Impact of COVID-19 lockdowns and seasonal variations on PM2.5 in Dhaka City

Abstract. The COVID-19 pandemic resulted in global lockdown measures, including in Bangladesh, which significantly affected daily life. This study evaluates the effect of the imposed lockdown measures on the air quality in Dhaka City, Bangladesh, focusing particularly on the concentrations of PM2.5. The daily average PM2.5 data from March 2016 to July 2023 were collected from air quality monitoring instruments at the U.S. Consulate in Dhaka. We analyzed PM2.5 concentrations during pre-lockdown, lockdown, and post-lockdown periods and seasonal variations from 2016 to 2023. Our study showed that the mean concentration of PM2.5 had a reduction of 14.78% during the 2020 lockdown in comparison to the values found in 2019. However, there was an increase in levels of PM2.5 in subsequent years, with mean concentrations increasing by 15.48% in 2021, 24% in 2022, and 38.71% in 2023 from the 2020 levels. Seasonal analysis showed that the winter season had the highest levels of PM2.5, which can be caused by less rainfall, and an increase in brick kiln activity. The lowest levels occur during the monsoon season due to heavy rainfall, higher wind speeds, and higher relative humidity. These findings assist decision-makers in formulating effective policies to reduce PM2.5 pollution by considering vehicular, industrial, and construction activities, and meteorological factors.