HR: 12:05h
AN: A12B-08    [Abstracts]
TI: Ground-based FTIR Measurements of Carbon Dioxide Isotopic Concentrations and Fluxes and Ecosystem-Atmosphere Exchange
AU: * Mount, G H
EM: gmount@wsu.edu
AF: Washington State University, Dept Civil/Env Engineering, Pullman, WA 99164-2910, United States
AU: Cambaliza, M
EM: cambaliz@wsu.edu
AF: Washington State University, Dept Civil/Env Engineering, Pullman, WA 99164-2910, United States
AB: Analysis of the isotopic content of atmospheric carbon dioxide provides a wealth of information about the complex interaction between the biosphere and the atmosphere. When combined with micrometeorological flux measurements, a much improved picture emerges of ecosystem-scale carbon cycling dynamics. Since photosynthesis and respiration impart a unique isotopic signature to the atmosphere, knowledge of the concentrations and fluxes of the individual CO₂ isotopologues can be used to constrain and partition net ecosystem exchange into its gross photosynthetic and respiration components. In this work, concentrations and fluxes of individual isotopologues of carbon dioxide in a forest ecosystem were determined using Fourier Transform Infrared (FTIR) spectroscopy and the Disjunct Eddy Covariance (DEC) flux measurement technique. We separately measure the concentrations of the ¹²CO₂ and ¹³CO₂ isotopomers of carbon dioxide at approximately one minute intervals with very high signal-to-noise ratio using molecular absorption in a 1-meter cell in the 2100 to 2600 cm-1 region of the isotopic vibration-rotation bands. The FTIR – DEC system was deployed during four field campaigns in the summers of 2005 and 2006 in north central Oregon. Fixed height or vertical profile concentration measurements of ¹²CO₂ and ¹³CO₂ were carried out in the canopy using a 25-meter tower fitted with air inlets at 0.3, 4.1, 7.5, 10.8, 14.0, and 20.6 meters. Isotopic flux measurements above the canopy were taken at constant height of 20.6 meters. Temporal and vertical profiles of CO₂ concentrations and carbon isotope ratios will be shown together with the total net ecosystem exchange and isotopic CO₂ fluxes.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0365 Troposphere: composition and chemistry
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting