Japan Geoscience Union Meeting 2015

Presentation information


Symbol A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW24] Isotope Hydrology 2015

Mon. May 25, 2015 11:00 AM - 12:45 PM 301A (3F)

Convener:*Masaya Yasuhara(Geological Survey of Japan, AIST), Kohei Kazahaya(Geological Survey of Japan, AIST), Shinji Ohsawa(Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Masaaki Takahashi(The National Institute of Advanced Industrial Science and Technology), YUICHI SUZUKI(Faculty of Geo-Environmental Sience,Rissho University), Futaba Kazama(Social Cystem Engineering, Division of Engineering, Interdiciplinary Graduate School of Medical and Engineering, University of Yamanashi), Kazuyoshi Asai(Geo Science Laboratory), Chair:Kazuyoshi Asai(Geo Science Laboratory), Takashi Nakamura(International Research Center for River Basin Environment, University of YAMANASHI)

12:00 PM - 12:15 PM

[AHW24-10] Isotopic characteristics of acid springs in Shunomata river basin in Mt. Chokai volcano

*Takeshi HAYASHI1, Masaya YASUHARA2, Noritoshi MORIKAWA2, Hiroshi TAKAHASHI2, Kazuyoshi ASAI3, Yukiko KUSANO4 (1.Akita Univ. Faculty of Education and Human Studies, 2.GSJ, AIST, 3.Geo-science Laboratory, 4.Graduate School of Frontier Sciences, The University of Tokyo)

Keywords:acid springs, environmental isotopes, limonite ore deposits, Mt. Chokai Volcano

There are some rivers that have low pH and deposition of Iron oxides on the east side of Mt. Chokai volcano. Shunomata river basin has some limonite ore deposits on the river bed of tributaries (EL: approximately 900m). These ore deposits are considered to have made by acid springs that are characterized by low pH (about 3 to 5) and relatively high temperature (about 20 to 25 degree Celsius). Also, previous studies pointed out that pH of the acid springs have decreased after a volcanic activity of Mt. Chokai in 1974. However, there are quite few studies on the origin and groundwater quality evolution process of the acid springs. Therefore, this study aims to clarify these points. We will show the results of measurements of major dissolved ions and environmental isotopes.
Temperature and pH of the acid springs showed 15.5 to 19.5 degree Celsius and 2.8 to 3.0, respectively. As for major dissolved ions, groundwater quality was characterized by high concentrations of SO42- and Cl (117 to 181 mg/L and 66 to 106 mg/L). Comparing these results with that of "Detsubo" spring that is located on the north side of Mt. Chokai volcano and is famous for low temperature (about 7 degree Celsius) and low pH (about 4.5), groundwater quality was largely different. Stable isotopic ratios of oxygen and hydrogen were about -11.5 per-mil and -68 to -69 per-mil, respectively. Elevation of recharge area of the acid springs was estimated more than 1,600 masl.
The results of this study suggest that there are some groundwater quality evolution systems of acid springs in Mt. Chokai volcano.