Seasonal Meteorological Influences on Particulate Matter (PM) Concentration in the Air of Dhaka City

Air Methods & Monitoring Part 1
Oral Presentation

Prepared by

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A 4-yr dataset (January 2013-December 2016) for PM2.5, PM10 and meteorological parameters is analyzed to investigate seasonal PM dependency on meteorology in the air of Dhaka-city. Seasonal interaction between PM and meteorology as well as different fluctuating pattern of PM2.5 and PM10 have not been well-explored in this region. Applying multiple-linear-regression model, it is observed that daily meteorological variation can explain up-to 56% of PM fluctuation. Wind-speed (PM2.5: r = -0.51; PM10: r = -0.49) and temperature (PM2.5: r = -0.54; PM10: r = -0.46) are found to be the two major predictors of PM variation. The dataset is classified into four seasons: winter, premonsoon, monsoon and postmonsoon. Cross-correlation analysis between PM and meteorological-variables reports distinctly different consequences of wind-speed, temperature and relative-humidity on PM for different seasons. Temperature shows high negative-correlation with winter-PM2.5 (PM2.5: r = -0.46; PM10: r = -0.29) and postmonsoon-PM (PM10 and PM2.5) (PM2.5: r = -0.43; PM10: r = -0.41), indicating the effect of reduction in boundary layer height and subsequent PM-level rise during low-temperature period. Negative-correlation is higher for winter-PM2.5 due to the increase in space-heating activities which primarily contribute to PM2.5. Regarding wind-speed, highest negative-correlation occurs for premonsoon-PM2.5 (r = -0.56) which represents the dilution-effect of increased win- speed on PM2.5, whereas for PM10, highest negative-correlation is obtained during winter (r = -0.54), indicating the near-surface wind-reduction effect of PM10. Considering relative-humidity, strongest negative-correlation is obtained for premonsoon (PM2.5: r = -0.66; PM10: and r = -0.64) and postmonsoon (PM2.5: r = -0.50; PM10: r = -0.52) season. In addition, during monsoon, negative-correlation is higher for PM10 compared to PM2.5 (PM10: r = -0.33; PM2.5: r = -0.22) which may refer to two-mechanisms: the wet-deposition effect of relative-humidity, which is more pronounced on PM10 compared to PM2.5 and growth of secondary-particulates in the presence of increased relative-humidity, which increases PM2.5. Findings from this study indicates that further research is needed in the field of meteorology to improve the air quality of Dhaka city.