Vertical dispersion of suspended particulates in urban area of Hong Kong

Field data are used to evaluate the vertical distribution of suspended particulates at different height levels in an urban area of Hong Kong. Four buildings in different street configurations and street environments were selected. According to the street configuration, they are classified into two groups: street canyon and open street. In street canyon, TSP and PM10 concentration varies with height exponentially. However, the rate of TSP, PM10 and PM2.5 decrease with distance from the ground floor is in decreasing order of TSP, PM10 and PM2.5. The particulate matter dispersion in street canyon is affected by the prevailing wind direction and the street configuration in particular the height-to-width ratio. In open streets, the vertical concentration depends on the vertical mixing, local dilution and other external factors such as sea breeze, as well as the proximity of trunk road and construction activity. Fine particulates contribute a major part of suspended particulates in Hong Kong and the impact can penetrate to the tenth floor and above. The PM2.5 level is high in Hong Kong and above 80% of the PM2.5 recorded in this field study exceeded the EPA NAAQS standards