Xenon-lamp simulated sunlight-induced photolysis of pyriclobenzuron in water: Kinetics, degradation pathways, and identification of photolysis products

Pyriclobenzuron 11PBU – pyriclobenzuron.(PBU) is a novel molluscicide developed to control Pomacea canaliculate, and little information on its environmental fate has been published. In this study, the photolysis of PBU in an aqueous environment was simulated using a xenon lamp. Results showed that the photolysis of PBU in water followed first-order kinetics, exhibiting a t0.5 of 95.1 h and 83.6 h in Milli-Q water and river water, respectively. Two main photolysis products 22PPs – photolysis products.(PPs) were detected by HPLC-UV and identified by UPLC-Q/TOF MS, which were formed via the hydroxylation and photocatalytic hydro-dehalogenation of PBU, respectively. The initial relative abundance of photolysis product 1 33PP-1 – photolysis product 1.(PP-1) in Milli-Q water was 1.55 times higher than that in river water. PP-1 was detected at 26.5 % and 76.8 % of the maximum relative abundance in the river water and Milli-Q water after 720 h, respectively. Photolysis product 2 44PP-2 – photolysis product 2.(PP-2) was stable in water because of its weak hydrophilicity. The PP-2 detected after 720 h in Milli-Q water and river water was 93.7 % and 93.5 % of the maximum relative abundance, respectively. Finally, ECOSAR software was used to evaluate the acute aquatic toxicity of PBU and its PPs, revealing that the PPs had lower toxicity levels to non-target aquatic organisms. [Display omitted] •Photolysis t0.5 values of PBU in two aqueous environments were 95.1 h and 83.6 h.•The photolysis pathways of PBU were hydroxylation and hydro-dehalogenation.•PP-2 was more stable than PP-1 in aqueous environments.•ECOSAR predicted that aquatic toxicity of PPs was lower than that of PBU.