Abstract
Particle emissions derived from construction activities have a significant impact on the local air quality, while the canyon effect with reduced natural ventilation contributes to the highest particulate pollution in urban environments. This study attempted to examine the effect of PM10 emissions derived from the construction of a rail transit system in an urban street canyon. Using a 3D computational fluid dynamic (CFD) model based on a real street canyon with different height ratios, this study formulates the impact of height ratio and wind directions on the dispersion and concentration of PM10. The results indicate that parallel flow would cause the concentration of PM10 at the end of the street canyons in all height ratios, and the trends in horizontal, vertical and lateral planes in all street canyons are similar. While in the condition of perpendicular flow, double-eddy circulations occur and lead to the concentration of PM10 in the middle part of the street canyon and leeward of backwind buildings in all height ratios. Furthermore, perpendicular flow will cause the concentration of PM10 to increase if the upwind buildings are higher than the backwind ones. This study also shows that the dispersion of PM10 is strongly associated with wind direction in and the height ratios of the street canyons. Certain measures could, therefore, be taken to prevent the impact on people in terms of the PM10 concentration and the heights of street canyons identified in this research. Potential mitigation strategies are suggested, include measurements below 4 m according to governmental regulations, dust shields, and atomized water.
Highlights
With declining urban environment quality due to increasing air pollution levels, the study of pollutant transport in urban areas has attracted considerable interest in the past few decades [1,2].The concentration of ultrafine particles has largely been singled out for their impact on human health, urban climate change and visibility impairment [3,4,5,6,7,8]
This study focuses on PM10 mass concentration and dispersion due to construction activities by examining three height ratios (0.5, 1 and 2)
These height ratios are crucial for the accurate computational fluid dynamic (CFD) simulation of perpendicular and parallel flow inside a street canyon [34]
Summary
With declining urban environment quality due to increasing air pollution levels, the study of pollutant transport in urban areas has attracted considerable interest in the past few decades [1,2]. Due to rapid urbanization and the resultant development, particles from construction activities play a crucial role in determining urban air quality [12,13]. Because of the adverse health effects of these particles, evaluating their concentration and dispersion in urban street canyons becomes a very important research focus. Others have investigated the emission factors and their impacts on air quality surrounding construction activities. Only very few researchers have studied the characteristics of real-world emissions of construction activities [18]. Such real street canyon modeling could generate information often ignored in most other studies, such as the influence of the heights of adjacent buildings (height ratio) and gaps between buildings which are very useful for devising mitigation strategies. The findings can assist construction contractors to develop prevention strategies for PM10 pollution and improve air quality within and outside construction sites
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