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Substantial nitrogen oxides emission reduction from China due to COVID-19 and its impact on surface ozone and aerosol pollution.

ABSTRACT: A top-down approach was employed to estimate the influence of lockdown measures implemented during the COVID-19 pandemic on NO_x emissions and subsequent influence on surface PM_2.5 and ozone in China. The nation-wide NO_x emission reduction of 53.4% due to the lockdown in 2020 quarter one in China may represent the current upper limit of China's NO_x emission control. During the Chinese New Year Holiday (P2), NO_x emission intensity in China declined by 44.7% compared to the preceding 3 weeks (P1). NO_x emission intensity increased by 20.3% during the 4 weeks after P2 (P3), despite the unchanged NO₂ column. It recovered to 2019 level at the end of March (P4). The East China (22°N - 42°N, 102°E - 122°E) received greater influence from COVID-19. Overall NO_x emission from East China for 2020 first quarter is 40.5% lower than 2019, and in P4 it is still 22.9% below the same period in 2019. The 40.5% decrease of NO_x emission in 2020 first quarter in East China lead to 36.5% increase of surface O₃ and 12.5% decrease of surface PM_2.5. The elevated O₃ promotes the secondary aerosol formation through heterogeneous pathways. We recommend that the complicated interaction between PM_2.5 and O₃ should be considered in the emission control strategy making process in the future.

SUBMITTER: Zhang Q

PROVIDER: S-EPMC7474802 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Substantial nitrogen oxides emission reduction from China due to COVID-19 and its impact on surface ozone and aerosol pollution.

Zhang Qianqian Q Pan Yuepeng Y He Yuexin Y Walters Wendell W WW Ni Qianyin Q Liu Xuyan X Xu Guangyi G Shao Jiali J Jiang Chunlai C

The Science of the total environment 20200906

A top-down approach was employed to estimate the influence of lockdown measures implemented during the COVID-19 pandemic on NOx emissions and subsequent influence on surface PM2.5 and ozone in China. The nation-wide NOx emission reduction of 53.4% due to the lockdown in 2020 quarter one in China may represent the current upper limit of China's NOx emission control. During the Chinese New Year Holiday (P2), NOx emission intensity in China dec ...[more]

PMID: 33207485

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Project description:COVID-19 related restrictions lowered particulate matter and trace gas concentrations across cities around the world, providing a natural opportunity to study effects of anthropogenic activities on emissions of air pollutants. In this paper, the impact of sudden suspension of human activities on air pollution was analyzed by studying the change in satellite retrieved NO2 concentrations and top-down NOx emission over the urban and rural areas around Delhi. NO2 was chosen for being the most indicative of emission intensity due to its short lifetime of the order of a few hours in the planetary boundary layer. We present a robust temporal comparison of Ozone Monitoring Instrument (OMI) retrieved NO2 column density during the lockdown with the counterfactual baseline concentrations, extrapolated from the long-term trend and seasonal cycle components of NO2 using observations during 2015 to 2019. NO2 concentration in the urban area of Delhi experienced an anomalous relative change ranging from 60.0% decline during the Phase 1 of lockdown (March 25-April 13, 2020) to 3.4% during the post-lockdown Phase 5. In contrast, we find no substantial reduction in NO2 concentrations over the rural areas. To segregate the impact of the lockdown from the meteorology, weekly top-down NOx emissions were estimated from high-resolution TROPOspheric Monitoring Instrument (TROPOMI) retrieved NO2 by accounting for horizontal advection derived from the steady state continuity equation. NOx emissions from urban Delhi and power plants exhibited a mean decline of 72.2% and 53.4% respectively in Phase 1 compared to the pre-lockdown business-as-usual phase. Emission estimates over urban areas and power-plants showed a good correlation with activity reports, suggesting the applicability of this approach for studying emission changes. A higher anomaly in emission estimates suggests that comparison of only concentration change, without accounting for the dynamical and photochemical conditions, may mislead evaluation of lockdown impact. Our results shall also have a broader impact for optimizing bottom-up emission inventories.

Dataset Information

Substantial nitrogen oxides emission reduction from China due to COVID-19 and its impact on surface ozone and aerosol pollution.

Publications

Substantial nitrogen oxides emission reduction from China due to COVID-19 and its impact on surface ozone and aerosol pollution.

Similar Datasets

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