气候变化领域集成服务门户(CCPortal): Secondary PM(2.5 )decreases significantly less than NO2 emission reductions during COVID lockdown in Germany

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DOI	10.5194/acp-22-7105-2022
	Secondary PM(2.5 )decreases significantly less than NO2 emission reductions during COVID lockdown in Germany
	Balamurugan, Vigneshkumar; Chen, Jia; Qu, Zhen; Bi, Xiao; Keutsch, Frank N.
发表日期	2022
ISSN	1680-7316
EISSN	1680-7324
起始页码	7105
结束页码	7129
卷号	22 期号:11 页码:25
英文摘要	This study estimates the influence of anthropogenic emission reductions on the concentration of particulate matter with a diameter smaller than 2.5 mu m (PM2.5) during the 2020 lockdown period in German metropolitan areas. After accounting for meteorological effects, PM2.5 concentrations during the spring 2020 lockdown period were 5 % lower compared to the same time period in 2019. However, during the 2020 pre-lockdown period (winter), PM2.5 concentrations with meteorology accounted for were 19 % lower than in 2019. Meanwhile, NO2 concentrations with meteorology accounted for dropped by 23 % during the 2020 lockdown period compared to an only 9 % drop for the 2020 pre-lockdown period, both compared to 2019. SO2 and CO concentrations with meteorology accounted for show no significant changes during the 2020 lockdown period compared to 2019. GEOS-Chem (GC) simulations with a COVID-19 emission reduction scenario based on the observations (23 % reduction in anthropogenic NOx emission with unchanged anthropogenic volatile organic compounds (VOCs) and SO2) are consistent with the small reductions of PM2.5 during the lockdown and are used to identify the underlying drivers for this. Due to being in a NOx-saturated ozone production regime, GC OH radical and O-3 concentrations increased (15 % and 9 %, respectively) during the lockdown compared to a business-as-usual (BAU, no lockdown) scenario. O-x (equal to NO2 + O-3) analysis implies that the increase in ozone at nighttime is solely due to reduced NO titration. The increased O-3 results in increased NO3 radical concentrations, primarily during the night, despite the large reductions in NO2. Thus, the oxidative capacity of the atmosphere is increased in all three important oxidants, OH, O-3, and NO3. PM nitrate formation from gas-phase nitric acid (HNO3) is decreased during the lockdown as the increased OH concentration cannot compensate for the strong reductions in NO2, resulting in decreased daytime HNO3 formation from the OH + NO2 reaction. However, nighttime formation of PM nitrate from N2O5 hydrolysis is relatively unchanged. This results from the fact that increased nighttime O-3 results in significantly increased NO3, which roughly balances the effect of the strong NO2 reductions on N2O5 formation. Ultimately, the only small observed decrease in lockdown PM2.5 concentrations can be explained by the large contribution of nighttime PM nitrate formation, generally enhanced sulfate formation, and slightly decreased ammonium. This study also suggests that high PM2.5 episodes in early spring are linked to high atmospheric ammonia concentrations combined with favorable meteorological conditions of low temperature and low boundary layer height. Northwest Germany is a hot-spot of NH3 emissions, primarily emitted from livestock farming and intensive agricultural activities (fertilizer application), with high NH3 concentrations in the early spring and summer months. Based on our findings, we suggest that appropriate NOx and VOC emission controls are required to limit ozone, and that should also help reduce PM2.5. Regulation of NH3 emissions, primarily from agricultural sectors, could result in significant reductions in PM2.5 pollution.
学科领域	Environmental Sciences; Meteorology & Atmospheric Sciences
语种	英语
WOS研究方向	Environmental Sciences & Ecology ; Meteorology & Atmospheric Sciences
WOS记录号	WOS:000804651300001
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/273366
作者单位	Technical University of Munich; Harvard University; Harvard University
推荐引用方式 GB/T 7714	Balamurugan, Vigneshkumar,Chen, Jia,Qu, Zhen,et al. Secondary PM(2.5 )decreases significantly less than NO2 emission reductions during COVID lockdown in Germany[J],2022,22(11):25.
APA	Balamurugan, Vigneshkumar,Chen, Jia,Qu, Zhen,Bi, Xiao,&Keutsch, Frank N..(2022).Secondary PM(2.5 )decreases significantly less than NO2 emission reductions during COVID lockdown in Germany.ATMOSPHERIC CHEMISTRY AND PHYSICS,22(11),25.
MLA	Balamurugan, Vigneshkumar,et al."Secondary PM(2.5 )decreases significantly less than NO2 emission reductions during COVID lockdown in Germany".ATMOSPHERIC CHEMISTRY AND PHYSICS 22.11(2022):25.