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Ikenoue, Tsubasa; Nakanishi, Takahiro; Shimadera, Hikari*; Kawamura, Hideyuki; Kondo, Akira*
E3S Web of Conferences (Internet), 530, p.02005_1 - 02005_10, 2024/05
The accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) caused a radioactive contamination in seabed sediment. The Cs supply from rivers could be an important process for the long-term behavior of
Cs in seabed sediment. In this study, a ten-year simulation of the
Cs behavior in seabed sediment was conducted using an oceanic dispersion model combined with a prediction model of
Cs behavior in land and river. In the waters north of FDNPP, the simulation results suggested that the
Cs supply from rivers had a great impact on the concentrations in coastal sediment due to the initial low concentrations in seabed sediment and the large supply of
Cs from rivers. In the waters near FDNPP and south of FDNPP, the simulation results suggested that the impact of the
Cs supply on the temporal variation of
Cs concentration in coastal sediment was relatively small due to the large initial adsorption from seawater. Overall, these results indicated that
Cs supply from rivers had an impact on the spatiotemporal distribution of
Cs concentrations in seabed sediment on a decadal time scale and the impact was especially great in the waters north of FDNPP.
Ikenoue, Tsubasa; Shimadera, Hikari*; Nakanishi, Takahiro; Kondo, Akira*
Water (Internet), 15(15), p.2734_1 - 2734_18, 2023/08
Times Cited Count:0 Percentile:0.00(Environmental Sciences)The Fukushima Daiichi Nuclear Power Plant accident caused an accumulation of Cs in coastal sediment. The
Cs supply from rivers to the ocean can affect the long-term fate of
Cs in coastal sediment. Since the Fukushima coastal river basins include large decontaminated and evacuation order areas, considering the decontamination work and resumption of agriculture is important for predicting the
Cs supply. We conducted a 30-year prediction of the
Cs supply from the Fukushima coastal rivers to the ocean using a distributed radiocesium prediction model, considering the effects of human activities. In river basins with decontaminated and evacuation order areas, human activities reduced the total
Cs outflow from agricultural lands, urban lands, and forest areas to the rivers and the
Cs supply to the ocean by 5.0% and 6.0%, respectively. These results indicated that human activities slightly impacted the
Cs outflow and supply. The
Cs supply from rivers impacted by the accident to the coastal sediment was estimated to correspond to 11-36% of the total
Cs in the coastal sediment in the early phase of the accident. Therefore, the
Cs supply from rivers to the ocean is important for the long-term behavior of
Cs in coastal sediment.
Ikenoue, Tsubasa; Shimadera, Hikari*; Nakanishi, Takahiro; Kondo, Akira*
Science of the Total Environment, 876, p.162846_1 - 162846_12, 2023/06
Times Cited Count:4 Percentile:58.87(Environmental Sciences)We conducted 30 years simulation of environmental fate of Cs in the Abukuma River basin considering the characteristics of the
Cs behavior in land uses. Overall, in the Abukuma River basin, the
Cs transported into the ocean for 30 years was estimated to correspond to 4.6% of the initial deposition in the basin, and the effective half-life of
Cs deposited in the basin was estimated to be 3.7 years shorter (by 11.6%) than its physical half-life. These results suggested that
Cs deposited from the accident could still remain for decades. Based on the analysis of the
Cs behavior in land use, in 2011, the contribution of
Cs export to the ocean from urban lands was estimated to correspond to 70% of the total
Cs export. Meanwhile, from 2012 to 2040, the contribution of
Cs export from agricultural lands was estimated to correspond to 75% of the total
Cs export. The reduction ratios excluding radioactive decay of
Cs remained in areas with and without human activities for 30 years after the accident, defined as the ratios of the total outflow to the initial deposition, were estimated to be 11.5%-17.7% and 0.4%-1.4%, respectively. These results suggested that human activities enhance the reduction of
Cs remaining in land in the past and future.
Ikenoue, Tsubasa; Shimadera, Hikari*; Kondo, Akira*
Journal of Environmental Radioactivity, 225, p.106452_1 - 106452_12, 2020/12
Times Cited Count:5 Percentile:20.28(Environmental Sciences)This study focused on the uncertainty of the factors of the Universal Soil Loss Equation (USLE) and evaluated its impacts on the environmental fate of Cs simulated by a radiocesium transport model in the Abukuma River basin. The USLE has five physically meaningful factors: the rainfall and runoff factor (R), soil erodibility factor (K), topographic factor (LS), cover and management factor (C), and support practice factor (P). The simulation results showed total suspended sediment and
Cs outflows were the most sensitive to C and P among the all factors. Therefore, land cover and soil erosion prevention act have the great impact on outflow of suspended sediment and
Cs. Focusing on land use, the outflow rates of
Cs from the forest areas, croplands, and undisturbed paddy fields were large. This study indicates that land use, especially forest areas, croplands, and undisturbed paddy fields, has a significant impact on the environmental fate of
Cs.
Ikenoue, Tsubasa; Shimadera, Hikari*; Kondo, Akira*
no journal, ,
We evaluated the environmental fate of Cs in the Abukuma River Basin from 2011 to 2040 by using a distributed radiocesium prediction model. The model well reproduced interannual variations in the concentration of
Cs in the suspended sediment and the total outflow of
Cs at Iwanuma near the estuary. Thirty years after the Fukushima Daiichi Nuclear Power Plant accident, it was estimated that the concentration of
Cs in the suspended sediment decreased to 1.9% of the concentration in the earliest phase after the accident and the total outflow of
Cs was equivalent to 4.6% of the initial deposition in the Abukuma River basin.
Nittono, Akira*; Ikenoue, Tsubasa; Shimadera, Hikari*; Matsuo, Tomohito*; Kondo, Akira*
no journal, ,
The Fukushima Daiichi Nuclear Power Plant accident caused extensive Cs contamination. Long-term simulations have been conducted to predict the amount of
Cs outflow from river basins to the ocean. However, there are uncertainties about the influences of rainfall, tree types and dams to the
Cs outflow. This study focused on how much these three factors influence the
Cs outflow in eastern Fukushima river basins from 2011 to 2040. The
Cs outflow varied by -10 to +17% depending on precipitation, and by -16 to +19% depending on tree species, decreased by 21% by dams.
Ikenoue, Tsubasa; Shimadera, Hikari*; Kondo, Akira*
no journal, ,
This study focused on the uncertainty of the factors of the USLE and evaluated its impacts on the environmental fate of Cs simulated by a radiocesium transport model in the Abukuma River basin. In the USLE, soil loss is expressed as a product of factors representing rainfall (R factor), geology (K factor), topographic (L
S factor) and land cover and soil erosion prevention act (C
P factor). The simulation results showed total outflows of suspended sediment and
Cs were the most sensitive to C
P factor among the all factors. Therefore, land cover and soil erosion prevention methods have the great impact on outflow of suspended sediment and
Cs.