Abstract
The Chemical Mass Balance (CMB) model is one of several receptor models that have been applied to air quality management. This model quantifies contributions using chemical signatures characterizing source-types rather than contributions from individual emitters. The CMB model uses the chemical composition of ambient pollution samples to estimate the contributions of different source types to the measured pollutant concentrations. The disadvantage of the model is that it cannot separate the sources having similar chemical compositions or for those sources for which source composition profiles are unavailable. Since CMB analysis is done on a sample-by-sample basis, it is possible to estimate the daily contributions of individual sources, and can thereby provide useful information based on a limited number of samples to address air quality management issues. Samples of fine and coarse fractions of airborne particulate matter (PM) were collected using a ‘Gent’ stacked filter unit in two fractions of 0-2.2 μm and 2.2-10 μm sizes in a semi-residential (Atomic Energy Centre Dhaka, AECD) area from June 2001 to June 2002 of Dhaka. These samples were analyzed for elemental concentrations with PIXE. The chemical composition data set was analyzed by CMB using local source profiles obtained using a Principal Components Analysis (PCA) and regression analysis of data from this site and the source contributions are quantitatively estimated for each of the samples. The results of the CMB analysis were compared with the results obtained using positive matrix factorization (PMF) that had been done previously. It is observed that CMB provides comparable results except for limited discrepancies, especially for the PM2.2 fractions where sources have similar elemental signatures.
Highlights
Air pollution is a common concern in the large and growing metropolitan areas throughout the world, especially in South East Asian cities
The yearly average values for both PM10 and PM2.2 masses (Begum et al, 2006a) are much higher than the 1997 United States Environmental Protection Agency (USEPA) standards as well as the Bangladesh national air quality standard for PM10 and PM2.5 that were set at 50 μg/m3 and 15 μg/m3, respectively
Principal Components Analysis (PCA) and positive matrix factorization (PMF) method can produce comparable source profiles, The PMF source profiles have been used for these sources
Summary
Air pollution is a common concern in the large and growing metropolitan areas throughout the world, especially in South East Asian cities. Particulate matter (PM) is recognized as the most important air pollutant in the Dhaka, the capital city of Bangladesh (Begum et al, 2006a). The vehicles are believed to constitute the dominant source of air pollution in Dhaka (Begum et al, 2004). Construction of roads and buildings is taking place continuously throughout the city. Brickfields that use coal and wood to fire the bricks, have grown up around Dhaka city because of the increased demand of construction materials and these brickfields are major contributors to the air pollution in winter since they operate only winter when the meteorological conditions are sufficiently dry (Salam et al, 2003)
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