5:15 PM - 6:30 PM
[MTT42-P03] Development and evaluation of wet-flow type isotope analyses for fluid-inclusions in speleothems
Keywords:speleothem, stable isotope, fluid inclusion, CRDS
Cavity-ringdown spectrometers (CRDS) are used for hydrogen/oxygen stable isotope ratio analyses of fluid inclusions in speleothems. Several methods for analyzing fluid inclusions in stalagmites have been developed (e.g., 1-3). However, stable isotope ratio analysis of water in fluid inclusions has a problem of memory effect (3). In this study, we develop and evaluate a method for measuring isotope ratios in fluid inclusions to improve the sample throughput by reducing the memory effect.
The measurement line consists of a water extraction unit and a detector (CRDS, Picarro 2140-i) that measures the water isotope ratio. Stalagmite sample was crushed under a vapor stream (i.e., moisturized carrier gas) in which the isotope ratio and concentration are constant. This wet flow type method has been improved due to various developments (1-2).
We succeeded in producing a stable water vapor concentration (± 6 ppm, standard deviation for 10 minutes). The repeated measurement precision(1σ) of working standard water (in the range of 0.1-0.4 μL ) was ± 0.1-0.2 ‰, ± 0.1-0.2 ‰ and ± 0.2-0.6 ‰ for δ17O, δ18O and δD, respectively. As reported in previously, the precision became worse as the sample volume was 0.1 μL or less. By adjusting the introduction rate of water vapor, the accuracy could be maintained even at 0.05 μL.
References: (1) Affolter et al., Clim. Past, 2014; (2) De Graaf et al., Rapid Commun Mass Spectrom., 2020; (3) Uemura et al., Geochim. Cosmochimi. Acta, 2016
The measurement line consists of a water extraction unit and a detector (CRDS, Picarro 2140-i) that measures the water isotope ratio. Stalagmite sample was crushed under a vapor stream (i.e., moisturized carrier gas) in which the isotope ratio and concentration are constant. This wet flow type method has been improved due to various developments (1-2).
We succeeded in producing a stable water vapor concentration (± 6 ppm, standard deviation for 10 minutes). The repeated measurement precision(1σ) of working standard water (in the range of 0.1-0.4 μL ) was ± 0.1-0.2 ‰, ± 0.1-0.2 ‰ and ± 0.2-0.6 ‰ for δ17O, δ18O and δD, respectively. As reported in previously, the precision became worse as the sample volume was 0.1 μL or less. By adjusting the introduction rate of water vapor, the accuracy could be maintained even at 0.05 μL.
References: (1) Affolter et al., Clim. Past, 2014; (2) De Graaf et al., Rapid Commun Mass Spectrom., 2020; (3) Uemura et al., Geochim. Cosmochimi. Acta, 2016