A. Reyhanitabar - Department of Soil Science, Faculty of Agriculture, University of Tabriz, Tabriz, Islamic Republic of Iran.
M. M. Ardalan - Department of Soil Science, Faculty of Soil and Water , University College of Agriculture and Natural Resources, University of Tehran, Karaj, Islamic Republic of Iran.
N. Karimian - Department of Soil Science, Faculty of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.
Gh. R. Savaghebi - Department of Soil Science, Faculty of Soil and Water , University College of Agriculture and Natural Resources, University of Tehran, Karaj, Islamic Republic of Iran.
R. J. Gilkes - School of Earth and Environment, Faculty of Natural and Agricultural Science, University of Western Australia, Crawley, WA ۶۰۰۹, Australia.

The kinetics of Zn sorption by ten calcareous soils of Iran were measured and fitted to several equations (zero-, first-, second-, third-order, parabolic diffusion, simple Elovich, and exponential equations). Two initial concentrations of zinc i.e. ۲۰ and ۸۰ mg Zn l-۱ were used and observations were carried out for ۱۰۰ hours. The time required to reach the near equilibrium state was about ۲۴ hours, by which time most of the Zn in solution had been sorbed. Zero-order, first-, second-, and third-order equations did not adequately describe zinc sorption kinetics. Both simple Elovich and exponential equations did adequately describe the data. Regression analysis indicated that the total CaCO۳, active CaCO۳, clay content, and specific surface area were closely related to the coefficients of these two equations. The magnitude coefficients of the equations were positively related to these soil properties. Thus, Zn sorption kinetics can be predicted from data collected during routine soil evaluation.

Aridisols, Soils of Iran, Carbonate, Entisols, Kinetic models, Zinc sorption