Japan Geoscience Union Meeting 2015

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Poster

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 6:15 PM - 7:30 PM Convention Hall (2F)

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)

6:15 PM - 7:30 PM

[AHW27-P08] Monitoring Radioactive Cs Concentration in a Small Agricultural Pond

*Tomijiro KUBOTA1, Moono SHIN2, Koji HAMADA1, Tadayoshi HITOMI1 (1.National Institute for Rural Engineering, 2.Tohoku Agricultural Research Center)

Keywords:radioactive cesium, agricultural pond, irrigation water

Radioactive materials were released over wide areas around the Tokyo Power Fukushima Daiichi Nuclear Power Plant after the accident caused by the earthquake and tsunami on March 11, 2011. Radioactive cesium pollution in agricultural ponds that supply irrigation water in this region was a concern for the restart of farming. Therefore, it is important to determine the movement characteristics of radioactive cesium around agricultural reservoirs. In this ongoing study since June 2013, we measured the concentrations of radioactive cesium in inflow, outflow, and pooled water in a small agricultural reservoir located in the Abukuma Mountains. The area of the pond was 0.37 ha, and its pondage was 7500 m3. The concentration of total radioactive cesium in the water was relatively high, around 1-3 Bq/kg, during the summer, but decreased to 0.2-1.5 Bq/kg after October. However, the concentration of total radioactive cesium of the outflow temporarily increased to 2.9-4.0 Bq/kg, when the water level decreased by 1.2 m in the middle of September. The increase in radioactivity was believed to be due to disturbance of the bottom water and sediment caused by relatively fast water flow. The dissolved radioactive cesium concentration in the inflow was 0.02-0.07 Bq/kg, whereas that in the outflow was 0.02-0.11 Bq/kg; both were considerably lower than the total radioactive cesium concentration. The ratios of dissolved radioactive cesium to total radioactive cesium were 1-5% in the inflow and 1-3% in the outflow. Thus, our results showed a positive correlation between the total radioactive cesium concentration in stored water and that in precipitation that occurred over the previous 5 days.