兰州地区大气自由基测量与研究

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. High concentration ultrafine particles affect the human health, ecological system and so on seriously. Free radicals are the core driver of the atmospheric oxidation capacity and the generation of ultrafine particles e.g. particulate matter 2.5 (PM 2.5). Free radicals are also the key to the temporal and spatial variation of atmospheric chemical constituents. The investigations of the sensitive detection of the atmospheric free radicals, the interaction relationships between free radicals and ultrafine particles, are therefore 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. The research for the detection of atmospheric free radicals by liquid chromatography tandem mass spectrometry will be carried out. A novel free radical reaction combined with liquid chromatography electrospray ionization tandem mass spectrometry method will be developed for the detection of atmospheric free radicals. The multiple reaction monitoring modes with soft ionization source will be used to determination atmospheric free radicals. The structures of the atmospheric free radicals will be identified using tandem mass spectrometry. The atmosphere in Lanzhou, China will be selected as an object of study for the detection of atmospheric free radicals in external field. The temporal and spatial variation, distributional characteristics and influencing factor of the atmospheric free radicals’ concentrations and structures will be studied. The relationships between the atmospheric free radicals’ concentrations and structures with the PM 2.5 concentration, with the PM 10 concentration, and with the Air Quality Index (AQI) will also be analyzed, respectively. New scientific data for the generation of ultrafine particulate contaminants e.g. generation of atmospheric haze caused by atmospheric free radicals will be investigated.

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的特点，高浓度超细颗粒物对人体健康，生态系统等产生重大影响。自由基是大气氧化性和PM2.5等超细颗粒物生成的核心驱动力，是大气成分时空演化的关键。因此，研究大气自由基高灵敏度探测，自由基与超细颗粒污染物形成关系，对深入理解光化学烟雾、雾霾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，开展大气自由基液质联用高灵敏度探测技术研究，建立自由基反应体系与液质联用系统的耦合技术及关键前体物和加合物的监测方法，软电离多反应监测同时定量多种类型自由基含量，多级质谱解析自由基分子结构；开展兰州地区大气样本外场实测工作，研究自由基浓度和结构类型的时空变化与分布特征及影响因素，进行自由基类型及含量与PM2.5、PM10含量及AQI指数间的关系研究，为探讨自由基驱动雾霾等超细颗粒污染物形成机制提供科学数据。

本研究以氧化性强、能见度低的区域大气为对象，以自由基化学及其氧化加合物形成的化学机制为核心，开展大气自由基液质光谱联用高灵敏度探测技术研究，建立了自由基反应体系与液质联用光谱系统的耦合技术及关键前体物和加合物的监测方法，软电离多反应监测MRM/FL模式同时定量多种类型自由基含量，依据多级质谱裂解机理和裂解途径解析确认自由基分子结构，发现新结构类型自由基；开展了兰州地区大气样本外场实测工作，进行自由基浓度和结构类型的时空变化与分布特征及影响因素，大气自由基与PM2.5、PM10含量及AQI指数间的关系研究，为探讨自由基驱动雾霾等超细颗粒污染物形成机制提供科学数据。大气自由基高灵敏度探测研究，自由基与细颗粒污染物形成关系，对深入理解光化学烟雾、雾霾等问题具有十分重要的意义。主要取得如下三方面研究进展：1. 建立自由基反应体系筛选调控与液质联用及光谱系统耦合技术，在建立自由基反应活性分子数据库的基础上，筛选适宜的活性分子体系，实现在活性体系中加速大气自由基与活性分子间的电子转移速率，并消除或削弱基质扰动干扰，实现自由基反应体系与液质联用及光谱系统的耦合，使复杂大气环境体系中的微观自由基信号直观并放大的反映在谱峰上。2. 筛选建立定量离子对（母离子--子离子离子对）实现高灵敏高精确的定量模式，使活性高、寿命短的痕量自由基得到准确的结构指认和精确的含量分析。通过积分谱峰面积计算有效跟踪自由基的含量波动变化，依据裂解机理和裂解途径解析与分子加合机制解析确认区域大气环境中自由基的分子结构。3. 兰州地区大气自由基波动变化与PM2.5和PM10及AQI指数关系研究中发现不同地域、不同时段、不同天气情况自由基结构类型含量变化呈现西（西固）高东（东岗）低，并存在累积增长效应。区域自由基的迁移转化受臭氧影响显著，区域PM2.5和PM10含量变化在静稳环境气象条件下与自由基的波动变化存在延时正向相关，在此区域内AQI指数变化趋势主要受PM10含量变化影响。