Photochemical reaction of glucocorticoids in aqueous solution: Influencing factors and photolysis products.

Glucocorticoids (GCs), as endocrine disruptors, have attracted widespread attention due to their impacts on organisms' growth, development, and reproduction. In the current study, the photodegradation of budesonide (BD) and clobetasol propionate (CP), as targeted GCs, was investigated including the effects of initial concentrations and typical environmental factors (Cl, NO, Fe, and fulvic acid (FA)). The results showed that the degradation rate constants (k) were 0.0060 and 0.0039 min for BD and CP at concentration of 50 μg·L, and increased with the initial concentrations. Under the addition of Cl, NO, and Fe to the GCs/water system, the photodegradation rate was decreased with increasing Cl, NO, and Fe concentrations, which were in contrast to the addition of FA. Electron resonance spectroscopy (EPR) analysis and the radical quenching experiments verified that GCs could transition to the triplet excited states of GCs (GCs*) for direct photolysis under irradiation to undergo, while NO, Fe, and FA could generate ·OH to induce indirect photolysis. According to HPLC-Q-TOF MS analysis, the structures of the three photodegradation products of BD and CP were elucidated, respectively, and the phototransformation pathways were inferred based on the product structures. These findings help to grasp the fate of synthetic GCs in the environment and contribute to the understanding of their ecological risks.