Trend and seasonal variations of atmospheric CH[sub4] in Beijing.

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]