傅里叶变换红外光谱法测量大气中CO_2和H_2O的稳定同位素

Measurements of Stable Isotopes in Atmospheric CO_2 and H_2O by Open-Path Fourier Transform Infrared Spectrometry

光谱技术的发展使得连续测量环境大气中的稳定同位素成为可能。描述了应用傅里叶变换红外(FTIR)光谱技术测量环境大气中稳定同位素的方法。为了验证该方法对环境大气中的稳定同位素进行连续测量的可行性,在七天的外场实验中,应用开放光程FTIR系统直接测量环境大气中CO2的稳定同位素12 CO2,13 CO2和H2O的稳定同位素H216 O和HD16 O,并得到大气中碳同位素比值δ13 C和氘同位素比值δD。对同位素比值δ13 C和δD,系统的测量精度分别约为1.08‰和1.32‰。采用Keeling图方法,在不同的时间尺度上对CO2和H2O的同位素数据进行分析,得到了水汽地表蒸散的氘同位素特征δET。外场实验的结果证明了开放光程FTIR系统长期测量环境大气中稳定同位素的潜力。

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 CO 2 and H 2 O in ambient air directly in a seven-day field experiment,including 12 CO2,3 CO2,H216O and HD 16 O.Also,the time course of carbon isotopic ratioδ 13 C and deuterium isotope compositionδD was calculated. The measurement precision is about 1.08‰forδ 13 C and 1.32‰forδD.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.