大气细颗粒物环境持久性自由基原位生成和稳定性的影响机制理论研究

Environmentally persistent free radicals (EPFRs) in airborne fine particulate matters (PM2.5) possess high stability and can persist in the atmospheric environment for days. Compared with the pristine fine particulate matters and the organic pollutants themselves, EPFRs are more readily to generate reactive oxygen species and cause organism damages, and thus raise enormous attentions nowadays. Owing to the unique air pollution characteristic in China, in situ formation of EPFRs in PM2.5 from primary aerosol components constitutes one of the most important sources of EPFRs in PM2.5 in China. However, the studies on in situ formation of EPFRs in PM2.5 are rather scarce, and the solution to the scientific issue as to how coexisting atmospheric components and environmental factors interfere with both EPFRs formation and stability cannot be readily achieved by other studies focusing on EPFRs in incineration and soil environment. Therefore, in this project, typical PM2.5 organic components such as chlorophenols and polycyclic aromatic hydrocarbon will be chosen as model compounds for precursors. The influence of typical environmental factors, such as humidity, temperature and coexistent chemical constituents, on the electronic and structural features of classical interfaces will be taken into consideration. Major efforts will be made to reveal the molecular mechanism of EPFR generation during the secondary aerosol formation process as well as the influencing factors which predominate EPFR formation and stability in PM2.5. By using the integrated approach based on quantum chemistry calculations and first-principle molecular dynamic simulations, the applicant believes that the theoretical results would provide valuable information of the key influencing factors to EPFR formation and stability and their interference mechanism . The progress made in the project not only may help understanding of in situ activation of chemicals in PM2.5, but also can provide theoretical support to the study on the health risk of atmospheric fine particulate matters.

大气细颗粒物中环境持久性自由基（EPFRs）因具有高稳定性，且比细颗粒和有机组分自身更易诱发机体氧化应激而引起人们的极大关注。我国特有的大气污染状况导致一次有机组分在细颗粒物界面原位生成EPFR成为中国大气细颗粒中EPFRs的重要来源之一。然而，大气细颗粒上原位EPFRs生成机制研究匮乏，其他相关研究不足以解答典型环境因素对于EPFRs原位形成和稳定性的影响机制。鉴于此，本项目选取氯酚等污染物分子为前体分子，充分考虑温度、共存化学组分等典型环境因素对细颗粒表面微结构的影响，重点关注一次颗粒形成二次颗粒过程中有机组分经界面反应转化为EPFRs的分子机制，通过量化计算和分子动力学模拟相结合的研究方法揭示大气细颗粒EPFRs生成反应历程和表面-自由基体系稳定性的关键影响因素。项目研究成果不仅能够促进大气细颗粒中化学组分原位活化机制的科学认识，而且可以为揭示细颗粒物污染健康危害提供数据和理论依据。

大气细颗粒物环境持久性自由基（Environmentally persistent free radicals, EPFRs）生成机制的研究相对匮乏，相关研究不足以回答典型环境因素对于EPFRs原位生成和稳定性的影响机制。本项目以计算化学手段研究了以苯酚、2-氯酚和邻苯二酚为代表的前体分子在氧化铜团簇模型表面生成表面负载自由基的分子历程，并考察了实际环境温度和湿度条件对于金属-自由基原位生成的影响，项目研究结果表明酚类前体物质可在实际环境温度条件下在氧化铜表面容易地生成表面负载自由基，而水分子可通过阻塞反应位点阻碍EPFRs的生成，即高湿度条件下不利于EPFRs的生成；项目基于构建的金属-自由基微观体系，进一步探讨了大气环境常见组分氧气对典型EPFR自身稳定性的影响，计算了热力学和动力学参数，建立了势能面剖面图，合理解释了自然大气环境EPFR的稳定机制。项目成果为深入理解大气细颗粒物中EPFR原位生成和稳定机制提供了理论依据。