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.

► Peaks of PM in summer and winter were due to secondary formation and heating sources.
► Size-resolved patterns of crustal elements showed no significant seasonal variations.
► The contribution of vehicle emission to PM became stronger in smaller size range.
► Vehicle emissions contributed more to roadside PM2.5 than in the urban areas.
► As an indicator of construction dust, Ca declined most during the Olympics, 80.9%.