二次细颗粒物对我国灰霾的形成具有重要贡献，而二次细颗粒物的产生与大气氧化过程紧密相关。本项目围绕活性卤素化合物的反应机制及其对大气氧化性和二次污染物的影响开展一系列研究，包括结合外场观测、实验室研究和模式模拟三个方面。采用化学电离质谱等手段获取实际大气中活性卤素分布特征与转化规律；结合烟雾箱及多种气相颗粒相检测设备开展活性卤素的光化学反应研究；建立和优化气溶胶流动管实验技术，用于研究N2O5和ClONO2与代表性大气颗粒物的非均相化学反应；获取气相光氧化过程中关键化学过程的动力学参数，二次颗粒物的生成产率及其物化特性，活性卤素化合物（以ClNO2、Cl2为代表）的产率、生成速率等关键参数，并在此基础上，结合模式模拟将外场观测数据及实验室研究结果参数化，建立完备的参数化方案供大气化学数值模式使用，从而为系统评估大气活性卤素化合物对大气氧化性和二次污染物的影响提供科学依据。

The secondary fine particles have an important contribution to the formation of haze in China, and the secondary fine particles are closely related to the atmospheric oxidation processes. This project will focus on the reaction mechanism of reactive halogen species (RHS) and their effects on atmospheric oxidation and secondary pollutants, including three aspects: field observation, laboratory research and model simulation.The concentration distribution of reactive halogens species was measured by chemical ionization mass spectrometry. The experimental study on the photochemical reactions of reactive halogens was carried out in smog chamber and various gas phase and particle phase detection equipments. The experimental technique of aerosol flow tube was established and optimized to study the heterogeous reaction of N2O5 and ClONO2 with the typical atmospheric particles. Furtheremore, the kinetic parameters, the yield and the physicochemical properties of reactive halogen compounds (ClNO2, Cl2 as the representative) and secondary organic aerosol in the process of gas phase photooxidation are obtained. On this basis, combined with the model simulation of field observations and laboratory research results of parameterization, we will establish a complete parameterization program for atmospheric chemical model to evaluate the effect of atmospheric reactive halogen species on atmospheric oxidation and secondary pollutants.The research is not only a challenging frontier problem in the field of atmospheric chemistry, but also can provide basic data for improving the air quality and alleviating the haze, and has important scientific significance and practical significance.