| Abstract: | Zinc (Zn) sorption curves were established for 11 cultivated sandy soils from central Vietnam. Soil samples (10 g) were equilibrated with 5 mM calcium chloride (CaCl2) solutions (50 mL) at five zinc chloride (ZnCl2) concentrations (0 to 80 mg Zn L–1). The experimental sorption data were fitted with the Freundlich equation. The amounts of Zn sorbed by soil (QZn) at different Zn concentrations in the equilibrium solution (CZn) were closely related to cation exchange capacity (CEC) and pH, that is, to the available exchange sites at given pH values. More specifically, an excellent correlation was found between Zn sorption and exchangeable calcium (Caex), which evidently also depends on CEC and pH. A unique equation was proposed to predict QZn from CZn and Caex in the range of Zn loading covered in our research, that is, from traces to QZn ≈ 60 mg Zn kg–1. |
