State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich 52428, Germany.
Environ Sci Technol. 2020 Aug 4;54(15):9243-9253. doi: 10.1021/acs.est.0c00972. Epub 2020 Jul 10.
Particulate nitrate (pNO) has often been found to be the major component of fine particles in urban air-sheds in China, the United States, and Europe during winter haze episodes in recent years. However, there is a lack of knowledge regarding the experimentally determined contribution of different chemical pathways to the formation of pNO. Here, for the first time, we combine ground and tall-tower observations to quantify the chemical formation of pNO using observationally constrained model approach based on direct observations of OH and NO for the urban air-shed. We find that the gas-phase oxidation pathway (OH+NO) during the daytime is the dominant channel over the nocturnal uptake of NO during pollution episodes, with percentages of 74% in urban areas and 76% in suburban areas. This is quite different from previous studies in some regions of the US, in which the uptake of NO was concluded to account for a larger contribution in winter. These results indicate that the driving factor of nitrate pollution in Beijing and different regions of the US is different, as are the mitigation strategies for particulate nitrate.
近年来，在中国、美国和欧洲的城市空气流域冬季雾霾期间，人们经常发现颗粒状硝酸盐（pNO）是细颗粒物的主要成分。然而，对于不同化学途径对 pNO 形成的实验确定贡献，人们知之甚少。在这里，我们首次结合地面和高塔观测，利用基于 OH 和 NO 直接观测的观测约束模型方法，对城市空气流域的 pNO 化学形成进行定量研究。我们发现，在污染期间，白天的气相氧化途径（OH+NO）是主导通道，而夜间 NO 的吸收则占主导地位，在城区的比例为 74%，在郊区的比例为 76%。这与美国一些地区以前的研究结果大不相同，以前的研究结果认为，在冬季，NO 的吸收对硝酸盐污染的贡献更大。这些结果表明，北京和美国不同地区硝酸盐污染的驱动因素不同，颗粒状硝酸盐的缓解策略也不同。
