水环境中抗生素不同解离形态的复合光化学行为：光降解、自由基氧化及光致毒性

Antibiotics are new pollutants that are ubiquitous in the aqueous environment, which urges new insights into the photochemical transformation of their different dissociation species. This project will select three classes of antibiotics (i.e., fluoroquinolones, sulfonamides and tetracyclines, which are frequently detected in surface waters) and investigate multivariate photochemical behavior of their dissociation species. A series of simulated experiments at different pH are designed to study the direct and self-sensitized photodegradation kinetics, contribution rates and products, and to reveal main degradation pathways of various antibiotic species. Competition kinetics will be used to quantify the bimolecular reaction kinetics between the antibiotic dissociation species and reactive oxygen species (ROS, such as ·OH, 1O2 and O2·-), based on which the corresponding environmental fates are to be assessed. Furthermore, the photo-oxidation intermediates with their evolution will be analyzed to propose the pathways. And, effects of metal ions on the ROS oxidation are to be examined. Photochlorination of the different antibiotic species via chlorine radicals are investigated to explore the corresponding mechanisms. Additionally, the project attempts to investigate the photoinduced toxicity and the antibacterial activity changes during the photodegradation and radical-reactions of the antibiotic species toward the goal of assessing their phototransformation risk. Based on the results obtained from the project, their photochemical behavior with that of other classes of pollutants including other antibiotics will be further summarized and compared. Moreover, some theoretical support will be supplied to the ecological risk management and pollution prevention of antibiotic contamination.

抗生素是水环境中普遍存在的新型污染物，但其不同解离形态的光化学转化却少有报道。本项目拟选取表层水体中常检出的3大类抗生素(氟喹诺酮类、磺胺类、四环素类)，研究其不同形态的复合光化学行为。采用模拟实验，考察不同pH下的直接光解和自敏化光解动力学、贡献率及转化产物，揭示不同形态的主要反应路径。采用竞争动力学方法，定量表达不同形态与光致活性氧物种(ROS，·OH、1O2和O2·-)的双分子反应动力学，重点分析产物及其演变，评估转化路径及相应的环境归宿，并考察金属离子对ROS光氧化的影响。探索氯自由基与抗生素不同形态的光致氯化反应产物，揭示光致氯化机理。深入研究抗生素不同形态光降解及其与光致ROS、氯自由基反应的光致毒性及抗菌活性变化，评价其光化学转化风险。通过以上研究，阐明这3类抗生素与其他类别污染物(包括其他抗生素)光化学行为规律的异同，为抗生素类污染物的风险管理及污染防治提供理论支持。

抗生素是水环境中普遍存在的新型污染物，但其不同解离形态的光化学转化却少有报道。本项目选取表层水体中常检出的3大类抗生素(磺胺类(SAs) 9种、氟喹诺酮类(FQs) 8种、四环素类(TCs) 3种)，深入研究了其不同解离形态的复合光化学行为。首先，发现环境表层水体中SAs与活性氧物种的光氧化反应至关重要，H2SAs+, HSAs0和SAs-的光氧化动力学依赖于pH和不同形态的反应活性；相对于直接光解与•OH氧化，1O2氧化对水环境中SAs的归趋具有关键作用，并且这三种转化反应(直接光解、•OH氧化、1O2氧化)具有不同的初始反应路径和产物。进一步，阐明了FQs不同解离形态(FQs-、HFQs0、H2FQs+)的光化学行为，其中HFQs0具有最高的表观光解效率和•OH氧化活性；基于主要的转化产物，揭示了这些反应的路径；并且清晰表征了FQs光降解过程中的抑菌活性变化。继而，清晰表达了TCs解离形态(TCs2-、HTCs-、H2TCs0)的光化学行为，其中TCs2-具有较高的表观光解速率常数和ROS氧化活性；表层水体中TCs的光化学转化半减期依赖于解离形态及相应的反应活性。此外，还比较研究了其他类别污染物(如羟基多环芳烃)的光化学行为规律。通过以上工作，深入揭示了抗生素不同解离形态直接光解、光致·OH氧化、光致1O2氧化等复合光化学降解反应的动力学特征，阐明并比较了这三种反应的产物和途径，评估了光解过程抗菌活性变化，并据此进一步评估了表层水体中抗生素的光化学转化归趋与风险。本项目可为抗生素的生态风险性评价与污染控制/修复提供科学依据。