The influence of meteorological factors on wintertime black carbon and PM2.5 pollution in Dhaka, Bangladesh

This study focuses on the alarming levels of black carbon (BC) and fine particulate matter (PM_2.5) pollution during winter in Dhaka, Bangladesh. The study period was chosen to coincide with the cold wave period during winter when temperatures were at their lowest. The average concentration of BC (24.2 µgm⁻³) and PM_2.5 (73.2 µgm⁻³) in Dhaka, the capital city, were measured and found to surpass national air quality standards and WHO guidelines. The study period had two distinct parts: a high pollution (HP) period from January 23–25, 2024, and a low pollution (LP) period from January 12–15, 2024. During the HP period, the average BC and PM_2.5 concentrations were 60 and 36% higher than the overall study period average. On the other hand, during the LP period, the average BC and PM_2.5 concentrations declined by about 30 and 26%, respectively, compared to the overall study period averages. High concentrations of BC (> 10 µgm⁻³) were detected daily, indicating significant pollution levels during the winter season. Distinct diurnal patterns were observed during the HP period. Specifically, the concentration of BC significantly increased during the night, in contrast to the mild diurnal patterns observed in the LP period. Moreover, both PM_2.5 and BC concentrations exhibited a statistically significant negative correlation with key meteorological parameters, including wind speed, wind direction, and visibility. This study highlights the critical role of meteorological factors in managing air pollution, which has broader implications for environmental sustainability.