HR: 0830h
AN: B31E-0346    [PDF]
TI: The D/H Ratio in Atmospheric Water Vapour: Continuous in situ Measurements of Soil-Plant-Atmosphere Exchange by Fourier Transform Infrared Spectroscopy
AU: * Griffith, D W
EM: griffith@uow.edu.au
AF: Department of Chemistry University of Wollongong, Northfields Ave., Wollongong, NSW 2522 Australia
AU: Jamie, I M
AF: Department of Chemistry University of Wollongong, Northfields Ave., Wollongong, NSW 2522 Australia
AU: Parkes, S D
AF: Department of Chemistry University of Wollongong, Northfields Ave., Wollongong, NSW 2522 Australia
AU: Wilson, S R
EM: swilson@uow.edu.au
AF: Department of Chemistry University of Wollongong, Northfields Ave., Wollongong, NSW 2522 Australia
AB: The D/H ratio in atmospheric water vapour provides a valuable tracer for exchange and transport processes. We present a novel method for real-time, continuous, in situ field measurements of the D/H ratio of atmospheric water vapour, and illustrate the method with measurements of vertical profiles of both water content and HDO/H$_{2}$O ratio over an agricultural pasture in SE Australia. We measured 7-point vertical profiles (0.5-22m) every 30 minutes continuously over a three week period in spring. The observed variations in the vertical profiles on diurnal and weekly timescales provide valuable constraints on the exchanges of water between atmosphere, soil and plants. The measurement technique used is Fourier Transform Infrared (FT-IR) spectroscopy. Whole air was drawn via a buffer volume into a multi-pass optical absorption cell from inlet lines on a 22m tower in the pasture paddock. The FT-IR absorption spectrum of the air was recorded with a Bomem MB100 FTIR spectrometer at 1 cm$^{-1}$ resolution, typically for 2 minutes per sample. Each of the 7 inlets was sampled twice per half hour to provide 30 minute average vertical profiles. Precision in $\delta$D is around 1-2 per mil. The instrument can be fully automated, and is mobile and suitable for field measurements.
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
DE: 0368 Troposphere--constituent transport and chemistry
DE: 0394 Instruments and techniques
SC: Biogeosciences [B]
MN: 2003 Fall Meeting