重污染天气细颗粒物表/界面多相反应与老化机制研究

Second species are important components of fine particles, which have important contributions to the foramtion of heavy pollution weather. This project will focus on the key questions about model simulation inacuracies for fine particle of atmosphere pollution complex in China, and understand deeply the new mechanisms of formation and ageing of second particles. Depending on the photochemical smog chamber of gas-liquid interface, coupling with online PTR-Tof-MS, GALIF, and DRIFT techniques, to gain accurately kinetic characteristics, to identify active intermediates possibly involved in this process, and to conclude the formation and age mechanisms of main second fine particles. On this basis, coupling with the field-measurements on the Yangtze River Delta (YRD) region, to evaluate preliminarily the potential capability of second fine particle formation via multi-phase reactions on the surface of the particles, and regional climate effect of aerosols. This study is situated at the challenging academic frontier in the field of international atmospheric chemistry, and is also an important fundamental scientific question to get breakthroughs in scientific and effective control of heavy pollution days. The smooth implementation of this project is helpful to develop the new air quality model suited to the situation of China, and has great scientific significance to research formation causes of regional complex pollutions of atmosphere.

二次组分是细粒子的重要成分，对重污染天气的形成具有重要贡献。本项目针对我国大气复合污染细颗粒物模式模拟不准确这一关键科学问题，开展气溶胶表/界面多相反应研究，深入理解重污染环境下二次细粒子生成和老化新机制。以气-液界面光化学烟雾箱为依托，结合质子转移反应飞行时间质谱（PTR-Tof-MS）、掠射角激光诱导荧光技术（GALIF）及原位傅立叶漫反射（DRIFTS）等技术，准确获取典型颗粒物表面、关键气-液界面反应动力学参数，辨别活性中间物种，推测主要二次细粒子生成及老化机制。在此基础上，结合长三角外场观测，探索颗粒物表/界面多相反应生成二次细粒子的潜势及区域气候效应。该研究即是国际大气化学领域具有挑战性的学术前沿，又是我国重污染天气科学有效控制工作取得突破的重要基础性科学问题。本项目的顺利实施有助于发展适合我国国情的空气质量数值新模式，对于研究区域大气复合污染成因具有重要的科学意义。

我国大气雾霾污染具有高湿度、强氧化性及成分复杂的特征. 颗粒物表/界面的非均相反应对大气氧化性及二次细粒子的形成具有重要贡献。本项目在实验室模拟结合外场观测研究了高湿度环境下的气-液界面、细颗粒物表面二次细粒子的生成过程、反应机理及动力学特征。发现了高湿度雾霾污染大气，硝酸盐液滴在有机物作用下可以光分解释放亚硝酸（HONO）、NO2等活性物种，共存的脂肪酸能够被分解成活泼的含氧挥发性有机物，并有进一步形成二次有机气溶胶的潜势；发现云雾过程能够改变矿尘颗粒表面铁形态，增加活泼铁的比例，从而促进SO2等关键污染气体向二次硫酸盐的转化；发现了NH3共存条件下，促进了SO2,NOx等前体物在矿物颗粒表面的消耗；外场观测表明，城市雾霾重污染期间HONO的浓度高于清洁天气，与颗粒物表面的非均相反应密切相关，颗粒物表面非均相过程贡献了大气氧化能力的提高。本项目加深了我国重污染大气环境下非均相的反应机制的理解，接近真实大气反应情况下的动力学参数可以完善相关大气模式，也为我国重污染天气防控提供了理论依据。