北京上甸子站气相色谱法大气CH4和CO在线观测方法研究

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.

Study on the in-situ Measurement of Atmospheric CH4 and CO by GC-FID Method at the Shangdianzi GAW Regional Station

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.