COMPARATIVE-STUDY ON THE QUANTUM YIELDS OF DIRECT PHOTOLYSIS OF ORGANOPHOSPHORUS PESTICIDES IN AQUEOUS-SOLUTION

The quantum yields for direct photolysis of 16 organophosphorus pesticides and their phenolic products in aqueous solutions were determined at 254 and 313 nm. Highly significant correlation between the quantum yields at 254 nm and those at 313 nm was obtained (r = 0.89, n = 14). There also exists a highly significant correlation between the quantum yields of the organophosphorus pesticides and those of their phenolic products (r = 0.92, n = 15). The pesticides tend to have quantum yields similar to those of their phenolic products. The relationship between the quantum yields and the molecular structure was also investigated. On the basis of the quantum yields, the UV spectra of the compounds, and the solar radiance intensity on the Earth's surface, the relative rate constants for direct photodegradation of the organophosphorus pesticides and their corresponding phenolic products was estimated. The phenolic compounds have much higher rate constants than their parent compounds due to their stronger absorption of solar radiance.