Photolysis rate of rimsulfuron as affected e soil sorption and organic matter content

In order to elucidate the photochemical behaviour of the sulfonylurea herbicides in the soil and the influence of soil organic matter, the photodegradation of rimsulfuron has been studied in soil suspension and on sorbed phase. For the experiments an Italian soil sampled from Sellata Mountain was utilised. The irradiation was realised using a solar simulator (Suntest). Natural soil samples and the same soil after oxidation with H2O2 (to destroy the organic matter) were treated with the herbicide and exposed to light irradiation or kept in the dark, as control samples. Kinetic parameters of reactions were calculated. Herbicide sorption was ascertained to be the more important reaction in the soil, but the retention of rimsulfuron was significantly reduced after H2O2 treatment of soil. Photoreaction kinetics of the herbicide are influenced by the sorbent capability of soil samples used in the experiments and the natural organic content