3:45 PM - 4:00 PM
[SVC42-08] Determination on the stable isotopic compositions of water vapor in volcanic plumes
Keywords:volcanic gases, stable isotopic compositions, Cavity Ring-Down Spectroscopy
In this study, we developed a new system to determine the isotopic ratios of H2O in volcanic plumes by using Cavity Ring-Down Spectroscopic system (CRDS) and applied for the measurements on the plume samples. The samples of a volcanic plume were taken around high temperature (> 700 °C) fumaroles in Satsuma-Iwojima volcano. We collected around 15 samples of the volcanic plume into pre-evacuated glass bottles (ca. 500 ml), while changing the distances from a fumarole. Besides, we also collected the fumarolic H2O through condensation using a cold trap. The isotopic ratios (δD and δ18O) of plume H2O showed strong linear correlation (R2 = 0.75 and 0.78, respectively) with the reciprocal of H2O concentration. The δD and δ18O values of the fumarole H2O estimated from the linear relationships were −16.2 ± 10.5 ‰ and +4.0 ± 1.9 ‰, respectively. Because the values coincided well with those of fumarolic H2O collected directly at the fumarole (−22.9 ± 1.2 ‰ and +7.8 ± 0.4 ‰, respectively), we concluded that we can apply the present method to determine the stable isotopic ratios of fumarolic H2O remotely using plume H2O, and to clarify the mechanisms of each volcanic eruption.
This study was supported by MEXT Scientific Research Program grants "Integrated Program for Next Generation Volcano Research and Human Resource Development ".