An experimental approach to the photolysis of pesticides adsorbed on soil: Thidiazuron

An experimental procedure has been developed for conducting photolysis studies with pesticides adsorbed by soil surfaces. In these experiments, solutions of thidiazuron were sprayed on segments of a 0.5‐mm layer of soil covering a glass plate. The soil surface was irradiated using simulated sunlight. The light source was a xenon arc in combination with glass filters that absorbed light of wavelength <290 nm. During irradiation, one half of the sprayed areas was covered to obtain nonirradiated samples. After various time intervals, groups of three irradiated and three non‐irradiated segments of the soil were scraped off and extracted; the extracts were analysed. Information was obtained on the photoproducts formed and on the kinetics of photodegradation of thidiazuron.