Effect of TiO_2 on photodegradation of several pesticides in surface soil

Photolysis of 4 pesticides (chlorpyrifos, fenamiphos, carbonfuran and carbendazim) with TiO2 as catalyst under sunlight illumination was investigated to determine the effect of TiO2 dosage, thickness of the surface soil and initial concentration of pesticides on photodegradation efficiency. The results showed that photodegradation of several pesticides fitted the quasi-first-order kinetic equation, the constant of photolysis kinetics increased with increasing the TiO2 dosage from 0 to 200 mg/kg. Thickness of the surface soil played an important role on pesticides photolysis, the pesticides in deep soil had a relative long half-life and slow photolysis rate. The degradation rate of chlorpyrifos and fenamiphos increased with decreasing their initial concentration.