Joint International Research Laboratory of Atmospheric and Earth System Research, School of Atmospheric Sciences, Nanjing University, Nanjing, China.
National Observation and Research Station for Atmospheric Processes and Environmental Change in Yangtze River Delta, Nanjing, Jiangsu Province, China.
Nat Commun. 2023 Jun 8;14(1):3347. doi: 10.1038/s41467-023-39066-4.
The interaction between nitrogen monoxide (NO) and organic peroxy radicals (RO) greatly impacts the formation of highly oxygenated organic molecules (HOM), the key precursors of secondary organic aerosols. It has been thought that HOM production can be significantly suppressed by NO even at low concentrations. Here, we perform dedicated experiments focusing on HOM formation from monoterpenes at low NO concentrations (0 - 82 pptv). We demonstrate that such low NO can enhance HOM production by modulating the RO loss and favoring the formation of alkoxy radicals that can continue to autoxidize through isomerization. These insights suggest that HOM yields from typical boreal forest emissions can vary between 2.5%-6.5%, and HOM formation will not be completely inhibited even at high NO concentrations. Our findings challenge the notion that NO monotonically reduces HOM yields by extending the knowledge of RO-NO interactions to the low-NO regime. This represents a major advance towards an accurate assessment of HOM budgets, especially in low-NO environments, which prevails in the pre-industrial atmosphere, pristine areas, and the upper boundary layer.
一氧化氮（NO）与有机过氧自由基（RO）之间的相互作用对高度含氧有机分子（HOM）的形成有很大影响，HOM 是二次有机气溶胶的关键前体。人们一直认为，即使在低浓度下，NO 也能显著抑制 HOM 的生成。在这里，我们进行了专门的实验，重点研究了低浓度 NO（0-82 pptv）下单萜烯形成 HOM 的情况。我们证明，这种低浓度的 NO 可以通过调节 RO 的损失来促进 HOM 的生成，并有利于形成烷氧基自由基，烷氧基自由基可以通过异构化继续自动氧化。这些发现表明，典型的北方森林排放物的 HOM 产率可能在 2.5%-6.5%之间变化，即使在高浓度的 NO 下，HOM 的形成也不会完全被抑制。我们的研究结果挑战了 NO 通过扩展 RO-NO 相互作用到低 NO 范围来单调降低 HOM 产率的观点。这代表了朝着准确评估 HOM 预算方向迈出的重要一步，特别是在低 NO 环境下，这种环境在工业前大气、原始区域和上边界层中普遍存在。
