Japan Geoscience Union Meeting 2016

Presentation information


Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG60] Crustal fluids and deformation

Tue. May 24, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Naoji Koizumi(School of Environmental Science,the University of Shiga Prefecture), Koji Umeda(Tono Geoscience Center,Japan Atomic Energy Agency), Norio Matsumoto(Tectono-Hydrology Research Group, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)), Hidemi Tanaka(School of Science, The University of Tokyo), Kohei Kazahaya(Geological Survey of Japan, AIST), Fumiaki Tsunomori(Geochemical Research Center, Graduate School of Science, University of Tokyo)

5:15 PM - 6:30 PM

[SCG60-P04] Time series of gas composition in groundwater monitored at Atotsugawa Well

*Fumiaki Tsunomori1, Hidemi Tanaka2 (1.Geochemical Research Center, Graduate School of Science, University of Tokyo, 2.Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo)

Keywords:Groundwater, Dissolved gas, Time variation

We discuss on time variation of gas composition dissolved in groundwater of Atotsugawa observatory from October 2010 to February 2013. An observation well of Atotsugawa observatory was drilled in southern-west part of Atotsugawa fault located in Gifu Prefecture. Groundwater is sampled directly from an aquifer with a TEFLON pipe by 1 L/min. Dissolved gas makes may bubbles in the TEFLON pipe because the pumping reduces the pressure of groundwater. All bubbles are collected in a gas-water separator on the ground, and are introduced into a quadrupole mass spectrometer in the observatory. A gas composition is analyzed by the mass spectrometer equipped with a gas dryer every 1 hour. Results are transported to our server computer, and all spectra are automatically analyzed. A gas ratio of He-N2-Ar tri-component is calculated from a mass spectrum. This ratio is corrected by oxygen component in order to subtract air contamination. Tri-component ratio scatters on a mixing line of the air and the crust. Some data point on a line between the air and the mantle. Time series of the tri-component plot might have a potential to monitor gas migrated from a deep part to the ground surface.