Influence of soil variability on single and competitive interaction of ammonium and potassium: experimental study on seven different soils

Purpose: Ammonium and potassium are nutrients that generally co-exist together in soils in municipal wasteland. The main objective of this study is to investigate the interactive effects of NH ₄ ⁺ and K ⁺ on their sorption characteristics in seven different soils. Materials and methods: The adsorption parameters (Freundlich partition coefficient K _F and maximum contaminant adsorbed by solid Q _m ) of both the isotherms for single and competitive interactions were correlated with soil-specific parameters (total specific surface area (SSA) and cation exchange capacity (CEC)). To depict the significant variation of the ions in the presence of other ions, percentage reduction of the isotherm parameters was calculated. Results and discussion: Both the ions exhibited a competitive mode of inhibition in the presence of one another. However, the effects varied with soils and the range of concentration. The study demonstrated that at lower concentration, the NH ₄ ⁺ and K ⁺ ion competed equally in all the soils. However, after a certain range of concentration unique for each soil, NH ₄ ⁺ retention was found to be marginally higher than K ⁺ . The study also signified some analogous values of the Freundlich and Langmuir isotherm parameters for soils like F Bent and Kao, which contradicted other experimental findings. Conclusions: This study can be useful for predicting fate of potassium and ammonium for risk assessment of contaminated sites and hence, in design or analysis of certain waste contaminant barrier under concept of sponge city.