Seasonal and diurnal variations of PM1.0, PM2.5 and PM10 in the roadside environment of hong kong

PM_1.0 (fine particles, with diameter < 1 μm), PM_2.5 (fine particles, with diameter < 2.5 μm) and PM₁₀ (coarse particles, with diameter < 10 μm) were measured at 24-hour intervals near a high-traffic road in Hong Kong, from October 2004 to September 2005. Mass concentrations were determined for the three particle fractions, averaging for PM_1.0, PM_2.5 and PM₁₀, respectively, 44.5±18.4, 55.4±25.5 and 81.3±37.7 μg·m⁻³. PM_2.5 was 3.7 times the U.S. EPA's annual NAAQS of 15 μg·m⁻³. Overall, PM_1.0 accounted for 44 to 69% (average 57%) of PM₁₀, while PM_2.5 accounted for 58 to 82% (average 71%) in this study. The particulate masses showed obvious seasonal patterns with high concentrations in cold seasons and low in warm seasons, especially high concentrations of PM_2.5-10 during the cold seasons. Diurnal variations of mass concentrations of PM_2.5 were determined during July, showing two major peaks in the morning and afternoon rush hours.