LONG-TERM TREND AND SEASONAL CYCLE OF ATMOSPHERIC METHANE

Ⅰ. INTRODUCTIONMethane is one of the most abundant trace gases in the earth’s atmosphere with the current concentration of 1.7 ppm. It appears to be primarily of biogenic origins, and has long been regarded as one natural component unchanging in concentration. However, the observations corroborated by our recent work have indicated that the concentration of at-

Concentration and Variation of Atmospheric Methane in Beijing

Methane is of radiational activity and chemical activity.An increase of atmospheric CH4 may cause great changes in climate and atmospheric chemical processes,which may lead to serious impact on environment.The

北京大气甲烷季变化及发展趋势

近年来北京大气中CH4含量仍在上升 ,但平均增长率已从 1985～ 1989年的 1 76 %·a- 1 ,下降到 1990～ 1997年的 0 50 %·a- 1 ;冬季和夏季两次出现峰值 ,表现出明显的双峰模态季节变化。但北京大气CH4变化的最大特点是年际季变化不均一 ,12年中 ,北京大气CH4共计增长185× 10 - 9混和体积比 ,其中冬季增长的贡献为 6 9× 10 - 9混和体积比 ,约占总增长的 37% ;而夏季的增长贡献不足 4 0× 10 - 9混和体积比 ,约占总增长的 2 1%。 90年代以后 ,北京大气CH4增长率进一步减慢 ,主要原因是生物源排放不再增加 ,而非生物源排放量的增长是大气CH4继续增长的主要原因。