10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Ambient Air Quality in Dhaka Bangladesh over Two Decades: Impacts of Policy on Air Quality
Bilkis Begum, PHILIP K. HOPKE, Atomic Energy Centre, Dhaka
Abstract Number: 279 Working Group: Air Quality in Megacities: from Sources to Control
Abstract Samples of fine and coarse fractions of airborne particulate matter (PM) have been collected using a 'Gent' stacked filter unit from a semi-residential area at Dhaka from December 1996 until the present. The site is located at the Atomic Energy Centre, Dhaka University Campus which is a relatively low traffic area. During this period, many policies have been implemented to clean the air of Dhaka. Among them, banning of leaded-gasoline and two-stroke engines were implemented and a policy regarding green technology for brick burning is in progress. To observe the effects of the policy implementations, analyses were performed on this long-term (December 1996 to September 2015) data set of PM10, PM2.5, black carbon (BC), and lead (Pb). Year-wise concentrations of PM10, PM2.5, BC, and Pb were computed. There are characteristic seasonal variations for the PM10 as well as for the PM2.5 particles with elevated concentrations during the winter. The reasons for the high peaks during the winter are not only caused by seasonal fluctuations of the emissions, but also by meteorological effects. The statistical analyses of fine PM data indicate that fine PM concentrations in winter are also influenced by transboundary air pollution. Significant lead concentrations were still observed throughout the early 2000s. Pb is still being used in an uncontrolled manner in paints and there are also fugitive emissions from battery and other industries. It is likely that the major peaks are emissions from small battery reclamation efforts where there are no controls on emissions. These large spikes largely disappeared by 2006. The lead concentrations over the past decade are lower but still exceed the United States NAAQS value of 0.150µg/m3. It is, therefore, essential to continue the fight for lowering lead level in air through the removal of lead in paints and through the control of emission from suspected industries especially lead based battery industries by regulatory measures. It can be observed from long-term data that the air quality of Dhaka has been stable over the past decade even though economic activity and the number of sources like passenger cars and brick kilns are increasing.
Source apportionments have been conducted for the periods of 2001-2002, 2005-2006, 2007-2009, and 2009-2015. The mean contributions of motor vehicles to PM2.5 were 7.16, 5.62, 13.1, 3.19 μg/m3, and the contributions to BC were 2.50, 0.38, 1.33, and 0.15 μg/m3, respectively, showing the influence of the shift from gasoline and diesel to CNG as the primary transport fuel. The 2001-2002 results showed that vehicles normally produced about 50% of PM2.5 particulate mass. The most recent source apportionment data (2009-2015) show that the contribution of BC from motor vehicles has also decreased following CNG adoption. Brick kilns continue to be a major source of PM and BC with mean PM2.5 contributions of 2.2, 11.1, 5.6, 14.1 μg/m3 and BC contributions of 1.37, 4.14, 1.53, 3.93 μg/m3, respectively for the four, time intervals. Thus, there have been positive results for the governmental policies, but significant further reductions will be required, particularly from brick production, to achieve concentrations that meet typical health protective air quality standards.