Status of air quality in Rajshahi metropolitan area, Bangladesh

Rajshahi is well-known as a model city for clean air in Bangladesh but in recent time air pollution is increasing in metropolitan areas. This study aims to examine the concentration of Particulate Matters (PM₁, PM₂.₅, and PM₁₀) in the Rajshahi metropolitan area during March 2021, with a focus on distinct land use categories. The research was carried out in 40 different sites within the Rajshahi metropolitan area, utilizing a portable device for measuring air quality. It was found that the average concentrations of PM₂.₅ and PM₁₀ were 56.41 and 72.63 µg/m³ respectively, which is 2.25 and 1.45-fold than World Health Organizations (WHO) Standards. According to this study, the three locations with the highest levels of PM₂.₅ pollution were the Mohanonda project gate (105.750 µg/m³), Textile Mill (79.750 µg/m³), and Sarkar Cold Storage (71.750 µg/m³). The concentration of PM₂.₅ in the most polluted location was found to be 1.63 times than the standard level set by Department of Environment (DoE) and 4.23 times higher than the WHO standard. Furthermore, it was calculated that the average PM₂.₅/PM₁₀ ratio was 77.70% and the average PM₁/PM₂.₅ ratio was 60.16%. It also revealed that temperature is negatively and humidity is positively correlated with PM₁, PM₂.₅ and PM₁₀, which means any change in the concentration of PM₁, PM₂.₅ and PM₁₀ can cause a significant change in the percentage of humidity in the same direction, for humidity the change would be in opposite direction. The concentration of PM₂.₅ in ambient air with respect to land use decreases as follows: industrial area > village area > road intersection area > sensitive area > mixed area > commercial area > residential area.