The environmental behavior and bioavailability of selenium (Se) in soils are greatly affected by its adsorption on soil components, which are largely discrepant with the different physicochemical properties of soils. 18 kinds of farmland soils with various physicochemical properties in China were used in batch adsorption experiments in this study to explore the influencs of soil pH, amorphous iron, aluminum oxides, organic matter and mechanical composition on the adsorption of SeO42-. The results showed that the adsorption of SeO42- on 18 soils was an initially fast phase followed by a slow process, during which the adsorption equilibrium was reached at 24 h. Second-order kinetic model(R2>0.976)and Freundlich isothermal model(R2>0.842)were the fittest for most of the adsorption process. SeO42- adsorption capacity of soil was negatively correlated with soil pH value (P<0.01) and the content of carbonate (P<0.05), while positively correlated with the content of amorphous iron, aluminum oxides (P<0.01) and organic matter content (P<0.05). The partition coefficient of solid to liquid (Kd values) of SeO42- in adsorption process for all the 18 soil types were very low and without big differences(0.99 L·kg-1-18.18 L·kg-1). The desorption rates for all tested soils were above 80%, which indicated the reversibility of SeO42- adsorption in soil. It was inferred from the above that the low Kd and high desorption rate reflected that selenate was featured by easy migration and leaching in soil, which should be emphasized in the regional evaluation and regulation of Se level.
Keywords: adsorption; desorption; physicochemical properties; selenate; soil.