Effect of illumination on degradation of pyriproxyfen in water-sediment system

The aerobic aquatic soil metabolism of pyriproxyfen [(4-phenoxyphenyl (RS)-2-(2-pyridyloxy) propyl ether] was examined in a UK lake water-sediment system together with the effect of illumination on its degradation profile. The partition of pyriproxyfen in water to the bottom sediment was more rapid under illumination with concomitantly enhanced degradation in the total system. The main photoproduct of pyriproxyfen in sterile water, 2-(pyridin-2-yloxy) propan-1-ol, formed via cleavage of the central ether bond, was further degraded via oxidation in the illuminated water-sediment system and no degradate was found to be accumulated. Hydroxylation at the 4'-position of the phenoxyphenyl moiety dominantly proceeding in darkness was observed as a transient reaction in the early period of illumination. (C) Pesticide Science Society of Japan