Dataset Information

Diverse response of surface ozone to COVID-19 lockdown in China.

ABSTRACT: Ozone (O₃) is a key oxidant and pollutant in the lower atmosphere. Significant increases in surface O₃ have been reported in many cities during the COVID-19 lockdown. Here we conduct comprehensive observation and modeling analyses of surface O₃ across China for periods before and during the lockdown. We find that daytime O₃ decreased in the subtropical south, in contrast to increases in most other regions. Meteorological changes and emission reductions both contributed to the O₃ changes, with a larger impact from the former especially in central China. The plunge in nitrogen oxide (NO_x) emission contributed to O₃ increases in populated regions, whereas the reduction in volatile organic compounds (VOC) contributed to O₃ decreases across the country. Due to a decreasing level of NO_x saturation from north to south, the emission reduction in NO_x (46%) and VOC (32%) contributed to net O₃ increases in north China; the opposite effects of NO_x decrease (49%) and VOC decrease (24%) balanced out in central China, whereas the comparable decreases (45-55%) in these two precursors contributed to net O₃ declines in south China. Our study highlights the complex dependence of O₃ on its precursors and the importance of meteorology in the short-term O₃ variability.

SUBMITTER: Liu Y

PROVIDER: S-EPMC8123531 | biostudies-literature | 2021 May

REPOSITORIES: biostudies-literature

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Diverse response of surface ozone to COVID-19 lockdown in China.

Liu Yiming Y Wang Tao T Stavrakou Trissevgeni T Elguindi Nellie N Doumbia Thierno T Granier Claire C Bouarar Idir I Gaubert Benjamin B Brasseur Guy P GP

The Science of the total environment 20210515

Ozone (O3) is a key oxidant and pollutant in the lower atmosphere. Significant increases in surface O3 have been reported in many cities during the COVID-19 lockdown. Here we conduct comprehensive observation and modeling analyses of surface O3 across China for periods before and during the lockdown. We find that daytime O3 decreased in the subtropical south, in contrast to increases in most other regions. Meteorological changes and emission reductions ...[more]

PMID: 34323848

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Project description:With the implementation of COVID-19 restrictions and consequent improvement in air quality due to the nationwide lockdown, ozone (O3) pollution was generally amplified in China. However, the O3 levels throughout the Guangxi region of South China showed a clear downward trend during the lockdown. To better understand this unusual phenomenon, we investigated the characteristics of conventional pollutants, the influence of meteorological and anthropogenic factors quantified by a multiple linear regression (MLR) model, and the impact of local sources and long-range transport based on a continuous emission monitoring system (CEMS) and the HYSPLIT model. Results show that in Guangxi, the conventional pollutants generally declined during the COVID-19 lockdown period (January 24 to February 9, 2020) compared with their concentrations during 2016-2019, while O3 gradually increased during the resumption (10 February to April 2020) and full operation periods (May and June 2020). Focusing on Beihai, a typical Guangxi region city, the correlations between the daily O3 concentrations and six meteorological parameters (wind speed, visibility, temperature, humidity, precipitation, and atmospheric pressure) and their corresponding regression coefficients indicate that meteorological conditions were generally conducive to O3 pollution mitigation during the lockdown. A 7.84 μg/m3 drop in O3 concentration was driven by meteorology, with other decreases (4.11 μg/m3) explained by reduced anthropogenic emissions of O3 precursors. Taken together, the lower NO2/SO2 ratios (1.25-2.33) and consistencies between real-time monitored primary emissions and ambient concentrations suggest that, with the closure of small-scale industries, residual industrial emissions have become dominant contributors to local primary pollutants. Backward trajectory cluster analyses show that the slump of O3 concentrations in Southern Guangxi could be partly attributed to clean air mass transfer (24-58%) from the South China Sea. Overall, the synergistic effects of the COVID-19 lockdown and meteorological factors intensified O3 reduction in the Guangxi region of South China.

Dataset Information

Diverse response of surface ozone to COVID-19 lockdown in China.

Publications

Diverse response of surface ozone to COVID-19 lockdown in China.

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