According to the Greenpeace South Asia report: “air pollution will cause around 7 million premature deaths globally next year and have a major economic impact”. Also mentioned Bangladesh, one of the most densely-populated countries in the world, has been struggling with air pollution for long. Dhaka, the country’s capital, often finds its place among the most polluted cities in global indices.
The report focuses on PM2.5 as a measurement of air pollution. PM2.5 refers to particulate matter (ambient airborne particles) which measure up to 2.5 microns in size, and has a range of chemical makeup and sources. “Pollution is not a new phenomenon; it is largely controllable and often avoidable, but considerably neglected”.
Meteorological conditions play a crucial role in ambient air pollution by affecting both and directly and indirectly the emissions, transport, formation, and deposition of air pollutants.
Bangladesh Present Scenario:
Dhaka, the capital city of Bangladesh, is one of the air pollution hotspot among the megacities in the world; however, the potential meteorological influences on criteria air pollutants for this megacity are remained less studied. The objectives of this research were to examine the relationships between meteorological parameters such as daily mean temperature (o C), relative humidity (%) and rainfall (mm) and, the concentration of criteria air pollutants (SO2, CO, NOx, O3, PM2.5 and PM10) from January, 2013 to December, 2017. This study also focused on the trend analysis of the air pollutants concentration over the period. Spearman correlation was applied to illustrate the relationships between air pollutants concentration and temperature, relative humidity and rainfall. Multiple linear and non-linear regressions were compared to explore potential role of meteorological parameters on air pollutants’ concentrations. Trend analysis resulted that concentration of SO2 is increasing in the air of Dhaka while others are decreasing. Most of the pollutants resulted negative correlation with atmospheric temperature and relative humidity, however, they showed variable response to seasonal variation of meteorological parameters
Dhaka is located in the central part of the country (23°41’N latitude and 90°22’E longitude) lying on the lower reaches of Ganges Delta. It covers a total area of 306.38 km2. Dhaka is vulnerable to flooding in heavy rainfall and a cyclone during rainy season due to its topographical condition as it is flat and close to sea level. The city is surrounded by Gazipur, Tangail, Munsiganj, Narayanganj and Rajbari districts. This study utilized continuous air quality data from three Continuous Air Monitoring Stations (CAMS) in Dhaka namely Parliament area (CAMS1), Bangladesh Agricultural Research Council (BARC, Farmgate Area, CAMS2) and Darus Salam (Mirpur, CAMS3) established by DoE, MoEFCC, Governtment of Bangladesh under the Clean Air and Sustainable Environment (CASE) project. Fig. 1 shows the map of study area with continuous air pollutants monitoring stations installed in Dhaka city.
Air quality data consisted of daily mean concentration of six criteria air pollutants such as PM10 (µg/m3), PM2.5 (µg/m3), NOx (µg/m3), CO (ppm), O3 (µg/m3), and SO2 (µg/m3) over the period of January 2013 to December 2017 were collected from Clean Air and Sustainable Development (CASE) project, Ministry of Environment, Forest and Climate Change, Government of Peoples Republic of Bangladesh. CASE records concentrations of air pollutants of Dhaka hourly from three continuous air monitoring stations indicated in Fig. 1. For measuring concentrations of PM2.5 and PM10 an automatic