大气复合污染形成过程中的多相反应机制研究

With the rapid development of economy, the air pollution complex in Beijing-Tianjin-Hebei urban agglomeration is increasingly serious, for example, haze events occur frequently. Recent researches have shown that second particles play an important role in the haze formation, and multiphase chemical reactions are one of the main driving forces of the explosive growth of the secondary particles. However, the physicochemical processes of pollutants during the haze evolution, the migration and transformation rules among different phases as well as the mechanisms of the gas-liquid-solid multiphase reactions remain largely unknown. Moreover, it is not characterized reasonably in the numerical model during the processes of multiphase reactions, including the formation and removal mechanisms of the oxidants and their precursors as well as the influence of changes in physical and chemical properties of aerosols. Therefore, according to the situation of the coal-motor vehicle exhaust coexist pollution in our country, we devote to understand and illuminate the kinetics and mechanism of multiphase reaction at a molecular level. The core steps and mechanisms of the formation of haze and air pollution complex are expected to be identified and clarified, the key kinetics parameters will be determined as well. Furthermore, the synergistic effect of a variety of pollutants under different environmental conditions will be analyzed, and the effect of multiphase transformation process for key atmospheric pollutants on the size, number concentration, chemical composition and physicochemical properties of fine particles will be explored, also, the numerical characterization scheme based on multiphase reaction mechanisms of our country will be developed.

随着经济的不断发展，我国京津冀城市群大气复合污染的态势日益严峻，突出表现在灰霾现象频发。研究表明二次颗粒物对灰霾形成具有重要贡献，多相化学反应是二次颗粒物爆发性增长的主要驱动力之一。然而灰霾形成过程中污染物的多相过程、相间迁移转化规律以及多相反应机制还很不清楚。多相化学过程中氧化剂及其前体物的生消机制，以及气溶胶理化特性变化对多相化学过程的影响还未在数值模式中合理表征。因此，本项目拟针对我国燃煤型-机动车尾气型共存的复合污染现状，从分子水平上理解和阐明多相过程的反应动力学和机理，识别灰霾及大气复合污染形成机制的核心步骤，确定关键反应动力学参数，解析不同环境条件下多种污染物的协同效应，探索大气关键污染物的多相转化过程对灰霾形成过程中的细颗粒物粒径、数浓度、化学组分、理化特性等的影响，并发展基于我国多相反应新机制的数值表征方案。

本项目针对多相化学转化过程在区域大气复合污染以及灰霾形成中的作用，应用多种手段开展二次颗粒物多相形成过程的研究，获得一系列动力学参数，为模式模拟提供关键数据，并发现新的形成机制，为外场实际现象提供解释。应用光腔衰荡光谱测量苯系物产生SOA的光学性质。首次定量给出非均相反应和低聚物对于SOA复折射率和消光效率的影响。这些结果对评估SOA对城市地区灰霾爆发性增长和全球辐射平衡的影响具有重要的意义。应用吸湿性串级微分电迁移率分析仪系统对硫酸铵与生物质燃烧释放的水溶性有机组分以及水溶性有机酸对硝酸盐吸湿性的影响研究。对于了解具有代表性的有机物和有机-无机气溶胶混合颗粒的吸湿性和对大气环境的影响有着重要作用。发展大气多相化学机制的数值表征方案，开展不同机制的三维数值模拟研究，将实验室获得的机制和参数化方案应用并改进模型，量化不同气象条件下新机制对我国区域灰霾的影响。本项目从分子层面解析重要气态前体物多相转化过程的关键过程，加深理解灰霾颗粒物相关物化性质在大气环境中的演变以及由此引发的环境效应，为掌握多相过程对灰霾形成贡献的评估提供科学基础。发表SCI论文29篇，培养博士生8名、硕士生1名，已经毕业的博士生6名、硕士生1名，圆满完成了预定任务。