Tracer Diffusion of Potassium in Four Soils of West Bengal

Apparent tracer-diffusion coefficient (D_a) of Kinfour soils of West Bengal having contrasting physicochemical properties was determined at a given soil water content and two bulk densities of the soils at three temperatures by following the standard half-cell technique. The determinations were conducted at two tracers: background cationic concentrations of 1: 32 and 1: 16 for each of the two background electrolytes, namely CaCl₂ and NaCl. The D_a values in the given soils registered an increase with increasing bulk density, temperature, the tracer level, and for NaCl background electrolyte. The associated energy of activation and the Arrhenius frequency factor were obtained from the temperature dependence of the given D_a values. The entropy factor of diffusion (σ), as introduced by the Eyring's theory of absolute reaction rates, was also evaluated for K-diffusion in the given soils. The results were related to the properties of the soils used, particularly the dominant clay minerals present, and the ionic interactions characteristic of the diffusion medium used.