One-year aerosol characterization study for PM2.5 and PM10 in Beijing

Abstract A one–year–long aerosol characterization study was conducted from July 2002 through July 2003, in Beijing, China. Twenty–four hour PM 2.5 and PM 10 filter samples were collected, and about 50 aerosol samples of each type were obtained. Organic, elemental, and total carbon, levoglucosan and other organic compounds, and inorganic ionic species were measured. The overall mean PM mass concentrations were 99 and 175 μg/m 3 for PM 2.5 and PM 10 , respectively. Total carbon was the main component in both PM 2.5 and PM 10 , with overall mean concentrations of 21 and 30 μg/m 3 , respectively. Of the organic compounds measured, levoglucosan exhibited the highest levels (overall mean of 0.31 ng/m 3 in PM 2.5 and of 0.40 ng/m 3 in PM 10 ). Sulfate was the most prominent inorganic ionic species, with overall mean levels of 15.6 and 17.0 μg/m 3 in PM 2.5 and PM 10 , respectively. Most components measured were predominantly present in the PM 2.5 size fraction; the overall mean PM 2.5 /PM 10 ratio was typically in the range of 0.7–0.8, but this ratio was only 0.55 for the PM mass and for Ca 2+ it was as low as 0.19. In PM 2.5 , total carbon exhibited relatively larger concentration levels (30 μg/m 3 ) in winter than in the other seasons. K + also exhibited a relatively high concentration level in the winter season, with 2.3 μg/m 3 in PM 2.5 . The contribution from biomass burning to K + in PM 2.5 was estimated on the basis of the levoglucosan data and the minimum K + /levoglucosan ratios obtained throughout the year; it was found that the contribution was largest in autumn, with 44%.