Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
J Environ Sci (China). 2013 Mar 1;25(3):547-53. doi: 10.1016/s1001-0742(12)60090-4.
Gas chromatography equipped with an electron capture detector (GC-ECD) has been widely used for measuring atmospheric N2O, but nonlinear response and the influence of atmospheric CO2 have been recognized as defects for quantification. An original GC-ECD method using N2 as carrier gas was improved by introducing a small flow rate of CO2 makeup gas into the ECD, which could well remedy the above defects. The N2O signal of the improved method was 4-fold higher than that of the original method and the relative standard deviation was reduced from > 1% to 0.31%. N2O concentrations with different CO2 concentrations (172.2 x 10(-6)-1722 x 10(-6) mol/mol) measured by the improved GC-ECD method were in line with the actual N2O concentrations. However, the N2O concentrations detected by the original method were largely biased with a variation range of -4.5%-7%. The N2O fluxes between an agricultural field and the atmosphere measured by the original method were greatly overestimated in comparison with those measured by the improved method. Good linear correlation (R2 = 0.9996) between the response of the improved ECD and N2O concentrations (93 x 10(-9)-1966 x 10(-9) mol/mol) indicated that atmospheric N2O could be accurately quantified via a single standard gas. Atmospheric N20 concentrations comparatively measured by the improved method and a high precision GC-ECD method were in good agreement.
配备电子俘获检测器（GC-ECD）的气相色谱法已广泛用于测量大气中的 N2O，但非线性响应和大气 CO2 的影响已被认为是定量的缺陷。一种原始的 GC-ECD 方法，使用 N2 作为载气，通过向 ECD 中引入少量 CO2 补充气体进行了改进，这很好地弥补了上述缺陷。改进后的方法的 N2O 信号比原始方法高 4 倍，相对标准偏差从>1%降低到 0.31%。改进后的 GC-ECD 方法测量的不同 CO2 浓度（172.2 x 10(-6)-1722 x 10(-6) mol/mol）的 N2O 浓度与实际 N2O 浓度相符。然而，原始方法检测到的 N2O 浓度存在很大偏差，变化范围为-4.5%-7%。与改进后的方法相比，原始方法测量的农田与大气之间的 N2O 通量被大大高估。改进后的 ECD 的响应与 N2O 浓度（93 x 10(-9)-1966 x 10(-9) mol/mol）之间具有良好的线性相关性（R2 = 0.9996），表明可以通过单一标准气体准确地定量大气中的 N2O。改进后的方法和高精度 GC-ECD 方法比较测量的大气 N20 浓度具有良好的一致性。
