A study of the human exposure to respirable suspended particulates in roadside microenvironments of metropolitan Hong Kong

Abstract

The aim of this research project is to use field study data to obtain the human exposure level to particulate concentration in metropolitan Hong Kong. The areas of interest cover the pollution level of particulates at roadside microenvironment in different season and district; their vertical distribution from ground level and chemical composition. In seasonal variation study, the weather condition and prevailing wind directions affect the concentration of Total Suspended Particulate (TSP), particulate matter less than l0um in aerodynamic diameter (PM10) and particulate matter with aerodynamic diameter between 2.5 and 10um (coarse particulate) even at roadside level. The variation of particulate matter less than 2.5um in aerodynamic diameter (PM2.5) is relatively insignificant and it contributes to a large fraction in the total particulate mass especially during the summer periods. The variations of the chemical components were divided into three groups. In spatial variation study, the result indicates that there are both inter-variation among the four land use categories and intra-variation within the districts in the same category. Four factors were extracted by the Principal Component Analysis (PCA) data analysis. They relate to 1) fossil fuel power plants and refineries emission; 2) oil burning; 3) vehicle emission, no interpretation has been made to the source of factor 4 yet. Results also showed that the sites with high TSP concentration have also high PM10 and PM2.5 concentrations and vice versa. Samples were collected at 4 sites including 2 open streets and 2 street canyons in vertical dispersion study. The concentration of TSP, PM10 and PM2.5 decreases with height in the 2 street canyons but the rate is different for each type of particulate matter. The vertical dispersion of particulate matters in open street is different. In general speaking, the problem of PM2.5 is serious in Hong Kong Metropolitan.