Raman Measurement of Uptake Coefficient for Heterogeneous SO2 Reactions Catalyzed by Transition Metal Ions on the Surface of Atmospheric Fine Particulate Matter
CAO Xue1, SUN Jiu-yi1, WANG Cai-li2, LI Ke-shu3, CAI Hua2
1. Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
2. Institute of Special Glass Fiber and Optoelectronic Functional Materials, China Building Materials Academy Co., Ltd., Beijing 100024, China
3. XYZ Storage Technology Co., Ltd., Beijing 102400, China
Abstract：Fine particulate matter (PM2.5) pollution was mainly caused by micron and submicron aerosol particles or micro-droplets generated by human activities. Still, the formation mechanism remains unclear, and corresponding effective solutions are lacking. The precise prevention and control of urban PM2.5 pollution in China depends on our in-depth understanding of the formation mechanism of secondary aerosols. The current bottleneck and difficulty lie in the fact that aerosols' key physicochemical parameters (such as uptake coefficients) and their precursors still cannot be accurately measured. This will greatly limit our understanding of the evolution laws, such as the formation, rapid growth, and collision recombination of secondary aerosols. Therefore, to understand the formation mechanism of atmospheric particulate matter, it is necessary to accurately measure the key physicochemical parameters in the evolution process of fine particulate matter. Sulfate was an important component of PM2.5 in the atmosphere of China. However, the current chemical models underestimate the sulfate concentration in PM2.5 haze pollution events. There were still many uncertainties regarding the surface oxidation process of SO2 in aerosol droplets and the catalytic process of transition metal ions(TMI) in droplets, indicating that our understanding of the transformation mechanism of SO2 in the atmosphere was still insufficient. Obtaining the kinetic data of sulfate secondary transformation, determining the rapid growth mechanism of secondary inorganic aerosols, and accurately determining the uptake reaction rate of trace gases in the atmosphere on the surface of particulate matter were the key parameters for quantitative analysis of atmospheric heterogeneous reactions. This study employed a laser confocal micro-Raman spectrometer to measure the kinetics of SO2 oxidation catalyzed by Fe(Ⅲ) in ammonium chloride droplets. Based on the temporal variation of the spontaneous Raman signal of SO2-4, we established an accurate method for measuring the uptake coefficient of SO2 in heterogeneous reactions with a single droplet. We investigated the reaction kinetics between trace SO2 gas and a single droplet under external field conditions. This method validated the surface kinetic processes, and determined the reaction uptake coefficient.
Key words：Uptake coefficient; Surface reaction; Heterogeneous reaction process
曹 雪，孙久乂，王彩丽，李可舒，蔡 华. 拉曼测量大气细颗粒物表面过渡金属离子催化的SO2非均相反应摄取系数[J]. 光谱学与光谱分析, 2025, 45(07): 2087-2092.
CAO Xue, SUN Jiu-yi, WANG Cai-li, LI Ke-shu, CAI Hua. Raman Measurement of Uptake Coefficient for Heterogeneous SO2 Reactions Catalyzed by Transition Metal Ions on the Surface of Atmospheric Fine Particulate Matter. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(07): 2087-2092.
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