Spatial and temporal variations of the PM_2.5 concentrations in Hanoi metropolitan area, Vietnam, during the COVID-19 lockdown

ABSTRACT

The Vietnamese government has issued several directives of lockdown in Hanoi, the capital city, for a month (1–30 April 2020) to prevent the human-to-human transmission of COVID-19. This action has affected air pollution due to a decline in transportation. Therefore, this study investigates spatial and temporal change in the PM_2.5 concentrations during the first 4 months of 2020 in Hanoi metropolitan area. Spatial distribution maps of the PM_2.5 concentration in Hanoi were provided for the first time. The average PM_2.5 concentrations at the 22 air monitoring stations were strongly correlated with the population. April had a significantly lower level of PM_2.5 than the other 3 months. In particular, the concentrations of PM_2.5 and NO₂ decreased by 12 and 54%, respectively, between March and April, especially at areas for commercial activities. In April, a higher level of PM_2.5 was recorded between Tuesday–Thursday, which is a reverse trend with that in March. Furthermore, Monday and Friday did not show rush hour peaks for the PM_2.5 levels in April. A decrease in the PM_2.5 concentrations was partly influenced by the long-range transport from the outside to Hanoi. This study implies that a reduction in traffic volumes and public activities may possibly improve the air quality.

KEYWORDS:

• Air quality
• COVID-19
• Hanoi
• PM_2.5
• lockdown

Supplemental data

Supplemental data for this article can be accessed here.

Acknowledgments

The authors are grateful to PAM Air, Vietnam, for data collection.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Disclosure of potential conflicts of interest

The authors declare that they have no competing interests.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

The authors thank for a generous support grant by the Vietnam Academy of Science and Technology [VAST.ĐLT12/16-17]. This work was partly supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MEST) [2020R1A2B5B01002669].