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 particles, the degradation patterns of 35 organophosphorus, 28 organonitrogens, 9 organochlorines and 7 pyrethroid pesticides in distilled water and on the silica gel plate during exposure to UV light (365 nm) for four hours were investigated. The percentages of the degradation of pyrethroid and organophosphorus pesticides were higher than those of organochlorine and organonitrogen pesticides under photoexposure in distilled water and on the silica gel plate. The percentages of degradation of all the pyrethroid pesticides were higher than 36%. Besides, the photochemical degradation on the thioether groups in disulfoton and fenthion were beyond 70%. Photochemical degradation products derived from disulfoton and fenthion were confirmed to be disulfoton sulfoxide and fenthion sulfoxide by GC-MS. The percentages of degradation of hormothion, disulfoton, fenthion, vamidothion, edifenfos and pyridafenthion on the silica gel plate were superior to those in distilled water. These findings suggested that those pesticides described above on the surface of solids such as agricultural leaves and clay particles were readily degradated as compared with those in natural water.