A new perspective on the 137Cs retention mechanism in surface soils during the early stage after the Fukushima nuclear accident

Koarashi, Jun; Nishimura, Syusaku; Atarashi-Andoh, Mariko; Muto, Kotomi; Matsunaga, Takeshi

doi:10.1038/s41598-019-43499-7

Cited by 38 publications

(13 citation statements)

References 58 publications

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“…The trajectories of higher concentrations were adopted for the spatial evaluation in this study, and we do not deny the possibility that the future concentration may be lower than the concentration we predicted. A possible explanation is that the possible fixation of 137 Cs by minerals may lower the 137 Cs uptake by trees (but also see Manaka et al 2019 and Koarashi et al 2019) 28,33 . The model modification performed in this study may affect the trajectory; in this study, the source of root uptake was changed from the organic compartment to the mineral compartment because the organic layer is very thin in Japan, and we believe this approach is more reasonable and provides more conservative estimates in terms of continued root uptake.…”

Section: Discussionmentioning

confidence: 99%

New predictions of 137Cs dynamics in forests after the Fukushima nuclear accident

Hirano

Imamura

Kaneko

et al. 2020

Sci Rep

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Most of the area contaminated by the Fukushima Daiichi Nuclear Power Plant accident is covered by forest. In this paper, we updated model predictions of temporal changes in the 137Cs dynamics using the latest observation data and newly provided maps of the predicted 137Cs activity concentration for wood, which is the most commercially important part of the tree body. Overall, the previous prediction and latest observation data were in very good agreement. However, further validation revealed that the migration from the soil surface organic layer to the mineral soil was overestimated for evergreen needleleaf forests. The new prediction of the 137Cs inventory showed that although the 137Cs distribution within forests differed among forest types in the first 5 years, the difference diminished in the later phase. Besides, the prediction of the wood 137Cs activity concentrations reproduced the different trends of the 137Cs activity concentrations for cedar, oak, and pine trees. Our simulation suggests that the changes of the wood 137Cs activity concentration over time will slow down after 5–10 years. Although the model uncertainty should be considered and monitoring and model updating must continue, the study provides helpful information on the 137Cs dynamics within forest ecosystems and the changes in wood contamination.

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Section: Discussionmentioning

confidence: 99%

New predictions of 137Cs dynamics in forests after the Fukushima nuclear accident

Hirano

Imamura

Kaneko

et al. 2020

Sci Rep

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“…The aggregated transfer factor (T ag ) values for 137 Cs in tree leaves were also generally similar across treatments (although estimated to be higher in the decontaminated area than in the untreated area in some cases) ( Table 3). These results seem reasonable given that, prior to decontamination, a large proportion of the deposited 137 Cs was immobilized in the surface mineral soil via its interactions with soil constituents [40][41][42][43][44][45] . This behavior could reduce 137 Cs availability for root uptake by plants 15,46,47 to a similar extent in both the untreated and decontaminated areas.…”

Section: Discussionmentioning

confidence: 61%

Effectiveness of decontamination by litter removal in Japanese forest ecosystems affected by the Fukushima nuclear accident

Koarashi

Atarashi-Andoh

Nishimura

et al. 2020

Sci Rep

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The Fukushima Daiichi nuclear power plant accident caused serious radiocesium ( 137 Cs) contamination of forest ecosystems over a wide area. The removal of the forest floor litter layer has been considered a potential method for forest decontamination; however, its effectiveness remains largely unknown. We conducted a pilot-scale decontamination study in a deciduous broadleaved forest in Fukushima. The entire forest was decontaminated by removing the litter layer in July 2014, approximately 3.3 years after the accident, with the exception of two untreated plots. For three years after decontamination, we quantified 137 Cs contamination levels in the litter and topsoil layers and in the tree leaves, in the untreated and decontaminated areas. The decreased inventories of litter materials and the litter-associated 137 Cs in the decontaminated areas were observed only in the first year after decontamination. Generally, no decontamination effects were observed on the 137 Cs transfer in tree leaves. The primary reason for this was the rapid shift in the main reservoir of 137 Cs from litter layers to the underlying mineral soil, which differs from the observations in post-Chernobyl studies of European forest ecosystems. The results suggest that litter-removal decontamination can only be successful if it is implemented more quickly (within 1-2 years after the accident) for Japanese forest ecosystems.The accident at the Fukushima Daiichi nuclear power plant (NPP) in March 2011 released large quantities of radionuclides into the atmosphere 1 and consequently caused serious radioactive contamination of terrestrial ecosystems over a wide area of eastern Japan 2 . Among the radionuclides deposited onto the terrestrial ecosystems, radiocesium ( 137 Cs), with a physical half-life of 30.1 years, is the primary cause for concern because 137 Cs-contaminated ecosystems can increase the radiation exposure to the local population for many years, via both an elevated ambient dose rate in the air (external exposure) and the consumption of contaminated food products (internal exposure) 3 .Decontamination is an important post-accident countermeasure to reduce the radiological impact of a nuclear accident on humans and ecosystems 3,4 . Although since the Fukushima NPP accident, decontamination efforts have been progressing in residential and agricultural areas, forested areas have received a low priority in the decontamination decision-making process, as in the case of the Chernobyl NPP accident 3 , and has not been carried out on a large scale 5 , even though forests provide a wide range of social, cultural, and economic values. This is because the forested areas are vast, occupying approximately 70% of the land in the heavily contaminated area 6 , but are generally not where people live permanently or regularly spend much time. Another reason may be that the forested areas in Japan are concentrated in mountainous and hilly regions with steep terrain, which makes them very sensitive areas to soil erosion. Technical, radiological, and econ...

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“…Chemical alteration of organic matter may also occur in the drying process. In contrast, under natural conditions, a special accumulation of 137 Cs on organic matter also was reported via size and density fractionation methods [12,57] and chemical sequential fractionation methods [13]. Biological absorption of radiocesium also should occur.…”

Section: Mobility and Bioavailability Of Cesium Sorbed By Each Samplementioning

confidence: 99%

“…In contrast, organic matter in the O horizon (the surface organic horizon), including leaves/ needles, bark, and wood can also sorb radiocesium. Monovalent cations of radiocesium can be electrostatically bound to negatively charged sites on the surface or physically trapped in the complex structures of this organic matter [12,13]. Generally, radiocesium sorbed on organic matter is relatively mobile because it rapidly migrates downward to the A horizon or is easily taken up by plant roots or microorganisms [6,14].…”

Section: Introductionmentioning

confidence: 99%

Sorption and desorption experiments using stable cesium: considerations for radiocesium retention by fresh plant residues in Fukushima forest soils

Manaka

Ohashi

Ogo

et al. 2021

J Radioanal Nucl Chem

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We conducted sorption experiments with stable cesium (133Cs) solution in different organic matter samples, aiming to understand the sorption of radiocesium (134Cs and 137Cs) in the initial throughfall by fresh plant residues (e.g., needles, wood, and bark from Japanese cedar trees) in the Oi horizon in forests in Fukushima. Among the organic matter samples, bark and wattle tannin sorbed relatively large amounts of Cs, whereas wood and cellulose powder sorbed small amounts. In contrast, samples containing clay minerals showed much higher Cs sorption. We also conducted desorption experiments, and suggested that Cs on the organic matter samples were relatively mobile.

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A new perspective on the 137Cs retention mechanism in surface soils during the early stage after the Fukushima nuclear accident

Cited by 38 publications

References 58 publications

New predictions of 137Cs dynamics in forests after the Fukushima nuclear accident

New predictions of 137Cs dynamics in forests after the Fukushima nuclear accident

Effectiveness of decontamination by litter removal in Japanese forest ecosystems affected by the Fukushima nuclear accident

Sorption and desorption experiments using stable cesium: considerations for radiocesium retention by fresh plant residues in Fukushima forest soils

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