You are here:
COMPARISON OF AN INNOVATIVE NONLINEAR ALGORITHM TO CLASSICAL LEAST SQUARES FOR ANALYZING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTRA COLLECTED AT A CONCENTRATED SWINE PRODUCTION FACILITY
Citation:
Childers, J. W., W. J. Phillips, E L. Thompson*, D B. Harris*, D A. Kirchgessner*, D. F. Natschke, AND M. J. Clayton. COMPARISON OF AN INNOVATIVE NONLINEAR ALGORITHM TO CLASSICAL LEAST SQUARES FOR ANALYZING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTRA COLLECTED AT A CONCENTRATED SWINE PRODUCTION FACILITY. APPLIED SPECTROSCOPY 56(3):325-336, (2002).
Description:
Open-path Fourier transform infrared (OP/FTIR) spectrometry was used to measure the concentrations of ammonia, methane, and other atmospheric gases at an integrated swine production facility. The concentration-pathlength products of the target gases at this site often exceeded the linear dynamic range of the OP/FTIR spectrometer. A piecewise, linear classical least squares (CLS) analysis method with a calibration set containing multiple reference spectra for each target gas at concentration-pathlength products that encompassed those found in the field spectra and an innovative nonlinear algorithm (NLA) were used to determine the path-averaged concentrations of the target gases in the OP/FTIR field spectra. The results from these two methods are compared to those produced by conventional linear CLS methods. The conventional CLS methods with a calibration set consisting of only one reference spectrum per target gas under-reported the target gas concentrations when the field spectra exhibited concentration-pathlength products larger than those of the reference spectra. The path-averaged concentrations reported by the NLA were generally higher than those determined by the piecewise, linear CLS method. The mean absolute percent differences between these two methods were 3.9% for methane, 6.8% for nitrous oxide, 7.7% for ammonia, and 14. 1 % for carbon dioxide.