The Multi-Time Scale Changes in Air Pollutant Concentrations and Its Mechanism before and during the COVID-19 Periods: A Case Study from Guiyang, Guizhou Province
The lockdown during the coronavirus disease 2019 (COVID-19) pandemic provides a scarce opportunity to assess the efficiency of air pollution mitigation. Herein, the monitoring data of air pollutants were thoroughly analyzed together with meteorological parameters to explore the impact of human activ...
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| Autores principales: | , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/59af328deada481bae8498185d888f8a |
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| Sumario: | The lockdown during the coronavirus disease 2019 (COVID-19) pandemic provides a scarce opportunity to assess the efficiency of air pollution mitigation. Herein, the monitoring data of air pollutants were thoroughly analyzed together with meteorological parameters to explore the impact of human activity on the multi-time scale changes of air pollutant concentrations in Guiyang city, located in Southwest China. The results show that the COVID-19 lockdown had different effects on the criteria air pollutants, i.e., PM<sub>2.5</sub> (diameter ≤ 2.5 μm), PM<sub>10</sub> (diameter ≤ 10 μm), sulfur dioxide (SO<sub>2</sub>), nitrogen dioxide (NO<sub>2</sub>), carbon monoxide (CO), and ozone (O<sub>3</sub>) concentrations. The lockdown caused a significant drop in NO<sub>2</sub> concentration. During the first-level lockdown period, the NO<sub>2</sub> concentration declined sharply by 8.41 μg·m<sup>−3</sup> (45.68%). The decrease in NO concentration caused the “titration effect” to weaken, leading to a sharp increase in O<sub>3</sub> concentration. Although human activities resumed partially and the “titration effect” enhanced certainly during the second-level lockdown period, the meteorological conditions became more conducive to the formation of O<sub>3</sub> by photochemical reactions. Atmosphere oxidation was enhanced to promote the generation of secondary aerosols through gas–particle transitions, thus compensating for the reduced primary emission of PM<sub>2.5</sub>. The implication of this study is that the appropriate air pollution control policies must be initiated to suppress the secondary generation of both PM<sub>2.5</sub> and O<sub>3</sub>. |
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