差分吸收光谱法测量大气痕量气体浓度误差分析及改善方法

Error Analysis and Improvement Method of Concentration Measurement of Trace Gas in the Atmosphere by Differential Optical Absorption Spectroscopy

差分吸收光谱技术 (DOAS)中采用线性最小二乘拟合方法 ,用痕量气体标准差分吸收截面对测量得到的差分吸收光谱进行拟合 ,得出大气中痕量气体的浓度 计算结果的准确性不仅取决于光谱的测量精度 ,而且受标准差分吸收截面以及仪器函数和温度等诸多因素的影响 详细地分析了计算误差的产生原因 ,提出了用高浓度样品池得到标准吸收截面的方法 ,针对光谱固有结构 ,以及温度对标准吸收截面的影响 ,改进了浓度反演算法 大量的实验表明 ,综合运用上述方法 ,即便对低浓度的样气 ,相对测量误差也能降低到 10

Differential optical absorption spectroscopy-DOAS has become a widely used method to measure trace gases in the atmosphere. The concentrations of trace gases can be retrieved by fitting differential absorption spectra with standard differential absorption cross-section using the linear least-square method. The accuracy of computational solution not only depends on the measurement precision of spectrum, but suffers influence of many factors such as absorption cross-section as well as instrument function and temperature etc. The paper has detailedly analyzed the causes giving rise to calculation error, and has put forward getting standard cross-section method using high density cell spectra, and improved algorithm to consider intrinsic structure of spectrum as well as the influence of the standard absorption cross-section with temperature changing. A large number of experiments indicate, using above-mentioned method synthetically, even for low density gas, can reduce the error of measuring to fewer than 10%.