4:45 PM - 5:00 PM
[SVC45-25] Sampling volcanic plume using aircraft for remote determinations on the temperature of fumaroles: Sakurajima volcano
Keywords:fumarolic gases, volcanic plume, molecular hydrogen, stable isotopes, remote temperature sensing, Sakurajima volcano
In this study, we used an aerial vehicle to take samples of volcanic plume ejected from highly active Sakurajima volcano in Japan, to determine the outlet temperature of fumaroles remotely by using HIReTS, at the distant of more than 3 km from the fumaroles. Sakurajima volcano has continued its explosive activity at the summit crater since 1955 so that nobody dared to determine the outlet temperature of fumaroles directly.
The average H2 concentration of the plume samples taken during two flights on Sep. 2014 was 0.76 ppm (from 0.60 to 1.29 ppm), while that taken apparently outside the volcanic plume was 0.60 ppm. Besides, the reciprocal of the H2 concentration in the plume samples showed a good linear relationship with the D/1H ratio ratio. By extrapolating the linear relationship to exclude the contribution of the tropospheric H2, we estimated that the δD value of the fumarolic H2 to be -134.6±6.5 ‰(vs. VSMOW) and the outlet temperature to be 1050±80 ℃, assuming global average δD value of magmatic H2O to the fumarolic H2O. The estimated temperature was close to the melting point of lava in the volcano, implying that magma have been close to the surface in the volcano, at least during the observation.