JWSS - Journal of Water and Soil Science

Adsorption is one of the most important processes controlling the concentration of zinc (Zn) in the soil solution. The presence of nutrient anions in the solution can affect Zn²⁺ adsorption. In this study, the effect of orthophosphate, nitrate and chloride anions on the Zn²⁺ adsorption in five calcareous soil samples of Chaharmahal-va-Bakhtiari province was investigated. In order to study the Zn adsorption isotherms, solutions containing 25, 50, 75, 100, 150 and 200 mg/L Zn of ZnSO₄ source were used in KH₂PO₄, KNO₃ and KCl electrolytes (electrolytes concentration equal to 50 mM). The Freundlich, Langmuir, and linear equations were used to investigate the ability to describe the Zn adsorption. Based on the results, the Freundlich and Langmuir equations could describe the Zn adsorption. The results of this study showed that Zn in the presence of orthophosphate anion had the maximum adsorption capacity and  an adsorption intensity higher than that of chloride and nitrate anions; meanwhile, in comparison with nitrate and orthophosphate anions, adsorption energy (k), maximum buffering capacity (MBC), and distribution coefficient (kf) in the presence of chloride anion were higher (p< 0.05). The results of this study, therefore, showed that in the presence of anion orthophosphate, Zn adsorbed more intensity and strongly, while adsorption energy was  less than the presence of  the other two anions. Therefore, it could be concluded that Zn and phosphate fertilizers should not be applied together in the soil.