Studies on photochemical behaviors of pesticides in environment

In order to know the photochemical behaviors of pesticides in natural water and on the surface of solids such as agricultural leaves and clay particle s, the degradation patterns of 35 organophosphorus, 28 organonitrogens, 9 o rganochlorines and 7 pyrethroid pesticides in distilled water and on the si lica gel plate during exposure to UV light (365 nm) for four hours were inv estigated. The percentages of the degradation of pyrethroid and organophosp horus pesticides were higher than those of organochlorine and organonitroge n pesticides under photoexposure in distilled water and on the silica gel p late. The percentages of degradation of all the pyrethroid pesticides were higher than 36%. Besides, the photochemical degradation on the thioether groups i n disulfoton and fenthion were beyond 70%. Photochemical degradation produc ts derived from disulfoton and fenthion were confirmed to be disulfoton sul foxide and fenthion sulfoxide by GC-MS. The percentages of degradation of h ormothion, disulfoton, fenthion, vamidothion, edifenfos and pyridafenthion on the silica gel plate were superior to those in distilled water. These fi ndings suggested that those pesticides described above on the surface of so lids such as agricultural leaves and clay particles were readily degradated as compared with those in natural water.