Sorption of Zinc in Soils of different Clay Mineralogical Composition

Six soils varying in clay mineralogical composition were calcium-saturated and subjected to different concentrations ofzinc and calcium to cover entire surface composition by maintaining constant ionic strength i.e 0.03. All soils sorbed zinc in excess of their exchange capacity; which was more pronounced in kaolinite dominant soils. The excess sorption did not take place up to 30 percent coverage of zinc on surface. The non-extractable zinc with ammonium acetate was higher in soils dominant in 1:1 clays. The acid extractable zinc was found to be constant irrespective of the composition of equilibrium solution. Higher selectivity coefficients ranging from 2 to 3 were observed in kaolinite dominant soils.