Original Articles: PDF OnlyDIFFUSION OF IONS IN VARIABLE-CHARGE SOILS 2. EFFECT OF SOIL SURFACE CHARGE ON DIFFUSION COEFFICIENTS OF CATIONS AND ANIONSWANG, E. J.1; YU, T. R.1, 2 Author Information 1 Institute of Soil Science, Academia Sinica, Nanjing, People's Republic of China. 2 To whom correspondence should be addressed. Soil Science 147(2):p 91-96, February 1989. Buy Abstract The diffusion coefficients of Cl−, NO−3, K+, and Ca2+ in soils were determined by a method using miniature ion-selective electrodes. The diffusion coefficient of anions increased with the increase in soil pH in variable-charge soils but was little affected by pH in a constant-charge soil. The addition of Fe2O3 to variable-charge soils resulted in a decrease in DCl- and DNO3-. The diffusion coefficients of cations decreased with increasing pH in all soils studied. The quantity of diffusing source, the kind of accompanying ions and soil exchangeable cations, and the presence of electrolyte affected the diffusion coefficients. The results were interpreted in terms of interactions of diffusing ions with soil surface charges and other ions. The calculated active fractions of Cl− in variable-charge soils were smaller than those of NO3− when soil pH was low. In addition to coulombic forces, another mechanism may be involved in the interactions between Cl− ions and soil surfaces when they are diffusing in these soils. © Williams & Wilkins 1989. All Rights Reserved.
