Role of positive charge in the competitive effect of phosphate on sulfate sorption by an allophanic soil

Abstract

The effect of phosphate (P) on the sorption of sulfate (S) by an allophanic soil with high surface positive charge was investigated in the pH range of 5.3-7.0 obtained by incubation with Ca(OH)2. The effect of P on S sorption was directly related to the effect of P on surface positive charge. At low soil pH, P reduced surface positive charge to a larger extent than at high pH and this was associated with a larger effect of P on S sorption.