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- Title
Key Factors Determining the Formation of Sulfate Aerosols Through Multiphase Chemistry—A Kinetic Modeling Study Based on Beijing Conditions.
- Authors
Wang, Tao; Liu, Yangyang; Zhou, Shengqian; Wang, Guochen; Liu, Xiansheng; Wang, Longqian; Fu, Hongbo; Chen, Jianmin; Zhang, Liwu
- Abstract
Severe haze in Beijing is characterized by the rapid formation of sulfate via the multiphase oxidation of SO2. While many factors, including aerosol oxidants and atmospheric variables, were discovered and investigated, their relative importance remains unclear. Herein, based on the field observation data obtained in Beijing, China, we developed a kinetic model to explore the key factors that determine the multiphase formation of sulfate. Sensitivity tests give the kinetics of each oxidation pathway varying with pH and temperature, based on which the total sulfate formation rate at room temperature (298 K) is calculated to be generally greater than that at standard temperature (273 K), especially during nighttime. Interfacial oxidants are responsible for sulfate formation within a wide pH range, and transition metal ions become more efficient with increased temperature. The multiphase chemistry is additionally affected by aerosol liquid water content (ALWC), particle radius (Rp), and ionic strength (IS). Within the usual aerosol acidity, the kinetic discrepancy induced by different ALWC levels is more significant at the lower temperature, in contrast to the temperature dependence related to Rp, and the effect of IS depends highly on pH. Machine learning reveals the potential importance of temperature, acidity, and Rp. Temperature and acidity are impactful for the formation of both aqueous and interfacial sulfates, whereas Rp only affects the interfacial processes. The discrepancy between nighttime and daytime is considered throughout this study. Overall, this study reveals the key factors for multiphase sulfate formation and is recommended for kinetic evaluation in future laboratory research. Plain Language Summary: Sulfate is an important constituent in the atmospheric aerosol community because it facilitates haze formation and affects public health. In the past years, scientists reproduced the multiphase oxidation of sulfur dioxide in the laboratory, as an attempt to explain the secondary sulfate burst. However, we should note that the sulfate formation rate calculated by the parameters derived from the experiments performed under room temperature (∼298 K) was normally compared with the kinetics estimated under standard temperature (∼273 K). Furthermore, other atmospheric variables besides temperature, including aerosol liquid water content, particle radius, and ionic strength, were normally set as constant rather than adjusted by experimental conditions. To solve the uncertainties, we developed a kinetic model by incorporating the documented multiphase sulfate formation pathways. Based on this model, researchers can evaluate the previously documented or newly discovered sulfate formation pathways in a more reasonable way. The developed kinetic model, and its improved versions in the following, are recommended for future laboratory works to reveal the key factors, including aerosol oxidants and atmospheric variables, that determine the multiphase formation of sulfate aerosols. Key Points: This work develops a kinetic model to reveal the key factors determining the multiphase formation of sulfate under Beijing conditionsResults emphasize the importance of transition metal ions, serving as both aqueous and interfacial catalystsTemperature, acidity, and particle radius could be key variables influencing the multiphase sulfate formation
- Subjects
BEIJING (China); SULFATE aerosols; TRANSITION metal ions; ATMOSPHERIC aerosols; IONIC strength; OXIDATION kinetics
- Publication
Journal of Geophysical Research. Atmospheres, 2023, Vol 128, Issue 20, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2022JD038382