Impact of wastewater irrigation on chemical composition and heavy metals accumulation in soil (study case: Helwan-El Saff area)

This investigation was conducted on nine sites at Helwan – El Saff area, Cairo, and Giza governorates (polluted area), and three sites, in Metrabeaa village, Monofia governorate (control). This study aimed to assess the impact of wastewater irrigation on soil quality and to test the possibility of using it as an alternative for fresh water in irrigation of agricultural land. Water and soil samples were collected from El-Khashab canal (polluted water) and Al-Bagoria canal (Nile water) and cultivated land sites adjacent to them during two seasons (July 2019 and July 2020). The values of electric conductivity (EC), sodium adsorption ratio (SAR), studied cations, anions and heavy metals were significantly higher; in wastewater samples than in Nile water samples; meanwhile, the opposite was true for hydrogen ion concentration (pH), available nitrogen and phosphorus (N and P). The values of EC, Ca++, Na+, Cl-, SO4--, CaCO3,organic matter(OM) and all studied heavy metals increased in soil irrigated with wastewater as compared with the soil irrigated with Nile water; meanwhile, the opposite was true for pH, Mg++, soluble K+, and HCO3-. The values of contamination factor followed the order: Co ˃ Cr ˃ Zn ˃ Mn ˃ Fe ˃ Cu ˃ Pb. Moreover, the pollution load index of soil ranged from 25.81 to 16.16. The data of this research revealed that wastewater of El-Khashab canal could effectively be used as fertility source for soil, but there are some risks as heavy metals may threaten sustainable agriculture in the study area.