Yu Chen, Liu Tengyu, Chi Xuguang, Huang Xin, Ding Aijun
Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China.
National Observation and Research Station for Atmospheric Processes and Environmental Change in Yangtze River Delta, Nanjing 210023, China.
Environ Sci Technol. 2025 Aug 5;59(30):15900-15906. doi: 10.1021/acs.est.5c06148. Epub 2025 Jul 24.
Hydroxymethanesulfonate (HMS) is an important reservoir of particulate sulfur, especially during winter haze episodes. However, the kinetics and mechanisms of HMS formation in aqueous aerosols remain poorly understood. In this study, we investigated the kinetics of the multiphase reaction between sulfur dioxide (SO) and formaldehyde (HCHO) in aqueous ammonium nitrate aerosol particles buffered by gas-phase NH at pH of 4.6 to 5.1 via well-controlled flow tube experiments. We found that high ionic strength inhibits the HMS formation rate in aqueous aerosol particles by up to a factor of 10 compared to that in dilute bulk solutions. Using the new kinetic parameters predicts a negligible formation rate of HMS in aerosol water relative to that in cloud/fog water for typical winter haze conditions in the North China Plain. Our results suggest that atmospheric models should consider the effects of ionic strength on the HMS formation rate in aqueous aerosol particles to better describe the HMS chemistry and evaluate its impact on air quality.
羟甲磺酸盐（HMS）是颗粒态硫的一个重要储存库，尤其是在冬季雾霾期间。然而，关于HMS在水性气溶胶中形成的动力学和机制仍知之甚少。在本研究中，我们通过控制良好的流动管实验，研究了在pH值为4.6至5.1的气相NH缓冲的硝酸铵气溶胶颗粒中，二氧化硫（SO）与甲醛（HCHO）之间的多相反应动力学。我们发现，与稀溶液相比，高离子强度可使水性气溶胶颗粒中HMS的形成速率降低多达10倍。使用新的动力学参数预测，对于华北平原典型的冬季雾霾条件，气溶胶水中HMS的形成速率相对于云/雾水中可忽略不计。我们的结果表明，大气模型应考虑离子强度对水性气溶胶颗粒中HMS形成速率的影响，以便更好地描述HMS化学过程并评估其对空气质量的影响。
