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Development of the long-term countermeasures for mitigating radioactive material transfer from soil to rice based on the transition mechanism and soil characteristics
After the accident of the Tokyo Electric Company's Fukushima Daiichi Nuclear Power Plant, we have conducted research on the application of potassium fertilizer up to the level of soil exchangeable (NH4OAc extractable) potassium content 25mg K2O/100g as a countermeasure to suppress radioactive cesium transfer from soil to paddy rice in the area contaminated with radioactive cesium. Instead of a uniform potassium application, the countermeasure with adequate amount of potassium fertilizer application to mitigate the radioactive cesium transfer is required according to the recent soil radioactive cesium concentration level and taking into account the risk associated with soil characteristics. Therefore, in order to set the appropriate soil exchangeable potassium level, we have carried out field experiments with several rate of potassium fertilizer application in paddy fields with various soil radioactive cesium contamination level and soil.
We are also studying the absorption mechanism of potassium and radioactive cesium, and their distribution in the paddy-rice plant with reference to the soil exchangeable potassium content.
Furthermore, in some paddy fields, we have observed that paddy rice absorbs considerable amount of radioactive cesium in spite of the potassium application countermeasure. So, we are trying to elucidate the soil characteristics and develop countermeasures to mitigate radioactive cesium transfer from these soils.
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Development of continuous monitoring technology and dynamics elucidation of radioactive substances in the agricultural water facilities and paddy fields
Towards the resumption of farming in the areas contaminated with radioactive cesium, it is also required to inhibit the influx of radioactive cesium to the paddy field from agricultural water, and clarify the impact on radioactive cesium absorption by paddy rice. Therefore, in order to prevent the influx of radioactive cesium into the paddy fields, we are trying to develop a system for monitoring the radioactive cesium concentration of the agriculture water that flows into the irrigation facility.
We are also studying the changes in the existing forms of radioactive cesium in agricultural water and their effects on the radioactive cesium absorption of paddy rice.
The experimental field to investigate the dynamics of radioactive cesium in agricultural water and the effect on the paddy rice is installed with a parshall flume flow meter to measure the amount of water at inlet and outlet, and an automatic water sampler for sampling the agricultural water.
