Effect of Water Quality on Heavy Metal Redistribution and Mobility in Polluted Agricultural Soils in a Semi-Arid Region

Mornag Plain is a coastal area of the Mediterranean basin, which has undergone an agricultural industrial boom. The aim of this study was to investigate the different water qualities used for irrigation on heavy metal mobility in these polluted agricultural soils. The geo-accumulation indices for heavy metals(Ni, Cr, Pb, Cd, Cu, and Zn) revealed that industrial activities and used treated wastewater(TWW) contributed to soil pollution, and water irrigation always decreased this contamination. After long-term use of different water types, high perturbation of heavy metal redistribution has occurred. Groundwater use altered all heavy metal redistributions in the irrigated soil among various soil-solid and soil-solution fractions, as compared to the unirrigated soil. Slight acid water use transferred some metals from different solid phase components into water-soluble and exchangeable fractions. However, TWW use transformed some Ni, Cr, Cd, Cu, and Zn from water-soluble and exchangeable fractions to less labile fractions, particularly into organically bound fractions. Reuse of conventional water within the same soil decreased the whole soil redistribution index values, indicating tendency to return to the pattern of distribution of groundwater-irrigated soil.