Influence of pH and Dissolved Organic Matter on Photolysis of Metsulfuron-Methyl

The chemical degradation of the herbicide metsulfuron-methyl was investigated in aqueous solutions at different pH values and dissolved organic matter (DOM) addition. The results indicated that the photoreaction rate of metsulfuron- methyl was conformed to first-order kinetics behavior in all case. Expose to the same light intensity, the photodegradation rate of metsulfuron-methyl was much faster in acidic than in neutral or basic conditions. The presence of DOM derived from rice straw (RS) and pig manure (PM) reduced degradation rates and had a quenching effect on the photodecomposition of metsulfuron-methyl, the quenching effect increases with increasing and RS and PM concentration in aqueous solutions. RS has a greater ability to quenching the photolysis compared to PM.