Liu Lei, Zhang Jian, Du Rongguang, Teng Xiaomi, Hu Rui, Yuan Qi, Tang Shanshan, Ren Chuanhua, Huang Xin, Xu Liang, Zhang Yinxiao, Zhang Xiaoye, Song Congbo, Liu Bowen, Lu Gongda, Shi Zongbo, Li Weijun
Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province Department of Atmospheric Sciences School of Earth Sciences, Zhejiang University Hangzhou China.
Hangzhou Meteorological Bureau Hangzhou China.
Geophys Res Lett. 2021 Jan 28;48(2):2020GL091611. doi: 10.1029/2020GL091611. Epub 2021 Jan 18.
Air pollution in megacities represents one of the greatest environmental challenges. Our observed results show that the dramatic NO decrease (77%) led to significant O increases (a factor of 2) during the COVID-19 lockdown in megacity Hangzhou, China. Model simulations further demonstrate large increases of daytime OH and HO radicals and nighttime NO radical, which can promote the gas-phase reaction and nocturnal multiphase chemistry. Therefore, enhanced NO and SO formation was observed during the COVID-19 lockdown because of the enhanced oxidizing capacity. The PM decrease was only partially offset by enhanced aerosol formation with its reduction reaching 50%. In particular, NO decreased largely by 68%. PM chemical analysis reveals that vehicular emissions mainly contributed to PM under normal conditions in Hangzhou. Whereas, stationary sources dominated the residual PM during the COVID-19 lockdown. This study provides evidence that large reductions in vehicular emissions can effectively mitigate air pollution in megacities.
特大城市的空气污染是最大的环境挑战之一。我们的观测结果表明，在中国特大城市杭州实施新冠疫情封锁期间，氮氧化物（NO）急剧减少（77%），导致臭氧（O）显著增加（增加了一倍）。模型模拟进一步表明，白天的羟基（OH）和氢氧自由基（HO）以及夜间的一氧化氮自由基（NO）大幅增加，这会促进气相反应和夜间多相化学过程。因此，由于氧化能力增强，在新冠疫情封锁期间观测到氮氧化物（NO）和二氧化硫（SO）的生成增加。细颗粒物（PM）的减少仅部分被气溶胶生成增加所抵消，其减少幅度达到50%。特别是，二氧化氮（NO₂）大幅下降了68%。细颗粒物化学分析表明，在正常情况下，车辆排放是杭州细颗粒物的主要来源。而在新冠疫情封锁期间，固定源排放主导了剩余的细颗粒物。这项研究证明，大幅减少车辆排放可以有效减轻特大城市的空气污染。
