Adsorption and Desorption Behavior of Herbicide Met ribuzin in Different Soils of Iran

Abstract

In this study, the batch equilibrium method was use d to conduct metribuzin adsorption/desorption experiments with eight soils from different regions of Iran. The results indicated that the organic carbon (OC) cont ent, clay content, cation exchange capacity (CEC), and pH had a combined effect on the metribuzin adsorption on soil. Under the experimental conditions, the adsorption a mount of metribuzin on soils was positively correlated with the content of soil orga nic carbon. Freundlich adsorption isotherm provided the best fit for all adsorption an d desorption data. The values of K f-ads , Freundlich adsorption capacity, ranged from 0.16 to 2.53 L kg -1 . Soil organic carbon content and pH were the main factors influencing ads orption. Adsorption was positively correlated with OC and negatively correlated with p H. Metribuzin desorption showed that almost all of the adsorbed metribuzin was deso rbed in all soils, except soil 1 and 8. However, adsorption was not completely reversible. Keywords: Hysteresis, Metribuzin, Soil, Soil organic carbon, Soil pH.