Meteorological influences on air quality in Bangladesh

Abstract

As the cities in Bangladesh get more industrialized, more development projects are undertaken, making the surrounding air more polluted. The air pollution in major cities of Bangladesh has become quite acute in recent years. Among all components, PM2.5 is considered to be one of the major harmful elements. Due to its tiny particle size, it can enter the bloodstreams of respiratory tracts and even can cause death.Therefore, it is crucially needed to understand the particulate matter characteristics, to bring it down to a moderate level. Since, studies showed that, meteorology has significant influence on PM variation, approach has been taken in this study to understand the influence of meteorology on PM variation over the region of Bangladesh. Air quality and meteorological data from Department of Environment (DoE) for the period of 2013-2018 for eleven stations (CAMSs) of Bangladesh are collected. Among eleven existing stations, we perform analysis on eight available stations and the remaining three are discarded due to theirpoor-quality data. We perform annual and seasonal cross correlation analysis to identify major influential parameters on PM variation at different times of the year. We also perform multiple linear regression analysis (MLR) using interaction terms to understand the combined effect of meteorological parameters on PM. Annual cross correlation analysis shows that, wind speed, temperature,solar radiation and relative humidity are effective parameters for PM2.5 and wind speed, relative humidity,rainfall duration andrainfall are effective parameters for PM10variation. Wind speed, relative humidity,temperature, rainfall duration and rainfall amount show negative correlation with PM and solar radiationshow positive correlation with PM. Seasonal analysis shows that, low wind speed causes PM accumulation in winter and post-monsoon, whereas, high wind speed causesPM dilution in pre-monsoon and monsoon. Change in temperature can change boundary layer height and subsequently alter ambient PM. This effect of temperature is found to be effective throughout the year. However, bioaerosol formation in presence of temperature is observed during monsoon. Relative humidity is inversely correlated with PM and the correlation is highest in monsoon for majority of thestations. However, due to its location in coastal area and intrusion of sea aerosol,Chattogram shows weak correlation between relative humidity and PM in monsoon. Solar radiationshows positive correlation with PM throughout the year. The duration of rainfallis found to be more effective in PM removal compared to amount of rainfall. Highest negative correlation between precipitation and PM is observed inSylhet, since it is the region of highest consistent rainfall in Bangladesh. MLR analysis showed that local meteorology could explain up to 17% to 78% PM variation in major cities of Bangladesh. The interaction between temperature, relative humidity and wind speed and their combined effect are found to have major influence on PM for most of the stations. This study gives a comprehensive idea on how much influence meteorological parameters can have on PM variation in different cities in Bangladesh for different seasons. Findings of this study are expected to be helpful in decision making for adoption of pollution control measures and evaluating different climate change mitigation and adaptation approaches.