Abstract.At a cropland and a grassland site field scale ammonia (NH 3 ) emissions from slurry application were determined simultaneously by two approaches based on (i) eddy covariance (EC) flux measurements using high temperature Chemical Ionisation Mass Spectrometry (HT-CIMS) and on (ii) backward Lagrangian Stochastic (bLS) dispersion modelling using concentration measurements by three optical open path Fourier Transform Infrared (FTIR) systems. Slurry was spread on the fields in sequential tracks over a period of one to two hours. In order to calculate field emissions, measured EC/HT-CIMS fluxes were combined with flux footprint analysis of individual slurry spreading tracks to parameterise the NH 3 volatilisation with a bi-exponential time dependence. Accordingly, track-resolved concentration footprints for the FTIR measurements were calculated using bLS. A consistency test with concentrations measured by impingers showed very low systematic deviations for the EC/HT-CIMS results (<8 %) but larger deviations for the bLS/FTIR results. For both slurry application events, the period during fertilisation and the subsequent two hours contributed by more than 80 % to the total field emissions. Averaged over the two measurement methods, the cumulated emissions of the first day amounted to 17 ± 3 % loss of applied total ammoniacal nitrogen over the cropland and 16 ± 3 % over the grassland field.

FTIR spectroscopy has been established for the monitoring of diffuse emissions into the open atmosphere. The method of choice for the evaluation of the atmospheric spectra uses the fitting of reference spectra by classical least squares. Important refinements can be achieved by selecting the optimal wavelength ranges based on objective mathematical criteria, improved spectral background strategies, and high-quality reference spectra that allow for the adaptation of nonlinearity effects. Under these improved conditions, new detection limits for atmospheric trace components are presented. The chemometric tools developed were integrated into an expert system, affording the evaluation of the atmospheric spectra with a minimum of user interaction. Results from several field campaign measurements within a municipal waste-treatment plant are presented, illustrating the reliability of the methods applied. Furthermore, extensive trace-gas concentration data were collected simultaneously with two FTIR spectrometer systems under various meteorological 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 inverse dispersion modeling based on Lagrangian model calculations. The results were obtained within a factor of 1.4 times the actual emission rate values.

At a cropland and a grassland site field scale ammonia (NH₃) emissions from slurry application were determined simultaneously by two approaches based on (i) eddy covariance (EC) flux measurements using high temperature Chemical Ionisation Mass Spectrometry (HT-CIMS) and on (ii) backward Lagrangian Stochastic (bLS) dispersion modelling using concentration measurements by three optical open path Fourier Transform Infrared (FTIR) systems. Slurry was spread on the fields in sequential tracks over a period of one to two hours. In order to calculate field emissions, measured EC/HT-CIMS fluxes were combined with flux footprint analysis of individual slurry spreading tracks to parameterise the NH₃ volatilisation with a bi-exponential time dependence. Accordingly, track-resolved concentration footprints for the FTIR measurements were calculated using bLS. Comparison of concentrations calculated from the parameterised fluxes with concentrations measured by impingers showed that the EC/HT-CIMS emissions on the two fertilisations corresponded to the impinger concentrations within 10 % while the bLS/FTIR results showed larger deviations. For both events, the period during fertilisation and the subsequent two hours contributed by more than 80 % to the total field emissions. Averaged over the two measurement methods, the cumulated emissions of the first day amounted to 17 ± 3 % loss of applied total ammoniacal nitrogen over the cropland and 16 ± 3 % over the grassland field