Abstract
Fourier-transform infrared (FTIR) spectroscopy is a rapid and nondestructive technology for monitoring atmospheric quality. The identification of each component from the FTIR spectra is a prerequisite for the accurate quantitative analysis of gaseous pollutants. Due to the overlap of different gas absorption peaks and the interference of water vapor in the actual measurement, the existing identification methods of gas spectra have drawbacks of low identification rate and the inability to carry out real-time online analysis in atmospheric quality monitoring. In this work, independent component analysis (ICA) is applied to the spectral separation of heavily overlapped spectra of gaseous pollutants. The proposed method is validated by the analysis of mixture spectra obtained in laboratory and actual atmospheric spectra collected from stationary source. The average time consumption of separation process is less than 0.2 seconds, and the identification rate of experimental gases is up to 100%, as shown by the results of peak searching and the analysis of the correction coefficient between the separated spectra and the standard spectra database. The identification results of actual atmospheric spectra demonstrated that the proposed method can effectively identify the gaseous pollutants whose concentration changes in the measured spectra, and it is a promising qualitative spectral analysis tool that can shorten the identification time, as well as increase the identification rate. Therefore, this method can be a useful alternative to traditional qualitative identification methods for real-time online atmospheric pollutant detection.
Highlights
Air is fundamental for living organisms on the Earth, and the quality of the atmospheric environment is closely related to human activities
We need to make sure that the system is under the assumption of a linear mixture model before we do the analysis. e Beer–Lambert law and absorbance additivity describe the relationship between the absorption intensity of multicomponent spectra and the concentration of each light-absorbing substance. e basic principles can be described as follows: Atotal(]) a1(])c1l + a2(])c2l + · · · + am(])cml, (3)
According to the absorbance additivity, the absorbance of multicomponent spectrum is the sum of absorbance of each component, and the change of concentration of the component will only cause the change of absorbance amplitude but not the position of absorption peaks and the spectral profile
Summary
Air is fundamental for living organisms on the Earth, and the quality of the atmospheric environment is closely related to human activities. With the development of modern industrialization and the improvement of human living standards, combustion of fossil fuels and emission of automobile exhaust cause severe atmospheric pollution, which has raised more concern in recent years. Typical gaseous pollutants include nitrogen oxides (NOX), sulfur dioxide (SOX) [1], volatile organic compounds (VOCs) [2], and ozone (O3) [3]. Ese gaseous pollutants exist as trace gases in the atmosphere but have detrimental effects on human health and the environment [4]. 12 spectra of experimental gases and 12 spectra of actual atmosphere are obtained by the background spectra elimination method.
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