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Modeling radiocesium transport from a river catchment based on a physically-based distributed hydrological and
Tsuyoshi Kinouchi1, Kazuya Yoshimura2, Teppei Omata1
1Department of Environmental Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho Midori-ku, Yokohama, 226-8502, Japan.
Journal of Environmental Radioactivity
|August 19, 2014
Summary
Fukushima fallout contaminated Japan with cesium. A new model shows contaminated sediment transport, estimating a 22-year half-life for cesium-137 due to land-surface processes.
Area of Science:
- Environmental Science
- Hydrology
- Radiochemistry
Background:
- The 2011 Fukushima Dai-ichi Nuclear Power Plant accident released significant radionuclides, including cesium-134 and cesium-137, contaminating eastern Japan.
- Radiocesium strongly adsorbs to soil, leading to its transport via eroded sediments through hydrological systems.
- Understanding sediment and radiocesium transport is crucial for predicting contamination distribution in downstream areas and the Pacific Ocean.
Purpose of the Study:
- To develop and apply a distributed hydrological model simulating water and contaminated sediment transport.
- To analyze the spatial distribution and long-term fate of radiocesium in a contaminated watershed.
- To assess the impact of land-surface processes on radiocesium migration.
Main Methods:
- Development of a distributed model for water and contaminated sediment transport simulation.
- Application of the model to a forested mountain catchment affected by radioactive fallout.
- Calibration and validation of the model using observed discharge, sediment, and cesium concentration data (June 2011–December 2012).
Main Results:
- The model accurately simulated discharge and sediment concentration, but underestimated initial cesium concentration.
- Leaching of radiocesium from forest canopies was identified as a significant, previously unconsidered transport pathway.
- Estimated effective half-life of cesium-137 in the study area is approximately 22 years due to sediment export.
Conclusions:
- Land-surface processes significantly influence radiocesium transport and long-term fate in contaminated catchments.
- Approximately 39% of the initial cesium-137 is predicted to remain in the catchment within 30 years post-contamination.
- The study provides valuable insights into suspended sediment and radiocesium dynamics in similar environments.
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