抗生素在入海河口和近岸海水中的光诱导卤化途径及机理

Antibiotics can trigger bacterial resistance and resistant genes, which seriously risks toward ecosystem and public health. Antibiotics have been detected ubiquitously in estuarine and coastal waters. Phototransformation has been improved to be an important factor on fate of antibiotics in the aquatic environment. Halide ions, the major constituents in seawater, are important participants in photochemical processes of halogenated organic pollutants. However, the mechanisms for the photo-halogenated mechanism, products, as well as the effects of major water constituents on antibiotics are unclear in saline waters. A combined field sampling, photochemical experiment, and quantum chemical calculation method will be employed to reveal this question in this project. Firstly, the effect of antibiotic substituents on the photo-halogenated reaction mechanisms will be clarified. Secondly, the influences of the pH, ionic strength, inorganic anions, and dissolved organic matter in seawater environment on the photo-halogenated processes and products are going to be unveiled. Finally, the prediction model for the photo-halogenated reactions of antibiotics will be constructed. The prospective results will facilitate to comprehensively understand the photochemical transform of antibiotics and also to provide theoretical bases for the risk assessment and pollution prevention in seawater environment.

抗生素可诱导细菌菌群抗药性和产生抗性基因，对生态和健康威胁巨大。入海河口和近岸海水中普遍存在抗生素。光化学转化是影响抗生素水环境归趋的重要因素，且受水中溶解性组分的影响。卤素离子是海水环境中主要的溶解组分，其参与的光化学反应是环境中卤代有机污染物的重要来源，但抗生素在高卤素离子水环境中的光诱导卤化机理、产物及重要水环境因子的影响仍不清楚。本项目拟通过实地采样、光化学模拟实验和理论计算相结合的方法，探明抗生素取代基对光诱导卤化影响的微观机理；揭示海水环境中pH、离子强度、无机阴离子及溶解性有机质等因子对抗生素光诱导卤化过程及产物的影响机制；构建抗生素光卤化反应的预测模型。研究成果有助于深入认识海水环境中抗生素的光化学转化，从而为评价抗生素在海水环境中的生态风险及污染防控提供理论支撑。

抗生素可诱导细菌菌群抗药性和产生抗性基因，对生态和健康构成潜在危害。入海河口和近岸海水中普遍存在抗生素。光化学转化是影响抗生素环境归趋的重要因素，且受水体中溶解性组分的影响。卤素离子是海水环境中主要的溶解组分，其参与的光化学反应是环境中卤代有机污染物的重要来源，但抗生素在河口和近岸海水等咸水中的光卤化机制及重要水环境因子的影响尚不明确。项目选取广西钦州湾河口水作为实际水体，研究了河口水中普遍存在的代表性抗生素在河口和近岸海水中的光卤化行为过程机制。通过本项目实施，发现激发三重态溶解性有机质（dissolved organic matter, 3DOM*）可与卤素离子作用产生卤素自由基（halogen radicals, HRs），HRs显著影响抗生素，特别是含有富电子基团抗生素的光降解，其光解速率随河口水盐度增加的流向显著增加，高盐度条件有利于其光解。河口水中其他溶解性组分，如环境水平的HCO3-、NO3-和Fe3+对抗生素光卤化反应影响不显著。基于不同抗生素与3DOM*和HRs之间的反应活性差异，构建了可预测抗生素沿河口水盐度梯度增加的方向光致卤化反应的模型，可用于河口和近岸海水环境中微污染物光诱导卤化反应的动力学预测。考虑到水产养殖活动和河流输运导致河口和沿海水域中DOM水平与陆地水体相当甚至更高，HRs参与的光氧化可能在含较高卤素离子水体中对磺胺等富含供电子基团的抗生素的降解更为重要。故在河口和海岸海水等高盐度水生系统中有机微污染物的归趋模型构建中，HRs的贡献应予以重视。