分辨率对DOAS测量二硫化碳影响的研究

差分光学吸收光谱技术(DOAS)由于易操作，耗费低，且具有高准确性和高分辨率等优点，非常适合对大气中难闻的有毒气体二硫化碳(CS₂)进行实时监测。在DOAS测量过程中，分辨率的选择直接决定了CS₂测量准确度。文章主要研究了分辨率对CS₂被检测到的特征吸收结构形状的影响，以及CS₂差分吸收截面随分辨率的变化趋势，从而确定了分辨率对CS₂的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CS₂的最佳信噪比范围为0.41～0.50 nm(FWHM)。在此范围既能够实现对CS₂的准确定性定量分析(五种标样线性相关性r＝0.999 9，测量10次的相对标准偏差小于0.3％)，又能达到对CS₂测量所需要的高灵敏度，高选择性和适用的时间分辨率同时保证了CS₂具有区别于其他物质的特征吸收结构。最后对北京市丰台区的CS₂进行了实时、连续地监测, 取得了良好的效果。

The Effect of Resolution on the Measurement of Carbon Bisulfide by DOAS

Featuring excellent response characteristics and detection sensitivity and with much lower operational cost,differential optical absorption spectroscopy(DOAS) can be a powerful tool to trace the concentration variation of carbon bisulfide(CS2),a kind of poisonous gas with bad smell.In the DOAS measurement,the accuracy of the carbon bisulfide results is determined by the selected spectral resolution.The present paper focuses on the effect of resolution on the detected characteristic absorption structure of CS2 and the variation in differential cross section of CS2 with the change in resolution,from which the effect of resolution on the detection limit of CS2 is deduced.In the end,the functional dependence of the ratio of signal to noise(S/N) on the resolution is reduced by studying the relationship between light intensity and resolution.And the optimized resolution is determined as 0.41-0.50 nm(FWHM) with the lowest S/N.The optimized resolution range can yield high sensitivity,good selectivity and a reasonable time resolution for the accurate qualitative and quantitative analysis of CS2(the results of five different concentration cells show linear correlation with r=0.999 9 and all the relative standard deviations are less than 0.3% with n=10).In the end,the long time,real time and continuous monitoring of CS2 was carried out in the Fengtai District of Beijing,and a good result was obtained.