Coupling NASA Satellite Aerosol Data with Surface Low-cost Air Sensor Observations for Mapping Brick Kiln Particle Emissions in and Around the Megacity of Dhaka, Bangladesh

H. Helmig¹, P. Zarrah², P.K. Saha², A. Bari³ and A. Salam⁴

¹University of Colorado, Environmental Engineering; 720-209-8243, E-mail: hehe5295@colorado.edu
²Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh
³Department of Environmental & Sustainable Engineering, University at Albany, Albany, NY 12222
⁴Department of Chemistry, University of Dhaka, Dhaka, Bangladesh

With a mean annual PM_2.5 concentration of 77.1 (µg/m3) Dhaka, the capital of Bangladesh, and the country of Bangladesh have emerged as the 1^st and 2^nd most polluted capital and country in the world.  The annual mean PM_2.5 concentration in Dhaka is currently ranked 18.3 times above the World Health Organization (WHO) annual air quality guideline value. Much of this pollution is contributed by the brick kiln industry throughout the country, specifically surrounding Dhaka. The pollution arising from the traditional energy-inefficient methods used in brick manufacturing is estimated to result in approximately 6,000 deaths per year (Eil et al., 2020). Accurate mapping of the pollution distribution is the first step for developing science-based solutions and tools for addressing the pollution resulting from brick kiln pollution in Bangladesh. This study investigates the geographical distribution and seasonal variability of brick kiln pollution and meteorology effects using satellite and ground data.  Satellite aerosol optical depth (AOD) data from NASA’s MODIS instrument aboard the Aqua and Terra satellites and observations from the deployment of ground sensors around brick kiln industries in Dhaka, were considered and a relationship between these data was investigated. Results show that AOD values extracted from the Aqua and Terra satellites show a correlation to elevated ground-based PM_2.5 measurements in subdistricts of Dhaka which contain high amounts of brick kiln clusters. There are clear differences in surface concentrations of PM_2.5 between seasons in which producing months have more than a 500% increase than non-producing months. Although there is a correlation of decreased AOD values in regards to non-producing versus producing months, the differences are quite minute compared to those of PM_2.5 surface measurement variability.

Figure 1. Seasonal variability of AOD around major brick kiln clusters in the Dhaka region for the 2022 brick-producing (December - March) and non-production (April - November) seasons.

Figure 2. Satellite AOD results (left) averaged over the November through March production season.  The right part of the figure shows a comparison of monthly mean satellite data with surface observations in two of the ground  PM2.5 concentration measurements in Dhaka subdistricts (Narayanganj and Savar).