Characterization of PM_2.5 Chemical Composition in the Ambient Air of Beijing, China

Weekly PM_2.5 measurements were performed continuously at two sampling sites for over 1 yr starting July 1999 to establish a comprehensive database to describe fine particulate pollution in Beijing. Mass, ions, carbon, and carbon 40 elements were measured. The Chegongzhuang site laid between the western second and third ring roads, both artery roads in the urban area with busy traffic, while the Tsinghua site laid outside of the northern fourth ring road also with busy traffic. PM_2.5 to PM₁₀ and total suspended particles peaked in winter and were lowest in spring, suggesting substantially increased heating sources in winter contributed more to fine particles, while frequently occurred dust storms in spring did more to coarse particles. Contrary to the seasonal patterns of SO₂ gas, summer average of sulfur was much higher than those in the spring and autumn.