Characterization and source apportionment of elemental species in PM2.5 with especial emphasis on seasonal variation in the capital city “Dhaka”, Bangladesh

Abstract

The deterioration of air quality is a growing concern in Bangladesh. This study investigated the seasonal variation of atmospheric pollutants and their potential major sources in the capital Dhaka City of Bangladesh. In total, 89 fine atmospheric particulate matter (PM2.5) samples were collected from January to December in 2016, and the concentration of over 18 elements present in PM2.5 was analyzed using accelerated based ion beam analysis (IBA) methods (PIXE and PIGE). The PM2.5 concentration for the whole year ranged from 5.27 to 105 μg/m3 with an annual average (± std.) value of 32.7 ± 20.3 μg/m3, which was higher than the recommended value of 10 μg/m3 set by WHO. A significant seasonal variation of PM2.5, black carbon (BC) and elemental concentrations were observed with their highest values during winter followed by pre-monsoon, post-monsoon and monsoon respectively. Among the PM2.5-hosted elements, the concentration of S was found to be the highest value (1.2 ± 0.8 μg/m3), possibly due to excessive use of sulfur-containing fuel. Apart from Al, Si and Fe, the concentrations of Zn and Pb were anomalously enriched in the atmosphere of Dhaka, suggesting the anthropogenic origin of these elements in PM2.5. The source apportionment using PCA-APCS-MLR receptor model illustrated that the degradation of air quality of Dhaka City was influenced by five possible factors including soil dust, motor vehicle exhaust, sea salt, industrial emission and paint-battery.