兰州地区大气自由基与有机气溶胶源汇作用机制研究

The atmosphere made up of a large number of chemical constituents is a complex system in which physical and chemical reactions are constantly taking place. At the present stage, the atmosphere in China has displayed strong oxidizing property and poor visibility features. The sources, sinks, and cyclic process of atmospheric free radicals are the core driver of the atmospheric oxidation capacity and the generation of the secondary organic aerosols. Therefore, the investigations of the source-sink and active mechanism of the atmospheric free radicals and organic aerosols in typical range, the interaction relationships between free radicals and organic aerosol, are very important to understand the generation mechanisms of photochemical smog and atmospheric haze. The aims of the project are at the core of chemical mechanisms of free radical chemistry and free radical adducts formation. Moreover, there is little air speed, more calm weather, dense temperature inversion layer, and plenty of organic aerosol in Lanzhou city. The atmosphere in Lanzhou, China will be selected as an object of study for the detection of atmospheric free radicals in external field. The research for the detection of atmospheric free radicals and organic aerosols will be carried out. The multiple reaction monitoring modes with soft ionization source will be used to determination atmospheric free radicals, organic aerosols and the relationship of peak value between atmospheric free radicals and organic aerosols. The moleculor structures of the atmospheric free radicals, adducts and conjunctions will be identified and detected using tandem mass spectrometry. The temporal and spatial variation, distributional characteristics and influencing factor of the atmospheric free radicals and organic aerolsols will be studied. The sources, sinks, cyclic and ageing process will be investigated. The Sources-Sinks mechanism and the scientific data for the generation of organic aerosol particulate contaminants caused by atmospheric free radicals will be provided.

大气是多组分相互作用的复杂混合体，我国大气现阶段表现出强氧化性和低能见度特点。大气自由基是大气氧化性和二次有机气溶胶等形成的核心驱动力，自由基的源、汇和循环过程是理解有机气溶胶污染物形成和消除的关键。因此，研究区域环境中大气自由基与有机气溶胶的源汇机制，自由基及有机气溶胶与雾霾的形成关系，对深入理解光化学烟雾、雾霾等问题具有十分重要的意义。本课题以自由基化学及其氧化加合物形成的化学机制为核心，结合兰州地区风速小，静风天气多，冬季逆温层厚且有机气溶胶强度大的特点，开展兰州地区大气样本外场实测工作，研究软电离多反应监测测量自由基与气溶胶含量分布特征及相互间峰值关系；研究多级质谱解析自由基分子、加合物分子结构与气溶胶成分结构的对应关系；研究自由基与有机气溶胶的时空变化与分布特征，自由基与有机气溶胶的源、汇与循环机制及老化过程，为探讨自由基驱动有机气溶胶污染物形成机制及源汇途径提供科学数据。

本项研究工作基于兰州地区风速小，静风天气多，冬季逆温层厚且有机气溶胶强度大的特点，开展了兰州地区大气自由基和气溶胶外场实测工作，得到了自由基和有机气溶胶的含量分布特征。掌握了典型工业区域的自由基与有机气溶胶的相互间峰值关系。研究得出了自由基与有机气溶胶的时空变化与分布特征，自由基与有机气溶胶的源、汇与循环机制及老化过程。厘清了有机气溶胶反应形成过程的基元反应及相关网络关系，为探讨自由基驱动有机气溶胶污染物形成机制及源汇途径提供了重要的科学数据。研究建立了自由基与有机气溶胶结构解析及定性定量方法，完成对监测点空气样本的采集及定量分析研究。完成兰州地区空气样本的采集及自由基、有机气溶胶结构解析和含量的同时测定、光谱特性检测分析、有机碳氮检测分析、粒度分布分析，总体分析数据收集汇总。解析了空气样本中自由基与有机气溶胶结构类型，测定了自由基含量，分析了光谱特性，获得了粒度分布及综合分析数据收集汇总。研究了年度变化规律与变化趋势，解析了大气自由基和有机气溶胶形成机理，大气自由基与有机气溶胶的分子结构，厘清了自由基与有机气溶胶的相互机制，提出了可能的相互作用机理并进行了外场验证。获得了大气环境中自由基类型及含量与峰值分布与有机气溶胶闭合循环体系间的关系，解析得出区域大气环境中自由基与有机气溶胶的时空变化和分布特征，分析了自由基与有机气溶胶的源、汇和循环过程及影响因素。本项目研究对掌握自由基源汇和循环过程，理解二次有机气溶胶污染生成与氧化清除，区域光化学烟雾、雾霾等问题的深入剖析，自由基与二次有机气溶胶的源汇机制，自由基及二次有机气溶胶与雾霾的形成关系深入理解具有十分重要的意义。