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Abstract: In 1999 aerosol samples were collected by cascade at Meteorological Tower in Beijing. The 12 group aerosol samples obtained were analyzed using PIXE method, which resulted in 20 elemental concentrations and size distribution of elemental concentrations. From the observation, the elemental concentrations, size distribution of elemental concentrations and their variations are analyzed. It shows that concentrations of the most elements in aerosols increase greatly compared with those in the past except that the concentrations of V, K, Sr, and the source of aerosols has changed greatly in the past decade. Fine mode aerosols increase more rapidly in the past decade, which may be due to the contribution of coal combustion and automobile exhaust. Pb content in aerosol is much higher than that at the beginning of 1980s, and has a decreasing trend in recent years because of using non-leaded gasoline. [ABSTRACT FROM AUTHOR]

Abstract: The atmospheric CH[sub 4] in Beijing is still increasing, even though its increasing rate has significantly decreased from 1.76%/a during 1985--1989 to 0.50%/la during 1990--1997. The seasonal variation of CH[sub 4] concentration showed a double-peak pattern, one peak appearing in winter and the other in summer. It is evident that the annually seasonal variations of atmospheric CH[sub 4] in Beijing are different. From 1986 to 1997, the atmospheric CH[sub 4] increased by 185 pphv, 37% and 21% of which were due to the increase in winter and in summer, respectively. After 1993, the annually seasonal increasing rate of CH[sub 4] concentration in summer (due to emission from biogenic sources) is negative while the increasing rate in winter (due to emission from non-biogenic sources) is positive about 25 ppbv/a. As a result, the increase of CH[sub 4] emission from non-biogenic sources in winter is the major reason that caused the annually seasonal increasing rate from 1993 to 1997. The biogenic sources in Beijing are shrinking while the non-biogenic ones (such as fossil fuel combustion) are enlarging. [ABSTRACT FROM AUTHOR]