Measurements of Stable Isotopes in Atmospheric CO2 and H2O by Open-Path Fourier Transform Infrared Spectrometry
WANG Wei1, 2，LIU Wen-qing2，ZHANG Tian-shu2
1. School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China 2. Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Abstract：The development of spectroscopic techniques has offered continuous measurement of stable isotopes in the ambient air. The method of measuring environmental stable isotopes based on Fourier transform infrared spectrometry (FTIR) is described. In order to verify the feasibility of the method for continuous measurement of the stable isotopes, an open-path FTIR system was used to measure stable isotopes of CO2 and H2O in ambient air directly in a seven-day field experiment, including 12CO2, 3CO2, H216O and HD16O. Also, the time course of carbon isotopic ratio δ13C and deuterium isotope composition δD was calculated. The measurement precision is about 1.08‰ for δ13C and 1.32‰ for δD. The measured stable isotopes of CO2 and H2O were analyzed on different time scales by Keeling plot methods, and the deuterium isotopic ratios of evapotranspiration were determined. The results of the field experiment demonstrate the potential of the open-path FTIR system for continuous measurement of stable isotopes in the air.
Key words：Spectroscopy;Stable isotopes;FTIR spectrometry;Carbon dioxide;Water vapor;Ambient air
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