Aqueous environmental photochemical behavior of different antibiotic dissociation forms

Numerous ionizable organic pollutants are present in the aqueous environment. Revealing the environmental photochemical behavior of their different dissociated forms is of great significance to assess the environmental persistence and risk of these pollutants in aquatic systems. Antibiotics are emerging pollutants that are ubiquitous in natural waters. Among them, fluoroquinolones (FQs), sulfonamides (SAs), tetracyclines (TCs) and many other antibiotics have attracted increasing attention because their molecular structures contain ionizable groups such as carboxyl, hydroxyl and/or amino groups. Various dissociation forms of antibiotics not only coexist in surface waters with different abundances, but also show different environmental photochemical transformation behavior and risk. In view of this, this paper summarizes the latest progress on the aqueous photochemical behavior of ionizable antibiotics, introduces the influence of pH on the direct and indirect photolysis kinetics, and highlights the photochemical reaction kinetics, transformation products and pathways of different antibiotic dissociation forms. Also, the corresponding environmental phototransformation fate and risk of ionizable antibiotics are discussed. Finally, the research prospects about the photochemical behavior of antibiotic dissociation forms are proposed.