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

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%以下.

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

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%.