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Laboratory Investigation of Renoxification from the Photolysis of Inorganic Particulate Nitrate
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2021-01-04 , DOI: 10.1021/acs.est.0c06049
Qianwen Shi 1 , Ye Tao 1 , Jordan E. Krechmer 2 , Colette L. Heald 3 , Jennifer G. Murphy 4 , Jesse H. Kroll 3 , Qing Ye 3
Affiliation  

Nitrogen oxides (NOx) play a key role in regulating the oxidizing capacity of the atmosphere through controlling the abundance of O3, OH, and other important gas and particle species. Some recent studies have suggested that particulate nitrate, which is conventionally considered as the ultimate oxidation product of NOx, can undergo “renoxification” via photolysis, recycling NOx and HONO back to the gas phase. However, there are large discrepancies in estimates of the importance of this channel, with reported renoxification rate constants spanning three orders of magnitude. In addition, previous laboratory studies derived the rate constant using bulk particle samples collected on substrates instead of suspended particles. In this work, we study renoxification of suspended submicron particulate sodium and ammonium nitrate through controlled laboratory photolysis experiments using an environmental chamber. We find that, under atmospherically relevant wavelengths and relative humidities, particulate inorganic nitrate releases NOx and HONO less than 10 times as rapidly as gaseous nitric acid, putting our measurements on the low end of recently reported renoxification rate constants. To the extent that our laboratory conditions are representative of the real atmosphere, renoxification from the photolysis of inorganic particulate nitrate appears to play a limited role in contributing to the NOx and OH budgets in remote environments. These results are based on simplified model systems; future studies should investigate renoxification of more complex aerosol mixtures that represent a broader spectrum of aerosol properties to better constrain the photolysis of ambient aerosols.

中文翻译:

无机微粒硝酸盐光解中氧化还原的实验室研究

氮氧化物(NO x)通过控制O 3,OH和其他重要气体和颗粒物的丰度,在调节大气的氧化能力中起关键作用。最近的一些研究表明,硝酸盐颗粒,这通常被认为是NO的最终氧化产物X,可以进行“renoxification”通过光分解,回收NO X和HONO回到气相。但是,对该通道重要性的估计存在很大差异,据报道的氧化还原速率常数跨越三个数量级。另外,以前的实验室研究使用在基材上收集的散装颗粒样品而不是悬浮颗粒得出速率常数。在这项工作中,我们通过使用环境室的受控实验室光解实验研究悬浮的亚微米颗粒钠和硝酸铵的再氧化。我们发现,在与大气有关的波长和相对湿度下,无机硝酸盐颗粒会释放NO x和HONO的速度不到气态硝酸的10倍,这使我们的测量值处于最近报道的氧化还原速率常数的低端。在一定程度上,以我们的实验室条件代表了真实的大气,无机微粒硝酸盐的光解产生的氧化还原作用在偏远环境中对NO x和OH预算的贡献中起着有限的作用。这些结果基于简化的模型系统;未来的研究应该研究更复杂的气雾混合物的氧化还原作用,这些混合物代表更广范围的气雾特性,以更好地限制环境气雾的光解。
更新日期:2021-01-19
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