ZINC ADSORPTION BY MINERAL SOILS OF FINLAND

Zinc adsorption by 10 (pH 4.0-6.5) cultivated mineral soils from Finla nd was studied in batch experiments. Additions of Zn ranged up to 600 mg kg-1 of soil and the corresponding equilibrium concentrations were 0.1-13 mg l-1. In each soil, Zn adsorption conformed to the Freundlich isotherm. Despite a relatively low initial Zn adsorption by the acidi c soils, each of the soils proved to have a high potential to adsorb Z n, but the capacity was highly pH dependent. In addition to the conven tional Freundlich adsorption isotherms, calculated separately for each soil, extended Freundlich-type isotherms that also incorporate soil p H and other soil characteristics were used to describe Zn adsorption o f several soils simultaneously in one equation. The pH-dependent Freun dlich adsorption isotherm proved to serve as a practical tool to asses s Zn adsorption by soils varying in pH and other characteristics.