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通过分析牧场附近测量的大气FTIR光谱中NH3在4种分辨率(分别为1、2、4cm-1和8cm-1)下的浓度,系统研究了不同分辨率下气体样品FTIR光谱定量分析的误差。选择72个实测光谱作为研究对象,其中NH3的光程积分浓度(Path-integrated concentration,PIC)分布在40—1300(μmol/mol).m。分析了NH3的最大吸收峰和次大吸收峰的选取对定量的影响。结果表明:选用NH3的次大吸收峰的定量误差更小;在允许的误差范围内(本研究中设为5%),不需要制作校准曲线,通过选用多个浓度适当的参考光谱,直接应用Beer定律仍能实现气体样品的定量分析;并且分辨率越低,定量分析所需的参考光谱数目越多。本研究通过合理选用多个参考光谱,实现了不同分辨率下FTIR光谱的定量分析;既充分利用了Beer定律,又克服了吸光度-浓度在低分辨率下的非线性问题;为不同分辨率下气体样品FTIR光谱的定量分析提供了参考。
By analyzing the concentrations of NH3 in the FTIR spectra measured at the pasture near the ranch at four resolutions (1, 2, 4 cm-1 and 8 cm-1, respectively), the error of quantitative analysis of FTIR spectra of gas samples at different resolutions . Seventy-two spectra were selected as the study objects, in which the path-integrated concentration (PIC) of NH3 was distributed in the range of 40-1300 μmol / mol. The effects of the maximum absorption peak and the next absorption peak of NH3 on the quantification were analyzed. The results show that the quantitative error of the second largest absorption peak of NH3 is smaller than that of NH3. In the allowable error range (5% in this study), no calibration curve is needed. By using several appropriate reference spectra, Beer’s Law still enables quantitative analysis of gas samples; and the lower the resolution, the more the number of reference spectra required for quantitative analysis. In this study, the quantitative analysis of FTIR spectra at different resolutions was achieved by rational selection of multiple reference spectra. Beer’s law was fully utilized and the non-linearity of absorbance-concentration at low resolution was overcome. Under different resolutions Gas sample FTIR spectroscopy quantitative analysis provides a reference.