北京上甸子站气相色谱法大气CH_4和CO在线观测方法研究

Study on the in-situ Measurement of Atmospheric CH_4 and CO by GC-FID Method at the Shangdianzi GAW Regional Station

参照瓦里关全球大气本底站气相色谱在线观测系统的设计,通过系统调试、测试和参数优化,于2009年在北京上甸子区域大气本底站建立了高精度气相色谱法大气CH4和CO在线观测系统.该系统对CH4和CO的测量精度分别优于0.03%和0.45%,达到世界气象组织全球大气观测计划(WMO/GAW)的质量目标.研究建立了与该系统配套的标气选取方法及运行序列:选取可基本涵盖该站大气CH4和CO浓度范围的2瓶标气作为工作标气,其中CH4浓度分别为2 007.1×10-9、1 809.5×10-9(摩尔分数,下同),CO浓度分别为405.6×10-9、123.8×10-9,在高低浓度工作标气之间穿插分析3次大气样品,能够保证测量的准确度(观测浓度的标准偏差CH4<1.7×10-9、CO<1×10-9),同时可最大程度地节省工作标气.该方法已应用于华北地区本底大气CH4和CO的高精度连续观测.

In-situ GC-FID system for atmospheric CH4 and CO mixing ratio measurements at the Shangdianzi （SDZ） GAW regional station in Beijing was designed and optimized in 2009 based on a comparable system at the Waliguan GAW global station in Qinhai. Results from this study indicate that the system＇s precisions for CH4 and CO are higher than 0.03% and 0.45% respectively, which can meet the quality target on background greenhouse gas observations by the World Meteorology Organization＇s Global Atmosphere Watch （WMO/GAW） program. The selection method of working standards for this system was established： two working standards（WH for the high concentration and WL for the low concentration） were selected, the concentrations of CH4 and CO in these two standards can cover the ambient mixing ratios of CH4 （2007.1×10-9 and 1809.5×10-9） and CO （405.6×10-9and 123.8×10-9）, an injection sequence was programmed so that the two standards were analyzed alternatively for every three runs. The measurement accuracies are high, as shown by the standard deviations less than 1.7×10-9 and 1×10-9, for CH4 and CO, respectively. This method has been applied to in-situ measurement of atmospheric CH4 and CO in North China.