| Abstract
| - A chemical database for PM2.5 and PM2.0 aerosols hasbeen assembled for various sampling sites in China. Theprimarily urban sites, sampled from 1980 to 1993, includeBeijing, Tianjin, Wuhan, Lanzhou, and Guangzhou. From 13to 22 inorganic chemical elements were measured butfew secondary and organic compounds. Previous sourceresolution studies are briefly summarized. A mass balancefor the Beijing aerosol indicates that the three largestcomponents are carbon-containing matter (∼50%), (NH4)2SO4 (∼18%), and silicon compounds (∼12% expressedas silica). Silicon concentrations in Beijing and Lanzhouwere 26−36 times higher than Los Angeles. The fine siliconprobably comes from coal combustion, crustal sources,and rice straw burning, but the relative amounts are notcertain. Mass concentration data for Chinese cities werecompared among themselves and with downtown LosAngeles using scatter diagrams. Compositions of the Beijingaerosol were generally higher than Los Angeles; theBeijing PM2.0 mass in 1992−1993 was about 5 times thatof Los Angeles PM2.5 in 1986. In addition to significant changesover the years measurements were made, seasonal andregional variations were also observed. Mass fractions ofcrustal elements Ca, Al, Mn, Ti, and Fe in Beijing werehigher than Los Angeles, while Cu, Pb, Zn, Cr, and Ni werelower. For Lanzhou (1983) and Tianjin (1984), most PM2.5components show higher concentrations than central Beijing.
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