Source apportionment of PM_2.5 in Beijing

One week integrated PM_2.5 samples were collected continuously at two sampling sites in Beijing: one at Chegongzhuang in a downtown area, and the other one on the campus of Tsinghua University in a residential area. The source contribution of ambient PM_2.5 by enrichment factor model and receptor model was studied. The enrichment factors of Na, Mg, Al, Si, Ca, and Fe at the two sites were all < 10 due to the contribution of biomass fuel combustion around Beijing. The other group was pollutant element including S, Cl, Cu, Zn, Se, Br, and Pb, The enrichment factors of these three elements were > 10, indicating that they were closely related with human activities. The enrichment factors of S, Zn, Se, Br, and Pb were even over 500. Sulfur mainly came from coal smoke and the conversion of SO₂ to sulfate. As Beijing now uses unleaded gasoline, lead may come from the coal and vegetation combustion. High enrichment level of these elements showed that the anthropogenic PM_2.5 in Beijing was caused by the combustion of fossil fuel. Coal boiler (residential boiler and industrial boiler) was the largest contributor of PM_2.5 at both sites, followed by secondary ammonium, road dust, vehicle exhaust and cement dust