Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident
Abstract Understanding the actual situation of radiocesium (137Cs) contamination of trees caused by the Fukushima nuclear accident is essential for predicting the future contamination of wood. Particularly important is determining whether the 137Cs dynamics within forests and trees have reached appa...
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2022-07-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-022-14576-1 |
| _version_ | 1811323555188572160 |
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| author | Shinta Ohashi Katsushi Kuroda Hisashi Abe Akira Kagawa Masabumi Komatsu Masaki Sugiyama Youki Suzuki Takeshi Fujiwara Tsutomu Takano |
| author_facet | Shinta Ohashi Katsushi Kuroda Hisashi Abe Akira Kagawa Masabumi Komatsu Masaki Sugiyama Youki Suzuki Takeshi Fujiwara Tsutomu Takano |
| author_sort | Shinta Ohashi |
| collection | DOAJ |
| description | Abstract Understanding the actual situation of radiocesium (137Cs) contamination of trees caused by the Fukushima nuclear accident is essential for predicting the future contamination of wood. Particularly important is determining whether the 137Cs dynamics within forests and trees have reached apparent steady state. We conducted a monitoring survey of four major tree species (Japanese cedar, Japanese cypress, konara oak, and Japanese red pine) at multiple sites. Using a dynamic linear model, we analyzed the temporal trends in 137Cs activity concentrations in the bark (whole), outer bark, inner bark, wood (whole), sapwood, and heartwood during the 2011–2020 period. The activity concentrations were decay-corrected to September 1, 2020, to exclude the decrease due to the radioactive decay. The 137Cs concentrations in the whole and outer bark samples showed an exponential decrease in most plots but a flat trend in one plot, where 137Cs root uptake is considered to be high. The 137Cs concentration ratio (CR) of inner bark/sapwood showed a flat trend but the CR of heartwood/sapwood increased in many plots, indicating that the 137Cs dynamics reached apparent steady state within one year in the biologically active parts (inner bark and sapwood) and after several to more than 10 years in the inactive part (heartwood). The 137Cs concentration in the whole wood showed an increasing trend in six plots. In four of these plots, the increasing trend shifted to a flat or decreasing trend. Overall, the results show that the 137Cs dynamics within forests and trees have reached apparent steady state in many plots, although the amount of 137Cs root uptake in some plots is possibly still increasing 10 years after the accident. Clarifying the mechanisms and key factors determining the amount of 137Cs root uptake will be crucial for predicting wood contamination. |
| first_indexed | 2024-04-13T13:57:16Z |
| format | Article |
| id | doaj.art-18568f9e91fe42afa775424c71ed231a |
| institution | Directory Open Access Journal |
| issn | 2045-2322 |
| language | English |
| last_indexed | 2024-04-13T13:57:16Z |
| publishDate | 2022-07-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Scientific Reports |
| spelling | doaj.art-18568f9e91fe42afa775424c71ed231a2022-12-22T02:44:08ZengNature PortfolioScientific Reports2045-23222022-07-0112111210.1038/s41598-022-14576-1Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accidentShinta Ohashi0Katsushi Kuroda1Hisashi Abe2Akira Kagawa3Masabumi Komatsu4Masaki Sugiyama5Youki Suzuki6Takeshi Fujiwara7Tsutomu Takano8Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI)Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI)Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI)Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI)Department of Mushroom Science and Forest Microbiology, FFPRIDepartment of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI)Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI)Hokkaido Research Center, FFPRICenter for Forest Restoration and Radioecology, FFPRIAbstract Understanding the actual situation of radiocesium (137Cs) contamination of trees caused by the Fukushima nuclear accident is essential for predicting the future contamination of wood. Particularly important is determining whether the 137Cs dynamics within forests and trees have reached apparent steady state. We conducted a monitoring survey of four major tree species (Japanese cedar, Japanese cypress, konara oak, and Japanese red pine) at multiple sites. Using a dynamic linear model, we analyzed the temporal trends in 137Cs activity concentrations in the bark (whole), outer bark, inner bark, wood (whole), sapwood, and heartwood during the 2011–2020 period. The activity concentrations were decay-corrected to September 1, 2020, to exclude the decrease due to the radioactive decay. The 137Cs concentrations in the whole and outer bark samples showed an exponential decrease in most plots but a flat trend in one plot, where 137Cs root uptake is considered to be high. The 137Cs concentration ratio (CR) of inner bark/sapwood showed a flat trend but the CR of heartwood/sapwood increased in many plots, indicating that the 137Cs dynamics reached apparent steady state within one year in the biologically active parts (inner bark and sapwood) and after several to more than 10 years in the inactive part (heartwood). The 137Cs concentration in the whole wood showed an increasing trend in six plots. In four of these plots, the increasing trend shifted to a flat or decreasing trend. Overall, the results show that the 137Cs dynamics within forests and trees have reached apparent steady state in many plots, although the amount of 137Cs root uptake in some plots is possibly still increasing 10 years after the accident. Clarifying the mechanisms and key factors determining the amount of 137Cs root uptake will be crucial for predicting wood contamination.https://doi.org/10.1038/s41598-022-14576-1 |
| spellingShingle | Shinta Ohashi Katsushi Kuroda Hisashi Abe Akira Kagawa Masabumi Komatsu Masaki Sugiyama Youki Suzuki Takeshi Fujiwara Tsutomu Takano Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident Scientific Reports |
| title | Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident |
| title_full | Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident |
| title_fullStr | Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident |
| title_full_unstemmed | Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident |
| title_short | Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident |
| title_sort | decadal trends in 137cs concentrations in the bark and wood of trees contaminated by the fukushima nuclear accident |
| url | https://doi.org/10.1038/s41598-022-14576-1 |
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