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Recycling decontaminated soil from the nuclear power plant accident is “no one’s business” Residents of Shinjuku, which has an unexpected connection with TEPCO, have stood up to stand up for the issue

Gen Hirai (second from right) and others protest the demonstration project to reuse decontaminated soil in Kabukicho, Tokyo, on December 12.

January 13, 2023
One month has passed since the announcement of a demonstration project to reuse so-called “decontaminated soil” collected during decontamination work after the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant in the Tokyo metropolitan area. People who live near Shinjuku Gyoen (Shinjuku-ku, Tokyo), one of the planned sites, have joined forces and established a group to oppose the reuse of the soil. Shinjuku has an unexpected connection with TEPCO. What do the locals think? Can other areas be left to their own devices? We took another look at the situation. (Takeshi Nakayama and Yoshiko Nakazawa)

◆No attempt has been made to reach a consensus among the residents.
 The local people are trying to push the project forward without the knowledge of many of them,” said one angry writer.
 Gen Hirai, 70, a writer, is angry. Gen Hirai, 70, is the chairman of the “Association Opposing the Introduction of Radioactively Contaminated Soil into Shinjuku Gyoen,” which lodged a complaint with the Shinjuku City government on March 12, claiming that there had been insufficient explanation of the demonstration project.
 On September 9, the Ministry of the Environment announced a demonstration project using Shinjuku Gyoen as a candidate site. The project will use the flower beds behind the office building, which are normally closed to the general public, and plant them by covering them with decontaminated soil.
 On the 21st, an explanatory meeting was held for residents of Shinjuku 1 and 2 chome facing the Gyoen. However, only 28 people attended the meeting, and Ms. Hirai, who lives in 1-chome, was unaware of it until she learned about it through the media.
 It cannot be said that we are trying to build consensus among the residents of the city,” said Hirai. Mr. Hirai felt a growing sense of crisis and held a study session on the issue of decontaminated soil on the 28th. On the 7th of this month, he established a group to oppose the project with other ward residents.
◆University professors, lawyers, theater performers, and restaurant owners in the Golden district

Gen Hirai speaks about his proposal for a demonstration project to reuse decontaminated soil at the Shinjuku City Office in Kabukicho, Tokyo, on December 12.

During his visit to the Shinjuku City Office on January 12, Gen Hirai submitted a written request to the city officials to inform the residents of the demonstration project and to stop bringing decontaminated soil into the city unless its safety is guaranteed.
 The 20 people who accompanied him were a diverse group, including not only local residents but also university professors, lawyers, theater people, and restaurant owners from the Golden Gaien district near the Gyoen. The participants questioned whether the law had been properly established for the reuse of decontaminated soil, and whether this would lead to the spread of contamination rather than alleviate the burden on Fukushima.
 Although Shinjuku has a strong impression of an entertainment district such as Kabukicho, there are many condominiums in the Shinjuku Gyoen area, and some people have lived in the area for three generations. Mr. Hirai used to play in Shinjuku Gyoen when he was in elementary school, and even now he takes a walk there once every three days. Many kindergarteners also visit the park, and there is a promenade where many people come and go. Why are they trying to conduct a demonstration project in such a park?
◆Shinjuku Metropolitan High School, which has produced successive generations of TEPCO executives
 Shinjuku is also characterized by its close ties to TEPCO.
 Graduates of Shinjuku Metropolitan High School, located near the Gyoen Garden, have produced successive generations of TEPCO executives. According to the “Choyo Alumni Association,” a group of graduates, Tsunehisa Katsumata, who was chairman at the time of the Fukushima nuclear accident, and Naomi Hirose, who served as president after the accident, are among the names on the list. In addition, the TEPCO Hospital was located in Shinanomachi near the Gyoen until February 2014. I would like to ask Katsumata and others what they think about bringing (decontaminated soil) so close to their alma mater,” he said.
 What stands out above all else is the Ministry of the Environment’s forward-looking attitude. This can be seen in a video shown at the briefing in Shinjuku, titled “Fukushima and the Environment Beyond. The video, “Fukushima and Beyond: Toward the Environment,” which was shown at the briefing in Shinjuku, also gives some indication.
 The decontaminated soil is described as “an issue that remains in the land of Fukushima, which continues to recover. The video shows images of temporary storage sites in Fukushima Prefecture lined with flexible container bags filled with decontaminated soil, and asks the question, “Is this really a problem only in Fukushima? Is this really only a problem in Fukushima?
 It seems as if he is trying to say that a demonstration project is needed to accept decontaminated soil outside of Fukushima Prefecture, but it is not clear that he is seriously trying to answer the questions of the local residents. The call center, which was listed in the briefing materials, is open only on weekdays, but the staff is curt: “We will use the ‘opinions’ we receive as reference in our future studies.

A park with a signboard showing underground storage of decontaminated soil in Funabashi City, Chiba Prefecture, in December 2022.

◆”Shinjuku City also believes what the government says.
 Mr. Hirai said that the government seems to be leaving residents behind.
 He points out that the Shinjuku City government is also accepting the government’s position that the decontaminated soil is safe, even though it cannot be scientifically proven that it is safe. The opposition group will hold an inaugural meeting on March 24, and will continue to raise the issue widely.
 The demonstration project is currently announced for Shinjuku City and Tokorozawa City in Saitama Prefecture, and Tsukuba City in Ibaraki Prefecture is also being discussed, but the cleanup of decontaminated soil is not limited to these areas.
 According to the Ministry of the Environment, decontaminated soil from Fukushima Prefecture will be collected at an interim storage facility near the Daiichi Nuclear Power Plant and then transported out of the prefecture for final disposal by 2045. As of the end of last year, about 13.38 million cubic meters of decontaminated soil had been collected. The company advocates the reuse of the soil to reduce the amount for final disposal and to make it easier to transport the soil out of the prefecture.
◆Decontaminated soil is becoming more and more familiar to people…
 The problem is the radioactive concentration of the decontaminated soil to be reused.
 According to the Ministry of Agriculture, Forestry and Fisheries, for about 50 years before the nuclear accident, the average radioactive concentration of farmland in Japan was about 20 becquerels per kilogram. On the other hand, the Ministry of the Environment has set a recycling standard for decontaminated soil of 8,000 becquerels or less, about 400 times higher. This is 80 times lower than the recycling standard of 100 becquerels or less for materials from decommissioned nuclear power plants.
 Yayoi Isono, professor emeritus of environmental law at Tokyo Keizai University, commented, “Under these standards, a considerable amount of waste is reused. If soil with a low concentration of radioactive materials is mixed with the soil, it can be diluted to the standard level. If the amount of soil to be reused increases, the number of areas subject to reuse could also increase. If more soil is reused, the number of areas where it will be reused could increase.

Workers seal and bury soil contaminated with radioactive materials in Seya Ward, Yokohama, March 2012.

There are other troubling issues. As a result of the widespread release of radioactive materials from the Fukushima Daiichi Nuclear Power Plant, decontamination was widely implemented in the Tohoku and Tokyo metropolitan areas. Decontaminated soil is stored at a total of 29,000 locations in seven prefectures outside of Fukushima Prefecture, including Iwate, Ibaraki, Gunma, and Chiba. The Ministry of the Environment is urging measures such as sealing the soil in bags or containers, covering them with tarps to shield them from water, and covering them with fill.
 However, the measures to be taken after storage differ between Fukushima Prefecture and other prefectures. The basic policy approved by the Cabinet in November 2011 stipulates that the government is responsible for securing interim storage facilities in prefectures where “a significant amount” of contaminated soil and other materials are generated. Fukushima Prefecture falls under this category, while other prefectures are to dispose of contaminated soil onsite.
◆Ministry of the Environment embarking on a demonstration project based on the idea that there is reuse of soil
 However, municipalities outside of Fukushima Prefecture that have decontaminated soil are facing a complicated situation. Marumori Town in Miyagi Prefecture, which is storing decontaminated soil at 44 locations including schools, has approached the Ministry of the Environment, saying, “The government and TEPCO are responsible for transporting the soil out of the town for disposal.
 An official from the town’s general affairs division said, “Some people in the town say, ‘It is not right that the people who dumped the waste did not clean it up, and that the people in the area where the waste was dumped are responsible for disposing of it. The government has not agreed to remove the waste from the town, but we are asking the government to do so, even if it means amending the law,” he said.
 The cleanup of decontaminated soil cannot be a personal matter. However, the grounds for the cleanup methods are not clear, and in some cases, the methods are not clear.
 Reuse of decontaminated soil within Fukushima Prefecture and on-site disposal of decontaminated soil outside of Fukushima Prefecture are merely policies approved by the Cabinet of the time. The question remains as to whether consensus building is sufficient. As for the final disposal of decontaminated soil in Fukushima Prefecture, the ministry official said, “We are currently discussing this at an experts’ meeting.
 In spite of this situation, the Ministry of the Environment is embarking on a demonstration project with the idea that the soil can be reused.
 Journalist Junko Masano criticized the Ministry, saying, “There is little legal basis for reusing the soil, and the push to do so is ridiculous. If the land is actually to be reused for road construction and other purposes, it will be necessary to verify protective measures.
 The aforementioned Mr. Isono also commented, “The response to the Fukushima accident will be the foundation for the future. We should have careful discussions on whether we should reuse the waste in the first place and, if so, how we should proceed.
◆Desk Memo
 Radioactive contamination caused by TEPCO’s nuclear power plants. TEPCO is supposed to be in charge of cleaning up the mess, but it is now forcing each region to accept the contaminated soil. The company is now pressuring each region to accept the contaminated soil, as if it were a natural disaster, saying that it is not someone’s fault and that everyone should cooperate for the recovery. This is the premise that makes us feel uncomfortable. This is where the question should be asked again. (Sakaki)

https://www.tokyo-np.co.jp/article/224939/2

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January 20, 2023 Posted by | Fuk 2023 | , , , | Leave a comment

Decontamination work to start in more parts of Fukushima in FY 2023

Dec. 16, 2022

The Japanese government says decontamination work will start next fiscal year in more parts of Fukushima Prefecture that remain off limits following the March 2011 nuclear accident.

Authorities designated the areas as “difficult-to-return zones”, and evacuation orders remain in effect.

On Friday, Reconstruction Minister Akiba Kenya said the decontamination work includes parts of Okuma and Futaba towns.

A detailed schedule remains undecided, but the work will begin in the fiscal year starting next April.

The government plans to fund the work with 6 billion yen, or nearly 44 million dollars, from the state budget.

Some parts of the “difficult-to-return zones” have already been cleaned up so that people can return.

The ruling coalition has been urging the government to decontaminate more areas.

https://www3.nhk.or.jp/nhkworld/en/news/20221217_01/

December 19, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Decontaminated soil taken out of Fukushima prefecture and reused for the first time outside of Fukushima, at a Ministry of the Environment facility

Storage of decontaminated soil at an interim storage facility in Okuma Town, Fukushima Prefecture, in June.

December 5, 2022
On December 5, it was learned that the Ministry of the Environment plans to conduct a demonstration test for reusing soil removed from decontamination sites in Fukushima Prefecture following the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant at its Environmental Research and Training Center in Tokorozawa City, Saitama Prefecture. This is the first test in which decontaminated soil will be taken out of Fukushima Prefecture, and the question is whether the test will gain the understanding of local residents. A briefing session for local residents will be held on March 16.
 The Ministry of the Environment has not revealed the amount of decontaminated soil to be brought in or the timing of the test, saying, “The details of the test will be announced after the briefing.
 The law stipulates that decontaminated soil from Fukushima Prefecture must be removed from the prefecture by 45 years for final disposal.
https://www.tokyo-np.co.jp/article/218081?rct=national&fbclid=IwAR3dokeQ-qpNfi1ly6cAA68x8goY-BuVi-fuq0pXUx-1UUhh_hJuUBq6neI

December 11, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Iitate will be 1st to lift evacuation order without decontamination

Akihiko Morota, deputy director-general of the government’s Nuclear Emergency Response Headquarters, explains the status of the difficult-to-return zone to Iitate village residents at a briefing in Fukushima city on Nov. 20.

November 21, 2022

FUKUSHIMA–Iitate village near the Fukushima No. 1 nuclear power plant plans to lift an evacuation order next spring for a small portion of the “difficult-to-return zone” so it can reclaim space for a park.

This marks the first time an evacuation order will be lifted without first carrying out decontamination work since the government made it easier to lift evacuation orders in 2020.

The order was originally issued due to high levels of radiation detected following the triple meltdown at the plant triggered by the 2011 earthquake and tsunami.

Iitate Mayor Makoto Sugioka and the central government’s Nuclear Emergency Response Headquarters made the announcement at a news conference following a briefing for residents in Fukushima city on Nov. 20.

Residents of Iitate in eastern Fukushima Prefecture had initially opposed lifting the evacuation order without first decontaminating the area, but the mayor said they were persuaded.

“We were able to obtain their consent at the briefing,” Sugioka said.

The area where the order will be lifted without any decontamination work is small. It spans just 0.64 hectares and includes only one household.

Workers will set up shields on the ground there to prevent exposure to radiation.

But the government has confirmed that even without the shielding, the radiation level is below the standard for issuing an evacuation order, at 20 millisieverts per year. The village plans to use this area as a park.

The government designated areas with readings of more than 50 millisieverts a year as difficult-to-return zones.

Iitate has a difficult-to-return zone measuring 1,080 hectares in total, according to the village and the central government.

Within this area, officials have designated a 186-hectare special zone for reconstruction and revitalization, which covers 63 households. That land will be decontaminated by removing topsoil contaminated with radioactive materials.

But there is no prospect for lifting the order for the remaining land outside the special zone, which covers 10 households.

In December 2020, the government created new criteria for lifting an evacuation order for land outside the special zone, where radiation levels are below the standard due to natural attenuation. Those conditions include a request from the local government and confirmation that no one will live there.

Among eight municipalities that have such special zones, this will be the first time that an evacuation order will be lifted outside the zone. No municipalities other than Iitate are seeking a lifting of the evacuation order under the new criteria. 

https://www.asahi.com/ajw/articles/14773728

November 27, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Fukushima Iitate Village Lifting of Evacuation Order for “Out of Base Area” First indication of timing

November 20, 2022

The national government and Iitate Village in Fukushima Prefecture have announced that they will lift the evacuation order for a part of the Nagadori area, which has been designated as a “difficult-to-return zone” due to the accident at the TEPCO’s Fukushima Daiichi Nuclear Power Plant, around the major holidays in spring next year under the so-called “lifting of evacuation order without decontamination.

This is the first time that a specific date for lifting the evacuation order for areas outside of the “base area” has been announced.

In the Nagadori area of Iitate Village, which is a hard-to-return zone where entry is severely restricted, 17% of the area has been designated as a “specific restoration and rehabilitation base zone” where decontamination and other measures will be carried out first, with the aim of lifting the evacuation order in the spring of next year.

On April 20, the central government and Iitate Village held a press conference after holding a briefing session for local residents in Fukushima City to discuss the possibility of lifting the evacuation order in the spring of next year under the framework of “lifting the evacuation order without decontamination,” which allows the lifting of the evacuation order even if the government has not decontaminated the land, provided that the local government has strong intentions to use the land and the radiation level is lowered and the residents do not return. The government has announced that it plans to lift the evacuation order for a part of the area outside the “base area” around the major holidays in the spring of next year.

The area to be removed is a 6,400-square-meter plot of land where a government demonstration experiment to block radiation by pouring concrete on the ground was being conducted, and it represents 0.07% of the area outside the “base area” in the village.

Since it has been confirmed that radiation levels have been sufficiently reduced, the government will allow people to freely enter the area to see the results of this demonstration project.

This is the first time that a specific date for the lifting of the evacuation order for “outside the base area” has been announced.

In conjunction with this, the policy of lifting all evacuation orders for the base area in the village was also announced.

Iitate Village Mayor Makoto Sugioka said, “We would like to consider using the site as a place where we can confirm the effects of the radiation dose reduction demonstration project and a place where we can pass on to future generations what has been done in the difficult-to-return zone and Nagadori area.
https://www3.nhk.or.jp/news/html/20221120/k10013897961000.html?fbclid=IwAR3mZj8YTUnBARRCJV-KqrxSGzF9OP-jVrRRRv2GY1kcSpDWnrIF0boiiNg

November 27, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Radiation dose and gene expression analysis of wild boar 10 years after the Fukushima Daiichi Nuclear Plant accident

Abstract

The Fukushima Daiichi Nuclear Power Plant accident led to contamination with radioactive cesium in an extensive environment in Japan in 2011. We evaluated the concentration of radioactive cesium in the skeletal muscles of 22 wild boars and the expression of IFN-γ, TLR3, and CyclinG1 in the small intestine and compared them with those of wild boar samples collected from Hyogo prefecture. The average 137Cs radioactivity concentration in wild boars in the ex-evacuation zone was 470 Bq/kg. Most of samples still showed radioactivity concentration that exceeded the regulatory limit for foods, but the dose remarkably decreased compared with samples just after the accident. IFN-γ expression was significantly higher in wild boars in the ex-evacuation zone than in samples from Hyogo prefecture. TLR3 expression was also upregulated. CyclinG1 expression also tended to be high. Hence, wild boars might have received some effects of low-dose radiation, and immune cells were activated to some extent. However, pathological examination revealed no inflammatory cell infiltration or pathological damage in the small intestine of wild boars in the ex-evacuation area. Long-term monitoring would be necessary, but we consider that the living body responds appropriately to a stimulus from a contaminated environment.

Introduction

On March 11, 2011, the Great East Japan Earthquake was one of the most significant disasters caused by earthquakes and tsunamis. Moreover, the accident at the Fukushima Daiichi Nuclear Power Plant resulted in widespread contamination of radioactive materials. After the accident, more than 165,000 people were evacuated, but wild and livestock animals were left behind in the evacuation zone at that time. We had earlier investigated the effect of radiation on those animals, and the results were published in several research papers1,2,3,4,5,6 and a book chapter7. However, because the half-life of 137Cesium is approximately 30 years, a long-term environmental survey in the ex-evacuation area is necessary to understand the impact of chronic low-dose radiation on wildlife physiology.

Ten years have elapsed since the earthquake, much of the area where people lived has been decontaminated already, and humans are returning now. Although several people are evacuating, the remaining wild animals are free to live contaminated with radioactive materials. Recent research has revealed that numerous wildlife species are now abundant throughout the ex-evacuation zone8. Hunters in Fukushima have exterminated numerous wild animals, but they are not used for human consumption due to the contamination. Even after the Chernobyl accident, wildlife surveys have reported high radioactive contamination rates in wild boars even after several years9. In a previous research that examined 213 wild boar muscles in Tomioka town, Fukushima Prefecture, in 2019, it was observed that 98.6% of the samples had radioactivity concentration that exceeded the standard value (100 Bq/kg)10 as a general food. Therefore, the meats of those wild boars are not edible and are discarded. However, these wild boars are considered to be affected by low doses of radiation, and analyzing them is important considering the effects on humans.

The physiological functions and immune systems of pigs are extremely similar to those of humans11,12,13. Therefore, we intended to understand the responses in abandoned pigs to radioactive contamination, which can be helpful in understanding the radiation effects and responses in humans. Our previous report demonstrated that there were alterations in gene expression in the small intestine of animals in the ex-evacuation zone after radiation4. The genes involved in inflammation showed significantly higher expression in pigs in the ex-evacuation zone than in control pigs. Therefore, exposed pigs could have an inflammatory response due to oxidative stress with the indirect action of radiation. This is caused by breaking the O–H bonds of water molecules in the body and generating reactive oxygen species14,15. As superoxide and hydroxyl radicals of reactive oxygen species have unpaired electrons, they oxidize DNA, proteins, and lipids16,17,18. Consequently, the biomolecules would be damaged. However, the body has a mechanism to eliminate reactive oxygen species. Nevertheless, if numerous reactive oxygen species are generated by radiation, the elimination will be insufficient, leading to oxidative stress. Chronic inflammation due to oxidative stress is known to induce cancer, lifestyle-related diseases, and immune-related diseases. Therefore, we performed a follow-up investigation using wild boars, which are biologically the same species as pigs, in this study. Muscles and small intestines were collected from the wild boars that were exterminated by the Hunting Association. These samples were evaluated for the amount of radioactive cesium, and the changes in the expression of genes responsible for immunological or physiological functions were analyzed (Fig. 1).

Results

Radioactivity concentration in skeletal muscles and total exposure dose rates of wild boars

Figure 2 shows relationship between the total exposure dose rates and the radioactivity concentration in the skeletal muscles of wild boars. The total exposure dose rates are summation of internal and external dose rates of whole body. Average 137Cs radioactivity concentration and total dose rates in 22 wild boars in the ex-evacuation zone were 470 Bq/kg and 7.2 µGy/d, respectively. The lowest and highest values were 124 and 1667 Bq/kg, respectively. And the medians were 289 Bq/kg and 6.8 µGy/d. In contrast, the average 137Cs radioactivity concentration and total dose rates of the three wild boars in Hyogo prefecture were 1.5 Bq/kg and 0.0 µGy. The lowest and highest values were 0.6 and 2.7 Bq/kg, respectively, and the median was 1.2 Bq/kg.

Gene expressions in the small intestine

In our previous study conducted in 2012, microarray analysis revealed that several genes in the small intestine exhibited significant expression differences after radiation in abandoned pigs. More detailed experiments using real-time PCR confirmed that IFN-γ and TLR3 expressions were significantly increased after radiation in abandoned pigs. Furthermore, our subsequent study of wild boars in the ex-evacuation zone in 2015 showed that CyclinG1 expression was significantly higher than that in the control group4. Therefore, we focused on the expression of IFN-γ, TLR3, and CyclinG1 in the present study as a follow-up survey. We found that IFN-γ and TLR3 expressions were significantly higher in Fukushima wild boars than in Hyogo wild boars. The expression of CyclinG1 also tended to be higher (Fig. 3).

Pathological and morphological changes in the small intestine

In the pathological analysis, tissues were fixed and cut for HE staining to examine whether intestinal tissues were damaged or showed inflammation because of radiation exposure. No morphological changes and infiltration of inflammatory cells were observed (Fig. 4).

Discussion

Although 10 years have elapsed since the earthquake, the reconstruction of the disaster area is in progress. In Fukushima, there are still areas where it is difficult to return home. However, decontamination of urban regions and agricultural land is progressing, and residents are rebuilding their lives. Moreover, agricultural products are sold after being thoroughly inspected for radiation dose and confirmed to be safe. It is the increase in the number of wild animals that threatens the livelihoods of the returning people. From 2016 to 2017, Lyons et al.8 surveyed the ecology of wild animals using network cameras. They found that wildlife preferred the environment without humans and increased in number in the ex-evacuation zone, despite chronic radiation exposure. The wild boar was the most abundant species in the ex-evacuation zone. Even before the Fukushima Daiichi accident, wild boars were targeted for extermination, and the Hunting Association was hunting, but at that time, the meat was also edible in this area. However, it is now just discarded after hunting. The wild boars present in the mountains have not been decontaminated but eat contaminated food and water. Several studies on the Chernobyl accident demonstrated that the pollution of mushrooms in the mountain range continued for a long time19,20.

The intestine can be significantly affected by radiation through internal exposure after oral intake of contaminated food. It is also one of the essential organs of the immune system. Therefore, we evaluated whether the expression of genes responsible for the immune system and cell cycles in the small intestine of wild boars in the ex-evacuation area is altered compared to that in animals in the noncontaminated area.

Our results demonstrated that IFN-γ and TLR3 were significantly upregulated in Fukushima wild boars compared to those in Hyogo wild boars. Moreover, CyclinG1 expression tended to increase. As mentioned earlier, these genes were selected from the microarray analysis in our previous research4. IFN-γ is one of the crucial cytokines for acquired immunity and inflammation. Recently, Zha et al. described that IFN-γ is a master regulator for several cytokines involved in numerous biological processes21. It functions as a master switch to operate cell activation or inhibition. In comparison, the major portion of innate immune cell activation is mediated by TLRs. TLR3 is involved in dsRNA recognition and is associated with antiviral responses. Furthermore, TLR3 is an important molecule for radiation susceptibility. Takemura et al. reported that TLR3-deficient mice exhibited substantial resistance to gastrointestinal syndrome (GIS)22. TLR3 is bound to cellular RNA leaking from damaged cells and induces inflammation. CyclinG1 is one of the target genes of the transcription factor p53 and is induced in response to DNA damage. It also plays a role in G2/M arrest in response to DNA damage recovery and growth promotion after cell stress23. Therefore, the changes in the expressions of the genes encoding these proteins suggested that the immune system and cell cycles in wild boars in the ex-evacuation zone were affected by low-dose radiation. These results are consistent with our previous investigation conducted in 2012. A state of high IFN-γ expression suggests an activated state of immune cells. Despite the low-dose, radiation-induced oxidative stress may result in elevated expression of inflammatory cytokines. However, no correlation was observed between IFN-γ expression and radiation levels in the skeletal muscle of wild boars in this study (data not shown). This could be due to the lower doses of 137Cs observed in the present study rather than those in the previous investigation. Furthermore, pathological examination revealed no infiltration of immune cells in the submucosa of small intestines of wild boars in the ex-evacuation area.

Therefore, the elevated expression of these genes can be considered as a consequence of the living body’s ability to appropriately process the effects of low-dose radiation. The highest radiation concentration in the skeletal muscle was 1667 Bq/kg, which was much lower than that in abandoned pigs investigated in 2012, at > 15,000 Bq/kg on average. Cui et al. investigated 213 wild boars and reported a median 137Cs value of 420 Bq/kg in 201910. Most samples collected from the wild boars in the ex-evacuation zone still showed radioactivity concentration that exceeded the regulatory radiocesium limit for foods in the present study, but the dose is steadily decreasing. Cunningham et al. investigated DNA damage and concluded that there was no evidence of significant harmful impacts to wild boars exposed to low-dose radiation24.

Furthermore, Pederson et al. investigated whether chronic low-dose radiation affects cataract prevalence in wild boars but reported no significantly higher risk in the animals in the exclusion zone25. Finally, we also report the results of this study as a record of 10 years after the accident. Although an increase in the expression of IFN-γ, TLR3, and CyclinG1 was detected, there were no pathological abnormalities in wild boars in the ex-evacuation zone. However, it is difficult to conclude the effects of radiation only ten years after the accident. We intend to continue conducting wild boar surveys regularly to elucidate the effects of long-term low-dose radiation exposure.

More at: https://www.nature.com/articles/s41598-022-21436-5

November 7, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

The Fukushima Area Has Seen Better Days as Nobuhiko Ito Shows

October 30, 2022

“The level of the contamination is too high to be inhabitable,” says photographer Nobuhiko Ito about the ever-present danger around the vicinity of the former Fukushima nuclear plant. A decade-old event that Japan is still recovering from, the impact of the accident there and resulting economic fallout was felt around the world for quite some time. As with all nuclear plant incidents, questions remain over whether life will ever return to normal in the surrounding areas.

Dominating the news for many weeks that year, the Fukushima Daiichi Accident, as it’s officially known, occurred at the city’s nuclear plant following a tsunami caused by a major earthquake in March, 2011. Almost 14-meter-high waves lashed the plant, flooding and severe damaging its reactors. It was classified as the most severe nuclear accident since Chernobyl, and over 150,000 people were evacuated from the city. Radiation-contaminated water seep into the Pacific Ocean for many days after the incident, even as late as 2013. It was estimated then that decontamination efforts could last up to 40 years. Almost a decade from later, Japanese photographer Nobuhiko Ito has begun a project to safely photograph the areas surrounding Fukushima. Large parts of it are still off-limits to the public.

The Phoblographer: Hi Nobuhiko. Please tell us about yourself and how you got into photography.

Nobuhiko Ito: I was born in 1970 in Kanagawa prefecture, Japan. I started taking pictures when I was 15 years old and have been involved in photography ever since. In 1998, I studied under photographer Hiromi Tsuchida. I became an independent photographer in 2003, and since then, I have been an active freelancer. Although I was not aware of it when I was young, the fact that seeing things through a camera is an objective and critical act is the most important reason why I continue to express myself through photography.

Photography is basically a solo activity, and I think I have been able to continue to do it because I am suited to this kind of work.

The Phoblographer: Where were you when the Fukushima Daiichi Accident occured? What was the general feeling for the next few days in your vicinity?

Nobuhiko Ito: The earthquake occurred at 14:46 on March 11, 2011, and approximately one hour later, the nuclear reactor meltdown caused by the loss of power due to tsunami damage was a direct cause of the Fukushima Daiichi nuclear accident. This was followed by three hydrogen explosions on March 12, 14, and 15, resulting in a serious situation in which a wide area of more than 30 km radius was contaminated by radioactive materials. I was in Tokyo when the earthquake hit, and I was scheduled to have a work meeting with a client at 3:00 p.m. I felt kind of silly because I was still meeting at the client’s office as scheduled, even with the numerous aftershocks that hit afterward. I drove myself home to my house in Yokohama, about 30 kilometers away, at around 5:00 p.m. All public transportation was stopped, the roads were jammed badly, and the sidewalks were full of people walking home, which was an unusual situation. It took me about 8 hours to get home, where it usually takes me about 45 minutes. It took me twice as long as it would have taken me to walk home.

I was in a car stuck in traffic, checking with relatives on my cell phone to make sure they were safe and listening to the news bulletins that came in one after another, but I was already worried about the meltdown at the Fukushima Daiichi Nuclear Power Plant at that point. I spent the next week or so at home. I heard that some people were buying up water, food, and stockpiles, but I did not act rashly and stayed put.

The Phoblographer: How long have you been working on your book, A Decade of Fukushima? Typically how many images do you photograph of the surrounding areas of the nuclear plant site each year?

Nobuhiko Ito: I started taking pictures in April 2020, so as of now it has only been 2 years and 6 months. When I started filming, it had been 9 years since the Great East Japan Earthquake and the Fukushima Daiichi Nuclear Power Plant accident and the people of this country were beginning to have fading memories of it. I may be one of them, but one thing that sets me apart from the rest of the survivors is that I have been visiting companies based around the hard-to-return zone in Fukushima Prefecture several times a year for commercial photography assignments since 2009, before the accident.

During those nine years, I watched the transition of the area from a moving car window. Buildings destroyed by the tsunami and left abandoned, cars washed away and rusting in the middle of fields, natural scenery where the topsoil is being gouged away by the large-scale decontamination work started by the government sometime after the accident… As a person involved in photography, I felt frustrated that I could do nothing in the face of this serious problem.

What prompted me to start taking photos of the hard-to-return zones in Fukushima was the fact that the 2020 Olympics would be held in Tokyo, the capital of this country. The government had billed it as a “reconstruction Olympics,” but this was not accompanied by any substance. The Olympics were postponed for a year due to the coronavirus, but I decided to document the hard-to-return areas of Fukushima, which have been neglected as time passed. The number of photos I take in a year is between 1,000 and 2,000, but in my case, I combine three shots into one, so the actual number would be one-third of that number. As you can see, the number of locations I photograph from a fixed point has been increasing, and the more times I go to Fukushima to take photographs, the more I move from searching for shooting locations to aiming for locations where I have already taken photographs one after another.

The Phoblographer: With so much happening in the world, people tend to forget the recent past. Is this like a documentation project so that the memory of the Fukushima Daiichi Accident doesn’t fade too soon?

Nobuhiko Ito: Yes, it is.

The Phoblographer: What were some of the challenges you faced in order to gain access to the surrounding areas? What safety measures did you take while doing this project?

Nobuhiko Ito: In my case, I do not go into areas that are forbidden to enter, and most of the time, I stay within their boundaries. However, the difficult-to-return zone does not mean that the entire area is sealed off. The roads that pass through the zone have gradually been open to anyone without permission since about the third year after the accident, and the area continues to expand. However, perhaps due to concerns about radiation exposure, in many cases, passage by car is permitted, but passage by foot or motorcycle is prohibited. Therefore, it is common to be questioned by police officers when you get out of your car and take pictures, as I did.

The Phoblographer: When visiting an area like this, which has been fenced off so much, how do you get images that are visually distinct from each other?

Nobuhiko Ito: Fences essentially restrict vehicular access, so it is easily possible to enter on foot. Some of the fences are such that the meaning of their installation is not clear. It may have been necessary to draw a line somewhere due to high or low radiation levels. However, considering what happened before the accident, we must be well aware of what this unusual view that is now spreading before our eyes means.

The Phoblographer: You’ve added the radiation level (μsv/h) alongside each photograph. Were there any sites where you noticed a dangerous level of radiation after arriving there?

Nobuhiko Ito: I try to record them at the same time because, unlike photographs, radiation levels are invisible. Most of the photo sites are on paved roads, and the measurements were taken at 1 meter above the ground.

Although there are regional differences, the mountains, forests, and former farmland on either side of the road have been left undisturbed since the accident and have not been decontaminated, so if you go into the area and take measurements, the radiation levels jump. The level of contamination is too high to be inhabitable.

The Phoblographer: why was panorama format chosen for this project?

Nobuhiko Ito: It is obvious, but we felt that the usual one shot was not enough to show the left and right sides of the area. When shooting with a fence in the center, it was necessary to capture a wide area in order to grasp the landscape at that point.

The Phoblographer: How long do you think it will take for life to return to normal in these areas (if ever)?

Nobuhiko Ito: Although it may not be well known internationally, government-led efforts are underway to intensively decontaminate parts of the hard-to-return zones to improve living infrastructure and promote re-housing there, and some people have returned this year. However, that is really a very small number.

Most of the areas within the zone are mountain forests, and it is practically impossible to remove the radioactive materials that have fallen on them to a complete level, let alone to make them safe, and it is meaningless to decontaminate only the areas with villages surrounded by these forests. Although it is very unfortunate, we have to assume that it is impossible for people to be able to live a normal life in these areas.

All images by Nobuhiko Ito. Used with permission. Visit his website as well as his Instagram and Facebook pages to stay up to date on this project. Want to be featured? Click here to find out how.

Source: https://www.thephoblographer.com/2022/10/30/the-fukushima-area-has-seen-better-days-as-nobuhiko-ito-shows/

October 31, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Return to Fukushima: Decontaminated town reopens to residents, but is anybody living there?

October 24, 2022

If you ever wanted to live in a post-apocalyptic zombie film, now’s your chance.

Back in 2020, our Japanese-language reporter Tasuku Egawa visited two towns in Fukushima Prefecture that were affected by the accident at Fukushima Daiichi Nuclear Power Plant, which occurred at the time of the March 2011 Great East Japan Earthquake.

▼ Tasuku visited Futaba and Tomioka, which are five kilometres (three miles) and 11 kilometres, respectively, from the nuclear power plant.

Being within the 20-kilometre exclusion zone, both towns were evacuated after the accident, turning them into ghost towns for two years. In 2013, the government opened some areas of the towns for daytime access only, with other areas remaining closed off due to elevated radiation levels, right up to 2020 when Tasuku visited.

At the time of Tasuku’s previous visit, new decontaminated areas around both stations had opened up, with old blockades being removed as a sign of the land becoming habitable once again.

The decontaminated Prefectural Route 165 and National Route 6 outside Tomioka’s Yonomori Station, as it looked in March 2020.

The west exit side of the station had returned to normal while the east side remained blocked. However, side streets on both sides remained cordoned off from the public, with permission required for anyone entering the other side of the blockade, including journalists like Tasuku.

Like all visitors, Tasuku was required to wear special protective wear due to the high radiation levels.

Back in 2020, nothing but the main roads and station buildings could be entered, and the only sign of life in the area was that of security guards at empty intersections and reconstruction-related vehicles and workers.

Both towns had their work cut out for them in terms of cleanup and redevelopment, especially as the local governments planned to repopulate the areas with thousands of residents in the next seven years.

Tasuku had high hopes they would achieve this goal, so when resettlement of the towns began in earnest earlier this year, he made a return trip to Tomioka and Yonomori Station to see what developments had taken place in the two years since he last visited.

So let’s take a look at his collection of photos chronicling the difference between 2020 and now, starting with Prefectural Route 165 and National Route 6 mentioned earlier.

Now, the barricades have totally disappeared, and the intersection looks like any other, complete with a cluster of vending machines on one street corner.

Continuing straight down this road, we come to a branch of the Yamazaki convenience store chain, located on the ground floor of a residential building.

Today, the barricades have gone, but the shutters remain closed and the curtains drawn, making it look like a scary house in a ghost town.

Heading south down National Route 6, Tasuku recalled a brightly coloured apartment block he’d photographed on his last visit.

Sure enough, the building was still there, and though the weeds and barricades had been cleared, the road, and the blinds on the store window on the left, looked a little worse for wear.

The more Tasuku walked around, the more he felt as if he were walking through a post-apocalyptic world, like the character of Jim in the British zombie flick 28 Days Later. Only this was no film set, it was a real-world town that once housed  around 4,000 people.

With curtains drawn on the windows of so many buildings he walked past, the place looked like it was inhabited…but it was eerily quiet, and deep down inside, Tasuku knew there was nobody behind those curtains, as these residences had been abandoned as a matter of emergency eleven years ago.

▼ Still he kept up hope that he would see signs of life somewhere, other than this road where he spotted a wild boar and a plump male pheasant.

After walking for a while, Tasuku finally breathed a sigh of relief when he came across this new apartment building, which was advertising for tenants, where he saw fresh laundry hanging on a balcony, suggesting that someone had already moved in.

Close by, there was a demountable building which looked to be the prefabricated office of a construction company, and it too appeared to be inhabited by people, likely here on temporary assignment for reconstruction-related work.

While the two main roads had been cleared and were open to traffic, Tasuku came across some salient reminders that the entire town wasn’t yet back to normal, with other areas like the local park blocked off as a restricted location.

Yonomoritsutsumi Park , as it’s known, is closed for good reason — according to the dosimeter on the other side of the fence, radiation levels here are 0.413 microSieverts per hour. The Ministry of the Environment’s requirements for decontaminated areas is 0.23 microSieverts per hour.

The high radiation levels in the park would put the public at risk of health problems, which is a great shame, seeing as it looks like it would’ve been a nice place to unwind and relax before the disaster.

It’s a vast space, though, which would make decontamination work difficult, and looking at the expanse from a nearby hill shows it’s become wild and overgrown, with what once must’ve been a lake (marked in blue below) now covered in grass and weeds.

Before coming to the town, Tasuku had been hoping to meet up with the owner of a beauty salon who used to live here but was moved to nearby Koriyama after the earthquake. She had joined Tasuku on his previous visit to Yonomori and once she’d heard the evacuation orders were being lifted this year, she said she was looking forward to moving back here.

However, the government ban on living in the area is still in effect over a large portion of the town, with only one designated zone on one side of the station open to residents from April this year. With only around a dozen or so people applying to live in the town so far, it would be a long while yet before Tasuku’s friend would be able to re-open her hair salon here.

▼ The former site of the hair salon is now an empty lot.

It’s hard to live in a ghost town, let alone run a business there, so the government hopes to make a larger area inhabitable by spring next year, in an effort to entice more residents to support local businesses.

Business owners will need a lot of support from the government, though, as a lot of them will be starting from scratch. This York-Benimaru supermarket, for instance, has since been totally demolished in the two years since 2020, and is now an empty parking lot.

If he’s being honest, the town hadn’t progressed as far as Tasuku had hoped in the past two years. Despite reopening part of the town, the place still had a real ghost-town feel to it, and the waiting room at the unstaffed station was particularly eerie, with nothing inside but a bathroom and chairs.

By comparison, the waiting room at Futaba Station, where Tasuku visited next, was a lot more inviting, with a sense of vibrancy and life to it.

Yonomori is famous for its cherry blossom trees, which line one particularly beautiful street, and while there were fears the trees would die out in the decade that humans were prohibited access to the area, the street was finally opened to visitors this year, who were able to enjoy them for the first time since 2011.

▼ The local “standard tree” by which the Meteorological Agency declares the official start of the cherry blossom season, is still alive and well.

At the moment, Yonomori is mostly home to ruins, wild boars and fat pheasants, which makes it less than appealing to potential residents. However, with the cherry blossoms still blooming, there’s hopes that the the area will soon bloom too.

Now with the station open and trains operating, it’s the start the town needs to get back on its feet, and we look forward to visiting in another two years’ time, when hopefully Tasuku’s friend’s hair salon will be open, along with other blossoming businesses.

October 26, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Magnitude 5 earthquake jolts Fukushima; ‘no issues’ at nearby nuclear plants

‘No issues’ at nearby nuclear plants…. So they claim as usual, everything is always fine in Fukushima Daiichi….

The epicenter of the earthquake that occurred on Oct. 21 at 3:19 p.m. is located in Fukushima offshore

Oct 21, 2022

A strong earthquake with an estimated magnitude of 5 jolted northeastern Japan on Friday afternoon.

The quake, which was revised downward from magnitude 5.1, occurred at a depth of about 30 kilometers off the coast of Fukushima Prefecture around 3:19 p.m., according to the Meteorological Agency.

The quake measured a lower 5 on Japan’s seismic intensity scale to 7 in the town of Naraha and 4 in the towns of Hirono, Tomioka, Okuma and Futaba.

According to the Secretariat of the Nuclear Regulation Authority, no issues have been reported at Tokyo Electric Power Company Holdings’s Fukushima No. 1 and No. 2 nuclear plants in the prefecture.

The No. 2 plant straddles Naraha and Tomioka, while the No. 1 plant, the site of the 2011 meltdowns following the Great East Japan Earthquake and tsunami, straddles Okuma and Futaba.

In a location close to the epicenter of Friday’s quake, a 7.4-magnitude temblor occurred at the depth of about 12 kilometers on Nov. 22, 2016, causing tsunami that reached up to 144 centimeters high at Sendai Port in the neighboring prefecture of Miyagi.

Unlike the 2016 temblor, which also registered up to lower 5 on the Japanese scale, Friday’s quake did not cause tsunami because it occurred at a greater depth and was smaller in scale.

https://www.japantimes.co.jp/news/2022/10/21/national/earthquake-jolts-fukushima/

October 26, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Reconstruction of hard-to-return zones from the perspective of structural violence

Symposium “Anthropology of Tribulation and Hope from Fukushima”

October 26, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Fukushima Reaches a Turning Point

by Citizens’ Nuclear Information Center · September 30, 2022

By Yamaguchi Yukio (CNIC Co-Director)

After the nuclear catastrophe in Fukushima in March 2011, the town of Futaba, located in Hamadori (the Fukushima coastline), became the only municipality in Fukushima Prefecture to decide to move its administration out of the prefecture. After changing evacuation sites several times, gradually moving further and further away from Futaba, the town’s government offices and many of its residents settled in a disused school in Kazo City, Saitama Prefecture, at the end of March 2011. It seemed as if the nuclear power plant town, where Fukushima Daiichi Nuclear Power Station (FDNPS) reactors Units 5 and 6 are located, had “drifted” 250 kilometers away from home. The evacuation was ordered based on the Special Act on Nuclear Emergency Preparedness and Response, and it was a difficult evacuation, the people evacuating “with nothing but the clothes on their back.”

The evacuation order for Futaba Town was lifted on August 30 this year, eleven-and-a-half years after it was imposed. However, there are very few who are willing to return to their hometown. As of March 2022, 19 households (26 people), or 0.4% of the pre-disaster level, had applied for “Preparation of Accommodation.”* The rich natural environment that was once part of the area no longer exists, and there is no prospect for the revival of community life.

The decommissioning of the plant at FDNPS is not expected to be completed anytime soon, as nothing like this has been experienced before and the radiation is likely to cause unexpected issues. That is not a problem when fission is used as a nuclear weapon, because the objective is to annihilate the opponent. However, that is not the case for “commercial use.” International organizations promoting nuclear power have set “standards” (radiation dose limits), but they are not reliable. It is impossible to properly evaluate the effects of low-dose exposure with current scientific knowledge alone. It is also a trans-scientific issue (a question that can be asked by science but cannot be answered by science).

The government decided on a plan to treat the radioactive water from FDNPS with ALPS, reduce its radioactivity level, and then discharge it into the ocean. The plan is to be implemented from 2023. The government and those who support the plan claim that there is no safety problem because the concentration will be much lower than the standard, even though the “standard” itself is questionable. However, that cannot be proven. It is only possible to prove it by repeating experiments under exactly the same conditions (including in the natural environment) as exist in reality and obtain results with a sufficiently high degree of confidence in the effects on humans as well as on ecosystems. It may be possible to do so, but it would probably take hundreds of years. The experiments might also lead to irreversible disasters. This kind of “experiment” is not feasible because it would take a long time and be too costly. In addition, simulations are also unlikely to allow us to draw solid conclusions.

There are many who are opposed to the oceanic release plan by the government and TEPCO, and who have presented reasons for their opposition. One thing I would like to add about “harmful rumors” is that this expression has the connotation of “irresponsible rumors that make something which is actually harmless appear to be harmful.” I do not agree with this connotation.

The government and nuclear energy proponents pushed forward the nuclear power plants without regard for the opinions of citizens and residents. This caused a nuclear catastrophe, the government has adopted an evacuee return policy without taking responsibility, and it is now about to discharge contaminated water into the ocean. The reason why such an absurdity has occurred is that the government has become extremely powerful. The separation of legislative, administrative, and judicial powers is said to be the basis of democracy, but the equilibrium of these three powers has been seriously disturbed. Nevertheless, the Mito District Court decision (Tokai Daini NPP Lawsuit, 18 March 2021) , the Sapporo District Court decision (Tomari NPP Lawsuit, 31 May 2022), the Supreme Court’s opinion by Justice Miura (17 June 2022), and the Tokyo District Court judgement (TEPCO Shareholder Lawsuit, 13 July 2022) remind us that the judiciary still exists.

Sun Yat-sen (1866-1925) once advocated the idea of a “five-power constitution” on the grounds that the three powers alone were not sufficient. Considering the current situation in Japan, I suggest the right to vote alone is powerless to curb the tyranny of the government. We need more powerful civic rights so that ordinary citizens can get together and be as powerful as the other three institutions.

Although the existence of “experts” is crucial in today’s world of science and technology, there are still many problems that cannot be answered by “experts” alone. Eleven-and-a-half years after March 11, METI committees, acting as if Fukushima is now history, often use expressions such as “innovative reactors” and insist that “nuclear power is the key to decarbonization.” I believe citizen power is needed more than ever before.

*”Preparation of Accommodation”: A system that allows disaster victims to stay overnight in their homes, which is prohibited in the evacuation zone, in order to facilitate preparations for a smooth resumption of life in their hometowns after the evacuation order is lifted.

Source: https://cnic.jp/english/?p=6286

October 1, 2022 Posted by | Fuk 2022 | , | Leave a comment

Ministry of the Environment – Draft Demonstration Plan for Reclamation of Removed Soil, Seeking Use as Road Fill

August 4, 2022

The Ministry of the Environment has compiled a draft plan for a demonstration project to recycle removed soil in order to reduce the final disposal volume of waste generated by the decontamination project for the Fukushima Daiichi Nuclear Power Plant accident. The project aims to expand the use of recycled materials based on removed soil at intermediate storage facilities in Fukushima Prefecture (in the towns of Okuma and Futaba), and is exploring the use of the materials for road fill. The design and construction methods and procedures will be studied until October, and construction will be carried out between October and January 2023. The project will be implemented from October to January 2023. After January, various tests and monitoring will be conducted. The project will also conduct demonstrations outside of the prefecture to demonstrate the use of recycled materials for parking lot construction and other purposes.
 On March 3, the first meeting of the “Working Group to Study the Recycling of Soil Removal at Interim Storage Facilities” (WG, chaired by Professor Takeshi Katsumi, Graduate School of Global Environmental Studies, Kyoto University) was held in Tokyo, where the draft plan was presented. The WG will organize and evaluate the findings from the demonstration project, and study measures to safely use the removed soil as recycled materials. A practical guide for recycling will also be prepared.
 According to the draft plan, recycled materials will be used for roadway fill in the interim storage facility. The road to be used for the general road standards is assumed to be a structure with sidewalks and a daily traffic volume of 4,000 to 20,000 vehicles (Class 3 and Class 2). The road is assumed to be a structure with sidewalks. Evaluation will be conducted after actual construction. The results of the project will be reflected in the guide.
 A demonstration project will be conducted outside of Fukushima Prefecture with the aim of realizing final disposal outside of Fukushima Prefecture. Recycled materials will be used for the roadbed of parking lots, and different reclamation patterns will be demonstrated, including differences in pavement and roadbed materials. Cases in which recycled materials are used to create flowerbeds and plazas will also be investigated. During the construction and use of the reclaimed materials, air dose rates in and around the reclaimed areas and radioactive concentrations in seepage water will be measured to confirm safety. Construction will be conducted this year, and monitoring will begin after completion.

August 5, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Japan Still Facing Challenges in Reconstructing Fukushim

Reconstruction without full decontamination is nothing else but a pipe dream, mostly made out of PR and propaganda…

July 19, 2022

Tokyo, July 19 (Jiji Press)–Reconstruction of areas in Fukushima Prefecture hit by the March 2011 nuclear accident has shown progress, but a number of challenges have yet to be overcome, including construction of essential facilities for everyday life and creation of jobs to bring back residents who evacuated to other prefectures.
The decommissioning of the meltdown-hit Fukushima No. 1 nuclear power plant of Tokyo Electric Power Company Holdings Inc. should also be pushed forward.
With evacuation orders in afflicted areas having been lifted in stages, the number of evacuees outside the northeastern prefecture has now fallen to some 30,000 from the peak level of over 160,000.
Most recently, it has been decided to remove Aug. 30 the evacuation order for the so-called specified reconstruction zone in the town of Futaba, which co-hosts the Fukushima No. 1 plant, crippled by the March 11, 2011 earthquake and tsunami, and is the only remaining completely evacuated municipality.
After the central and Futaba town governments reached the agreement to lift the order for the area around Futaba Station on the JR Joban Line, Chief Cabinet Secretary Hirokazu Matsuno visited nuclear accident-hit areas for two days through Saturday.

July 22, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Fukushima Prefecture Bar Association makes an emergency statement on the Supreme Court ruling on the nuclear power plant lawsuit

July 19, 2022
In response to the Supreme Court’s ruling last month that the government is not responsible for the nuclear power plant accident, the Fukushima Prefecture Bar Association called for a decision based on the actual situation in the other lawsuits.

On March 17, the Supreme Court ruled against the government’s responsibility in four class action lawsuits over the nuclear accident, stating that even if the government had obliged TEPCO to take measures to prevent a nuclear accident, there is a high possibility that an accident would have occurred.

In response, the Fukushima Prefecture Bar Association held a press conference in Fukushima City on March 19 and issued an emergency statement.

Daisuke Yorikane, attorney-at-law of the Fukushima Prefecture Bar Association, said, “In terms of responding to the wishes of the litigants, we are disappointed because we wanted the Supreme Court to give a proper opinion on the state of nuclear safety regulations in the country.

The statement pointed out that the Supreme Court’s decision was based solely on the theory of causality and could not be said to be responsive to the wishes of the plaintiffs.

The statement called for the Supreme Court to make a decision that recognizes the responsibility of the government based on the actual conditions of the other cases that are still ongoing.

Attorney Yorikane said, “I hope that (the government) will actively fulfill its responsibilities regarding the exercise of its authority based on scientific findings.

The Fukushima Prefecture Bar Association also referred to the government’s interim guidelines, which serve as the standard for compensation for damages, and called for a review of the guidelines according to the actual conditions of the damage in the future.
https://newsdig.tbs.co.jp/articles/tuf/99511?display=1&fbclid=IwAR1My4O3GcaHfiS3tUv-gwAaC2TiRnu0VK5ZeY4UQ8t-Sv7CL5Ig4bwuLBc

July 22, 2022 Posted by | Fuk 2022 | , , , , , | Leave a comment

Persistent impact of Fukushima decontamination on soil erosion and suspended sediment.

Published: 14 July 2022

Abstract

In Fukushima, government-led decontamination reduced radiation risk and recovered 137Cs-contaminated soil, yet its long-term downstream impacts remain unclear. Here we provide the comprehensive decontamination impact assessment from 2013 to 2018 using governmental decontamination data, high-resolution satellite images and concurrent river monitoring results. We find that regional erosion potential intensified during decontamination (2013–2016) but decreased in the subsequent revegetation stage. Compared with 2013, suspended sediment at the 1-year-flood discharge increased by 237.1% in 2016. A mixing model suggests that the gradually increasing sediment from decontaminated regions caused a rapid particulate 137Cs decline, whereas no significant changes in downstream discharge-normalized 137Cs flux were observed after decontamination. Our findings demonstrate that upstream decontamination caused persistently excessive suspended sediment loads downstream, though with reduced 137Cs concentration, and that rapid vegetation recovery can shorten the duration of such unsustainable impacts. Future upstream remediation should thus consider pre-assessing local natural restoration and preparing appropriate revegetation measures in remediated regions for downstream sustainability.

Main

Radioactive material leakage from nuclear industry activities or nuclear accidents poses a major threat to the environment and the economy1,2. Historically, widespread radioactive contamination has been observed several times, such as the Kyshtym accident (Soviet Union) in the 1940s–50s3, Windscale accident (England) in 1957 (ref. 4) and Chernobyl accident (Soviet Union) in 1986 (ref. 5). Long-term radiation exposure and radiophobia have increased the health risk and psychological pressure on the people of these regions, resulting in the abandonment of large areas rich in environmental resources and consequently in constrained sustainable human development6,7. As a key means for recovering contaminated regions, mechanical decontamination has been implemented in many legacy sites, including Hanford (United States)8 and Chernobyl9. However, almost all attention has been directed to understanding in situ decontamination effects10,11 and atmospheric particle resuspension issues12 and little is known about if these perturbations would have secondary environmental impacts on their downstream catchments for the long-term.

On 11 March 2011, the most recent large-scale nuclear accident happened at the Fukushima Daiichi Nuclear Power Plant (FDNPP), Japan13. Over 2.7 PBq of fallout 137Cs (half-life T1/2 = 30.1 yr) from the FDNPP was deposited in the terrestrial environment, causing long-term radioactive contamination on large-scale neighbouring catchments13,14. To recover contaminated soil and decrease the exposure dose in Fukushima, the Japanese government evacuated the residents in 2011 and large-scale decontamination was implemented in contaminated villages15,16 in 2012. Within a few years, dramatic land-cover changes occurred in the agricultural regions where 5 cm of the surface soil and vegetation were removed and replaced with uncontaminated soil (Fig. 1), with the subsequent natural restoration promoting revegetation in these decontaminated regions11,13,16.

The effectiveness of such intensive decontamination at reducing radiation exposure in situ is apparent, with air dose rates decreasing by 20–70% after decontamination13. However, as 137Cs can firmly bind to clay minerals, it is transported along with suspended sediments (particulate 137Cs) in the river system to the Pacific Ocean17,18. Comprehensively assessing the impacts of land-use changes in decontaminated regions on the downstream ecosystem is also necessary from the perspective of environmental sustainability. Moreover, recent studies have shown notable differences in the reduction in the particulate 137Cs concentration over time across 30 rivers in Fukushima19,20, further underscoring the need to study land-use impacts on downstream particulate 137Cs discharge into the ocean.

In addition to contaminant migration, land-use changes induced by strong perturbations (for example, decontamination) also alter land–ocean sediment transfer patterns21,22, which in turn affect elemental cycles23, biodiversity24 and global climate25. Systematically assessing the perturbations’ impacts on downstream river suspended sediments (SS) has thus become a joint goal of many related disciplines and a key part of developing science-based catchment management strategies26,27,28,29. However, owing to the limited availability of reliable and concurrent river monitoring data, how downstream river SS variations and land-use changes are linked remains unclear21.

With approximately 11.9% of the watershed area subjected to government-led decontamination between 2013 and early 2017, the Niida River Basin in Fukushima (Fig. 2a)11,30 provides an excellent opportunity to examine the long-term impact on the dynamics of SS and particulate 137Cs in river systems. Previous short-term river studies19,20,31,32,33,34 have suggested an increased river SS load and decreased particulate 137Cs concentrations during decontamination. Several studies that analysed geochemical fingerprints in deposited sediments have implied a significant contribution of sediment sources from the decontaminated regions to the river35,36,37. Yet, given that threats to sustainable catchment management from anthropogenic perturbations are often long-term28,29, more comprehensive and reliable data on quantified land cover and continuous river records are required to explore the effect of decontamination on river SS and particulate 137Cs discharge.

Here we provide a comprehensive assessment of the impacts of land-use changes in decontaminated regions on river SS and particulate 137Cs dynamics, as well as the downstream discharge. We mapped the evolution of decontaminated region boundaries using governmental decontamination documents (Fig. 2b), photographed the land cover in the decontaminated regions using drones and quantified the land-use changes using the normalized difference vegetation index (NDVI) at 10 m spatial resolution. Meanwhile, we conducted a long-term field investigation (Methods and Supplementary Table 1) spanning the decontamination (2013–2016) and natural restoration (2017–2018) stages to continuously record the fluctuations in water discharge and turbidity (10 min temporal resolution) and particulate 137Cs concentrations, both upstream and downstream. Combining the above quantitative data, we systematically reveal that long-term land-use changes in upstream decontaminated regions greatly affect sediment and 137Cs discharge from downstream river systems into the Pacific Ocean.

Land-cover changes in decontaminated regions

Regional decontamination was accomplished in March 2017, spanning over 22.9% and 11.9% of the upstream (Notegami) and downstream (Haramachi) watershed areas, respectively (Fig. 2c). In 2014, agricultural land (18.02 km2) was one of the major land uses in the regions where decontamination was ordered, with a significant increase of over 720% compared with that in 2012. Conversely, the changes in the ordered grassland (1.93 km2) were minimal, with an approximately 26% increase between 2012 and 2014. Given that overall land-cover changes were more pronounced in agricultural lands than in grasslands or residential lands, large-scale agricultural land decontamination may severely alter landscape erodibility and consequently the sediment supply. Moreover, the proximity of the decontaminated agricultural land to rivers increases sediment transport from terrestrial environments.

Drone photographs (Fig. 3a and Supplementary Fig. 1) showed significant land-cover changes in the upstream decontaminated regions. For instance, the agricultural land at the Hiso site (D3, Fig. 3a) was almost bare in August 2016 when the decontamination was completed. However, natural restoration caused the recovery of vegetation during the post-decontamination stage (August 2018). Considering the decontamination sequence and seasonal dependence of the plant growth cycle38, drastic spatiotemporal land-cover changes in the decontamination regions are conceivable.

To quantitatively estimate and compare land-cover changes in the decontaminated regions, we generated NDVI maps in these regions based on the available satellite images from Sentinel 2 and the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2011 and 2018. The comparison between realistic scenarios and Sentinel 2-based NDVI maps (spatial resolution: 10 m) from drone observation sites (Fig. 3a and Supplementary Fig. 1) confirmed the feasibility of NDVI images in distinguishing bare land and agricultural land with vegetation cover. To improve the temporal–spatial resolution of the NDVI dataset, we used the enhanced spatial and temporal adaptive reflectance fusion model (ESTARFM)39 to fuse Sentinel 2 and MODIS maps. Subsequently, we used interpolation to link these newly generated NDVI data (spatial resolution: 10 m) and plotted daily NDVI variations for all decontaminated regions between 2011 and 2018 (Fig. 3b).

In the daily NDVI variation curve, the peak NDVI during 2013–2014 was similar to the pre-decontamination stage (2012) but decreased by approximately 10% in 2016. After decontamination, the peak value presented an increasing trend under the influence of vegetation recovery. However, as the government lifted the evacuation zone after 2017 and allowed the residents to return, vegetation was again removed from some areas planned for agricultural activities in 2018 (Supplementary Fig. 1b). Further analyses of the NDVI variations in the decontaminated regions scheduled in 2012 (Fig. 3c), 2013 (Fig. 3d) and 2014 (Fig. 3e) showed that the NDVI peaks were decreased by approximately 12%, 11% and 15%, respectively, within 2–3 years after decontamination was ordered, thereby providing unambiguous evidence for decreasing vegetation land cover caused by decontamination.

We converted all NDVI maps derived from ESTARFM-images to C × P (cover management and support practice factors, respectively) maps using empirical models40,41. We then estimated erosion potential (that is, K × LS × C × P in the revised Universal Soil Loss Equation (RUSLE); Methods) maps using the LS (slope length and slope steepness factors, respectively) map (Supplementary Fig. 2) and K (soil erodibility) factor in the decontaminated regions. We found that the slopes of decontaminated regions were generally similar for each decontamination-ordered year (Supplementary Fig. 2), suggesting that the erosion potential was consistent with the NDVI in the decontaminated regions. Therefore, we also estimated the daily variation curve of the erosion potential using the mean CP, LS and K factors in the decontaminated regions.

Here we show the ESTARFM-based NDVI (Fig. 3f) and erosion potential (Fig. 3g) during the summer season for each year (specific periods in Supplementary Table 2). NDVI showed a decreasing trend from 2013 to 2016, while the erosion potential peaked in 2016, representing approximately 98% and 52% increases over the pre-decontamination (2011) and natural restoration (2018) stages, respectively. Combining the corresponding NDVI (Supplementary Fig. 3) and erosion potential maps (Supplementary Fig. 4), significant changes in the spatial differences between the land cover and erosion potential during decontamination were also observed.

Response of river SS to land-cover changes

The downstream river SS load (L; Fig. 4a) exhibited a strong correlation with water discharge (Q) during the monitoring periods (Supplementary Fig. 5 and Supplementary Table 3). Under the range of water discharges from 0.1 to 100 m3 s−1, river SS carrying capacity exhibited a considerable increase from 2013 to 2016 and a slight decrease after decontamination (2017 to 2018). Contrastingly, the range of water discharges was relatively narrow upstream, and a steady decrease in SS loads has been observed since 2015. Although the above result suggests an increase in SS supply during the decontamination stage, the high SS carrying capacity in 2015 is not consistent with the actual decontamination progress. Since decontaminated regions tend to be bare land, sediment loads are prone to increasing during rainstorms due to soil erosion. Governmental decontamination plans showed that over 50% of agricultural land decontamination was planned to be implemented in 2016, implying that the erosion potential of the decontaminated regions should have been higher in 2016, rather than in 2015.

The variations in downstream river SS loads over the 6 years (Supplementary Table 4) exhibited a similar trend to peak river SS load in 2015 (126.7 ± 0.3 Gg yr−1). This was an approximately 1,776%, 140% and 215% increase relative to that of 2013, 2016 and 2018, respectively. The historical rainfall records (Fig. 4b) show that the rainfall in September 2015 (551 mm) was more than two-fold greater than that during the same period in 2016 (274 mm), implying that the SS peak may be related to strong runoff. Here we estimate the SS loads at 1-year-flood discharge (Q = 95 m3 s−1) using established LQ curves, which allow for the comparison of dynamic variations in SS loads under the same flood conditions. In Fig. 4b, a significant increasing trend during the decontamination period is shown, with a 237.1% increase in 2016 compared with 2013. After decontamination, the SS loads drastically decreased by approximately 41% from 2016 to 2017, implying changes in sediment yield and transfer patterns due to natural restoration. These results reveal that river SS loads responded closely to land-cover changes during the study period.

To better explore the response of river SS load to land-cover changes, we extracted river monitoring data during each rainfall event and quantitatively linked the river SS to the corresponding soil loss from the decontaminated regions. We found that SS loads during rainstorms were highly correlated with water discharges in both upstream and downstream areas (Supplementary Fig. 6). Comparing similar rainfall events, significantly greater SS concentrations are observed in 2015–2016 than in other years (Supplementary Figs. 7 and 8). Considering that the land-cover changes induced by decontamination were more pronounced in the summer season, the regression was performed for SS loads between May and October and soil loss during the corresponding period. A more significant correlation was observed (Fig. 4c) between estimated soil loss by RUSLE and SS load upstream (R2 = 0.55, P < 0.01, N = 34) than downstream (R2 = 0.27, P < 0.01, N = 52). Eliminating the effect of rainfall and normalizing by discharge (Fig. 4d) results in a more evident relationship between the erosion potential and SS loads downstream (R2 = 0.35, P < 0.01, N = 52). Overall, these results demonstrate the connection between river SS dynamics and land-cover changes in the decontaminated regions. The short distance between the upstream catchment and decontaminated regions makes soil erosion a critical driver for upstream river SS transport, whereas the downstream river is dependent on long-distance SS transport, making water discharge an important driver for the downstream catchment.

Long-term impact on river SS and 137Cs discharge

From August 2014 to March 2017, the particulate 137Cs concentration in Haramachi exhibited a steep decrease, contrasting remarkably with the limited 137Cs variation observed in the early decontamination stages (January 2013 to August 2014; Fig. 5a). The effective half-life of the particulate 137Cs (eliminated by the natural attenuation factor) during this decontamination period (1.87 yr) was considerably faster than that of physical decay of 137Cs (30.1 yr), the early decontamination period (16.9 yr) and the surrounding contaminated catchments (mean of 4.92 yr)20. Such a sharp decrease in the 137Cs concentration was also observed at the other three monitoring sites (Supplementary Fig. 9a). Because the 137Cs concentration in decontaminated soil was considerably lower than that in the contaminated soil37,42, these results suggest the contribution of sediment from decontaminated regions to the river system. Moreover, strong negative correlations were observed between measured 137Cs levels and decontamination progress at all monitoring sites (Fig. 5b and Supplementary Fig. 9b), which further supports our interpretation. The observed 137Cs concentration increased by approximately 150% in 2018 compared with that at the end of 2016, which may be caused by the weakened sediment supply from decontaminated regions owing to natural restoration and resulting in a relatively increased contribution of sediments from contaminated forest regions13.

Given that the variation in 137Cs concentrations reflects a change in sediment source, the deviations between the measured 137Cs and the natural decrease in 137Cs derived from surrounding contaminated catchments provide a way to quantitatively estimate the contribution of sediment from decontaminated regions (Fig. 5c). In the early decontamination period, our results showed slight variations in the 137Cs concentration (Fig. 5a), which could be attributed to the contribution of sediment from upstream regions with different degrees of contamination. During the main decontamination period, the erosion potential in the summer of 2015 was approximately 22% higher than that in 2014 and the heavy rainfall caused the largest flooding event during the study period (26-year flood). This may result in the sediment from decontaminated regions not being the dominant source for downstream. In 2016, decontamination caused an increase by approximately 59% in the erosion potential compared with 2013, with the contribution percentage steadily increasing over this period to a maximum of 75.7% ± 3.2% (value ± 95% uncertainty). After decontamination, the decreased contribution of sediment from decontaminated regions and the increased 137Cs concentrations can both be attributed to the reduction of soil loss from upstream due to natural restoration.

The 137Cs discharge from contaminated catchments around the Fukushima region into the Pacific Ocean is another ecological issue of global concern. Our data show that the export flux of particulate 137Cs from the downstream of the Niida river (that is, Haramachi) peaked in 2015 (1.24 TBq yr−1, equalling 0.65% 137Cs loss), which is an approximately 667%, 233% and 429% increase relative to that in 2013, 2016 and 2018, respectively (Fig. 5d). Although such 137Cs loss is negligible compared with the terrestrial inventory, it is approximately 105 times greater than that in the pre-Fukushima stage43,44. Accordingly, the dynamic variations in 137Cs discharge from terrestrial environments into the Pacific Ocean, and its drivers, require more attention in the future.

Here we used SS loads at one-year-flood discharge to normalize the 137Cs flux and found its peak occurred in 2015 (Fig. 5e). Additionally, the reduction of the normalized 137Cs flux from 2013 to 2016 (~32%) was similar to natural attenuation in the non-contaminated catchment (~34%) over same period, which may be due to the increased SS load during decontamination offsetting the role of declining 137Cs concentrations in reducing 137Cs emission. During the subsequent natural restoration period, the rapid NDVI increase (Fig. 3f) suggested vegetation recovery in decontaminated regions and a decrease in regional erosion potential (Fig. 3g). This resulted in an approximately 24% decrease in sediment yield from the catchment and an approximately 31% decrease in the contribution of sediment from decontaminated regions (Fig. 5c) from 2016 to 2018. Due to the mutual balance of these effects, there were no significant changes in normalized particulate 137Cs flux in 2018 compared with 2016.

Discussion

Our work highlights the great potential of interdisciplinary analyses for understanding river SS variation and quantifying the contribution of sediment from specific regions. Fukushima decontamination practices, like a controllable validation experiment, justified the reliability of using long-term 137Cs monitoring data for tracing sediment source dynamics due to specific perturbation. Combining the long-term dataset of 137Cs (or other fallout radionuclides) in SS with remote sensing images would provide additional evidence to determine if the changes in the downstream SS transport pattern are linked to the upstream perturbation.

With these interdisciplinary analyses, we systematically reveal how changes in land use in the decontaminated regions significantly influences downstream river SS and 137Cs discharge into the ocean. Indeed, the secondary environmental impacts of surface remediation are being increasingly considered in the broader field concerning remediation of regions contaminated with hazardous materials (for example, heavy metals and organic contaminants)45. The concept of environmental sustainability-centred green remediation has also been brought up in many scenarios46,47. The Fukushima decontamination practice provides evidence showing that mechanical remediation can cause persistently excessive SS load downstream, though it also reduced river 137Cs concentrations. Since persistently excessive turbidity in rivers affects not only surrounding residents’ water use but also trophic level structure in aquatic environments48, the unsustainable downstream impacts caused by upstream decontamination should be highly regarded. The vegetation recovery after land development is highly dependent on local conditions49, and the soil used for decontamination and local high rainfall amount in Fukushima promoted rapid vegetation recovery11,13, which shortened the duration of such unsustainable impacts. Therefore, future upstream contaminated lands that await mechanical remediation need to consider the pre-assessment of local natural restoration conditions or the preparation of appropriate revegetation measures in the catchments’ regulatory frameworks, which would minimize the impact of long-term decontamination on downstream sustainability.

Methods

Study region

The Niida River Basin (265 km2) is located about 40 km northwest of the damaged FDNPP. The topography of its upstream is almost mountainous and its soil types are mainly cambisols and andosols, while fluvisols are the dominant soil type in the downstream plain50. The monitoring data from the Japan Meteorological Agency show that the average rainfall in the Niida River Basin is greater than 1,300 mm, with more than 75% of the rainfall occurring between May and October. According to the third airborne monitoring survey by the Japanese government, the 137Cs inventory in the Niida River Basin was over 700 kBq m−2 (ref. 14). Because of particularly high contamination in its upstream watershed (over 1,000 kBq m−2)51, the government-led decontamination was implemented in the upstream basin from 2013 to 2016 (~1% of the area was extended to March 2017).

Land-cover observation

We constructed the vector decontamination maps based on the paper maps from the Ministry of the Environment, Japan. The boundaries of the decontaminated regions with different land-use types were first outlined by creating polygons using Google Earth. Subsequently, the projections of these polygons were imported to ArcMap v.10.3 to quantitatively evaluate their area.

During the decontamination (2016) and post-decontamination stages (2018), drone photography was utilized (Fig. 2a, triangle) to compare land-cover changes. A commercially available drone (Phantom 4, DJI product) was employed at 100 m above the ground in Matsuzuka (D1; 37.689° N, 140.720° E), Iitoi (D2; 37.663° N, 140.723° E) and Hiso (D3; 37.613° N, 140.711° E) to take photographs.

Quantification of land-cover changes in decontaminated regions

We calculated NDVI within the boundary of the decontaminated regions to quantify the land-cover changes. Through the spectral reflectance dataset in the red (R, nm) and near-infrared (NIR, nm) regions, the NDVI was calculated as52:

NDVI=NIR−RNIR+R.

(1)

The available satellite images from 2011 to 2018 from Sentinel 2 were downloaded from the United States Geological Survey53, while the concurrent MODIS images were derived from the National Aeronautics and Space Administration’s Reverb54. The wavelength bands and spatiotemporal resolutions of the satellite images used here are summarized in Supplementary Tables 5 and 6.

To confirm the reliability of the newly generated NDVI variation curve, NDVIs for the same date as the Sentinel 2 images were estimated using the interpolation and compared with the Sentinel 2-based NDVI. The linear regression analysis showed that the fitting R2 was 0.99 (N = 16, P < 0.01). We also calculated the NDVI in the decontaminated region based on available satellite images of Landsat 5/7/8 (ref. 53) and established a daily NDVI variation curve. The linear regression analysis also showed a high R2 between two daily NDVI curves (R2 = 0.97, N = 2868, P < 0.01). Therefore, these NDVIs calculated by different satellite images confirmed the reliability of the NDVI variation curve based on ESTARFM.

Estimation of erosion potential in decontaminated regions

To link the land-cover changes in decontaminated regions with the soil erosion dynamics, we defined an erosion potential (K × LS × C × P) based on the RUSLE.

The soil loss (A, t ha−1 yr−1) of a specific region can be estimated as55:

A=R×K×LS×C×P,

(2)

where R is the precipitation erosivity factor (MJ mm ha−1 h−1 yr−1), K represents the soil erodibility factor (t h MJ−1 mm−1), L and S are slope length factor (dimensionless) and slope steepness factor (dimensionless), respectively, and C and P are the cover management factor (dimensionless) and support practice factor (dimensionless), respectively. Because these parameters are often set as fixed values, it is difficult to assess the soil loss dynamics during anthropogenic disturbances. To address this problem, we used daily NDVI data to estimate C × P and then considered these dynamic factors in RUSLE.

Wakiyama et al.40 reported a correlation between vegetation cover in Fukushima and the sediment discharges from the standard USLE plot (that is, soil loss, A) that have been normalized by R, K, S and L factors40,56. Therefore, this empirical equation reflects the quantitative relationship between vegetation fractions (VF) and C × P.

To quantify daily C × P changes in decontaminated regions, we first converted the interpolated daily NDVI into the VF by a semi-empirical equation41:

VF=1−(NDVI−NDVI∞NDVIs−NDVI∞)0.6175,

(3)

where NDVIs and NDVI represent the NDVI value for land cover corresponding to no plants and 100% green vegetation cover, respectively. Since these values mainly depend on plant species and soil types, we followed previous methods applied to agricultural land and set NDVIs and NDVI as 0.05 and 0.88, respectively41.

Subsequently, the C × P was estimated by the empirical equation derived from uncultivated farmlands and grasslands (R2 = 0.47, N = 145)40:

C×P=0.083×e−5.666×VF.

(4)

Since the soil type used for decontamination is generally the same, the K factor was set as a constant (0.039; ref. 40). For the LS factor, we downloaded a digital elevation model from the Geospatial Information Authority of Japan (spatial resolution: 10 m) to build an LS map using55:

LS=[QM22.13]y×(0.065+0.045×Sg+0.0065×S2g),

(5)

where Qa is the flow accumulation grid, Sg represents the grid slope as a percentage, M is the grid size and y is a parameter depended on slope steepness. We here used the y values recommended by a published study, ref. 55.

The calculated LS-factor map (Supplementary Fig. 2) showed a relatively consistent LS distribution in space. Based on the ESTARFM-generated satellite images, we compared C×P and erosion potential (K × LS × C × P) and found a significant correlation (R2 = 0.99, P < 0.01, N = 174). Since these results suggest that LS factors in decontaminated regions have a negligible effect on the erosion potential, the mean LS factor and interpolated NDVI based on the daily variation curve (Fig. 3b) were used to estimate the daily erosion potential.

Monitoring of river discharge and turbidity

The water-level gauges (in situ Rugged TROLL100 Data Logger) and a turbidimeter (ANALITE turbidity NEP9530, McVan Instruments) were installed in each monitoring site to continuously recording the water level and turbidity with a temporal resolution of 10 min. As ocean tides may influence the accuracy of water-level monitoring, the Sakekawa site (M4 in Fig. 2) was excluded from the river monitoring programme.

The recorded water level (H, m) was converted to the water discharge (Q, m3 h−1) based on the annual HQ curves for each monitoring site. These curves were calibrated using a synchronous monitoring dataset of 10-min-resolution water level and discharge provided by the Fukushima prefecture’s official monitoring network57. Because of occasional damage to the water-level gauge at the Haramachi site, the available monitoring data with a temporal resolution of 10 min recorded by the Fukushima prefecture’s official monitoring network57 were used to fill the gaps. The percentages of filling data from official monitoring network were all less than 34% except for 2015 (56.6%). Although similar situations occurred in Notegami, we were unable to fill in gaps with other data due to the lack of a concurrent monitoring network.

The hourly SS concentration (Css, g m−3) at each monitoring site was calculated from the measured turbidity (T, mV) using a calibrated curve20. As the turbidimeter was susceptible to the moss and debris flowing in the river, the dataset was verified with an automated check by HEC-DSSVue (The U.S. Army Corps of Engineers’ Hydrologic Engineering Center Data Storage System) before transforming the data.

The SS load was estimated as the product of the corresponding datasets of discharge and SS concentration, after which we can obtain the annual SS load (L, ton yr−1) by taking the sum:

L=∑(Q×Css).

(6)

We estimated values for gaps including missing and abnormal data through a linear model established by 10-min-resolution monitoring data at the same site. The reliability of the gap-filling strategies used in this study has been documented by Taniguchi et al.19,20 These procedures vastly enhance the possibility of reconstructing the complete dataset. In this study, only the error in converting from water discharge to SS load was considered in the uncertainty assessment, and all estimates were within 0.5% (95% confidential interval) in this case. To reduce the uncertainty of LQ fitting, the 10-min monitoring dataset (discharge and SS load) was transformed to a 1-hour dataset.

Considering the river SS is often transported by discharge, we used downstream LQ curves to estimate river SS loads at 1-year-flood discharge (Q = 95 m3 s−1), which eliminates the influence caused by different annual water discharges. The 1-year-flood discharge was calculated from the daily maximum discharge data from 1 January 2013 to 30 September 2020 at the Haramachi site.

To compare river SS dynamics during rainfall events, we here defined a rainfall event as the increase in water discharge exceeding 1.4 and 1.6 times the baseflow before precipitation for the upstream and downstream catchments, respectively. As a result, a total of 64 and 72 rainfall events from the Notegami and Haramachi sites were identified.

To study the dynamic relationship between soil loss from decontaminated regions and river SS load, we estimated eroded soil amount during each rainstorm using RUSLE. Specifically, the NDVI during a specific rainfall was determined by interpolation. Subsequently, the corresponding C × P can be estimated using equations (3) and (4). With the mean values of the K and LS factors, the erosion potential can then be calculated. Finally, precipitation erosivity factor (Supplementary Table 7) for each rainfall event can be calculated as58:

R=1nj=1nk=1mj(EI30)k,

(7)

where n is the number of years used, mj is the number of precipitation events in each given year j and E and I30 represent each event’s kinetic energy (MJ) and maximum 30 min precipitation intensity (mm h−1), respectively, for each event k. The event’s erosivity, EI30, can be calculated as58:

EI30=(∑r=10ervr)I30,

(8)

where er denotes the unit rainfall energy (MJ ha−1 mm−1) and vr provides the rainfall volume during a set period (r) (mm). For this calculation, the criterion for the identification of a precipitation event is consistent with previous work, that is, the cumulative rainfall of an event is greater than 12.7 mm (ref. 58). If another rainfall event occurs within 6 h of the end of a rainfall event, they are counted as one event. Therefore, the unit rainfall energy (er) can be derived for each time interval based on rainfall intensity (ir, mm h−1)58:

er=0.29[1−0.72e(−0.05×ir)].

(9)

The calculation’s required parameters were derived from the historical precipitation record from the Japan Meteorological Agency59. For the Notegami catchment, the precipitation monitoring data were derived from Iitate. For the Haramachi catchment, the precipitation was obtained from three adjacent monitoring sites (that is, Haramachi, Iitate and Tsushima) with the specific weights of 0.143, 0.545 and 0.312, respectively. These weights were determined by the Voronoi diagram method in a Geographic Information System60.

River monitoring of particulate 137Cs

At each monitoring site, the suspended sediment sampler proposed by Phillips et al.61 was installed at 20–30 cm above the riverbed for the time‐integrated sampling of river suspended sediment. The reliability of this sampler has been widely proven in past studies19,20. After sampling, the trapped turbid water and SS samples were transferred into a clean polyethylene container and stored until laboratory analysis.

The SS samples were separated from the collected water mixture via natural precipitation and physical filtration, dried at 105 °C for 24 h and subsequently packed into a plastic container. The activities of 137Cs in the SS samples (C, Bq kg−1) were determined via the measurement system, which consists of a high-purity germanium γ-ray spectrometer (GCW2022S, Canberra−Eurisys, Meriden) coupled to an amplifier (PSC822, Canberra, Meriden) and multichannel analyser (DSA1000, Canberra, Meriden). The measurement system was calibrated with the standard soil sample from the International Atomic Energy Agency. Under the 662 keV energy channel, each measurement batch would take approximately 1–24 h to make the analytical precision of the measurements within 10% (95% confidential interval). All measured 137Cs concentrations were decay-corrected to their sampling date. Moreover, the results obtained in this study were also normalized by their initial average 137Cs inventory in the catchment (D, Bq m−2) to eliminate the effect caused by spatial differences.

As 137Cs concentration in the sediment sample depends on particle size19,20, we conducted a particle size correction for all measured data in Takase, Ukedo and Haramachi to eliminate this effect. The particle size distributions for dried SS samples were analysed using the laser diffraction particle size analyser (SALD-3100, Shimadzu Co., Ltd.). With the parameterized particle size distributions, the particle size correction coefficient (Pc) can be calculated by19:

Pc=(SsSr)v,

(10)

where Sr and Ss represent the reference and collected samples’ specific surface areas (m2 g−1). The exponent coefficient, v, is a fitting parameter associated with chemical and mineral compositions. In this study, the same parameters measured in the Abukuma River, the major river in the Fukushima area, were applied for Sr (0.202 m2 g−1) and v (0.65). The specific surface area for collected SS samples was estimated by the following equation under a spherical approximation20:

Ss=∑(6×ρ−1×d−1i×p−1i),

(11)

where ρ is the particle density and di and pi denote the ratio and diameter of the particle size fraction for particle i. Therefore, the 137Cs concentration corrected for particle size can be obtained by dividing the measured 137Cs concentration by Pc.

Considering that the decrease in particulate 137Cs concentration in a catchment was also affected by natural attenuation, there is a need to eliminate this effect from the declining trend of our observed 137Cs dataset to highlight the impacts of decontamination. The Ukedo and Takase are rivers surrounding the Niida River with similar contaminated situations. Our long-term 137Cs monitoring data from downstream of these two catchments showed that their 137Cs decline trends were relatively steady. Although there is a dam reservoir upstream of Ukedo, the 137Cs concentration observed both upstream and downstream showed a similar declining trend62. Therefore, the above evidence suggests that natural attenuation was the dominant factor controlling the 137Cs decrease in these two rivers. Here we assumed that the natural attenuation trend of 137Cs in the surrounding catchments (Ukedo and Takase) with little effect by decontamination was similar to that of the Haramachi catchment. Thus, we fitted their time change curves of 137Cs concentration (normalized by average 137Cs inventory of the corresponding catchment) using an exponential model. We then estimated the 137Cs concentration at the same sampling time as Haramachi in the two catchments by using the fitting models. Finally, we calculated the mean value of the two datasets and recalculated the effective half-life (Teff = ln(2)/λ; λ is the fitting exponential term) of the natural attenuation by the exponential model.

The 137Cs flux (LCs, Bq) for each monitoring site was estimated by the product of the SS flux and the 137Cs concentration in the suspended sediment sample. We then took the sum over that year:

LCs=∑(Q×Css×C).

(12)

According to the law of error propagation, we considered the error from SS load and 137Cs measurement in the combined uncertainty assessment for 137Cs fluxes and found their values are all within 1.1% (95% confidential interval).

Using 137Cs as a tracer in estimating SS source contribution

Although 137Cs has been widely used in tracing sediment source, the spatial variability of the 137Cs deposition inventory in the Fukushima catchment hinders the estimation of the source contribution from a specific region. However, for the decontaminated catchments, as the 137Cs concentration in decontaminated soil was much lower than that in contaminated regions (for example, forested regions and the riverbank)11,13,63, the fluctuations in the particulate 137Cs concentration can help to identify the sediment from the decontamination regions. Specifically, we assumed that the particulate 137Cs concentrations in surrounding contaminated watersheds (that is, having similar land-use composition) follow a similar decline trend driven by natural reasons, while the decontamination-induced land-cover changes cause other sediment sources to mix with the original river SS and thus result in a deviation in observed 137Cs concentrations from this natural trend. Therefore, the relative contribution (RC) of the specific sediment source can be expressed as:

RC=(Cm−Cn)(Cs−Cn),

(13)

where the Cm is the measured 137Cs concentration and Cs and Cn represent the 137Cs concentration in a specific sediment source and the naturally varied 137Cs concentration at the same time as the measured 137Cs. For data comparability, all 137Cs concentrations presented here were corrected by their particle size and 137Cs inventory. We also excluded the samples with collection weights below 0.5 g from the calculations due to their high uncertainty in Pc measurement.

In this study, the specific sediment source is the decontaminated soil in the Niida River Basin where the 137Cs concentration was approximately 53.99 ± 40.90 Bq kg−1 (refs. 37,42; mean ± standard deviation, N = 8). The natural decline of the 137Cs concentration (that is, λ) was established using temporal variation in 137Cs data originating from the Ukedo and Takase rivers, which were scarcely influenced by decontamination. The first measured 137Cs data in Haramachi were set as the starting point of its natural decline curve. The total uncertainty for the contribution percentage of SS from the decontaminated regions was calculated by the propagation of error from each part with the uncertainties originating from the measured 137Cs concentration, 137Cs concentration in a specific source and the natural 137Cs concentration. For the uncertainty in the 137Cs concentration in decontaminated soil (Cs), we set the standard deviation as its error source, while the natural 137Cs concentrations were calculated by the propagation of the 95% confidential interval of the fitting curves.

Reporting summary

Further information on research design is available in the Nature Research Reporting Summary linked to this article.

Data availability

Ordered decontamination process data are available from http://josen.env.go.jp/plaza/info/weekly/weekly_190607.html. Particulate 137Cs monitoring data in Haramachi, Takase and Ukedo during 2012–2017 are available from: https://doi.org/10.34355/Fukushima.Pref.CEC.00014, https://doi.org/10.34355/CRiED.U.Tsukuba.00020 and https://doi.org/10.34355/Fukushima.Pref.CEC.00021. The rest of data presented in this study are available from the corresponding author upon request.

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Acknowledgements

We appreciate B. Matsushita for his valuable suggestions on satellite image processing and NDVI calculation, J. Chen for sharing the code for ESTARFM, J. Takahashi for sharing 137Cs in decontaminated soil data, H. Kato for his suggestions on presenting the results, S. Fujiwara for his assistance on calculating the precipitation erosivity factor, Y. Yamanaka and T. Kubo for their work on decontamination map development, field investigation and preliminary data analysis and Y. He and F. Yoshimura for their constructive suggestions on improving figure quality. We also acknowledge funding support from the commissioned study from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) FY2011–2012, Nuclear Regulation Authority FY2013–2014, Japan Atomic Energy Agency-funded FY2015–2021, Grant-in-Aid for Scientific Research on Innovative Areas grant number 24110005, Grant-in-Aid for Scientific Research (A) 22H00556, Agence Nationale de la Recherche ANR-11-RSNR-0002 and the Japan Science and Technology Agency as part of the Belmont Forum.

Author information

Authors and Affiliations

  1. Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Tsukuba, Japan Bin Feng, Yuichi Onda, Asahi Hashimoto & Yupan Zhang
  2. Institute of Environmental Radioactivity, Fukushima University, Fukushima, JapanYoshifumi Wakiyama
  3. National Institute of Technology, Tsuyama College, Tsuyama, JapanKeisuke Taniguchi

Contributions

B.F. and Y.O. conceived the study; B.F. performed the data evaluation and all analyses, interpreted the data, wrote the manuscript and prepared all figures and tables in close discussion with Y.O.; Y.O. provided funding support for the field monitoring and all needed resources; K.T. and Y.Z outlined the boundary of the decontamination regions and implemented the drone observations of the sites; and Y.W. and K.T. performed the field river monitoring and determined the particulate 137Cs concentration. B.F., A.H. and Y.Z. prepared all satellite images, ran the NDVI calculation and processed ESTARFM. All listed authors contributed to the editing of the manuscript and approved the final version.

Source: https://www.nature.com/articles/s41893-022-00924-6

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