Hydrolysis and photolysis of flupyradifurone in aqueous solution and natural water: Degradation kinetics and pathway.

Flupyradifurone (FPO) easily spreads to the water environment after application because of its high solubility in water (3200 mg/L, 20 °C), but as a novel neonicotinoid pesticide, its environmental fate study is still lacking. Here, laboratory experiments were conducted to investigate the degradation kinetics and pathways of FPO in aqueous solutions and natural waters. The results showed that FPO was fairly stable in water under natural conditions (the hydrolysis half-lives at 15 °C, 25 °C, and 35 °C were >150 d, and the photolysis half-lives under sunlight were >168 h). However, FPO was photodegraded rapidly under ultraviolet (UV) light (half-lives of 2.37-3.81 min). Then, indirect photolysis under UV light was examined with the addition of photosensitizers, revealing that direct photolysis is the main FPO degradation pathway in water, and the contribution of indirect photolysis was limited. Moreover, two photoproducts were separated, purified and collected via preparative HPLC, and identified via high resolution mass spectrometry. Then, the plausible photolysis pathway was proposed. The results of this study will contribute to a better understanding of the fate of FPO in the water environment.