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During 2001–2006, PM_2.5 (particle matter with aerodynamic diameter less than 2.5 microns) and PM₁₀ (particle matter with aerodynamic diameter less than 10 microns) were collected at the Beijng Normal University (BNU) site, China, and in 2006, at a background site in Duolun (DL). The long-term monitoring data of elements, ions, and black carbon showed that the major constituents of PM_2.5 were black carbon (BC) crustal elements, nitrates, ammonium salts, and sulfates. These five major components accounted for 20%–80% of the total PM_2.5. During this period, levels of Pb and S in PM remained rather high, as compared with the levels in other large cities in the world. Source apportionment results suggest that there were 6 common sources for PM_2.5 and PM₁₀, i.e., soil dust, vehicular emission, coal combustion, secondary aerosol, industrial emission, and biomass burning. Coal combustion was the largest …