Vertical dispersion of the air pollutants of indoor environment in urban areas

Abstract

Due to rapid urbanization in developing countries more and more multi storey buildings including high-rise buildings are constructed along the main roads obstructing the air movement. With the increased traffic densities, vehicular air pollutants tend to be stagnant near the ground level, allowing vertical dispersion to be prominent which requires a detailed study. Even though there are studies on the vertical dispersion of air pollutants in the troposphere, only a few numbers of studies has been carried out to investigate the air pollutant variation with respect to the height of a middle-rise building which also can be affected by the local conditions. This study was aimed at investigating the vertical profile of air pollutants of middle-rise buildings located adjacent to a road which is having the highest annual daily traffic in Colombo, the capital city of a developing country, Sri Lanka. In the selected building which is having eight stories, short term measurements of NCL, CO2 and PM2.5 concentrations were obtained in five locations at each floor level covering free running and air conditioned spaces. The measurements were taken for five days during office hours. The experimental results show a negative trend of NO2 and PM2.5 distribution with height of the building whereas the vertical profile of CO2 concentration shows a positive trend in the free running spaces. Diverging from this observation, the pollutant concentrations in the mechanically ventilated spaces show a random variation with the increasing height. These results will aid the building planners to design and plan the building ventilation system in order to maintain comfortable and healthier indoor environment.