Spatial variation of mass concentration of roadside suspended particulate matter in metropolitan Hong Kong

This study conducted roadside particulate sampling to measure the total suspended particulate (TSP), PM10 (particles <10 μm in aerodynamic diameter) and PM2.5 (particles <2.5 μm in aerodynamic diameter) mass concentration in 11 urbanized and densely populated districts in Hong Kong. One hundred and thirty-three samples were obtained to measure the mass concentrations of TSP, PM10 and PM2.5. According to these results, the TSP, PM10 and PM2.5 mass concentrations varied from 94.85 to 301.63 μg m−3, 67.67 to 142.68 μg m−3 and 50.01 to 125.12 μg m−3, respectively. The PM2.5/PM10 ratio of all samples was 0.82 which ranged from 0.62 to 0.95. The PM levels and PM ratios in metropolitan Hong Kong significantly fluctuated from site-to-site and over time. The PM2.5 mass concentration in different districts corresponding to urban industrial, new town, urban residential and urban commercial were 77.64, 87.50, 106.96 and 88.54 μg m−3, respectively. The PM2.5 level is high in Hong Kong, and for individual sampling, more than 60% daily measurements exceeded the NAAQS. The mass fraction of PM2.5 in PM10 and TSP is relatively high when compared with overseas studies.