[en] High-resolution Fourier-transform IR (FTIR) absorption spectroscopy is presently used over open paths in biomass-fire smoke plumes to remotely sense emissions. FTIR can be employed in simultaneous measurements of a wide range of gas-phase species. Measurements are integrated over a long path through the smoke plume, and are therefore not subject to small-scale local variations. The emissions of all nitrogen species from the four field fires studied can be compared to the nitrogen content of the fuels burned; valuable insight has been gained into the relationships between biomass burning emissions and fire parameters

[en] Isotope Ratio Mass Spectrometry (IRMS) discriminates chemical species solely on the basis of their mass. Infrared spectroscopy of gases, however, distinguishes molecular species by their vibrational and rotational frequencies, which depend on both the mass and the molecular structure. This provides a potentially important advantage in determining isotope ratios for species of the sme mass. We have developed methods of precise analysis of atmospheric trace gases such as CO₂, CH₄, CO and N₂O based on Fourier Transform Infrared (FTIR) spectroscopy. More recently we have extend the measurements to encompass individual isotopic species. FTIR absorption spectra of gas samples are recorded and the individual isotopomers analysed as independent species in the spectra. We report on two pilot studies to assess the technique, using a low (1 cm^-1) resolution, benchtop spectrometer for ¹³C analysis in CO₂, and a high resolution spectrometer to quantify ¹³C, ¹⁷O and ¹⁸O isotopomers independently in CO₂. (author)

[en] Full text: The Australian forest fires near Canberra in the summer of 2002/2003 produced large quantities of smoke and various emission products. These fires were very intense to the point where smoke was injected in to the lower stratosphere, as well as being transported many thousands of kilometers zonally. These fire emissions were recorded in both Wollongong, (34.4S, 150.5E, 0.03 km asl), Australia, some hundreds of kilometers to the north east, as well as Lauder (45.0S, 169.7E, 0.37 km asl), New Zealand, nearly 2000 km to the south east of the fire sources. Both of these locations (Wollongong and Lauder), are instrumented sites as part of the Network for the Detection of Atmospheric Composition Change (NDACC). Wollongong has a high resolution FTIR spectrometer with a collocated UV/Visible spectrometer. Lauder is a fully instrumented primary NDAAC site that includes FTIR and UV/Visible spectrometers as well as various ozone measuring capabilities (lidar, balloons, Dobson). Several smoke events were captured at both sites, with enhanced levels of a number of key biomass burning gases recorded by the remote sensing instruments. Included in this suite of scientific data are model studies of the fire events using the 3-D chemical transport model GEOSCHEM, which uses emission data from GFED2 (biomass burning) and EDGAR (global NOx, CO). GEOSCHEM is driven by assimilated meteorological fields from the Goddard Earth Observing System of the NASA Global Modeling and Assimilation Office (GMAO). This presentation will describe the instrumentation involved, the relevant emission gases retrieved and subsequent interpretation in terms of the 3-D model output from GEOSCHEM. (author)

[en] This work introduces remote sensing of biomass burning emissions using high-resolution Fourier transform infrared (FTRI) absorption spectroscopy over open paths in smoke plumes from biomass fires. This technique provides an overview of the combustion products from burning not available from any other single technique used to date and can yield much valuable information on the gaseous emission products from biomass burning and the factors which control the balance of those emissions. Using FTIR absorption spectroscopy over long, open paths, the authors have made measurements of the smoke composition from sagebrush and forestry slash fires in rural areas of Wyoming and Montana, and from various fuels in the stack of a large-scale combustion laboratory. In this chapter they report a preliminary analysis of the spectra obtained from the field studies and presnt simultaneous measurements of CO₂, CO, CH₄, CH₂O, NO, NO₂, NH₃, N₂O, and HCN in the plumes of four fires

[en] Full text: We describe a portable Fourier Transform InfraRed (FTIR) spectrometer for laboratory and field measurements of δ¹³C in CO₂ and δD in water vapour at ambient atmospheric levels. The instrument is based on a commercial 1 cm^-1 resolution FTIR spectrometer fitted with a mid-IR globar source, 26 m multipass white cell and thermoelectrically-cooled MCT detector operating between 2000 and 7500 cm^--1. δD in water vapour is measured in whole air passed at 1-2 L min^-1 through the cell in real time without any pre-treatment. For δ¹³C measurements the sample airstream is dried to < 20 μmol mol^-1 to avoid interference from water vapour. An inlet selection manifold allows automated sequential analysis of samples from up to 12 inlet lines, with typical measurement times of 4-5 minutes per line. The spectrometer, inlet sampling sequence, real-time spectrum analysis, data logging and real-time display are all under the control of a single program running on a laptop PC, and can be left unattended for continuous measurements over periods of days to weeks. Selected spectral regions of typically 100-200 cm^-1 width are analyzed by a least squares fitting technique to retrieve concentrations of trace gases and isotopologues. Typical precision is 1-2 %_o for δD and 0.1 - 0.2 %_o for δ¹³C. Calibration and performance are described in more detail in an associated poster. The collected spectra also provide simultaneous analysis of concentrations of CO₂, CH₄, CO and N₂O in the analyzed air samples with high precision, typically 0.1%. Performance of the FTIR analyzer will be illustrated with results from a recent field campaign in which we measured vertical profiles of δD in water vapour and δ¹³C in CO₂ on a 70 m tower in a eucalypt forest in SE Australia. Hourly 7-point profiles were obtained continuously for 3 weeks interspersed with measurements from soil and leaf chambers. The results, combined with a multilayer ecosystem model of water and carbon exchange, are described in detail in the paper by Haverd et al. (this conference). (author)