Long-term monitoring and source apportionment of PM2.5/PM10 in Beijing, China.

During 2001-2006, PM2.5 (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 PM2.5 were black carbon (BC) crustal elements, nitrates, ammonium salts, and sulfates. These five major components accounted for 20%-80% of the total PM2.5. 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 PM2.5 and PM10, i.e., soil dust, vehicular emission, coal combustion, secondary aerosol, industrial emission, and biomass burning. Coal combustion was the largest contributor of PM2.5 with a percentage of 16.6%, whereas soil dust played the most important role in PM10 with a percentage of 27%. In contrast, only three common types of sources could be resolved at the background DL site, namely, soil dust, biomass combustion, and secondary aerosol from combustion sources.