AbstractWeekly PM2.5 samples were simultaneously collected at a residential (Tsinghua University) and a downtown(Chegongzhuang) site in Beijing from July 1999 through September 2000. The ambient mass concentration andchemical composition of the PM2.5 were determined. Analyses included elemental composition, water-soluble ions, andorganic and elemental carbon. Weekly PM2.5 mass concentrations ranged from 37 to 357 mg/m3, with little differencefound between the two sites. Seasonal variation of PM2.5 concentrations was significant, with the highest concentrationin the winter and the lowest in the summer. Spring dust storms had a strong impact on the PM2.5. Overall, organiccarbon was the most abundant species, constituting no less than 30% of the total PM2.5 mass at both sites.Concentrations of organic and elemental carbon were 35% and 16% higher at Tsinghua University than atChegongzhuang. Ammonium, nitrate and sulfate were comparable at the sites, accounting for 25–30% of the PM2.5mass. r 2001 Elsevier Science Ltd. All rights reserved.
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