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Deposition of radiocesium on the river flood plains around Fukushima
Πέμπτη, 14 Ιουλίου 2016, 9:18:18 πμ
Publication date: November 2016
Source:Journal of Environmental Radioactivity, Volume 164
Author(s): Hiromitsu Saegusa, Takuya Ohyama, Kazuki Iijima, Hironori Onoe, Ryuji Takeuchi, Hiroki Hagiwara
The environment in the area around Fukushima Daiichi Nuclear Power Plant has been contaminated by widely deposited significant amount of radioactive materials, which were released to the atmosphere caused by the Fukushima Daiichi Nuclear Power Plant accident due to the Great East Japan Earthquake, which occurred on March 11, 2011. The radiocesium released in the accident mainly affects radiation dose in the environment. Decontamination work in the contaminated area except a mountain forests has been conducted to decrease the radiation dose. However, there are concerns that the redistribution of this radiation due to water discharge will occur due to the resulting transport of radiocesium. In particular, the deposition of soil particles containing radiocesium on the flood plains in the downstream areas of Fukushima's rivers can potentially increase the local radiation dose. Therefore, it is important to understand the influence of the deposition behavior of radiocesium on the radiation dose. Investigations of rivers have been performed to enhance the understanding of the mechanisms by which radiocesium is deposited on these flood plains. It was found that the spatial distribution of the radiocesium concentration on the flood plain along the river is heterogeneous with a dependence on the depositional condition and that the number of points with high air dose rates is limited. In detail, the radiocesium concentration and air dose rates in flood channels are higher than those at the edges of the river channels. Based on these heterogeneity and hydrological events, the deposition and transport mechanisms of the radiocesium due to water discharge at rivers were also interpreted, and a conceptual model was constructed.
Source:Journal of Environmental Radioactivity, Volume 164
Author(s): Hiromitsu Saegusa, Takuya Ohyama, Kazuki Iijima, Hironori Onoe, Ryuji Takeuchi, Hiroki Hagiwara
The environment in the area around Fukushima Daiichi Nuclear Power Plant has been contaminated by widely deposited significant amount of radioactive materials, which were released to the atmosphere caused by the Fukushima Daiichi Nuclear Power Plant accident due to the Great East Japan Earthquake, which occurred on March 11, 2011. The radiocesium released in the accident mainly affects radiation dose in the environment. Decontamination work in the contaminated area except a mountain forests has been conducted to decrease the radiation dose. However, there are concerns that the redistribution of this radiation due to water discharge will occur due to the resulting transport of radiocesium. In particular, the deposition of soil particles containing radiocesium on the flood plains in the downstream areas of Fukushima's rivers can potentially increase the local radiation dose. Therefore, it is important to understand the influence of the deposition behavior of radiocesium on the radiation dose. Investigations of rivers have been performed to enhance the understanding of the mechanisms by which radiocesium is deposited on these flood plains. It was found that the spatial distribution of the radiocesium concentration on the flood plain along the river is heterogeneous with a dependence on the depositional condition and that the number of points with high air dose rates is limited. In detail, the radiocesium concentration and air dose rates in flood channels are higher than those at the edges of the river channels. Based on these heterogeneity and hydrological events, the deposition and transport mechanisms of the radiocesium due to water discharge at rivers were also interpreted, and a conceptual model was constructed.
High-resolution radiation mapping to investigate FDNPP derived contaminant migration
Πέμπτη, 14 Ιουλίου 2016, 9:18:18 πμ
Publication date: November 2016
Source:Journal of Environmental Radioactivity, Volume 164
Author(s): P.G. Martin, O.D. Payton, Y. Yamashiki, D.A. Richards, T.B. Scott
As of March 2016, five years will have passed since the earthquake and ensuing tsunami that crippled the Fukushima Daiichi Nuclear Power Plant on Japan’s eastern coast, resulting in the explosive release of significant quantities of radioactive material. Over this period, significant time and resource has been expended on both the study of the contamination as well as its remediation from the affected environments. Presented in this work is a high-spatial resolution foot-based radiation mapping study using gamma-spectrometry at a site in the contaminated Iitate Village; conducted at different times, seventeen months apart. The specific site selected for this work was one in which consistent uniform agriculture was observed across its entire extent. From these surveys, obtained from along the main northwest trending line of the fallout plume, it was possible to determine the rate of reduction in the levels of contamination around the site attributable to the natural decay of the radiocesium, remediation efforts or material transport. Results from the work suggest that neither the natural decay of radiocesium nor its downward migration through the soil horizons were responsible for the decline in measured activity levels across the site, with the mobilisation of contaminant species likely adhered to soil particulate and the subsequent fluvial transport responsible for the measurable reduction in activity. This transport of contaminant via fluvial methods has already well studied implications for the input of contaminant material entering the neighbouring Pacific Ocean, as well as the deposition of material along rivers within previously decontaminated areas.
Source:Journal of Environmental Radioactivity, Volume 164
Author(s): P.G. Martin, O.D. Payton, Y. Yamashiki, D.A. Richards, T.B. Scott
As of March 2016, five years will have passed since the earthquake and ensuing tsunami that crippled the Fukushima Daiichi Nuclear Power Plant on Japan’s eastern coast, resulting in the explosive release of significant quantities of radioactive material. Over this period, significant time and resource has been expended on both the study of the contamination as well as its remediation from the affected environments. Presented in this work is a high-spatial resolution foot-based radiation mapping study using gamma-spectrometry at a site in the contaminated Iitate Village; conducted at different times, seventeen months apart. The specific site selected for this work was one in which consistent uniform agriculture was observed across its entire extent. From these surveys, obtained from along the main northwest trending line of the fallout plume, it was possible to determine the rate of reduction in the levels of contamination around the site attributable to the natural decay of the radiocesium, remediation efforts or material transport. Results from the work suggest that neither the natural decay of radiocesium nor its downward migration through the soil horizons were responsible for the decline in measured activity levels across the site, with the mobilisation of contaminant species likely adhered to soil particulate and the subsequent fluvial transport responsible for the measurable reduction in activity. This transport of contaminant via fluvial methods has already well studied implications for the input of contaminant material entering the neighbouring Pacific Ocean, as well as the deposition of material along rivers within previously decontaminated areas.
Ageing impact on the transfer factor of 137Cs and 90Sr to lettuce and winter wheat
Πέμπτη, 14 Ιουλίου 2016, 9:18:18 πμ
Publication date: November 2016
Source:Journal of Environmental Radioactivity, Volume 164
Author(s): Lina Al Attar, Mohammad Al-Oudat, Bassam Safia, Basem Abdul Ghani
The study focuses on long-term (extending from 1 to 10 years) lysimeter experiments of the transfer factor of 137Cs and 90Sr to lettuce and winter wheat crops. Transfer factors (F v s) were the ratio of the activity concentrations of the radionuclides in crops to those in soil, both as dry weight (Bq kg−1). F v s of 137Cs to lettuce decreased significantly with ageing; geometric means for the 1st, 2nd and 10th year contaminated soil were 0.114, 0.030 and 0.013, respectively. However, a significant decline of F v s for 137Cs was only seen between the 1st and 2nd year for both wheat compartments (straw and grains) which disappeared thereafter. The dynamic of 137Cs F v s may be explained according to the distribution coefficient experiment (K d) which had a value of 3600 L kg−1 showing a high affinity of the clay minerals for caesium. Desorption data revealed that Cs fixation enhanced with ageing. The mechanism involved may be an initial sorption of caesium species to the surface soil particles followed by progressive irreversible fixation to the interlayer of the porous clay minerals. F v s of 90Sr were high and showed trivial variation for both crops for the time course studied. Sorption of Sr2+ species to the clay mineral may be the governing process, which was supported by high desorption percentage (ranged 77%) with low K d, i.e. 10 L kg−1. In general, higher F v s of 137Cs and 90Sr for lettuce was observed in comparison to winter wheat. The diversity of plant species and root systems would play essential roles for such behaviours.
Source:Journal of Environmental Radioactivity, Volume 164
Author(s): Lina Al Attar, Mohammad Al-Oudat, Bassam Safia, Basem Abdul Ghani
The study focuses on long-term (extending from 1 to 10 years) lysimeter experiments of the transfer factor of 137Cs and 90Sr to lettuce and winter wheat crops. Transfer factors (F v s) were the ratio of the activity concentrations of the radionuclides in crops to those in soil, both as dry weight (Bq kg−1). F v s of 137Cs to lettuce decreased significantly with ageing; geometric means for the 1st, 2nd and 10th year contaminated soil were 0.114, 0.030 and 0.013, respectively. However, a significant decline of F v s for 137Cs was only seen between the 1st and 2nd year for both wheat compartments (straw and grains) which disappeared thereafter. The dynamic of 137Cs F v s may be explained according to the distribution coefficient experiment (K d) which had a value of 3600 L kg−1 showing a high affinity of the clay minerals for caesium. Desorption data revealed that Cs fixation enhanced with ageing. The mechanism involved may be an initial sorption of caesium species to the surface soil particles followed by progressive irreversible fixation to the interlayer of the porous clay minerals. F v s of 90Sr were high and showed trivial variation for both crops for the time course studied. Sorption of Sr2+ species to the clay mineral may be the governing process, which was supported by high desorption percentage (ranged 77%) with low K d, i.e. 10 L kg−1. In general, higher F v s of 137Cs and 90Sr for lettuce was observed in comparison to winter wheat. The diversity of plant species and root systems would play essential roles for such behaviours.
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