Laboratory Investigation of Renoxification from the Photolysis of Inorganic Particulate Nitrate
Laboratory Investigation of Renoxification from the Photolysis of Inorganic Particulate Nitrate
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DOI：
10.1021/acs.est.0c06049
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发表时间：
2021-01-04
影响因子：
11.4
通讯作者：
Ye, Qing
中科院分区：
文献类型：
--
作者：
Shi, Qianwen;Tao, Ye;Ye, Qing
氮氧化物(NOx)通过控制O-3、OH和其他重要气体和颗粒物的丰度，在调节大气氧化能力方面发挥着关键作用。最近的一些研究表明，传统上被认为是NOx最终氧化产物的颗粒物硝酸盐可以通过光解进行“再氧化”，将NOx和HONO循环回到气相。然而，对这一通道的重要性的估计存在很大的差异，报道的再氧化速率常数跨越三个数量级。此外，以前的实验室研究使用在基质上收集的散装颗粒样品而不是悬浮颗粒来推导速度常数。在这项工作中，我们研究了悬浮亚微米颗粒物钠和硝酸铵的再氧化通过控制的实验室光解实验在环境室内。我们发现，在与大气相关的波长和相对湿度下，颗粒无机硝酸盐释放NOx和HONO的速度不到气态硝酸的10倍，这使我们的测量处于最近报道的再氧化速率常数的低端。在一定程度上，我们的实验室条件代表了真实的大气，无机颗粒硝酸盐的光解引起的再氧化似乎在偏远环境中对NOx和OH预算的贡献有限。这些结果是基于简化的模型系统；未来的研究应该调查代表更广泛的气溶胶性质光谱的更复杂的气溶胶混合物的再氧化作用，以更好地限制环境气溶胶的光解。
Nitrogen oxides (NOx) play a key role in regulating the oxidizing capacity of the atmosphere through controlling the abundance of O-3, 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.