The Occurrence of Heavy Air Pollution during the COVID-19 Outbreak in Beijing, China: Roles of Emission Reduction, Meteorological Conditions, and Regional Transport

Xiao Yan,Aijun Shi,Miao Lv,Rui Zhang,Jing Wei,Xuesong Sun,Jingyuan Cao,Xionghui Qiu,Tingting Li,Miao Liang,Yanxue Li,Chunlan Liu

doi:10.3390/su132112312

Abstract

To prevent the spread of coronavirus disease (COVID-19) and mitigate the epidemic risk, strict lockdown measures were implemented in Beijing during the quarantine period, significantly reducing human activities. However, severe air pollution episodes occurred frequently in Beijing. To explore the occurrence of severe air pollution during the quarantine period, the impacts of emission reductions, meteorological conditions, and regional transport on heavy air pollution were individually evaluated using the Community Multiscale Air Quality (CMAQ) model. Observations showed that the more unfavorable meteorological conditions which occurred during the pandemic as compared to the corresponding 2019 levels, including higher temperature, relative humidity, and frequency of strong southerly winds, and lower HPBL, led to an increase in PM2.5 concentrations. The model results also showed that the meteorological conditions in February 2020 favored PM2.5 formation. The PM2.5 concentrations were mainly dominated by regional transport, which became more significant in the quarantine period than in 2019, suggesting the importance of joint control on regional sources for reducing heavy air pollution. This study highlights that, although the emissions in Beijing and surrounding regions were largely reduced during the quarantine period, severe air pollution in Beijing did not reduce due to the unfavorable meteorological conditions.

Highlights

Introduction distributed under the terms andIn recent years, air pollution in Beijing has become a matter of public concern, due to high PM2.5 concentration, and frequent and severe heavy haze episodes [1,2]
Even though the air pollutant emissions have largely been reduced, heavy air pollution events often occurred during this time period, for example, during the coronavirus disease (COVID-19) epidemic which broke out at the end of 2019 and continues to spread globally [5,6]
This study provides the first evidence that COVID-19 cases were associated with regional variations in air pollution across Beijing

Summary

Introduction

Air pollution in Beijing has become a matter of public concern, due to high PM2.5 concentration, and frequent and severe heavy haze episodes [1,2]. Sustainability 2021, 13, 12312 implementation of these measures, the air quality in Beijing has continuously improved, and the concentration of air pollutants has significantly reduced. Even though the air pollutant emissions have largely been reduced, heavy air pollution events often occurred during this time period, for example, during the coronavirus disease (COVID-19) epidemic which broke out at the end of 2019 and continues to spread globally [5,6]. The observed concentrations of fine particulate matter (PM2.5 ) in Beijing unexpectedly increased from 53 μg m−3 in February 2019 to 63 μg m−3 in February 2020

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Results

Conclusion