Photodecomposition of pesticide constituents in aerosols and thin films under sunlight

Contamination of atmosphere by pesticides is an inevitable factor of their application for plant protection, and a substantial part of pesticide pollutants exists as airborne particles. The ingress of particulate matter into air takes place during pesticide aerosol treatments of crops. Besides, it is caused by ground or aerial spraying upon fast evaporation of water out of small "pesticide+water" droplets, i.e. due to "drop-to-particle conversion" followed by dissipation in atmosphere. The third pathway is the adsorption of pesticide vapour on atmospheric aerosols existing permanently in the air. Negative ecological consequences of pesticide application are often assigned to their persistence in biosphere. The kinetics and photophysical mechanism of photolysis of photochemically unstable insecticides Resmethrin (as a commercial formulation Isathrin 10% e.c.) and Phenothrin (Sumithrin 10% e.c.) together with stable compound Deltamethrin (Decis 2.5% e.c.) were studied in both the aerosol state (of particle diameters within 0.5-7 mu m) and the thin films (of 0.1-100 mu m thickness on glass plates). Both the direct and sensitized photodecompositions of the above substances were examined under sunlight and halogen lamp.