The adsorption kinetics of alginate matrix-immobilized metazachlor and clomazone herbicides were studied in water/soil and water/bottom sediment systems. The adsorption of both herbicides depended on org. C content in the systems. Initial adsorption rate, rate const. of adsorption and the equil. adsorption were calcd. for both herbicides by using the pseudo second-order kinetics model.