{"title":"Aquatic photo-transformation and enhanced photoinduced toxicity of ionizable tetracycline antibiotics","authors":"Linke Ge, Jinshuai Zheng, Crispin Halsall, Chang-Er Chen, Xuanyan Li, Shengkai Cao, Peng Zhang","doi":"10.1007/s11783-024-1899-x","DOIUrl":null,"url":null,"abstract":"<p>Most antibiotics contain ionizable groups that undergo acid-base dissociation giving rise to diverse dissociated forms in aquatic systems depending on the pH of the system. In sunlit surface waters, photochemical transformation plays a crucial role in determining the fate of antibiotics. This study presents a comprehensive examination of the photo-transformation degradation kinetics, pathways and photoinduced toxicity of three widely detected tetracyclines (TCs): tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC). Under simulated sunlight (<i>λ</i> > 290 nm), their apparent photolysis followed pseudo-first-order kinetics, with rate constants significantly increasing from H<sub>2</sub>TCs<sup>0</sup> to TCs<sup>2−</sup>. Through competition kinetic experiments and matrix calculations, it was found that the anions HTCs<sup>−</sup> or TCs<sup>2−</sup> (pH ∼ 8–10) were more reactive toward hydroxyl radicals (•OH), while TCs<sup>2−</sup> (pH ∼ 10) reacted the fastest with singlet oxygen (<sup>1</sup>O<sub>2</sub>). Considering the dissociated species, the total environmental photo-transformation half-lives of TCs were determined, revealing a strong dependence on the water pH and seasonal variation in sunlight. Generally, apparent photolysis was the dominant photochemical process, followed by <sup>1</sup>O<sub>2</sub> and •OH oxidation. Different transformation pathways for the three reactions were determined based on the key photoproducts identified using HPLC-MS/MS. Toxicity tests and ECOSAR software calculations confirmed that the intermediates produced by the •OH and <sup>1</sup>O<sub>2</sub> photo-oxidation processes were more toxic than the parent compounds. These findings significantly enhance our understanding of the complex photochemical fate and associated risks of TCs in aqueous environments.\n</p>","PeriodicalId":12720,"journal":{"name":"Frontiers of Environmental Science & Engineering","volume":"8 1","pages":""},"PeriodicalIF":6.1000,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Frontiers of Environmental Science & Engineering","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1007/s11783-024-1899-x","RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
Abstract
Most antibiotics contain ionizable groups that undergo acid-base dissociation giving rise to diverse dissociated forms in aquatic systems depending on the pH of the system. In sunlit surface waters, photochemical transformation plays a crucial role in determining the fate of antibiotics. This study presents a comprehensive examination of the photo-transformation degradation kinetics, pathways and photoinduced toxicity of three widely detected tetracyclines (TCs): tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC). Under simulated sunlight (λ > 290 nm), their apparent photolysis followed pseudo-first-order kinetics, with rate constants significantly increasing from H2TCs0 to TCs2−. Through competition kinetic experiments and matrix calculations, it was found that the anions HTCs− or TCs2− (pH ∼ 8–10) were more reactive toward hydroxyl radicals (•OH), while TCs2− (pH ∼ 10) reacted the fastest with singlet oxygen (1O2). Considering the dissociated species, the total environmental photo-transformation half-lives of TCs were determined, revealing a strong dependence on the water pH and seasonal variation in sunlight. Generally, apparent photolysis was the dominant photochemical process, followed by 1O2 and •OH oxidation. Different transformation pathways for the three reactions were determined based on the key photoproducts identified using HPLC-MS/MS. Toxicity tests and ECOSAR software calculations confirmed that the intermediates produced by the •OH and 1O2 photo-oxidation processes were more toxic than the parent compounds. These findings significantly enhance our understanding of the complex photochemical fate and associated risks of TCs in aqueous environments.
期刊介绍:
Frontiers of Environmental Science & Engineering (FESE) is an international journal for researchers interested in a wide range of environmental disciplines. The journal''s aim is to advance and disseminate knowledge in all main branches of environmental science & engineering. The journal emphasizes papers in developing fields, as well as papers showing the interaction between environmental disciplines and other disciplines.
FESE is a bi-monthly journal. Its peer-reviewed contents consist of a broad blend of reviews, research papers, policy analyses, short communications, and opinions. Nonscheduled “special issue” and "hot topic", including a review article followed by a couple of related research articles, are organized to publish novel contributions and breaking results on all aspects of environmental field.