Mechanism of apparent salt absorption in ando soils

Abstract

Determinations of Na⁺ and Cl^- retentions by silica, aluminum hydroxide and their mixtures were carried out to identify the mechanism of apparent salt absorption in ando soils which is defined as the simultaneous adsorption of a cation and the equivalent amount of anion without release of exchangeable ions. Neither the silica nor the aluminum hydroxide, alone, exhibited the apparent salt absorption phenomenon but their mixtures did. And the amounts of Na⁺ and CI^- retained by the mixtures were close to those expected from the negative and positive charge characteristics of the silica and the aluminum hydroxide, respectively. From these observations, it is concluded that the phenomenon of apparent salt absorption occurs when cations and anions are adsorbed separately on variable negative- and variable positive-charge sites, respectively.