PROGRESSES IN RESEARCH ON SPECIAL CHEMICAL PHENOMENA AND THEIR MECHANISMS IN VARIABLE CHARGE SOILS

Xu Renkou;Li Jiuyu;Jiang Jun;State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences;

Electric double layer;;Overlapping of diffuse layers;;Specific adsorption;;Soil acidification;;Surface charge;;Surface potential

In this paper,the authors summarized progresses in the study on variable charge soil chemistry in recent years with emphasis on special chemical phenomena,such as salt adsorption,the effect of Fe / Al oxides inhibiting natural acidification of the soil and the effect of ionic strength affecting specific adsorption of ions and their microscopic mechanisms in the soil. The phenomena of salt adsorption and iron and aluminum oxides inhibiting natural acidification of the soil can be explained with the principle of overlapping of diffuse layers on the surfaces of oppositely charged particles which led to decrease in effective surface charge in the soils. The authors also elucidated the mechanism of ionic strength affecting specific adsorption of anions and heavy metal cations by variable charge soils and explained the effect with a four-layer adsorption model,and further verified on the basis of the variation of zeta potential of the colloids with ionic strength that electrostatic potential in specific adsorption planes of colloids decreases in absolute value with rising ionic strength,which is the main cause for the increase in specific adsorption of anions and heavy metals by the soils and Fe / Al oxides. The extensive investigation of the interactions between the electric double layers on oppositely charged particles and the structure of electric double layer not only helps elucidation of some of the special chemical phenomena in variable charge soils,but also enriches theories of variable charge soil chemistry.