State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Key Laboratory of Cluster Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
J Environ Sci (China). 2025 Feb;148:489-501. doi: 10.1016/j.jes.2023.09.010. Epub 2023 Sep 15.
The chemistry of sulfur cycle contributes significantly to the atmospheric nucleation process, which is the first step of new particle formation (NPF). In the present study, cycloaddition reaction mechanism of sulfur trioxide (SO) to hydrogen sulfide (HS) which is a typical air pollutant and toxic gas detrimental to the environment were comprehensively investigate through theoretical calculations and Atmospheric Cluster Dynamic Code simulations. Gas-phase stability and nucleation potential of the product thiosulfuric acid (HSO, TSA) were further analyzed to evaluate its atmospheric impact. Without any catalysts, the HS + SO reaction is infeasible with a barrier of 24.2 kcal/mol. Atmospheric nucleation precursors formic acid (FA), sulfuric acid (SA), and water (HO) could effectively lower the reaction barriers as catalysts, even to a barrierless reaction with the efficiency of cis-SA > trans-FA > trans-SA > HO. Subsequently, the gas-phase stability of TSA was investigated. A hydrolysis reaction barrier of up to 61.4 kcal/mol alone with an endothermic isomerization reaction barrier of 5.1 kcal/mol under the catalytic effect of SA demonstrates the sufficient stability of TSA. Furthermore, topological and kinetic analysis were conducted to determine the nucleation potential of TSA. Atmospheric clusters formed by TSA and atmospheric nucleation precursors (SA, ammonia NH, and dimethylamine DMA) were thermodynamically stable. Moreover, the gradually decreasing evaporation coefficients for TSA-base clusters, particularly for TSA-DMA, suggests that TSA may participate in NPF where the concentration of base molecules are relatively higher. The present new reaction mechanism may contributes to a better understanding of atmospheric sulfur cycle and NPF.
硫循环的化学过程对大气成核过程有重要贡献，而大气成核过程是新粒子形成（NPF）的第一步。在本研究中，通过理论计算和大气团簇动力学代码模拟，全面研究了三氧化硫（SO）与硫化氢（HS）的环加成反应机制，HS 是一种典型的空气污染物和有毒气体，对环境有害。进一步分析了产物硫代硫酸（HSO，TSA）的气相稳定性和成核潜力，以评估其对大气的影响。在没有任何催化剂的情况下，HS + SO 反应由于 24.2 kcal/mol 的能垒而不可行。大气成核前体甲酸（FA）、硫酸（SA）和水（HO）可以作为催化剂有效地降低反应能垒，甚至可以使反应无阻碍，其效率为 cis-SA > trans-FA > trans-SA > HO。随后，研究了 TSA 的气相稳定性。单独的水解反应能垒高达 61.4 kcal/mol，在 SA 的催化作用下，异构化反应能垒为 5.1 kcal/mol，表明 TSA 具有足够的稳定性。此外，还进行了拓扑和动力学分析，以确定 TSA 的成核潜力。在 TS 和大气成核前体（SA、氨 NH 和二甲胺 DMA）形成的大气团簇中，TSA 是热力学稳定的。此外，TSA-碱基团簇的蒸发系数逐渐减小，特别是 TSA-DMA，这表明 TSA 可能参与 NPF，在 NPF 中碱基分子的浓度相对较高。本新反应机制可能有助于更好地理解大气硫循环和 NPF。
