富铝土-有机污染物相互作用中自由基的产生、稳定及迁移

Reactive radicals are generated during the interactions between transitional elements and organic contaminants. Previous studies indicated that these radicals are protected and stabilized during their interactions with particles and thus are called environmentally persistent free radicals (EPFRs). These new type of contaminants are detected in soil/sediment, suspended particles, natural organic matter and water and thus are ubiquitous. The presence of EPFRs may bring uncertainties of the quantitative analysis of organic contaminants. In addition, EPFRs may have higher risks to organisms than the parent organic chemicals and thus it is urgent to understand the mechanisms for EPFRs generation and environmental behavior. The extended study on this area will definitely deepen our knowledge on organic chemical risks. The transitional element, iron, is abundant in oxisol. Under ultraviolet light irradiation, iron could interact with organic chemicals and thus EPFRs generate. Our preliminary study has indicated that under natural sunlight irradiation, the red soil-adsorbed phenol could be degraded and a very strong radial signal was observed. This signal was very clear after 5 days. This preliminary work indicated that oxisol may generally interact with organic contaminants and generate EPFRs. In these soils, although the detectable contaminant concentration is not high, the soil-organic contaminant system may have very high risk. Thus, a series of unsolved scientific questions were proposed and discussed in the proposal. This work is proposed to systematically study the sorption, desorption, degradation, and EPFRs generation during the interactions between organic chemicals and oxisol under light irradiation. The contributions of these processes to the environmental behavior of organic contaminants will be identified. The major research focus is the generation, persistence, and transport of EPFRs in oxisol. The effect of environmental conditions, such as natural organic matter, pH, ionic strength, and humidity will be investigated. This work includes sample collection and analysis for organic contaminants and EPFRs, traditional batch sorption/desorption experiment, photodegradation experiment, and column study. The research group will focus on the area of Yunnan-Kweichow Plateau, where the oxisol contains abundant of iron and UV-light is strong. The primary investigator's previous work was focused on the environmental fate of organic contaminants and the applicants have conducted some preliminary studies in this area. All the instruments needed in this study are conveniently available. This study will establish a fundamental database for EPFRs environmental risk assessment and provide further information to understand the extended health risks of organic contaminants.

有机污染物在与固体颗粒的反应过程中产生自由基，这些自由基因为与固体颗粒相互作用而被稳定下来，寿命变长，称为环境可持续性自由基（EPFRs）。这类物质在环境中普遍存在，并且比原始有机物有更高的环境风险，因此，对EPFRs产生机制和行为规律的认识刻不容缓。本研究组前期结果证实，红土高原地区富铝土中过渡金属元素铁元素含量丰富，在紫外线照射下，可与有机污染物相互作用，广泛产生EPFRs。因此，本研究拟从典型有机污染区域的调查开始，研究EPFRs在富铝土中的产生、分布特征与土壤特性之间的关系；在实验室模拟的受控条件下研究氯酚类有机污染物与固体颗粒相互作用中，EPFRs的产生机制、寿命变化和迁移特征，及其受环境地球化学条件的影响。拟探明吸附、降解以及EPFRs产生各过程在氯酚类有机污染物环境行为中的贡献，为系统认识EPFRs环境风险提供重要的基础数据，并为有机污染物的生态与健康风险研究提供新的思路。

经过四年的持续研究，基本上实现了预期的科研目标，并在此基础上，针对发现的新问题，将研究内容进行了有效扩展；因此，在保证项目完成的前提下，也体现了科学研究中发现新问题、解决问题的思路。本项目执行中重点解决的问题包括：有机污染物与富铝土相互作用中，吸附过程和降解过程各自所占的比例，及其受环境条件的影响，重点关注不同环境条件下（紫外光照、不同气体氛围等），氧化铁－有机污染物相互作用过程中EPFRs生成及其对有机污染物降解的影响，天然有机质的存在对EPFRs生成及其对有机污染物降解的环境功效，为理解EPFRs的环境行为及风险评估提供基础数据。.在本项目的支持下，发表学术论文17篇，其中以第一及通讯作者发表二区及以上SCI论文13篇。本研究的主要结果为：.1. 邻苯二酚在紫外光照或无光照的自然条件下能与过渡金属铁和铜相互作用而广泛生成EPFRs。电子由邻苯二酚转移至铁和铜，形成的自由基与还原的铁和铜结合而稳定。.2. 在干燥条件下，EPFRs的生成能降低赤铁矿/氧化铜-二氧化硅表面上邻苯二酚的降解，在低浓度尤为明显。稳定自由基在赤铁矿/氧化铜-二氧化硅表面的生成阻碍了其进一步降解；邻苯二酚相关的EPFRs在溶剂萃取过程中可能转化回原始的CT。但是在富氧条件下，Fe(III)/Fe(II) 循环能促进邻苯二酚的降解。.3. 水分的加入会增加赤铁矿-二氧化硅表面上邻苯二酚的降解，EPFRs在水相条件下产生ROS是导致其降解增加的原因。.4.单宁酸和富马酸（天然有机质模型化合物）对于邻苯二酚在二氧化硅-赤铁矿表面降解及其自由基信号特征存在不同的影响，反映出天然有机质作为一种有机质集合，具有复杂的结构和不同性质的官能团，其对土壤中有机污染物的降解和自由基生成的影响较为复杂，需要综合分析和更深层次的研究。.本研究结果表明，EPFRs的形成在环境中广泛存在，并且是有机化合物环境归趋的重要组成之一，忽略该过程可能导致对有机污染物环境行为和风险理解的偏差。迫切需要后续研究对EPFRs产生的机制、受环境条件的影响以及行为和风险进行更加系统深入理解。