Air Quality Improvement during COVID-19 Lockdown in Bangkok Metropolitan, Thailand: Effect of the Long-range Transport of Air Pollutants

Abstract

Lockdown measures have been adopted in many countries worldwide due to the onset of the COVID-19 pandemic, including in Thailand. Air quality improvements with regard to restrictions of daily movement among Bangkok people have been reported. This study explores the impact of the COVID-19 outbreak and long-range pollution on air quality in Bangkok Metropolitan, Thailand by using ground-based and satellite measurements such as MODIS and TROPOMI data. Moreover, the results project some possible future trends of air quality in Bangkok Metropolitan. The 24-hr average concentrations of PM2.5, O3, NO2, CO and SO2 were compared between the periods of Normal, Lockdown and New Normal. PM2.5 concentrations increased by 20.56% during the Normal period and decreased by-15.79% and-23.34% during the Lockdown and New Normal periods, respectively, compared to the same periods in 2017-2019. There were also significant decreasing trends in O 3 :-7.13% and 4.72%; and CO-8.01% and 23.59% during the Lockdown and New Normal periods, respectively, while NO2 and SO2 concentrations showed increasing trends during the three periods. The MODIS and TROPOMI data analyses indicate the COVID-19 outbreak has had significant positive impact on surface pollution, but no impact on upper atmospheric pollution due to added pollution from long-range transport. The results also demonstrate that surface air pollution had a combination effect from biomass burning, traffic, industrial and household sources during the Lockdown period, except for SO2 concentrations, which were attributed to long-range transport pollution loading. In some cases, a negative impact of the COVID-19 lockdown on air pollution can be observed due to certain activities increasing within Bangkok Metropolitan. Additionally, the results also show that changing the lifestyle into a 'new normal' for people in Bangkok after the Lockdown period has had a positive effect on air pollution.

Aerosol Loading and Radiation Budget Perturbations in Densely Populated and Highly Polluted Indo‐Gangetic Plain by COVID‐19: Influences on Cloud Properties and Air Temperature

“…The COVID‐19 lockdown drastically constrained human activities on a scale larger than those campaigns, providing a good opportunity to revisit a less polluted atmosphere to understand the level of human engagement in degrading the environment and climate. This resulted in an exponential increase of COVID‐19 related studies after the outbreak, mostly focusing on the degree of air quality improvement (e.g., Dumka et al., 2021 ; Manchanda et al., 2021 ; Mishra et al., 2021 ; Misra et al., 2021 ; Wetchayont et al., 2021 ). Aerosols affect the climate by scattering and absorbing solar radiation (direct effect) (e.g., Coakley et al., 1983 ), changing the atmospheric stability and burning clouds (semi‐direct effect) (e.g., Hansen et al., 1997 ), and modifying the cloud microphysical and optical properties (indirect effect) (e.g., Albrecht, 1989 ; Twomey, 1977 ).…”

Impacts of the COVID-19 Lockdown Measures on the 2020 Columnar and Surface Air Pollution Parameters over South-Eastern Italy

“…The highest PM10-APD% values (−23%, −6%, and −10%, in June, July, and August, respectively) were found at Site 10, which is a background site, while the smallest values (up to −92% in June) were found at Site 6, which is a rural/industrial site. Wetchayont et al [32] identified a reduction in PM2.5 concentration by −15.79% in the LD period and by −23.34% in the Post-LD period by analysing measurements performed in Bangkok (Thailand) in a highly urbanized area and considering the same reference years of this study. The PM2.5 and PM10 mass concentration reductions observed in 2020 with respect to the ref-year are within the variability range evaluated by Sicard et al [31], who also considered 2017, 2018, and 2019 as reference years.…”

“…Firstly, the statistics of Pre-LD, LD, and Post-LD periods have been compared estimating the respective mean values and the 5th, 25th, 50th, 75th, and 95th percentiles of each tested parameter that have been represented by box plots. Then, we have defined a so-called reference year (ref-year) based on measurements performed in the years 2017, 2018, and 2019, according to the selection performed in other studies [31,32]. In more detail, the daily mean values of each tested parameter referring to each of these three years have been averaged to calculate the corresponding monthly mean values of the ref-year.…”

Local and transboundary impacts of PM2.5 sources identified in Seoul during the early stage of the COVID-19 outbreak

“…However, air quality did not consistently improve in China during the lockdown due to local and transboundary impacts of PM 2.5 sources ( Chang et al, 2020b ; Dai et al, 2021a ; Le et al, 2020b ), and similar cases were reported in Spain and Thailand. ( Briz et al, 2022 ; Wetchayont et al, 2021 ). These results can help understand the local and transboundary impacts of PM 2.5 sources by providing an unprecedented cross-country experiment.…”