分析温室气体及CO2碳同位素比值的傅里叶变换红外光谱仪

改进了傅里叶变换红外分析仪（FTIR）的硬件设计以实现温室气体及CO₂碳同位素比值的多组分、高精度、连续自动测量。首先，对FTIR分析仪测量系统进行了设计和理论分析，引入了温度和压力监控系统以及全密封气路干燥系统。然后，讨论了光谱的定量分析过程。最后，设计了标准气体对比测量实验。实验结果表明：分析仪测量CH₄，CO，CO₂和δ¹³CO₂值的标准偏差分别为0.01×10^-6，0.011×10^-6，0.239×10^-6和0.572‰，与常规FTIR测量系统相比，其检测的标准不确定度分别提高了6.3，8.45，10.54和14.73倍，其系统误差分别提高了2.88，1.93，4.67和4.66倍；对比分析仪与同位素质谱仪对δ¹³CO₂值的测量结果，标准偏差分别为0.572‰和0.171‰，二者测量的标准不确定度相近。所设计的温室气体及CO₂碳同位素比值FTIR分析仪能够满足多组分、高精度、连续自动测量的需要。

Fourier transform infrared greenhouse analyzer for gases and carbon isotope ratio

The hardware design of a Fourier Transform Infrared (FTIR) analyzer was improved to realize the simultaneous and continuous measurements of greenhouse gases and δ¹³CO₂ values in high Precision. Firstly, the FTIR measurement system was designed and analyzed theoretically, and the temperature and pressure monitoring systems and sealed drying gas circuit were introduced into the spectroscopy. Then the process of quantitative spectral analysis was presented. Finally, the comparative measurements were designed by using standard gases. Experimental results on CH₄, CO, CO₂ and δ¹³CO₂ indicate that the Standard Deviations(STD) measured by the designed analyzer are 0.01, 0.011, 0.239× 10^-6 and 0.572‰, the standard uncertainty of designed measurement system is improved about 6.3, 8.45, 10.54 and 14.73 times that of routine FTIR measurements, and the system errors are improved about 2.88, 1.93, 4.67 and 4.66 times, respectively. The comparison of the measurement results between the analyzer and the Isotope Ratio Mass Spectrometer (IRMS) for δ¹³CO₂ value shows that the STDs are 0.572‰ and 0.171‰ respectively, and the standard uncertainty of the both methods is similar. The FTIR analyzer for greenhouse gases and carbon isotope ratios satisfies the requirements of measurements for multi-species, online and high precision.