不同类型铁氧化物上有机自由基稳定机制的比较性研究

Environmentally persistent free radicals (EPFRs) have recently attracted extensive attention due to their significant roles in controlling the fate of organic chemicals. In addition, studies have provided evidences that EPFRs are more toxic than the parent chemicals. The presence of EPFRs will challenge the regular method of assessing the environmental risks of contaminants based on their concentrations, which neglected the toxicity contributed by these free radicals stabilized on particles. Most studies generally discussed the formation mechanisms of EPFRs in combustion and high temperature systems, but our previous study suggested that EPFRs may be generated in the ambient environment. Although the formation mechanism of EPFRs on iron oxide has been preliminarily investigated, the role of the types of iron oxides in stabilizing organic free radicals and their environment risks are still unclear. Ignoring this process may lead to potential deviation on understanding the environmental behaviors and risks of organic pollutants. Previous studies have emphasized that EPFRs are formed through a mechanism that chemicals are firstly adsorbed on the hydroxyl groups of iron oxide surface. Then the electrons transfer from chemicals to transition metal. The types and amounts of hydroxyl groups on iron oxides varied depending on the types of iron oxides, and their reduction potential, which may have profound effect on formation and stabilization of EPFRs. Different from EPFRs formed in combustion condition, EPFRs formed in ambient environment are continuously generated and quenched. EPFRs are a type of emerging contaminants. Their risks are normally assessed based on their apparent EPR signal intensities, which however, may not be linearly correlated to their toxicity. The reason is the missing link between the type of radicals and their toxicity. Biological studies have proved that reactive oxygen species (ROS) formed via EPFRs in aqueous posed oxidative stress and resulted in tissue damage and disease. Thus, monitoring ROS may better assess the reactivity and risk of EPFRs. In this study, three types of iron oxides including ferrihydrite, goethite and hematite were selected as model particles based on their differences in surface structure (e.g. hydroxyl groups) and physicochemical properties. The formation and stabilization of EPFRs, and the generated ROS in aqueous will be investigated. The extended study on this area will be beneficial to reveal the active sites of and the stabilization mechanism of EPFRs on iron oxides. This line of work will establish a fundamental database for EPFRs environmental risk assessment and provide further information to understand the environmental behavior and health risks of organic contaminants.

环境持久性自由基（EPFRs）作为一类新型的环境污染物由于其独特的性质及其显著的毒性效应而引起了研究者们的广泛关注。虽然铁氧化物在EPFRs产生中的作用已有初步研究，但铁氧化物类型与有机污染物降解过程中EPFRs的稳定机制如何关联还未知，而这是理解EPFRs形成机制和有机污染物环境归趋及风险的重要基础。本项目拟选用土壤中常见的水铁矿、针铁矿和赤铁矿，在自然条件下通过比较不同类型铁氧化物的表面结构及理化性质对EPFRs生成、稳定性及其在液相中介导产生活性氧（ROS）的影响。深入解析铁氧化物表面羟基、氧化还原电位等在EPFRs生成、稳定过程中的功能，复合有机污染物降解，探究EPFRs的产生动力学和持久性特征，并从反应活性的角度，揭示铁氧化物上EPFRs的环境风险。以上研究将为EPFRs形成机制提供重要的视角，也将为铁氧化物环境效应的评估、有机污染物的环境归趋及风险评价提供新的思路。

环境持久性自由基(EPFRs)因其独特的性质和显著的毒性而受到研究者们的广泛关注。虽然铁氧化物和铝氧化物在EPFRs产生中的作用已有初步研究，但铁氧化物及铝氧化物类型与有机污染物降解过程中EPFRs的稳定机制如何关联还未知，而这是理解EPFRs形成机制和有机污染物环境归趋及风险的重要基础。经过三年的持续研究，围绕有机污染物与铁氧化物、铝氧化物相互作用生成EPFRs的机制开展了系统研究，基本上实现了预期的科研目标。本项目主要研究内容包括：系统研究了邻苯二酚与铁氧化物以及铝氧化物相互作用生成EFPRs的机制，探究了铁氧化物以及铝氧化物上生成EPFRs的活性位点及稳定机制，研究了铝氧化物上ROS的生成情况，采用秀丽隐杆线虫初步评价了铝氧化物上EPFRs的毒性效应。获得的主要成果包括：1. 发现铁氧化物表面羟基为生成EPFRs的活性位点，羟基结构类型及有机污染物与羟基结合形式与EFPRs稳定性相关；2. 发现铝氧化物上的路易斯酸位点为生成EPFRs的活性位点；3. 铝氧化物上的EPFRs能在液相中介导生产ROS，对线虫产生显著毒性效应。以上研究成果将为全面理解自然条件下EPFRs的生成机制及评价EPFRs的环境风险提供重要的视角及理论支持。发表SCI收录期刊论文2篇，中文核心期刊论文2篇。