[A-CG05_30PO1] Continental-Oceanic Mutual Interaction: Global-scale Material Circulation through River Runoff

[ACG05-P02] modelling of radiocesium movement in catchment area of abukuma river, japan

*Mochamad adhiraga PRATAMA¹, Yosuke YAMASHIKI², Minoru YONEDA¹ (1.Department of Environmental Engineering, Kyoto University, 2.Graduate School of Advanced Integrated Studies in Human Survivability, Kyoto University)

Keywords:model, influx, radiocesium, Abukuma River

The great earthquake on March of 2011 followed by tsunami caused Fukushima Dai-ichi reactor meltdown which led to explosion and emission of radioactive substances into environment. As a result, Abukuma River, one of the most important rivers in Japan and its catchment area, received up to 2.25 x 10⁶ Bq/m² of radiocesium. Previous study found that 80-90% of radiocesium influx to Abukuma River was in particulate form and it was estimated that 10 TBq of the radionuclide was released into the end point of the river, coastal sea of Sendai Bay. A lot of models of radionuclides movement had been developed, however just few models that account solid wash off process in catchment area . This study tried to simulate the influx of radiocesium into Abukuma River from its catchment area by modifying MOIRA model with addition on solid transport which was calculated with SWAT model. Deposition of the radiocesium was used as an input of the model. Then after, fixation process into surface ground, liquid wash-off by surface run off, and solid wash off by erosion are the mechanisms which govern the dynamic of the radiocesium in this model. The result at the model shows an agreement compared to the observed data. With R² value of 0.8 showed that the model could explain seasonal variability of observed data. However, as several uncertainties were observed such as quantification of storm effect and decontamination activities, further study to optimize and improve the result of the model is deemed necessary