红外光谱大气CO2及其碳同位素探测中的测量误差和反演算法研究

Precise atmospheric CO2 and its carbon isotope ratio observations provide the fundamental data on which our understanding greenhouse gas emission is based. Fourier Transform Infrared (FTIR) spectroscopy has the advantages of high precision, multi-component and real-time on-line measurement. However, the current detection precision cannot meet the needs of ecosystem greenhouse gas circulation research, because that the nonlinear effect of instrument line-shape, gas temperature, gas pressure and water vapor absorption which will result in measurement error. .In view of this, the program will study nonlinear least square fitting multi-component retrieval algorithm based on digital synthetic calibration spectra. In the base of the exploration of influence rules of spectrum quantitative analysis affected by gases temperature and pressure, water vapor absorption in the detection of CO2 and its stable carbon isotope ration, the FTIR detection method model based on the combination of environmental parameter control and error correction algorithm will be established, improving the measurement precision of CO2 and δ13CO2 value based on infrared spectroscopy, then make the method develop into an significant technology and method of monitoring the emission of greenhouse gases and understanding the process of greenhouse gases dynamic change.

高精度大气CO2及其稳定碳同位素比值连续观测数据是研究温室气体排放的数据基础。傅里叶变换红外光谱技术具有高精度、多组分、实时在线监测的优势，但由于仪器线型、气体温度、气压和水汽吸收等因素对光谱的非线性作用所导致的测量误差，使其检测精度不能满足生态系统温室气体循环研究的需求。.鉴于此，本项目拟研究基于数字合成校准光谱的非线性最小二乘拟合多组分反演算法，探索傅里叶变换红外光谱法检测大气CO2及其稳定碳同位素比值中气体温度、气压和水汽吸收对光谱定量分析的影响规律，构建环境参数控制和误差修正算法相结合的FTIR检测方法，提高红外光谱法探测大气CO2和δ13CO2值的检测精度，使其发展为监测温室气体排放、理解温室气体动态变化过程的重要技术和方法。

傅里叶变换红外光谱（FTIR）技术具有频带宽、通量大、分辨率高等优势，具备满足ILC目标进行多组分同时检测的潜质。然而目前国内基于FTIR技术开展的温室气体检测研究，其检测精度和准确度与ILC目标均存在较大差距，尚不能满足大气本底检测的需求；国内基于FTIR技术开展δ13CO2值检测的报道也见诸甚少。其主要原因是基于FTIR技术的光谱定量反演受到光谱仪分辨率、信噪比等仪器参数，气体温度和气压不稳定性，以及水汽等干扰组分交叉吸收的影响。.项目对光谱响应波段，分辨率，吸收光程和信噪比的需求进行计算分析，并提出气体温度稳定性控制，压强稳定性控制和水汽吸收控制的设计方案和思路，在此基础上，优化设计检测系统，检测系统包括光谱仪系统，温度控制与监测系统，气压控制与监测系统和全密封气路干燥系统；结合分子红外吸收特征，研究了适于多组分同时检测的光谱反演波段。.提出敏感性误差修正方法。从理论模拟和实验验证两方面，定量研究温度敏感性，气压敏感性和水汽交叉吸收敏感性，提出气体特性控制和敏感性修正相结合的误差控制方法，提高测量精度。.最后，通过标准气体实测实验，测试了检测系统的测量精密度和准确度性能，实验表明，连续检测CO2和δ13CO2值的精度分别为0.24µmol•mol-1和0.523‰，测量准确度分别为0.46µmol•mol-1和-0.499‰，检测系统对温室气体浓度的检测基本满足ILC目标，并能同时对δ13CO2值进行连续测量；开展了环境大气连续测量实验，为FTIR技术在本底大气检测领域的应用奠定了理论基础。