受污染水体有机质的光敏化三线态生成、反应活性及归趋研究

Municipal wastewater treatment plants (WWTPs) discharge effluent organic matter (EfOM) into surface water, and has received increasingly attention regarding its environmental impacts and potential threat to human health. Photochemical degradation is one of the major transformation processes for organic matters in surface aqueous environments. Despite the photochemistry of natural organic matters (NOM) has been extensively studied, there is lack of understanding the photochemical transformation of EfOM in the surface water, highly due to its complex constitutions and interactions with NOM. Relative to NOM, EfOM exhibits distinct properties, including a specific SUVA, greater hydrophilic organic matter concentrations, fluorescence index (FI) values and polysaccharide contents, and a clear protein-like peak in its EEM. The current project will emphasis on the photochemical transformation of EfOM, more specifically on photo-excited triplet states of EfOM (3EfOM*), which is the precursor for reactive oxygen species, such as hydroxyl radical, singlet oxygen and peroxide radical et al. Firstly solid phase extractions (SPE) and membrane separation will be employed to isolate EfOM into varied components. We will characterize each component using state of art analytical technologies, such as FT-ICR MS, LC-TOF MS and High resolution NMR et al. A new chemical probe will be developed to explore the energy transfer processes of 3EfOM*. Furthermore electron transfer mechanism of 3EfOM* will also be investigated with chemical probe, trimethylphenol. The formation rate, quenching rate and photo quantum yields of 3EfOM* are three major kinetic parameters which will be reported in this study. Secondly we will try to discover the relationships between the spectrum parameters and 3EfOM* quantum yields, and comparing with allochthonous and autochthonous NOMs. The internal correlation between 3EfOM* and ROS will also be established. Finally the photo-bleaching process of EfOM will be discussed based on above investigations. The effect of water parameters, such as pH, carbonate ion, metal ions, will be explored. These kinetic and mechanistic studies will be useful for predicting the environmental fate of EfOM in the aqueous system.

市政污水处理厂出水中含有一定量的难生物降解的有机质（EfOM），排放到水生生态系统后会引起严重的负面环境效应。光降解是污染物在环境中归趋的重要途径之一，而当前的光降解研究多集中在天然有机质，对EfOM的光降解研究相对薄弱。本项目拟探讨EfOM在太阳光照的条件下的光化学转化机理，侧重于光激发三线态EfOM（3EfOM*）的研究。发展一种新型的探针分子探讨3EfOM*的能量传递机制，并协同3EfOM*的电荷转移机制的研究，系统的分析3EfOM*的产生机制、光量子产率和反应活性。建立3EfOM*和羟基自由基，单态氧和超氧根离子等活性氧物种与之间的关联，进而与天然有机质的三线态活性相比较。结合光谱学，高分辨质谱和核磁共振等研究手段，研究EfOM在环境光化学过程中的降解机理。尝试揭示受污染水体有机质的光化学转化规律，进而达到预测污水有机质的环境光化学归趋过程、优化新型污染物光降解模型的目的。

天然有机质（NOM）和市政污水处理厂出水的有机质（EfOM）光化学生成的活性物种是本项目的研究重点，尤其是激发的三线态光敏物种的生成，反应活性和转化规律。依据研究计划，本项目顺利完成了预期研究内容。主要学术贡献为：1）开发了山梨酸、山梨醇和山梨胺一系列研究三线态能量传递的探针分子，定性和定量了其光敏化异构化产物并发展了其测定激发三线态的方法。2）运用这一系列新型探针分子并结合电子转移型探针分子研究了天然有机质和污水有机质的三线态光化学性质的异同并区分了高能级三线态和低能级三线态的分布和化学组成。3）运用其研究手段解析了水中溶解性黑炭的光化学性质并发现了其高电子转移三线态的光化学特性。4）建立了三线态活性物种和羟基自由基、单态氧、碳酸根自由基和超氧根离子等活性氧物种与之间的关联。阐述了超氧根自由基的化学活性前体。5）运用高分辨质谱结合数理统计分析的方法对污水有机组分的光化学转化进行了非靶向研究。发现其光化学活性组分的转化特性并阐明羟基加成为主要的转化反应。 标注本基金资助，项目负责人以通讯作者共发表SCI论文17篇，其中EST 9篇，Water Research 4篇。本项目资助的核心论文获得了2017年度EST最佳论文奖。