Identification and Apportionment of Sources from Air Particulate Matter at Urban Environments in Bangladesh

Abstract

Particulate air pollution is the major concern in four major cities, Rajshahi, Dhaka, Khulna and Chittagong, in Bangladesh and thus it is necessary to understand the characteristics of the pollutant as well as sources for further improvement of the air quality. In this view particulate matter (PM) sampling was done between September 2010 to July 2012 from four Continuous Air Monitoring Stations (CAMS) located at Sapura in Rajshahi, Farm Gate in Dhaka, Baira in Khulna and a TV station, Khulshi, in Chittagong. PM sampling was performed using dichotomous samplers, which collect samples in two sizes: PM2.5 and PM2.5-10. All the samples were analyzed for mass, black carbon (BC), delta-C and elemental compositions. The data sets for each site were analyzed for sources with PMF2 modeling. The identified sources include brick kilns, soil dust, road dust, motor vehicle, metal smelter, fugitive Pb, Zn source and sea salt sources in case of coarse particles (PM2.5-10) depending on site. Among them, more than 62% of the PM2.5-10 was soil and road dust in Rajshahi, Chittagong and Khulna sites but in Dhaka, the dust contribution was about 38%. For fine particles (PM2.5), the identified sources are similar to those for the coarse particle samples, but their contributions are different. It was found that more than 63% of the fine particle mass comes from anthropogenic sources such as brick kilns, wood burning, biomass burning, and motor vehicles. The contribution of mass as well as black carbon and delta-C from the motor vehicles is much less than from brick kilns or biomass burning sources. The Government of Bangladesh is trying to reduce the emission from brick kilns by adopting green technologies for brick production. There is also long range transport of fine particles during winter time. The impacts of local sources also increase due to poorer dispersion conditions in the winter. Hence in order to reduce the local particulate pollution, it will be necessary to take policy actions regionally.