School of Metallurgy, Northeastern University, Shenyang 110819, China.
Qingdao Key Laboratory for Prevention and Control of Atmospheric Pollution in Coastal Cities, Environment Research Institute, Shandong University, Qingdao 266237, China.
Environ Sci Technol. 2024 Sep 3;58(35):15722-15731. doi: 10.1021/acs.est.4c05048. Epub 2024 Aug 23.
Nitrites (NO/HONO), as the primary source of hydroxyl radicals (OH) in the atmosphere, play a key role in atmospheric chemistry. However, the current understanding of the source of NO/HONO is insufficient and therefore hinders the accurate quantification of atmospheric oxidation capacity. Herein, we highlighted an overlooked HONO source by the reaction between nitrophenols (NPs) and OH in the aqueous phase and provided kinetic data to better evaluate the contribution of this process to atmospheric HONO. Three typical NPs, including 4-nitrophenol (4NP), 2-nitrophenol (2NP), and 4-nitrocatechol (4NC), underwent a denitration process to form aqueous NO and gaseous HONO through the OH oxidation, with the yield of NO/HONO varied from 15.0 to 33.5%. According to chemical composition and structure analysis, the reaction pathway, where the ipso addition of OH to the NO group on 4NP generated hydroquinone, can contribute to more than 61.9% of the NO/HONO formation. The aqueous photooxidation of NPs may account for HONO in the atmosphere, depending on the specific conditions. The results clearly suggest that the photooxidation of NPs should be considered in the field observation and calculation to better evaluate the HONO budget in the atmosphere.
亚硝酸盐（NO/HONO）作为大气中羟基自由基（OH）的主要来源，在大气化学中起着关键作用。然而，目前对 NO/HONO 来源的认识还不够充分，因此阻碍了对大气氧化能力的准确量化。在此，我们通过在水相中硝基酚（NPs）与 OH 的反应强调了一个被忽视的 HONO 来源，并提供了动力学数据以更好地评估该过程对大气 HONO 的贡献。三种典型的 NPs，包括 4-硝基苯酚（4NP）、2-硝基苯酚（2NP）和 4-硝基邻苯二酚（4NC），通过 OH 氧化经历了脱硝过程，形成水相 NO 和气相 HONO，NO/HONO 的产率从 15.0%到 33.5%不等。根据化学成分和结构分析，OH 在 4NP 的 NO 基团上的 ipso 添加生成对苯二酚的反应途径，可以促成超过 61.9%的 NO/HONO 形成。NPs 的水相光氧化可能是大气中 HONO 的来源，这取决于具体条件。结果清楚地表明，在现场观测和计算中应考虑 NPs 的光氧化作用，以更好地评估大气中 HONO 的预算。
