Zinc Sorption by Acid, Calcareous and Gypsiferous Soils as Related to Soil Mineralogy

Zinc (Zn) availability and mobility in soils is controlled by its interaction with the soil matrix and amendments. Contradicting evidence has been reported for factors influencing Zn behavior in soils. The aim of this study was to investigate the Zn sorption in selected acid, calcareous and gypsiferous soils with different background electrolytes (Na+, K+ and H2PO4, NO3 and Cl backgrounds). Isotherm curves for Zn sorption were examined on 2 calcareous, 2 acid and 2 gypsiferous soils. Lability of the adsorbed Zn was evaluated by DTPA following sorption. The Zn adsorption data showed a highly significant fit to the Langmuir, Freundlich and Temkin adsorption isotherms. The fit of the present experiment’s data to Langmuir isotherm proved to be more suitable as compared with Freundlich or Temkin isotherms. The presence of Na+ increased total Zn adsorption as opposed to K+ in all soils. Gypsiferous soils exhibited greater Zn adsorption than calcareous and acid soils. The high adsorption of Zn by gypsiferous soils could be related to the presence of a palygorskite mineral with a large surface area, but for acid soils with high contents of kaolonite and illite minerals, minimum Zn sorption was observed. In acid soils, the largest Zn sorption was observed with H2PO4, whereas in gypsiferous and calcareous soils, H2PO4 decreased Zn sorption. The lability of Zn affected the clay minerals amount and type. The results showed that a large percentage (90 to 98%) of the sorbed Zn was associated with nonlabile pool. It is concluded that other nutrients and clay minerals have significant effect on Zn applied to soils.