Mobilities of cations in soils and clays at very low moisture content

Very often the cation exchange capacity of a soil depends more upon organic matter than upon inorganic colloids. It is not known what happens to the soil organic matter at very low moisture contents, but it is almost certain that very complex denaturation phenomena affect the ability of the product to bind ions so that study of cation mobilities is very difficult. When considering the mechanism of cationic mobility, practically all questions which arise may be inferred from the state of adsorbed water. Water determines the electrical work required to remove a cation from the close vicinity of lattice oxygens, through its dielectric constant. It determines the geometry of the diffusion path. It determines the properties of the cation itself towards a migration process, if we assume, as in the case of solutions, that hydration is a factor governing diffusion