Low-NO atmospheric oxidation pathways in a polluted megacity
Low-NO atmospheric oxidation pathways in a polluted megacity
复制标题
DOI：
10.5194/acp-21-1613-2021
复制
发表时间：
2021-02
影响因子：
6.3
通讯作者：
M. Newland;D. Bryant;R. Dunmore;T. Bannan;W. Acton;B. Langford;J. Hopkins;F. Squires;William J.
中科院分区：
文献类型：
--
作者：
M. Newland;D. Bryant;R. Dunmore;T. Bannan;W. Acton;B. Langford;J. Hopkins;F. Squires;William J.
抽象。挥发性有机化合物（VOCs）排放到大气中对二次污染物（如臭氧和二次有机气溶胶（SOA））产生的影响由一氧化氮（NO）浓度介导。被污染的城市大气通常被认为是“高NO”环境，而偏远地区，如热带雨林，人为影响最小，被认为是“低NO”。然而，我们从北京中心的观察表明，这种简单的政权分离是有缺陷的。尽管是在世界上最大的特大城市之一，我们观察到形成的气体和气溶胶相氧化产物通常与低NO的“雨林般”的大气氧化途径在下午，在这个时候，由极端抑制NO浓度。箱模型计算表明，在上午高NO化学占主导地位（95%），但在下午低NO化学起着更大的作用（30%）。目前的排放清单中应用的GEOS-Chem模型表明，这种模式，在区域尺度上运行时，不能准确地预测这样一个极端的昼夜循环中的NO浓度。随着全球越来越重视减少空气污染，用于制定城市空气质量政策的建模工具必须能够准确地表示NO的极端日变化，以准确预测SOA和臭氧等污染物的形成。
Abstract. The impact of emissions of volatile organic compounds (VOCs) to the atmosphere on the production of secondary pollutants, such as ozone and secondary organic aerosol (SOA), is mediated by the concentration of nitric oxide (NO). Polluted urban atmospheres are typically considered to be “high-NO” environments, while remote regions such as rainforests, with minimal anthropogenic influences, are considered to be “low NO”. However, our observations from central Beijing show that this simplistic separation of regimes is flawed. Despite being in one of the largest megacities in the world, we observe formation of gas- and aerosol-phase oxidation products usually associated with low-NO “rainforest-like” atmospheric oxidation pathways during the afternoon, caused by extreme suppression of NO concentrations at this time. Box model calculations suggest that during the morning high-NO chemistry predominates (95 %) but in the afternoon low-NO chemistry plays a greater role (30 %). Current emissions inventories are applied in the GEOS-Chem model which shows that such models, when run at the regional scale, fail to accurately predict such an extreme diurnal cycle in the NO concentration. With increasing global emphasis on reducing air pollution, it is crucial for the modelling tools used to develop urban air quality policy to be able to accurately represent such extreme diurnal variations in NO to accurately predict the formation of pollutants such as SOA and ozone.