Carbonaceous species in total suspended particulate matters at different urban and suburban locations in the Greater Dhaka region, Bangladesh

Abstract

Particulate matters were collected at different urban and suburban locations in greater Dhaka region with a low volume sampler on Quartz filter papers. Total carbon (TC) was determined with combustion method and elemental carbon (EC) with two steps thermal method. Organic carbon (OC) was calculated from the difference between TC and EC. The grand average TC, EC, and OC concentrations in greater Dhaka were 81.2, 25.4, and 55.4 μg m−3, respectively. Average EC concentration was 32.4 ± 17.1 μg m−3 (urban Dhaka) and 18.4 ± 7.9 μg m−3 (suburban Dhaka). Average OC concentration was 76.7 ± 58.0 μg m−3 (urban Dhaka) and 34.1 ± 21.7 μg m−3 (suburban Dhaka). The average TC, OC, and EC concentrations at urban Dhaka were 52.2%, 55.5%, and 43.2% higher than the suburban Dhaka values, respectively. Very high concentrations were observed for carbonaceous species in Dhaka region. These may be due to the increased number of traffic vehicles, traffic jams, and also contributions from industrial growth in Dhaka city. Average EC/TC ratios are 0.34 for urban Dhaka and 0.37 for suburban Dhaka indicating typical fossil fuel is the source of carbonaceous species in greater Dhaka. The OC/EC ratio at urban Dhaka is 2.17, which is an indication of secondary OC formation rather than primary. The suburban Dhaka OC/EC ratio is 1.86 indicating OC is mostly primary origin. OC was the major carbonaceous component representing about 68% of the TC content (65% for suburban Dhaka and 70% urban Dhaka). A high fraction of OC in Dhaka aerosol may have serious implications for human health and climate change.