Improved chemometric strategies for quantitative FTIR spectral analysis and applications in atmospheric open-path monitoring

FTIR spectroscopy has been established for the monitoring of diffuse emissi ons into the open atmosphere. The method of choice for the evaluation of th e atmospheric spectra uses the fitting of reference spectra by classical le ast squares. Important refinements can be achieved by selecting the optimal wavelength ranges based on objective mathematical criteria, improved spect ral background strategies, and high-quality reference spectra that allow fo r the adaptation of nonlinearity effects. Under these improved conditions, new detection limits for atmospheric trace components are presented. The ch emometric tools developed were integrated into an expert system, affording the evaluation of the atmospheric spectra with a minimum of user interactio n, Results from several field campaign measurements within a municipal wast e-treatment plant are presented, illustrating the reliability of the method s applied. Furthermore, extensive trace-gas concentration data were collect ed simultaneously with two FTIR spectrometer systems ender various meteorol ogical conditions and spatial scenarios for dispersion modeling of diffuse emissions from different sites, Emission rates of ammonia area sources were determined from path-integrated spectroscopic remote measurements and inve rse dispersion modeling based on Lagrangian model calculations. The results were obtained within a factor of 1.4 times the actual emission rate values , (C) 2001 John Wiley & Sons, Inc.