Effect of polluted water on soil, sediments and plant contamination by heavy metals in El-Mahla El-Kobra, Egypt

Abstract. The discharge of untreated wastewater in drains Zefta and No. 5 is becoming a problem for many farmers in El-Mahla El-Kobra area, Egypt. The discharging water contains high levels of contaminants considered hazardous to the ecosystem. Some plants, soil, water, and sediment samples were collected from El-Mahla El-Kobra area to evaluate the contamination by heavy metals. The results showed that the heavy metals, pH, sodium adsorption ratio (SAR), BOD and COD in the water of drains Zefta and No. 5 exceeded permissible limits for irrigation. In rice and maize plants grown in soils irrigated by water from Zefta and No. 5 drains, the bioaccumulation factors for Cd, Pb, Zn, Cu and Mn were higher than 1.0. The heavy metals of irrigated soils from drains Zefta and No. 5 exceeded the upper limit of background heavy metals. In this study, the mean contaminant factor values of the drain No. 5 sediments revealed that Zn, Mn, Cu, Cd, Pb and Ni > 6, indicating very high contamination, which receive a huge amount of metallic pollution due to the direct discharge of wastewater from the urban and industrial area. The high bioaccumulation coefficients of Cynodon dactylon Phragmites australis and Typha domingensis growing in Zefta drain. These species can be considered as hyperaccumulators for, decontamination of polluted water. Thus, the wastewater in El-Mahla El-Kobra area must be treated before discharge in drains (Zefta and No. 5) and remediation of polluted soils from heavy metals.