. Fe, Zn, Mn, and Cr have been measured in soils and plants with relative higher concentration. The heavy metals show some higher anomalies only in the upper soil. Except Fe, the metals Zn, Mn, and Cr have been measured in mean values around the permissible EU and WHO limits. According to the results of study of the soil, percolated water, groundwater and plants in sewage farm area, the negative environmental impact of sewage application is lower in comparison to the one in Leon/Mexico and Berlin/Germany.