Potassium fertilisation reduces radiocesium uptake by Japanese cypress seedlings grown in a stand contaminated by the Fukushima Daiichi nuclear accident

Self Cite

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.

Section: Discussionmentioning

confidence: 99%

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

Hirano

Imamura

Kaneko

et al. 2020

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“…Although 137 Cs fixation potentials were not measured at all four sampling sites in the present study, all of them have brown forest soils with granitic rocks as the surface geology 36 . Therefore, the 137 Cs fixation potentials may be high 37 (Yamaguchi et al 38 ) and have little influence on the among-site differences in root uptake by Koshiabura. Similarly, with regard to potassium and ammonium ions in the soil solution, although they were not measured in the present study, the concentration of ammonium ion is usually very low compared with that of potassium ions because of rapid nitrification by microorganisms at the surface of forest soils.…”

Section: Resultsmentioning

confidence: 99%

Explaining the variation in 137Cs aggregated transfer factor for wild edible plants as a case study on Koshiabura (Eleutherococcus sciadophylloides) buds

Hayashi,

Watanabe,

Kanao Koshikawa

et al. 2023

The aggregated transfer factor (Tag) is commonly used to represent the actual transfer of radiocesium from soil to wild edible plants, but the values have shown substantial variation since the Fukushima nuclear accident. To elucidate the factors causing this variation, we investigated the effects of spatial scale and vertical 137Cs distribution in the soil on the variation of Tag-137Cs values for one of the most severely contaminated wild edible plants, Eleutherococcus sciadophylloides Franch. et Sav. (Koshiabura). The variation in Tag-137Cs values was not reduced by direct measurement of 137Cs deposition in soil samples from the Koshiabura habitat, as a substitute for using spatially averaged airborne survey data at the administrative district scale. The 137Cs activity concentration in Koshiabura buds showed a significant positive correlation with the 137Cs inventories only in the organic horizon of soil from the Koshiabura habitat. The ratio of 137Cs inventories in the organic horizon to the total 137Cs deposition in soil exhibited substantial variation, especially in broad-leaved deciduous forests that Koshiabura primarily inhabits. This variation may be the cause of the wide range of Tag-137Cs values observed in Koshiabura buds when calculated from the total 137Cs deposition in soil.

“…It is generally considered that K act as a competitor of 137 Cs through uptake processes in forest soils 14 , 16 , 52 . In contrast, some of the studies listed in Table S2 also examined the leaching and extraction of other alkali metals: Hara et al (2020) 31 in needles of Japanese cedar, Sakai et al (2015) 47 in fallen needles of Japanese cedar, and Kurihara et al (2020) 32 in the organic layer under both species.…”

Section: Discussionmentioning

confidence: 99%

Radiocesium mobility in different parts of the two major tree species in Fukushima

Manaka

Araki

Ohashi

et al. 2023

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Radiocesium (137Cs) released in the Fukushima Dai-ichi Nuclear Power Plant accident is still cycling in the forest ecosystem. We examined the mobility of 137Cs in the external parts—leaves/needles, branches, and bark—of the two major tree species in Fukushima, Japanese cedar (Cryptomeria japonica) and konara oak (Quercus serrata). This variable mobility will likely lead to spatial heterogeneity of 137Cs and difficulty in predicting its dynamics for decades. We conducted leaching experiments on these samples by using ultrapure water and ammonium acetate. In Japanese cedar, the 137Cs percentage leached from current-year needles was 26–45% (ultrapure water) and 27–60% (ammonium acetate)—similar to those from old needles and branches. In konara oak, the 137Cs percentage leached from leaves was 47–72% (ultrapure water) and 70–100% (ammonium acetate)—comparable to those from current-year and old branches. Relatively poor 137Cs mobility was observed in the outer bark of Japanese cedar and in organic layer samples from both species. Comparison of the results from corresponding parts revealed greater 137Cs mobility in konara oak than in Japanese cedar. We suggest that more active cycling of 137Cs occurs in konara oak.