EFFECTS OF CATION EXCHANGE MATERIAL ON ZINC ADSORPTION BY SOILS |
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| Authors: | KOJI WADA ALY ABD-ELFATTAH |
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| Institution: | (Faculty of Agriculture, Kyushu University 46, Fukuoka 812, Japan) |
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| Abstract: | The adsorption of Zn by soils which are different in their major cation-exchange materials was measured at equilibrium Zn concentrations up to 10?2 M in 10?2 to 10?3 M CaCl2. The results are interpreted on KZnCaZn]soil plots, where KZnCa is the selectivity coefficient defined by the equation  All natural samples except those containing halloysite exhibited no or very small specific Zn adsorption. All Ca-saturated samples exhibited specific Zn adsorption dependent on cation-exchange materials. The cation-exchange sites with high selectivities for Zn (KZnCa > 10) constitute more than 40 per cent of the total exchange sites in soils containing allophane, imogolite, and halloysite, whereas those with moderate to low selectivities for Zn (KZaCa < 10) predominate in montmorillonitic, vermiculitic, and humic soils. Differences in the contribution of the respective cation-exchange materials to specific Zn adsorption are discussed relating to differences in the origin of their negative charge. |
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