Effects of Potassium, Ammonium, and Calcium Chlorides on the Sorption of Metamitron in Soil

摘要

The effects of three electrolytes (KCl, NH_4Cl, and CaCl_2) on the sorption of the herbicide metamitron in a loamy soil was studied. The sorption of metamitron was measured using the batch equilibrium technique. The experimental data were fitted to the Freundlich and Dubinin-Radushkevich isotherm equations. It was noted that the fraction of metamitron sorbed in soil decreased with the increasing initial concentration of the herbicide in soil solution. In soil with organic matter removed, the sorption of metamitron was lower than in the original soil. The soil-herbicide solution contact time ranging from 60 to 720 minutes and had only a slight effect on metamitron sorption. In soil with the addition of KCl and NH_4Cl, significantly higher sorption of metamitron was observed than in the soil system without these electrolytes. The extent of sorption increased with increasing concentrations of aqueous KCl or NH_4Cl solutions, but the increase of sorption in the presence of NH_4Cl was lower compared to the presence of KCl. A similar effect of the two electrolytes on the sorption of metamitron was observed in the soil with organic matter removed. In the single-component systems with CaCl_2, a decrease of metamitron sorption was observed in the original soil. Whereas the presence of CaCl_2 in the two-component systems KCl+CaCl_2 and NH_4Cl+CaCl_2 limited the extent of sorption of metamitron in relation to that obtained in the single-component systems with KCl or NH_4Cl, the adsorbed amount of metamitron was still much higher than in soil systems with no electrolyte.