Study on the Concentration Estimation Equation of Nitrogen Dioxide using Hyperspectral Sensor

The CleanSYS(Clean SYStem) is operated to monitor air pollutants emitted from specific industrial complexes in Korea. So the industrial complexes without the system are directly monitored by the control officers. For efficient monitoring, studies using various sensors have been conducted to monitor air pollutants emitted from industrial complex. In this study, hyperspectral sensors were used to model and verify the equations for estimating the concentration of NO2(nitrogen dioxide) in air pollutants emitted. For development of the equations, spectral radiance were observed for NO2 at various concentrations with different SZA(Solar Zenith Angle), VZA(Viewing Zenith Angle), and RAA(Relative Azimuth Angle). From the observed spectral radiance, the calculated value of the difference between the values of the specific wavelengths was taken as an absorption depth, and the equations were developed using the relationship between the depth and the NO2 concentration. The spectral radiance mixed gas of NO2 and SO2(sulfur dioxide) was used to verify the equations. As a result, the R(coefficient of determination) and RMSE(Root Mean Square Error) were different from 0.71~0.88 and 72~323 ppm according to the form of the equation, and R of the exponential form was the highest among the equations. Depending on the type of the equations, the accuracy of the estimated concentration with varying concentrations is not constant. However, if the equations are advanced in the future, hyperspectral sensors can be used to monitor the NO2 emitted from the industrial complex.