Modeling dynamics of 137Cs in forest surface environments: Application to a contaminated forest site near Fukushima and assessment of potential impacts of soil organic matter interactions

Ota, Masakazu; Nagai, Hiroki; Koarashi, Jun

doi:10.1016/j.scitotenv.2016.02.068

Cited by 39 publications

(16 citation statements)

References 98 publications

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“…The scenario for the CF site highly contrasts that for the DBF site (see above), demonstrating that the forest type significantly influences both the short- and long-term behaviors of 137 Cs within a forest ecosystem739, and clearly, the retention of 137 Cs in organic layers plays a key role in controlling the overall 137 Cs behavior526. The observations conducted in European forests after the Chernobyl NPP accident have consistently shown that a large proportion of 137 Cs persisted in forest organic layers for over a decade, resulting in long-lasting 137 Cs bioavailability in the soil–plant system3456728.…”

Section: Discussionmentioning

confidence: 95%

“…The rate of decomposition of litter materials in organic layers is also influenced by climatological factors such as temperature and precipitation. Therefore, it is suggested that the behavior of 137 Cs in organic layers differs between European forests (affected by the Chernobyl NPP accident) and Japanese forests (affected by the Fukushima NPP accident)242526; studies under specific climatological and ecological conditions in Japan are urgently required to assess the environmental consequences of the Fukushima NPP accident. In addition, forests have complex stand structures and microtopography, and therefore, the quantity and quality (degrees of degradation) of litter materials accumulated in organic layers are highly spatially variable, even within a forest ecosystem27.…”

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confidence: 99%

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Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident

Koarashi

Atarashi-Andoh

Matsunaga

et al. 2016

Sci Rep

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The Fukushima Daiichi nuclear power plant disaster caused serious radiocesium (137Cs) contamination of forest ecosystems over a wide area. Forest-floor organic layers play a key role in controlling the overall bioavailability of 137Cs in forest ecosystems; however, there is still an insufficient understanding of how forest types influence the retention capability of 137Cs in organic layers in Japanese forest ecosystems. Here we conducted plot-scale investigations on the retention of 137Cs in organic layers at two contrasting forest sites in Fukushima. In a deciduous broad-leaved forest, approximately 80% of the deposited 137Cs migrated to mineral soil located below the organic layers within two years after the accident, with an ecological half-life of approximately one year. Conversely, in an evergreen coniferous forest, more than half of the deposited 137Cs remained in the organic layers, with an ecological half-life of 2.1 years. The observed retention behavior can be well explained by the tree phenology and accumulation of 137Cs associated with litter materials with different degrees of degradation in the organic layers. Spatial and temporal patterns of gamma-ray dose rates depended on the retention capability. Our results demonstrate that enhanced radiation risks last longer in evergreen coniferous forests than in deciduous broad-leaved forests.

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Section: Discussionmentioning

confidence: 95%

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confidence: 99%

Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident

Koarashi

Atarashi-Andoh

Matsunaga

et al. 2016

Sci Rep

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“…After the Chernobyl nuclear accident, many models were developed 7,8 , and an intercomparison project was conducted to assess model performance and uncertainty 7 . Similarly, after the FDNPP accident, several modelling studies were conducted to understand the 137 Cs dynamics and evaluate the ability and uncertainty of the obtained results [9][10][11][12][13][14] . For instance, Nishina et al developed a new radionuclide model by combining the forest growth model and the soil carbon dynamics model and validated the model using 7-year monitoring data 10,11 .…”

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confidence: 99%

“…For instance, Nishina et al developed a new radionuclide model by combining the forest growth model and the soil carbon dynamics model and validated the model using 7-year monitoring data 10,11 . Furthermore, Ota et al developed a model to track the detailed 137 Cs dynamics in forest soils 13 . Calmon et al also simulated the tree-to-soil surface migration in the early phase 14 , whereas Mahara et al predicted the future tree uptake of soil 137 Cs [ref.…”

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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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“…Strontium and cesium are important contaminants in LLW and ILW, because these radionuclides are most often present in the cooling water of nuclear reactors. These nuclides have long half-lives ( 90 Sr has a half-life of 28.8 years and 137 Cs has a half-life of 30.5 years), can readily migrate, and are known to cause carcinogenesis in contaminated living organisms [1][2][3][4][5][6]. Therefore, the management of low-and intermediate-level radioactive wastes containing Cs and Sr remains a major challenge to the nuclear energy industry.…”

Section: Introductionmentioning

confidence: 99%

Stabilization/Solidification of Strontium Using Magnesium Silicate Hydrate Cement

Zhang

Zou

et al. 2020

Processes

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Magnesium silicate hydrate (M–S–H) cement, formed by reacting MgO, SiO2, and H2O, was used to encapsulate strontium (Sr) radionuclide. Samples were prepared using light-burned magnesium oxide and silica fume, with sodium hexametaphosphate added to the mix water as a dispersant. The performance of the materials formed was evaluated by leach testing and the microstructure of the samples was also characterized. The stabilizing/solidifying effect on Sr radionuclide in the MgO–SiO2–H2O system with low alkalinity is demonstrated in the study. The leaching rate in a standard 42-day test was 2.53 × 10−4 cm/d, and the cumulative 42-day leaching fraction was 0.06 cm. This meets the relevant national standard performance for leaching requirements. Sr2+ was effectively incorporated into the M–S–H hydration products and new phase formation resulted in low Sr leaching being observed.

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Modeling dynamics of 137Cs in forest surface environments: Application to a contaminated forest site near Fukushima and assessment of potential impacts of soil organic matter interactions

Cited by 39 publications

References 98 publications

Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident

Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident

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

Stabilization/Solidification of Strontium Using Magnesium Silicate Hydrate Cement

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