分辨率对大气中痕量污染气体的DOAS测量性能影响研究

Effect of Spectral Resolution on Measurement of Trace Gases in Atmosphere by Differential Optical Absorption Spectroscopy

在差分吸收光谱(DOAS)测量过程中,光谱分辨率的选择直接决定了污染气体浓度的测量准确度。主要研究了光谱分辨率对污染气体被检测到的特征吸收结构形状的影响,以及差分吸收截面随分辨率的变化趋势,从而确定了光谱分辨率对污染气体最低可检测浓度的影响,通过研究分辨率与光强的关系,确定了分辨率与信噪比(S/N)的函数关系式,得出了DOAS测量NO2,O3和SO2的最佳信噪比范围,对多种污染物标准气体进行了同时监测,计算出标准气体在不同光谱分辨率下的测量误差,确定了对NO2,O3和SO2监测的最适用的分辨率范围。在此分辨率范围既能够实现对痕量气体的准确定性定量测量,又能达到测量所需要的高灵敏度,强选择性和适用的时间分辨率。通过在北京丰台区的实际监测得到了与点式仪器测量结果很好的一致性。

In the differential optical absorption spectroscopy （DOAS） measurement, the accuracy of the pollutant concentration is determined by the selected spectral resolution. The effect of spectra resolution on the detected characteristic absorption structure of gaseous pollutants and the variation of differential cross section of gaseous pollutants with the change of resolution are studied. The effect of spectra resolution on the detection limits of gaseous pollutants is deduced, and the functional dependence of the signal-to-noise ratio （S/N） on the spectral resolution is reduced by studying the relationship between light intensity and spectral resolution, from which the resolution is determined for all the gaseous pollutants with the optimal S/N. The measurement error in detecting the standard gases at different spectral resolution is calculated. The optimized resolution range are determined for the gaseous pollutants, which can yield high sensitivity, good selectivity and reasonable time resolution for the accurate qualitative and quantitative analysis of NO2, O2 and SO2 . The real time monitoring of NO2, O3 and SO2 are carried out in the Fengtai district of Beijing, and the measurement result is in good agreement with the result of point instruments.