水体颗粒态NOM中环境持久性自由基的形成及对典型有机污染物光解的影响机制研究

Environmentally persistent free radicals (EPFRs) are a class of emerging organic pollutants with strong biological toxicity. Compared to traditional free radicals, EPFRs have longer lifetime up to several hours or even more. EPFRs were firstly found in the combustion-generated particles in 2008, and then they were successively detected in various environment matrices including airborne PM2.5, soils and sediment, et al. At present, the studies about the formation of EPFRs in environment, their sources and environmental behavior have aroused people’s attention. .Halogenated phenols (HPs) are ubiquitous in the natural water due to wide use in various industrial products such as dyes, pulp, paints, polymer intermediates, flame retardants, herbicides and wood preservatives. Only in 2001, the global production of 2,4,6-tribromophenol alone reached 9500 tons. The high concentrations of HPs in the natural water have been reported and are up to μg/L. Since these HPs are able to generate phenoxyl radicals under UV irradiation, HPs are one of the important precursors for the formation of EPFRs. Natural organic matter (NOM) widely exists in water as an important component in the global carbon cycle. NOM mainly includes humic substances with strong adsorption property. Previous studies have proved that NOM is capable of adsorbing HPs and different metal ions in the natural water, which provide favorable conditions to the formation of EPFRs. Therefore it is necessary to explore if under UV irradiation, the HPs adsorbed by NOM are able to convert into EPFRs in water..In this study, we choose NOM and HPs as model compounds, and systematically investigate the formation of EPFRs from HPs adsorbed by NOM in the aqueous solution and their influences on photodegradation of the typical organic pollutants in the natural water. The main research work is listed below: .(1).Study the adsorption of NOM to HPs (2-MCP, 4-MCP, 2,4-DCP, 2,6-DCP, 2,4,6-TCP, PCP, 2,4-DBP and 2,4,6-TBP) and to transition metal ions (Fe3+、Cu2+、Mn2+and Zn2+);.(2).Set up the analytical methods of EPFRs by electron paramagnetic resonance technique (EPR), which includes qualitative and quantitative methods;.(3).Study the formation rules of EPFRs at different metal ions/ from different HP precursors. By EPR analysis, obtain the characteristic parameters of EPFRs including g factor, hyperfine splitting constant α, line width△Hpp, spin/g and DI/N, determine the structure and content of EPFRs in NOM, and then explain the formation rules of EPFRs on NOM;.(4).Study influences of environmental factors (pH, Cl-, NO2-, et al) on formation of EPFRs from HPs on NOM;.(5).Study effects of EPFRs on photodegradation of typical organic pollutants (OPs) in water. By determining the degradation products of OPs by GC-MS/HPLC-MS/MS and EPFRs/possible formed active free radicals by EPR, study the influence mechanism of EPRFs on photodegradation of OPs. .Taken together, these findings are important, and they will facilitate the thorough understanding of EPFRs sources in the environment and be helpful to their environmental risk evalution and management.

环境持久性自由基(EPFRs)是一类新兴污染物，具有很强的生物危害性。自08年在燃烧颗粒中被发现以来，已在多种环境介质中检出。目前有关EPFRs来源及环境行为研究已引起人们的关注。本项目拟以水体中存在的天然有机质(NOM)和卤代苯酚(HPs)为研究对象，系统开展水体颗粒态NOM中HPs光致生成EPFRs的研究。通过采集天然样品、实验室模拟，研究NOM对HPs、过渡金属离子的吸附，探讨不同金属作用下，HPs形成EPFRs的分子结构-反应活性规律，结合EPR对EPFRs定性参数(g因子，△Hpp等)及含量测定，揭示水体颗粒态NOM中EPFRs的形成机理。在此基础上，开展该类EPFRs作用下水中典型有机污染物(OPs)的光解研究。通过探讨EPFRs对OPs光解动力学及产物分布的影响，阐明EPFRs对水中典型OPs光解的影响机制。本研究对揭示环境中EPFRs的来源途径及其生态风险评价具有重要意义。

环境持久性自由基（EPFRs）是一类能够长时间存在于颗粒物表面及内部的有机自由基，具有很高的生物危害性和反应活性。目前有关EPFRs的来源及环境行为研究已经引起了人们的广泛关注。本项目以水体中存在的颗粒态有机质（NOM）为研究对象，利用实地采集和实验室可控模拟，系统开展了颗粒态NOM中EPFRs的光形成机制研究，并在此基础上探究了该类EPFRs对水中典型有机污染物（双酚A等）的光降解影响。研究发现：（1）蒙脱土-腐殖酸（Mnt-HA）复合体系在光照条件下能够生成EPFRs。过渡金属对该体系EPFRs的形成起到了抑制作用，这一作用与不同金属的氧化还原电位有关，而卤代苯酚类前驱体物质起到了一定的促进作用，不同取代基个数和不同取代卤素能够影响体系中EPFRs的生成。（2）蒙脱土-卤代苯酚（HPs）复合体系中的卤代苯酚类物质在光照条件下能够激发形成顺磁性前驱体物质，典型的水环境因子（pH值、NO2-和Fe3+）能够影响顺磁性前驱体形成从而进一步影响复合体系中EPFRs的生成。（3）在实际颗粒态NOM和实验室模拟NOM参与下，水体中的有机前驱体物质在发生光化学转化过程能够与颗粒态NOM发生相互作用从而形成EPFRs，这是水体颗粒态NOM中除腐殖质物质形成EPFRs外的又一来源，同时揭示了该过程中EPFRs的光形成机制。（4）颗粒态NOM对水体中磷酸三甲苯酯光降解起到了抑制作用，对双酚A光降解起到了促进作用，这可能与EPFRs诱导生成的活性氧物种有关。不同水环境因子（无机盐离子、pH值等）的参与同样能够进一步影响有机污染物的光降解。本项目的研究结果对揭示环境中EPFRs的天然来源途径及其生态风险评价具有重要意义。