Seasonal variations of gaseous air pollutants (SO2, NO2, O3, CO) and particulates (PM2.5, PM10) in Gazipur: an industrial city in Bangladesh

The present study assessed the impacts of seasonal variation on the atmospheric abundance of gaseous air pollutants (SO2, NO2, O3, CO) and particulates (PM2.5 and PM10) at Gazipur city. The air pollution data was collected from the study area using a Continuous Air Monitoring Station (CAMS) (CAMS-4, Gazipur) of DoE from October 2017 to September 2018. The highest concentrations of air pollutants were found in the winter (PM2.5=208 μg/m3, PM10=300 μg/m3, NO2=45.1 ppb, CO=3.91 ppm, O3=4.17 ppb) as opposed to those of the post-monsoon (PM2.5=133μg/m3, PM10=169 μg/m3, NO2=23.52 ppb, CO=2.25 ppm, O3=7.71 ppb), pre-monsoon (PM2.5=115 μg/m3, PM10=216 μg/m3, NO2=33.5 ppb, CO=1.75 ppm, O3=4.23 ppb), and monsoon (PM2.5=37.5 μg/m3, PM10=85.6 μg/m3, NO2=13.9 ppb, CO=0.84 ppm, O3=4.23 ppb). The highest concentration of five air pollutants (PM10, PM2.5, NO2, CO, O3)indicated that the higher pollutant load in the winter was associated with large-scale polluted air transported from the brick kiln at a distance of 5-7 km at the sampling site. The wind-rose data analysis indicated that most of the air during the winter season came to the sampling site from the northern part of the Gazipur district, from the brickfield zones. In contrast, a reverse relationship between the rainfall and atmospheric pollution, temperature, and atmospheric pollution load was observed during the pre-monsoon, monsoon, post-monsoon, and winter. This finding revealed that the lowest concentration of air pollutants during monsoon was associated with the washout effect of precipitation on atmospheric pollutants. A moderate correlation (R2=0.58) between CO and O3 pollutants during the study indicated their atmospheric origin by photochemical reactions was associated with volatile organic compounds (VOCs). PM2.5 showed a positive correlation with PM10 (R2=0.84), indicating that both PM2.5 and PM10 were produced from similar pathways of fossil fuel combustion by automobiles and industrial activities. Further, the air quality index (AQI) analysis showed unhealthy atmospheric conditions throughout the year for city dwellers around the study area.