Li Mengmeng, Wang Tijian, Xie Min, Li Shu, Zhuang Bingliang, Fu Qingyan, Zhao Ming, Wu Hao, Liu Jane, Saikawa Eri, Liao Kuo
School of Atmospheric Sciences, Nanjing University, Nanjing, 210023, China.
Shanghai Environmental Monitoring Center, Shanghai, 200030, China.
Atmos Environ (1994). 2021 Feb 1;246:118103. doi: 10.1016/j.atmosenv.2020.118103. Epub 2020 Nov 25.
China's lockdown to control COVID-19 brought significant declines in air pollutant emissions, but haze was still a serious problem in North China Plain (NCP) during late-January to mid-February of 2020. We seek the potential causes for the poor air quality in NCP combining satellite data, ground measurements and model analyses. Efforts to constrain COVID-19 result in a drop-off of primary gaseous pollutants, e.g., -42.4% for surface nitrogen dioxide (NO) and -38.9% for tropospheric NO column, but fine particulate matter (PM) still remains high and ozone (O) even increases sharply (+84.1%). Stagnant weather during COVID-19 outbreak, e.g., persistent low wind speed, frequent temperature inversion and wind convergence, is one of the major drivers for the poor air quality in NCP. The surface PM levels vary between -12.9~+15.1% in NCP driven by the varying climate conditions between the years 2000 and 2020. Besides, the persistent PM pollution might be maintained by the still intensive industrial and residential emissions (primary PM), and increased atmospheric oxidants (+26.1% for ozone and +29.4% for hydroxyl radical) in response to the NO decline (secondary PM). Further understanding the nonlinear response between atmospheric secondary aerosols and NO emissions is meaningful to cope with the emerging air pollution problems in China.
中国为控制新冠疫情实施的封锁措施使空气污染物排放量大幅下降，但在2020年1月下旬至2月中旬期间，华北平原的雾霾问题依然严重。我们结合卫星数据、地面测量和模型分析，探寻华北平原空气质量不佳的潜在原因。控制新冠疫情的措施导致主要气态污染物减少，例如地面二氧化氮（NO）下降了42.4%，对流层NO柱下降了38.9%，但细颗粒物（PM）仍然居高不下，臭氧（O）甚至急剧增加（+84.1%）。新冠疫情爆发期间的静稳天气，如持续的低风速、频繁的逆温现象和风场辐合，是华北平原空气质量不佳的主要驱动因素之一。受2000年至2020年间不同气候条件影响，华北平原地面PM水平变化幅度在-12.9%至+15.1%之间。此外，持续的PM污染可能由仍然密集的工业和居民排放（一次PM）以及因NO下降而增加的大气氧化剂（臭氧增加26.1%，羟基自由基增加29.4%）（二次PM）维持。进一步了解大气二次气溶胶与NO排放之间的非线性响应，对于应对中国新出现的空气污染问题具有重要意义。
