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Hydrodynamic Dispersion Involving Cationic Adsorption During Unsaturated, Transient Water Flow in Soil

K. B. Laryea, D. E. Elrick, M. J. L. Robin
Soil Science Society of America journal 1982 v.46 no.4 pp. 667-671
clay loam soils, computer software, dispersibility, equations, hydrodynamic dispersion, potassium chloride, soil water movement, solutes, sorption isotherms, unsaturated flow
The analysis of hydrodynamic dispersion of solutes during one-dimensional absorption (horizontal flow) of solution into soil columns is extended to solutes which interact with the soil particle surfaces. The exchange process involved is assumed to be instantaneous and is described by a nonlinear adsorption isotherm. The relevant equations are solved for the apparent longitudinal dispersion coefficient using a computer program written in system/360 CSMP. Experiments with a clay loam soil indicated that when a concentrated solution of potassium chloride (KCl) (1N) infiltrates into a Ca²⁺-saturated soil, the apparent longitudinal dispersion coefficient is effectively velocity independent. This calculated coefficient reflects the possible combined effects of an immobile water fraction and salt exclusion.