Study of the Photodegradation Kinetics and Pathways of Hexaflumuron in Liquid Media

Hexaflumuron, one of the benzoylphenylurea insect growth regulators, can be leached into surface water and thus having a potential impact on aquatic organisms. In this study, the photodegradation processes of hexaflumuron under high‐pressure mercury lamp irradiation were assessed. The photodegradation kinetics were studied, as were the effects of pH, different light sources, organic solvents and environmental substances, including nitrate ions (NO₃^?), nitrite ions (NO₂^?), ferrous ions (Fe²⁺), ferric ions (Fe³⁺), humic acid, sodium dodecyl sulfate (SDS) and hydrogen peroxide (H₂O₂). Three photodegradation products in methanol were identified by gas chromatography‐mass spectrometry (GC‐MS). In general, the degradation of hexaflumuron followed first‐order kinetics. In the four media studied, the photodegradation rate order was n‐hexane > methanol > ultrapure water > acetone. Faster degradation was observed under high‐pressure mercury lamp irradiation than under xenon lamp irradiation. The pH had a considerable effect, with the most rapid degradation occurring at pH 5.0. The photodegradation rate of hexaflumuron was promoted in the presence of NO₃^?, NO₂^?, Fe²⁺, humic acid, SDS and H₂O₂, but inhibited by Fe³⁺. Moreover, the presumed photodegradation pathway was proposed to be the cleavage of the urea linkage.