Department of Chemistry , University of California Berkeley , Berkeley , California 94720 , United States.
Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States.
Environ Sci Technol. 2018 Dec 4;52(23):13738-13746. doi: 10.1021/acs.est.8b03861. Epub 2018 Nov 20.
The concentration of nitrogen oxides (NO ) plays a central role in controlling air quality. On a global scale, the primary sink of NO is oxidation to form HNO. Gas-phase HNO photolyses slowly with a lifetime in the troposphere of 10 days or more. However, several recent studies examining HONO chemistry have proposed that particle-phase HNO undergoes photolysis 10-300 times more rapidly than gas-phase HNO. We present here constraints on the rate of particle-phase HNO photolysis based on observations of NO and HNO collected over the Yellow Sea during the KORUS-AQ study in summer 2016. The fastest proposed photolysis rates are inconsistent with the observed NO to HNO ratios. Negligible to moderate enhancements of the HNO photolysis rate in particles, 1-30 times faster than in the gas phase, are most consistent with the observations. Small or moderate enhancement of particle-phase HNO photolysis would not significantly affect the HNO budget but could help explain observations of HONO and NO in highly aged air.
氮氧化物（NOx）的浓度在控制空气质量方面起着核心作用。在全球范围内，NO 的主要汇是氧化形成 HNO3。气相 HNO3 的光解速度较慢，在对流层中的半衰期为 10 天或更长。然而，最近的几项研究表明，HONO 化学物质的形成可能与气相 HNO3 的光解速度相比，颗粒相 HNO3 的光解速度要快 10-300 倍。本研究基于 2016 年 KORUS-AQ 研究期间在黄海采集的 NOx 和 HNO3 观测数据，提出了对颗粒相 HNO3 光解速率的限制。最快的光解速率与观测到的 NOx 与 HNO3 的比值不一致。颗粒相 HNO3 的光解速率适度增强（比气相快 1-30 倍）或轻微增强，与观测结果最一致。颗粒相 HNO3 光解的适度增强不会显著影响 HNO3 的收支平衡，但可能有助于解释高度老化空气中 HONO 和 NOx 的观测结果。
