Yang Yu, Huang Liubin, Zhao Min, Wu Yan, Xu Yihang, Li Qinyi, Wang Wenxing, Xue Likun
Environment Research Institute, Shandong University, Qingdao, Shandong, China.
School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China.
Nat Commun. 2025 Jul 1;16(1):5437. doi: 10.1038/s41467-025-60696-3.
Organic nitrates (ONs) are considered as important tracers of secondary organic aerosol formation and are ubiquitous in ambient aerosols. However, the mechanisms of ON formation in the atmosphere are not well understood. Here, we show that ONs can be formed via multiphase reactions of organic peroxides with nitrite. Yields of ONs are measured as 12.8-14.9% at pH 3. The mechanism involves the recombination of a [RO• •NO] caged radical pair resulting from the homolytic cleavage of alkyl peroxynitrite intermediate. ON yield decreases with the decreasing pH values, which may be ascribed to the positive dependence of its hydrolysis rate on the solution acidity. Additionally, it is found that the second-order rate constant of the reaction is closely dependent on pH and the molecular structure of organic peroxides. Extrapolation of kinetic and mechanistic results to the real atmosphere suggests that this pathway is important for ON formation in aerosols under typical atmospheric conditions, particularly in polluted urban areas.
有机硝酸盐（ONs）被认为是二次有机气溶胶形成的重要示踪剂，且在环境气溶胶中普遍存在。然而，大气中ONs的形成机制尚未得到充分理解。在此，我们表明ONs可通过有机过氧化物与亚硝酸盐的多相反应形成。在pH值为3时，ONs的产率测定为12.8 - 14.9%。该机制涉及由烷基过氧亚硝酸盐中间体均裂产生的[RO• •NO]笼形自由基对的重组。ON产率随pH值降低而降低，这可能归因于其水解速率对溶液酸度的正相关性。此外，发现该反应的二级速率常数密切依赖于pH值和有机过氧化物的分子结构。将动力学和机理结果外推至实际大气表明，该途径对于典型大气条件下气溶胶中ONs的形成很重要，特别是在污染的城市地区。
