Japan Geoscience Union Meeting 2015

Presentation information


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

[A-HW27] Water and material transport and cycle in watersheds: from headwater to coastal area

Sun. May 24, 2015 2:15 PM - 4:00 PM 301B (3F)

Convener:*Shinji Nakaya(Department of Civil Engineering, Faculty of Engineering, Shinshu University), Mitsuyo Saito(Graduate School of Environmental and Life Science, Okayama University), Shin-ichi Onodera(Graduate School of Integrated and Arts Sciences, Hiroshima University), Kazuhisa Chikita(Department of Natural History Sciences, Faculty of Science, Hokkaido University), Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Masahiro Kobayashi(Forestry and Forest Products Research Institute), Seiko Yoshikawa(Narional Institute for Agro-Environmental Sciences), Noboru Okuda(Research Institute for Humanity and Nature), Chair:Shin-ichi Onodera(Graduate School of Integrated and Arts Sciences, Hiroshima University)

3:00 PM - 3:15 PM

[AHW27-18] Cesium decrease with groundwater residence time in natural spring drinking water

*Shinji NAKAYA1, Hoang minh ha PHAN1, Yoshiki IWAI1, Akihiro ITOH1, Hideto AOKI1, Takanori NAKANO2 (1.Department of Civil Engineering, Shinshu University, 2.Research Institute for Humanity and Nature)

Keywords:Cesium, Groundwater, Residence time, Sulfur hexafluoride, Yatugatake

It is known that the active Cs sorption onto colloidal-size clay minerals in groundwater is observed and the active Cs can be transported with the colloidal fraction of groundwater by water flows. However, the longtime behavior of radioactive and non-active Cs, contained in the flowing groundwater in the aquifers of groundwater source areas, is unknown in terms of the natural water cycle. Herein, we investigate the non-active Cs concentration in natural spring drinking water with the residence time in a groundwater source area of a mountainside composed of volcanic rock, compared with those of other trace elements. This investigation demonstrates that the observed Cs concentration in natural spring drinking water exponentially decreases slowly with the groundwater residence time (~ 45 yr), while several trace elements, namely, P, V, Ga, and Ge, increase in concentration with the groundwater residence time through chemical weathering. The findings suggest that active Cs, contained in flowing groundwater in mountain water source areas, may decrease exponentially at the rate of one-tenth in twenty-two years, by sorption onto the aquifer through rock-water interaction excluding radioactive decay. For the sustainable management of water sources and ecosystems, the long-term (~50 yrs.) monitoring of the active Cs in groundwater is needed in mountain water source areas where radioactive cesium has been dispersed at times of nuclear power plant accidents.