Potential Pb,Cd, Zn and B contamination of sandy soils after different irrigation periods with sewage effluent

Long-term use of sewage water for irrigation enhances the accumulation of trace elements in the soil and may contribute to contamination in low-lying areas. Therefore, this study investigated the extent of pollution introduced by Pb, Cd, Zn and B to the sandy soils of Abu Rawash and El-Gabal El-Asfar areas, Egypt, which have been irrigated with sewage water for up to 67 yr. Results revealed that prolonging the periods of irrigation was associated with significant increases in the total and available forms of Pb, Cd, Zn and B. These elements tended to accumulate in the surface layers, with the exception of B which increased at lower depths. The relative percentage of the available to total element forms reflected the low solubility and availability of both Pb and B compared with Cd and Zn. However, in all cases, the concentrations of these elements have not accumulated to toxic levels after 67 yr of sewage irrigation. Nevertheless, care and good management should be considered in the future with continuous use of sewage water for irrigation.