JpGU-AGU Joint Meeting 2017

Presentation information

[EJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-AG Applied Geosciences

[M-AG34] [EJ] Dynamics of radionuclides emitted from Fukuchima Dai-ichi Nuclear Power Plant in the environment

Thu. May 25, 2017 1:45 PM - 3:15 PM Convention Hall A (International Conference Hall 2F)

convener:Kazuyuki Kita(Faculty of Science, Ibaraki University), Yuichi Onda(Center for Research on Isotopes and Environmental Dynamics, University of Tsukuba), Yasuhito Igarashi(Atmospheric Environment and Applied Meteorology Research Department, Meteorological Research Institute), Masatoshi Yamada(Institute of Radiation Emergency Medicine, Hirosaki University), Chairperson:Michio Aoyama(Institute of Environmnetal Radioactivity, Fukushima University), Chairperson:Yayoi Inomata(Kanazawa University)

2:30 PM - 2:45 PM

[MAG34-16] Transport of Fukushima-derived radiocesium into the coastal ocean via submarine groundwater discharge: an approach from geochemical character of pore water

*Shota Kambayashi1, JING ZHANG2, Hisashi Narita3 (1.Graduate School of Science and Engineer for Education, University of Toyama, 2.Graduate School of Science and Engineer for Research , University of Toyama, 3.School of Marine Science and Technology, Tokai University)

Keywords:Fukushima-derived radiocesium, Submarine Groundwater discharge, Pore water, Matsukawa-ura Lagoon

Submarine groundwater discharge (SGD) has been recognized as a route of Fukushima-derived radiocesium (Cs) from land to the ocean tougher with rivers. However, it is difficult to take large volume SGD samples compared with river water, which can be collected more easily. Therefore, quantitative evaluation of its impact as a source of Cs has not been carried out. In this study, we analyzed Cs activity and chemical component in pore water in Matsukawa-ura Lagoon to explore the transport and flux from land to ocean including SGD.
The measured 137Cs activity in pore water samples and the overlying water were 1,398 mBq/L and 117.7 mBq/L, respectively. This indicates that a significant amount of Cs in sediment has been desorbed into pore water. The 137Cs flux between the sediment and overlying water was calculated to be 11.3 mBq/cm2/h, using Fick’s First Law of diffusion. Moreover, the 137Cs flux from the bottom to overlying water of the lagoon was estimated to be 0.08 GBq/day based on the weighted average of 137Cs activity in bottom sediment of the lagoon and the Kd value between the sediment and the pore water. This value accounts of the majority of 137Cs which supplies the lagoon. Thus, it can be expected that large quantities of Cs have been supplying the coastal area by pore water exchange, that is to say, recycled SGD (RSGD). In the coastal area and the open ocean, it is suggested that SGD is vitally important as a source of Cs to assess it.