Chemical characteristics of size-resolved PM₂.₅ at a roadside environment in Beijing, China

Size-resolved particulate matter in the three size ranges (0.2–0.5 μm, 0.5–1.0 μm, and 1.0–2.5 μm) were collected at a roadside site in Beijing during and after the 2008 Olympic Games. The concentrations of PM mass, 14 elements, 3 major inorganic ions, and carbonaceous species were determined. The main contributors to PM₂.₅ were crustal sources, vehicle emissions, secondary aerosol formation along with coal combustion, biomass from burning, and industrial processes, with vehicle emissions contributing more to roadside PM₂.₅ than in the urban areas. The peaks at 0.5–1.0 μm in summer for PM mass and inorganic ions were most likely due to secondary aerosol formation, whereas the peaks at 0.2–0.5 μm in winter for PM mass and some elements were probably attributed to combustion from heating sources. The temporary control measures applied during the Olympics showed different effects on various emission sources and chemical species.