State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, Beijing 100029, China; College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, Beijing 100029, China.
J Environ Sci (China). 2020 Aug;94:81-87. doi: 10.1016/j.jes.2020.03.039. Epub 2020 May 4.
As an important secondary photochemical pollutant, peroxyacetyl nitrate (PAN) has been studied over decades, yet its simulations usually underestimate the corresponding observations, especially in polluted areas. Recent observations in north China found unusually high concentrations of PAN during wintertime heavy haze events, but the current model still cannot reproduce the observations, and researchers speculated that nitrous acid (HONO) played a key role in PAN formation. For the first time we systematically assessed the impact of potential HONO sources on PAN formation mechanisms in eastern China using the Weather Research and Forecasting/Chemistry (WRF-Chem) model in February of 2017. The results showed that the potential HONO sources significantly improved the PAN simulations, remarkably accelerated the RO (sum of hydroxyl, hydroperoxyl, and organic peroxy radicals) cycles, and resulted in 80%-150% enhancements of PAN near the ground in the coastal areas of eastern China and 10%-50% enhancements in the areas around 35-40°N within 3 km during a heavy haze period. The direct precursors of PAN were aldehyde and methylglyoxal, and the primary precursors of PAN were alkenes with C > 3, xylenes, propene and toluene. The above results suggest that the potential HONO sources should be considered in regional and global chemical transport models when conducting PAN studies.
作为一种重要的次生光化学污染物，过氧乙酰硝酸酯 (PAN) 已经被研究了几十年，但它的模拟通常低估了相应的观测结果，尤其是在污染地区。最近在中国北方的观测发现，在冬季重霾事件期间 PAN 浓度异常高，但目前的模型仍然无法再现这些观测结果，研究人员推测亚硝酸（HONO）在 PAN 形成中起关键作用。我们首次使用气象研究与预报/化学（WRF-Chem）模型，在 2017 年 2 月系统评估了潜在 HONO 源对中国东部 PAN 形成机制的影响。结果表明，潜在 HONO 源显著改善了 PAN 的模拟，显著加速了 RO（羟基、过氧羟基和有机过氧自由基的总和）循环，并导致中国东部沿海地区地面附近的 PAN 增加了 80%-150%，在重霾期间 35-40°N 周围 3 公里范围内的 PAN 增加了 10%-50%。PAN 的直接前体物为醛和甲基乙二醛，PAN 的主要前体物为 C>3 的烯烃、二甲苯、丙烯和甲苯。上述结果表明，在进行 PAN 研究时，区域和全球化学输送模型应考虑潜在的 HONO 源。
