HR: 14:10h
AN: A53G-02 INVITED    [Abstracts]
TI: A Portable FTIR Analyser for Field Measurements of Trace Gases and their Isotopologues: CO2, CH4, N2O, CO, del13C in CO2 and delD in water vapour
AU: * Griffith, D W
EM: griffith@uow.edu.au
AF: University of Wollongong, Centre for Atmospheric Chemistry, Wollongong, NSW 2522,
AU: Bryant, G R
EM: glenn.bryant@bhpbilliton.com
AF: University of Wollongong, Centre for Atmospheric Chemistry, Wollongong, NSW 2522,
AU: Deutscher, N M
EM: nmd03@uow.edu.au
AF: University of Wollongong, Centre for Atmospheric Chemistry, Wollongong, NSW 2522,
AU: Wilson, S R
EM: swilson@uow.edu.au
AF: University of Wollongong, Centre for Atmospheric Chemistry, Wollongong, NSW 2522,
AU: Kettlewell, G
EM: grahamk@uow.edu.au
AF: University of Wollongong, Centre for Atmospheric Chemistry, Wollongong, NSW 2522,
AU: Riggenbach, M
AF: University of Wollongong, Centre for Atmospheric Chemistry, Wollongong, NSW 2522,
AB: We describe a portable Fourier Transform InfraRed (FTIR) analyser capable of simultaneous high precision analysis of CO₂, CH₄, N₂O and CO in air, as well as δ¹³C in CO₂ and δD in water vapour. 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. Air is passed through the cell and analysed in real time without any pre-treatment except for (optional) drying. An inlet selection manifold allows automated sequential analysis of samples from one or more inlet lines, with typical measurement times of 1-10 minutes per sample. The spectrometer, inlet sampling sequence, real-time quantitative spectrum analysis, data logging and 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 weeks to months. Selected spectral regions of typically 100-200 cm^-1 width are analysed by a least squares fitting technique to retrieve concentrations of trace gases, ¹³CO₂ and HDO. Typical precision is better than 0.1% without the need for calibration gases. Accuracy is similar if measurements are referenced to calibration standard gases. δ¹³C precision is typically around 0.1‰, and for δD it is 1‰. Applications of the analyser include clean and polluted air monitoring, tower-based flux measurements such as flux gradient or integrated horizontal flux measurements, automated soil chambers, and field-based measurements of isotopic fractionation in soil-plant-atmosphere systems. The simultaneous multi–component advantages can be exploited in tracer-type emission measurements, for example of CH₄ from livestock using a co-released tracer gas and downwind measurement. We have also developed an open path variant especially suited to tracer release studies and measurements of NH3 emissions from agricultural sources. An illustrative selection of applications will be presented.
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting