State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Environ Sci Technol. 2023 Nov 21;57(46):17718-17726. doi: 10.1021/acs.est.2c09674. Epub 2023 Mar 15.
The heterogeneous oxidation of SO by NO has been extensively proposed as an important pathway of sulfate production during haze events in China. However, the kinetics and mechanism of oxidation of SO by NO on the surface of complex particles remain poorly understood. Here, we systematically explore the mechanism and kinetics of the reaction between SO and NO on diesel black carbon (DBC) under light irradiation. The experimental results prove that DBC photochemistry can not only significantly promote the heterogeneous reduction of NO to produce HONO via transferring photoinduced electrons but also indirectly promote OH radical formation. These reduction products of NO as well as NO itself greatly promote the heterogeneous oxidation of SO on DBC. NO oxidation, HONO oxidation, and the surface photo-oxidation process are proven to be three major surface oxidation pathways of SO. The kinetics results indicate that the surface photooxidation pathway accounts for the majority of the total SO uptake (∼63%), followed by the HONO oxidation pathway (∼27%) and direct oxidation by NO (∼10%). This work highlights the significant synergistic roles of DBC, NO, and light irradiation in enhancing the atmospheric oxidation capacity and promoting the heterogeneous formation of sulfate.
NO 对 SO 的非均相氧化已被广泛提出，是中国雾霾事件中硫酸盐生成的重要途径。然而，复杂颗粒表面上 SO 与 NO 的氧化动力学和机制仍不清楚。在本研究中，我们系统地探索了在光照下柴油机黑碳（DBC）表面上 SO 与 NO 之间的反应机制和动力学。实验结果证明，DBC 光化学不仅可以通过转移光致电子显著促进 NO 的非均相还原，产生 HONO，还可以间接促进 OH 自由基的形成。这些 NO 的还原产物以及 NO 本身大大促进了 SO 在 DBC 上的非均相氧化。NO 氧化、HONO 氧化和表面光氧化过程被证明是 SO 的三种主要表面氧化途径。动力学结果表明，表面光氧化途径占总 SO 吸收量的大部分（约 63%），其次是 HONO 氧化途径（约 27%）和 NO 的直接氧化（约 10%）。本工作强调了 DBC、NO 和光照在增强大气氧化能力和促进硫酸盐异相形成方面的显著协同作用。
