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一、引言二氧化硫气体已作为大气污染的一个重要指标,它的浓度测定颇为人们所重视。 SO_2气体在中红外和近红外区域的三条谱带位置分别在7.3μ、8.7μ和18.5μ,而在7.3μ处吸收系数最大(见图1),这一点对提高灵敏度颇为有利。一般我们在无其他气体存在时测量SO_2气体浓度可选择此谱带较为合适,但在测量大气中的SO_2气体浓度就存在着CO_2、水蒸气及其他污染气体的干扰。CO_2与水蒸气基本上是新鲜大气中的主要成份,它们在7.3μ附近具有一定的,甚至很强的吸收,因此就不宜采用7.3μ谱带。根据Sadte Ler光谱图中可以看出上述两种大气中的主要成份CO_2、水蒸气以及其它大部分污染气体在8.7μ附近并无光谱带。为避免干扰,利用8.7μ光谱测定SO_2气体浓度,虽然吸收系数较小但应该是可行的,用一般红外分光计对较低浓度的SO_2气体浓度还是能够测量的。为此进行了实验验证。
I. Introduction Sulfur dioxide gas has been used as an important indicator of air pollution, and its concentration measurement is quite valued. SO2 gas in the mid-infrared and near-infrared region of the three bands were 7.3μ, 8.7μ and 18.5μ, respectively, and 7.3μ at the absorption coefficient of the largest (see Figure 1), which is quite beneficial to improve the sensitivity. Generally, we can select this band for measuring SO 2 gas concentration in the absence of other gases, but there is interference of CO 2, water vapor and other polluting gases in measuring SO 2 gas concentration in the atmosphere. CO 2 and water vapor are basically the main components of the fresh air. Since they have a certain and even strong absorption around 7.3μ, it is not advisable to use a 7.3μ band. According to the Sadte Ler spectrum, it can be seen that the main components CO 2, water vapor and most of the other polluting gases in the above two atmospheres have no spectral band near 8.7 μ. To avoid interference, the determination of SO 2 gas concentration by 8.7 μ spectroscopy should be feasible, although with a small absorption coefficient, and can be measured by conventional infrared spectroscopy for lower concentrations of SO 2 gas. To this end, experimental verification.