Chemical fractionation of some heavy metals in soils irrigated from El-Saff wastewater drainage canal, Egypt

Abstract

Assessment of heavy metals fractions in soils irrigated with wastewater can directly reflect their bioavailability and contamination level in soil depths. The present study was conducted to assess the heavy metals (Cd, Cu, Pb, Mn, and Fe) fractionation in agricultural soils illegally irrigated with El-Saff wastewater drain, southern Giza Governorate, Egypt. Generally, practices of wastewater irrigation increased pH values in the deeper depths of irrigated soils. Results revealed that long-term wastewater irrigation profoundly affected the studied heavy metals fractions in soil depths. Generally, the ranges of studied heavy metals concentrations in soils irrigated with wastewater were apparently different. All fractions were significantly higher in the upper soil depths (0–60 cm and 30–60 cm) than the deeper depths. (60–90 cm and 90–120 cm). Heavy metals concentrations varied in the soils as Fe > Mn > Cu > Pb > Cd after irrigation. The heavy metals fractions were dominant in the residual form followed by oxides bound and organically bound fractions. Lower contents of heavy metals in the soil were obtained in the exchangeable fraction. Wastewater irrigation resulted in the transformation of heavy metals into different fractions as residual > oxide associated > organically bound > carbonate associated > exchangeable form. Monitoring of heavy metals concentration in El-Saff wastewater effluent is periodically required.

Keywords

• Wastewater
• Heavy metals
• Soil contamination
• Fractionation