硫酸盐是大气气溶胶重要无机组分，对华北平原重霾有重要贡献。已有研究提出，高浓度NH3能够中和气溶胶酸性，促进NO2参与的非均相反应和硫酸盐二次生成。但因缺乏直接定量研究，气溶胶酸度如何影响该反应途径仍存在争议。申请人前期做了实验室调节气溶胶酸度方法探索。本研究拟采用激光共聚焦显微拉曼光谱，针对NO2+O2+SO2+NH3单颗粒反应体系开展硫酸盐生成动力学的实验室模拟。通过在线追踪硫酸盐生成速率，实测SO2的反应摄取系数；通过调节NH3浓度改变气溶胶酸度，并依据SO42-/HSO4-离子对的拉曼信号，在线标定气溶胶酸度；进一步结合温湿度和反应气体浓度的控制条件实验，综合分析硫酸盐二次生成速率与气溶胶酸度、相对湿度、NO2和SO2浓度之间的定量关系。拉曼光谱反应体系提供了非均相反应速率定量技术和有效的气溶胶pH在线测量能力；两者结合，有望为硫酸盐生成机理提供进一步科学认识和更准确的参数化方案。

Sulfate is an important inorganic component of aerosols with significant contribution to the development of severe haze in the North China Plain. Previous studies have suggested that high concentration of NH3 can neutralize aerosol acidity, and thus accelerate sulfate formation by promoting the NO2-mediated heterogenous reaction pathway. Due to lack of direct quantitative research, the influence of aerosol acidity on the sulfate formation pathway is still controversial. We have made pre-experiment on the method of adjusting aerosol acidity. In this study, we use the laser confocal micro-Raman spectroscopy to measure the kinetics of sulfate formation in the single-particle reaction system of NO2+O2+SO2+NH3. Firstly, the reaction uptake coefficient of SO2 is measured by tracking sulfate formation rate online. Secondly, the aerosol acidity is adjusted by concentration of NH3 and determined by the Raman signal of sulfate/bisulfate ion pair. Finally, the relationship between the secondary sulfate formation rate and aerosol acidity, relative humidity, NO2 and SO2 concentration is investigated by condition experiments. The laser confocal micro-Raman spectroscopy system provides a quantification technique of heterogeneous reaction rate and an effective on-line measurement capability of aerosol pH. The combination of the two is expected to provide further scientific understanding of the sulfate formation mechanism and more accurate parameterization scheme for modeling.