气相色谱法对本底大气氧化亚氮浓度的标气定量方法研究

利用气相色谱-电子捕获检测器法(GC-ECD)测量大气中氧化亚氮(N_2O)浓度是目前广泛使用的方法,但ECD分析N_2O时存在线性范围较窄的缺点,因此,标气数量和定量方式是决定分析结果的关键因素.基于此,本文对比分析了单点线性校正法(S)、多点线性拟合法(D)、单瓶标气近似校正法(SA)、单瓶标气比值校正法(SC)对N_2O检测分析结果的差异.结果表明,SA定量相对误差最小,对测试使用的6瓶标气定值平均误差为0.09×10~(-9).根据本底大气N_2O观测精度要求,以及我国大气N_2O浓度变化范围较大的特征,推荐选用SA法对大气中N_2O浓度进行定值.依据所选方法对黑龙江龙凤山本底站大气N_2O浓度进行观测(2015年1—12月),结果显示,黑龙江龙凤山站大气N_2O浓度最高值出现在4—5月,平均值超过330×10~(-9).该站大气N_2O浓度主要受人为活动排放的影响.

Research on the working standards calibration method for measuring atmospheric nitrous oxide concentration

Gas Chromatography-Electron Capture Detector (GC-ECD) is a widely used method for measuring atmospheric nitrous oxide (N₂O). As ECD detector has a very narrow linearity response range, the number and calibration method of the standard gases are the key factors for determining the N₂O mole fractions. In this study, four commonly used N₂O calibration methods were compared on the calibration results, which were single-point calibration with linear regression (S), multi-point calibration with linear regression (D), single standards with offset compensation (SA), and single standards with curve ratio correction (SC). The results indicate that, the relative errors of SA was the smallest among the four methods, with the average bias of 0.09×10^-9 for the 6 testing standards. Considering the precision need and the large variation of atmospheric N₂O in China, the SA was strongly recommended to be adopted. By using the SA method, atmospheric N₂O was continuous measured at the Longfengshan background station during 2015. The results showed that the peak N₂O values were observed from April to May, with the average mole fractions exceeding 330×10^-9. The atmospheric N₂O concentrations at Longfengshan were mainly influenced by emissions from agricultural field in summer-autumn period, whereas were influenced by anthropogenic emissions during winter-spring period.