Investigation of sources of atmospheric aerosol at urban and semi-urban areas in Bangladesh

Samples of fine and coarse fractions of airborne particulate matter (PM) were collected in a semi-residential (AECD) area from June 2001 to June 2002 of Dhaka and in an urban area of Rajshahi, a city in northwestern region of Bangladesh from August 2001 to May 2002. The samples were collected using a 'Gent' stacked filter sampler in two fractions of < 2.5 mum fine and 2.5-10 mum coarse sizes. The samples were analyzed for elemental concentrations by PIXE. The data sets were then analyzed by positive matrix factorization technique to identify the possible sources of atmospheric aerosols in these areas. The best solutions were found to be six and seven factors for elemental compositions for coarse and fine PM fractions in semi-residential Dhaka and five factors for elemental compositions of each of the coarse and fine PM respectively in the urban area of Rajshahi. The sources are soil dust, road dust, cement, sea salt, motor vehicles and biomass burning. The PMF results show that a large fraction of about more than 50% of the PM2.5-10 mass at both sites comes from soil dust and road dust. The motor vehicle including two strokes contributes about 48% of the PM2.5 mass in case of semi-residential area Dhaka. On the other hand, the biomass-burning factor contributes about 50% of the PM2.5 mass in Rajshahi. (C) 2004 Elsevier Ltd. All rights reserved.