Masami Oyamada

Photolysis Rate of the Herbicide Naproanilide under Xenon Lamp Irradiation in Water

The relationship between the photolysis rate of naproanilide and irradiation wavelengths was investigated. The photolysis rate (conversion per unit energy) was higher under 340nm ultraviolet irradiation than under the wavelengths longer than 35nm, when measured by conversion per unit energy (cal/cm2). The molar absorptivity was high (about 1000) at 310-330nm and low (less than 30) at 350nm, showing the photolysis rate is related to the absorptivity. When the photolysis rate was measured by time, the relationship between the photolysis rate and irradiation wavelengths was not clear. The process of naproanilide photolysis was fitted to a pseudo first-order kinetic at an energy (cal/cm2) of 300-340nm with a xenon lamp. The difference in the reaction rate between at 10°C and 30°C was very small. The photolysis rate of the granule formulation was lower than that of the active ingredient in water, indicating that the photolysis in a paddy field takes place when naproanilide is relased from a granule.