Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China; Shaanxi Key Laboratory of Atmospheric and Haze-fog Pollution Prevention, Xi'an 710061, China.
Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China; Shaanxi Key Laboratory of Atmospheric and Haze-fog Pollution Prevention, Xi'an 710061, China.
Environ Int. 2021 May;150:106426. doi: 10.1016/j.envint.2021.106426. Epub 2021 Feb 9.
Restrictions on human activities were implemented in China to cope with the outbreak of the Coronavirus Disease 2019 (COVID-19), providing an opportunity to investigate the impacts of anthropogenic emissions on air quality. Intensive real-time measurements were made to compare primary emissions and secondary aerosol formation in Xi'an, China before and during the COVID-19 lockdown. Decreases in mass concentrations of particulate matter (PM) and its components were observed during the lockdown with reductions of 32-51%. The dominant contributor of PM was organic aerosol (OA), and results of a hybrid environmental receptor model indicated OA was composed of four primary OA (POA) factors (hydrocarbon-like OA (HOA), cooking OA (COA), biomass burning OA (BBOA), and coal combustion OA (CCOA)) and two oxygenated OA (OOA) factors (less-oxidized OOA (LO-OOA) and more-oxidized OOA (MO-OOA)). The mass concentrations of OA factors decreased from before to during the lockdown over a range of 17% to 58%, and they were affected by control measures and secondary processes. Correlations of secondary aerosols/ΔCO with O (NO + O) and aerosol liquid water content indicated that photochemical oxidation had a greater effect on the formation of nitrate and two OOAs than sulfate; however, aqueous-phase reaction presented a more complex effect on secondary aerosols formation at different relative humidity condition. The formation efficiencies of secondary aerosols were enhanced during the lockdown as the increase of atmospheric oxidation capacity. Analyses of pollution episodes highlighted the importance of OA, especially the LO-OOA, for air pollution during the lockdown.
中国实施了人类活动限制以应对 2019 年冠状病毒病（COVID-19）的爆发，为研究人为排放对空气质量的影响提供了机会。在中国西安进行了密集的实时测量，以比较 COVID-19 封锁前后的一次排放和二次气溶胶形成。封锁期间观察到颗粒物（PM）及其成分的质量浓度下降，降幅为 32-51%。PM 的主要贡献者是有机气溶胶（OA），混合环境受体模型的结果表明 OA 由四个一次有机气溶胶（POA）因子（烃类 OA（HOA）、烹饪 OA（COA）、生物质燃烧 OA（BBOA）和煤燃烧 OA（CCOA））和两个含氧 OA（OOA）因子（较少氧化的 OOA（LO-OOA）和更多氧化的 OOA（MO-OOA））组成。封锁期间，OA 因子的质量浓度从之前到之后下降了 17%至 58%，它们受到控制措施和二次过程的影响。二次气溶胶/ΔCO 与 O（NO+O）和气溶胶液态水含量的相关性表明，光化学氧化对硝酸盐和两种 OOAs 的形成比硫酸盐的影响更大；然而，水相反应在不同相对湿度条件下对二次气溶胶形成的影响更为复杂。由于大气氧化能力的增加，封锁期间二次气溶胶的形成效率增强。污染事件的分析突出了 OA，特别是 LO-OOA，在封锁期间对空气污染的重要性。
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