Surface Charge and Solute Interactions in Soils

Abstract

Many soil physical and chemical properties are controlled by the nature and the amount of surface charge and the variation of surface charge with soil solution characteristics. These properties include dispersion and flocculation, electrophoretic mobility, solubility, and the adsorption and movement of solutes. The surface reactions of charged particles are essential to the biogeochemical cycling of nutrients and pollutants and the pathway of detoxification of the latter when present at hazardous concentrations. Surface charge can be manipulated to take advantage of solid phase interactions relating to the movement of nutrient and pollutant ions in soils, the degradation of pesticides, and the decontamination of soils. This chapter brings together fundamental aspects of surface charge and recent developments on the implications of surface charge in relation to other soil properties, particularly solute interactions in soils. We first outline the development of charge on both permanent- and variable-charge surfaces. Then we discuss the various methods used to measure surface charge and factors affecting this charge. An attempt has been made to compare current theories on the nature of the charged solid surface-solution interface. The manipulation of surface charge can be achieved through liming and the addition of fertilizers containing specifically adsorbed ions. The practical implications of surface charge to soil properties have been discussed in relation to the dispersion and the flocculation of soils and the adsorption and leaching of inorganic cations and anions. Future research should focus on the development of methods to measure surface charge under in situ conditions and to explore further the role of surface charge in remediating contaminated soils