Photolysis of fluoroquinolone antibiotics in aquatic environments: mechanisms, influencing factors and environmental implications—a mini review

Abstract Fluoroquinolone antibiotics (FQs) are widely used synthetic antimicrobials that have become prevalent contaminants in aquatic environments owing to their incomplete metabolism and poor removal by conventional wastewater treatment processes. Once released into natural waters, FQs are subjected to transformation primarily through photolysis, which significantly influences their environmental fate and associated risks. This review provides a comprehensive summary of the current understanding of FQ photodegradation, focusing on three major pathways: direct, indirect and self-sensitized photolysis. Key factors affecting photolysis efficiency, including pH, dissolved oxygen, dissolved organic matter and coexisting ions and pollutants, were critically examined. The molecular structures, ionization states and metal complexation behaviours of FQs are also discussed in relation to their photoreactivity. Emphasis is placed on the formation and toxicity of the photoproducts, some of which may exhibit greater persistence or ecotoxicity than the parent compounds. Finally, knowledge gaps and future research needs are highlighted, particularly in relation to real-world aquatic matrices and the role of emerging contaminants in modulating photodegradation processes. This review offers valuable insights for scientists and policymakers seeking to assess the risks and environmental behaviour of FQs.