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Journal Articles

Role of advection in atmospheric ammonia; A Case study at a Japanese lake basin influenced by agricultural ammonia sources

Kubota, Tomohiro; Kuroda, Hisao*; Watanabe, Mirai*; Takahashi, Akiko*; Nakazato, Ryoji*; Tarui, Mika*; Matsumoto, Shunichi*; Nakagawa, Keita*; Numata, Yasuko*; Ouchi, Takao*; et al.

Atmospheric Environment, 243, p.117856_1 - 117856_9, 2020/12

The dry and wet depositions of atmospheric ammonia (NH$$_{3}$$) is one of the important pathways of nitrogen loads to aquatic ecosystems. Crop and livestock agriculture, one of the largest emitters of NH$$_{3}$$ in Asian countries, are known to cause high spatial and seasonal variation of NH$$_{3}$$ and influence the surrounding lake basin areas via its dry and wet deposition. However, the spatial characteristics of the NH$$_{3}$$ concentration in basin scale are not completely understood for regulation in NH$$_{3}$$ emission. Here we aim to clarify dominant factors of spatial and seasonal variations of the NH$$_{3}$$ concentration in a eutrophic lake basin surrounded by agricultural areas in Japan. Passive sampling over various land use categories in the basin was conducted at 36 sites in total from October 2018 to January 2020. Interestingly, the observed NH$$_{3}$$ concentration near the livestock houses were higher in winter than summer, which was inconsistent with knowledge of seasonal changes of current NH$$_{3}$$ emission inventory based on temperature-driven volatilization process. Comparing monthly NH$$_{3}$$ concentrations with various meteorological factors, we suggested the importance of seasonal advection of NH$$_{3}$$ from high emission sources to which has been rarely paid attention by the previous past studies. As for this, should be considered for lake ecosystem management since deposition of NH$$_{3}$$ is known to be closely related to the ecological processes such as phytoplankton blooming.

JAEA Reports

Practical guide on soil sampling, treatment, and carbon isotope analysis for carbon cycle studies

Koarashi, Jun; Atarashi-Andoh, Mariko; Nagano, Hirohiko*; Sugiharto, U.*; Saengkorakot, C.*; Suzuki, Takashi; Kokubu, Yoko; Fujita, Natsuko; Kinoshita, Naoki; Nagai, Haruyasu; et al.

JAEA-Technology 2020-012, 53 Pages, 2020/10

JAEA-Technology-2020-012.pdf:3.71MB

There is growing concern that recent rapid changes in climate and environment could have a significant influence on carbon cycling in terrestrial ecosystems (especially forest ecosystems) and could consequently lead to a positive feedback for global warming. The magnitude and timing of this feedback remain highly uncertain largely due to a lack of quantitative understanding of the dynamics of organic carbon stored in soils and its responses to changes in climate and environment. The tracing of radiocarbon (natural and bomb-derived $$^{14}$$C) and stable carbon ($$^{13}$$C) isotopes through terrestrial ecosystems can be a powerful tool for studying soil organic carbon (SOC) dynamics. The primary aim of this guide is to promote the use of isotope-based approaches to improve our understanding of the carbon cycling in soils, particularly in the Asian region. The guide covers practical methods of soil sampling; treatment and fractionation of soil samples; preparation of soil samples for $$^{13}$$C (and stable nitrogen isotope, $$^{15}$$N) and $$^{14}$$C analyses; and $$^{13}$$C, $$^{15}$$N, and $$^{14}$$C measurements by the use of isotope ratio mass spectrometry and accelerator mass spectrometry (AMS). The guide briefly introduces ways to report $$^{14}$$C data, which are frequently used for soil carbon cycling studies. The guide also reports results of a case study conducted in a Japanese forest ecosystem, as a practical application of the use of isotope-based approaches. This guide is mainly intended for researchers who are interested but are not experienced in this research field. The guide will hopefully encourage readers to participate in soil carbon cycling studies, including field works, laboratory experiments, isotope analyses, and discussions with great interest.

Journal Articles

A Model intercomparison of atmospheric $$^{137}$$Cs concentrations from the Fukushima Daiichi Nuclear Power Plant accident, phase III; Simulation with an identical source term and meteorological field at 1-km resolution

Sato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qu$'e$rel, A.*; Qu$'e$lo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.

Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10

The third model intercomparison project for investigating the atmospheric behavior of $$^{137}$$Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric $$^{137}$$Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.

JAEA Reports

Registration and related activities of the Japan Atomic Energy Agency for the response and assistance network of the International Atomic Energy Agency

Togawa, Orihiko; Hayakawa, Tsuyoshi; Tanaka, Tadao; Yamamoto, Kazuya; Okuno, Hiroshi

JAEA-Review 2020-017, 36 Pages, 2020/09

JAEA-Review-2020-017.pdf:2.24MB

In 2010, the government of Japan joined the Response and Assistance Network (RANET) of the International Atomic Energy Agency (IAEA), in order to contribute to offering international assistance in the case of a nuclear accident or radiological emergency. At that occasion, the Japan Atomic Energy Agency (JAEA) was registered as the National Assistance Capability (NAC) having resources capable of the External Based Support (EBS) in the following seven areas: (1) aerial survey, (2) radiation monitoring, (3) environmental measurements, (4) assessment and advice, (5) internal dose assessment, (6) bioassay and (7) dose reconstruction. After the registration, three inquiries were directed to the JAEA about a possibility of its support. However, the JAEA's assistance has not eventually been realized. On the other hand, the JAEA participated almost every year in the international Convention Exercise (ConvEx) carried out by the IAEA in connection with RANET. This report describes an outline of the RANET and related activities of the JAEA for RANET registration and participation in the ConvEx.

Journal Articles

Formation and mobility of soil organic carbon in a buried humic horizon of a volcanic ash soil

Wijesinghe, J. N.*; Koarashi, Jun; Atarashi-Andoh, Mariko; Kokubu, Yoko; Yamaguchi, Noriko*; Sase, Takashi*; Hosono, Mamoru*; Inoue, Yuzuru*; Mori, Yuki*; Hiradate, Shuntaro*

Geoderma, 374, p.114417_1 - 114417_10, 2020/09

 Times Cited Count:0 Percentile:100(Soil Science)

Journal Articles

Observation of morphological abnormalities in silkworm pupae after feeding $$^{137}$$CsCl-supplemented diet to evaluate the effects of low dose-rate exposure

Tanaka, Sota; Kinouchi, Tadatoshi*; Fujii, Tsuguru*; Imanaka, Tetsuji*; Takahashi, Tomoyuki*; Fukutani, Satoshi*; Maki, Daisuke*; Notomi, Akihiro*; Takahashi, Sentaro*

Scientific Reports (Internet), 10, p.16055_1 - 16055_7, 2020/09

Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, morphological abnormalities of the lepidopteran insects have been reported. However, it is unclear whether the abnormalities were caused directly by radiation because they did not study on absorbed dose and dose-effect relationship. In this study, we conducted an internal exposure experiment on silkworm using $$^{137}$$CsCl-supplemented artificial diet and estimated the absorbed dose to evaluate the morphological abnormalities in silkworm. The ratio of wing to whole body of pupae was compared between the $$^{137}$$CsCl-exposured and control groups and no significant differences were observed between the groups. This result suggest that morphological abnormalities in lepidopterans are unlikely due to direct radiation effects from $$^{137}$$Cs contamination after the FDNPP accident.

Journal Articles

Seven-year temporal variation of caesium-137 discharge inventory from the port of Fukushima Daiichi Nuclear Power Plant; Continuous monthly estimation of caesium-137 discharge in the period from April 2011 to June 2018

Machida, Masahiko; Yamada, Susumu; Iwata, Ayako; Otosaka, Shigeyoshi; Kobayashi, Takuya; Watanabe, Masahisa; Funasaka, Hideyuki; Morita, Takami*

Journal of Nuclear Science and Technology, 57(8), p.939 - 950, 2020/08

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

After direct discharges of highly contaminated water of the Fukushima Daiichi Nuclear Power Plant (1F) from April to May 2011, Kanda suggested that relatively small amounts of run-off of radionuclides from the 1F port into the Fukushima coastal region subsequently continued by his estimation method. However, the estimation period was limited to up to September 2012. Therefore, this paper estimates the discharge inventory up to June 2018. In the missing period, the Japanese government and Tokyo Electric Power Company Holdings have continued efforts to stop the discharge, and consequently, the radionuclide concentration in seawater inside the 1F port has gradually diminished. We show the monthly discharge inventory of $$^{137}$$Cs up to June 2018 by two methods, i.e., Kanda method partially improved by the authors and a more sophisticated method using Voronoi tessellation reflecting the increase in the number of monitoring points inside the 1 F port. The results show that the former always yields overestimated results compared with the latter, but the ratio of the former to the latter is less than one order of magnitude. Using these results, we evaluate the impact of the discharge inventory from the 1F port into the coastal area and radiation dose upon fish ingestion.

Journal Articles

Development of a combined LES/RANS model to predict atmospheric dispersion over urban areas

Yoshida, Toshiya; Nakayama, Hiromasa

Nippon Keisan Kogakkai Rombunshu (Internet), 2020, p.20200013_1 - 20200013_9, 2020/07

To quickly and accurately predict the dispersion of hazardous materials released over urban areas, we propose a combined method in which dispersion fields are simulated using a Reynolds-averaged Navier-Stokes model with pre-calculated flow fields from a large-eddy simulation (LES) model. First, the combined model is conducted for dispersion in a simple street canyon. The results of the combined model are compared with those of a wind-tunnel experiment to adjust empirical parameters in the turbulent scalar flux. The horizontal dispersion fields predicted in the combined model with the best parameters are well consistent with those calculated from our LES model. We then apply the combined model to predict the scalar dispersion over a real urban area. The combined model well predicts the results obtained from the LES model with less calculation time. Therefore, we find that the combined model is potentially effective for emergency response to hazardous-material release over urban areas.

Journal Articles

Development of a user-friendly interface IRONS for atmospheric dispersion database for nuclear emergency preparedness based on the Fukushima database

El-Asaad, H.*; Nagai, Haruyasu; Sagara, Hiroshi*; Han, C. Y.*

Annals of Nuclear Energy, 141, p.107292_1 - 107292_9, 2020/06

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Atmospheric dispersion simulations can provide crucial information to assess radioactive plumes in the environment for nuclear emergency preparedness. However, it is a difficult and time-consuming task to make simulations assuming many possible scenarios and to derive data from a vast number of results. Therefore, an interface was developed to assist users in conveying characteristics of plumes from simulation results. The interface uses a large database that contains WSPEEDI-II simulations for the first 20-days of radioactive release from the Fukushima Daiichi Nuclear Power Plant, and it displays essential quantitative data to the user from the database. The user may conduct sensitivity analysis with the help of the interface by changing release condition to generate many different case scenarios.

Journal Articles

Atmospheric-dispersion database system that can immediately provide calculation results for various source term and meteorological conditions

Terada, Hiroaki; Nagai, Haruyasu; Tanaka, Atsunori*; Tsuzuki, Katsunori; Kadowaki, Masanao

Journal of Nuclear Science and Technology, 57(6), p.745 - 754, 2020/06

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

We have estimated source term and analyzed processes of atmospheric dispersion of radioactive materials released during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident by the Worldwide version of System for Environmental Emergency Dose Information. On the basis of this experience, we developed an dispersion calculation method that can respond to various needs in a nuclear emergency and provide useful information for emergency-response planning. By this method, if a release point is known, it is possible to immediately obtain the prediction results by applying provided source term to the database of dispersion-calculation results prepared in advance. With this function, it is easy to compare results by applying various source term with monitoring data, and to find out the optimum source term, which was applied for the source term estimation of the FDNPS accident. By performing this calculation with past meteorological-analysis data, it is possible to immediately get dispersion-calculation results for various source term and meteorological conditions. This database can be used for pre-accident planning, such as optimization of a monitoring plan and understanding of events to be supposed in considering emergency countermeasures.

Journal Articles

Vertical distributions of Iodine-129 and iodide in the Chukchi Sea and Bering Sea

Miwa, Kazuji; Obata, Hajime*; Suzuki, Takashi

Journal of Nuclear Science and Technology, 57(5), p.537 - 545, 2020/05

 Times Cited Count:1 Percentile:53.3(Nuclear Science & Technology)

This study investigated the vertical distribution of Iodine-129 ($$^{129}$$I) which is mainly produced by European nuclear reprocessing plants in the Chukchi Sea and Bering Sea. $$^{129}$$I was found to be distributed almost uniformly in fallout level, and an increasing in $$^{129}$$I concentration levels caused by high $$^{129}$$I water inflow from the Atlantic Ocean was not observed. Additionally, we revealed the vertical distribution of iodide, one chemical form of iodine, from the Bering Shelf area to the Chukchi Sea for the first time. The increasing tendency of iodide near sea bottom was observed.

Journal Articles

Preliminary investigation of pretreatment methods for liquid scintillation measurements of environmental water samples using ion exchange resins

Nakasone, Shunya*; Yokoyama, Sumi*; Takahashi, Tomoyuki*; Ota, Masakazu; Kakiuchi, Hideki*; Sugihara, Shinji*; Hirao, Shigekazu*; Momoshima, Noriyuki*; Tamari, Toshiya*; Shima, Nagayoshi*; et al.

Plasma and Fusion Research (Internet), 15, p.2405027_1 - 2405027_3, 2020/05

A quick preprocessing system for tritium analysis of environmental samples is important to judge environmental influence of tritium releases due to accident or tritium-handling facilities. Analysis of tritium in water samples with liquid scintillation counting method requires removal of impurities such as organic matter and ion species from water samples. Generally, a distillation method is adopted as a pretreatment of analysis for tritium; however, the distillation method is a time-consuming process. The aim of this study is to evaluate a rapid pretreatment method for tritium analysis with ion exchange resin. From batch and column experiments that used inland water and ion exchange resin, we confirmed removals of impurities of the water sample and that the removal of impurities was possible for a short time (by 5 minutes).

Journal Articles

Predictability of a short-term emergency assessment system of the marine environmental radioactivity

Kawamura, Hideyuki; Kamidaira, Yuki; Kobayashi, Takuya

Journal of Nuclear Science and Technology, 57(4), p.472 - 485, 2020/04

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The Japan Atomic Energy Agency developed a Short-Term Emergency Assessment system of the Marine Environmental Radioactivity (STEAMER) to predict the oceanic dispersion of radionuclides in the ocean around Japan. The purpose of this study is to validate the predictability of STEAMER using oceanographic forecast and reanalysis data, which were saved for past several years. Results of oceanic dispersion simulations that are driven by oceanographic reanalysis data are assumed to be true solutions. Oceanic dispersion simulations are conducted for Cs-137 released hypothetically from the Fukushima Daiichi Nuclear Power Plant. The predictability of STEAMER is quantitatively examined for the length of the forecast period. Ensemble forecast simulations are also conducted to successfully improve the predictability of STEAMER.

Journal Articles

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

Koarashi, Jun; Atarashi-Andoh, Mariko; Nishimura, Shusaku; Muto, Kotomi*

Scientific Reports (Internet), 10(1), p.6614_1 - 6614_11, 2020/04

 Times Cited Count:0 Percentile:100(Multidisciplinary Sciences)

We conducted a pilot-scale decontamination study in a deciduous broadleaved forest in Fukushima. The entire forest, other than two untreated areas, was decontaminated by removing the litter layer approximately 3.3 years after the accident. For three years after decontamination, we quantified $$^{137}$$Cs contamination levels in the litter and topsoil layers and in the tree leaves, in the untreated and decontaminated areas. The decreased inventories of litter-associated $$^{137}$$Cs in the decontaminated areas were observed only in the first year after decontamination. Generally, no decontamination effects were observed on the $$^{137}$$Cs transfer in tree leaves. The primary reason for this was the rapid shift in the main reservoir of $$^{137}$$Cs from litter layers to the underlying mineral soil, which differs from the observations in post-Chernobyl studies of European forest ecosystems. The results suggest that litter-removal decontamination can only be successful if it is implemented more quickly for Japanese forest ecosystems.

Journal Articles

Refinement of source term and atmospheric dispersion simulations of radionuclides during the Fukushima Daiichi Nuclear Power Station accident

Terada, Hiroaki; Nagai, Haruyasu; Tsuzuki, Katsunori; Furuno, Akiko; Kadowaki, Masanao; Kakefuda, Toyokazu*

Journal of Environmental Radioactivity, 213, p.106104_1 - 106104_13, 2020/03

 Times Cited Count:4 Percentile:6.48(Environmental Sciences)

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station accident in Japan, the spatial and temporal distribution of radioactive materials in the environment is necessary to be reconstructed by computer simulations with the atmospheric transport, dispersion and deposition model (ATDM) and source term of radioactive materials discharged into the atmosphere is essential. In this study, we carried out refinement of the source term and improvement of ATDM simulation by using an optimization method based on Bayesian inference with various measurements (air concentration, surface deposition, and fallout). We also constructed the spatiotemporal distribution of some major radionuclides in the air and on the surface (optimized dispersion database) by using the optimized release rates and ATDM simulations which is used for the comprehensive dose assessment by coupling with the behavioral pattern of evacuees from the accident.

Journal Articles

Wintertime grassland dynamics may influence belowground biomass under climate change; A Model analysis

Katata, Genki*; Grote, R.*; Mauder, M.*; Zeeman, M. J.*; Ota, Masakazu

Biogeosciences, 17(4), p.1071 - 1085, 2020/02

 Times Cited Count:1 Percentile:23.21(Ecology)

Mountain grassland productivity is limited by cold and long winters; thus, rising temperatures and changes in snow cover expected in the future may have large impacts on the grassland yields. To investigate this, we enhanced land surface model (SOLVEG) to account for snow, freeze-thaw events, and grass growth, and the model was applied to the managed grasslands affected by extremely warm winter. The model reproduced temporal variability of observed heat fluxes, soil temperatures and snow depth throughout the 3-year simulation period. High physiological activity during the extremely warm winter led to a CO$$_{2}$$ uptake of 100 g-C m$$^{-2}$$, which was, surprisingly, mainly allocated into the below-ground biomass and rarely used for plant growth during spring. This process, which is so far largely unaccounted for in global terrestrial biosphere models, may lead to carbon accumulation in the soil and/or heterotrophic respiration as a response to global warming.

Journal Articles

Verification of safety margin of reactor pressure vessel exposed to various thermal transients based on probabilistic approach

Suzuki, Masahide*; Murakami, Kenta*; Suzuki, Takashi*; Okayama, Ryuta*; Katsuyama, Jinya; Li, Y.

E-Journal of Advanced Maintenance (Internet), 11(4), p.172 - 178, 2020/02

no abstracts in English

Journal Articles

Processes affecting land-surface dynamics of $$^{129}$$I impacted by atmospheric $$^{129}$$I releases from a spent nuclear fuel reprocessing plant

Ota, Masakazu; Terada, Hiroaki; Hasegawa, Hidenao*; Kakiuchi, Hideki*

Science of the Total Environment, 704, p.135319_1 - 135319_15, 2020/02

 Times Cited Count:1 Percentile:100(Environmental Sciences)

Land-surface transfers of $$^{129}$$I are modeled and incorporated into a land-surface model (SOLVEG-II), and the model was applied to the observed transfer of $$^{129}$$I at a vegetated field impacted by atmospheric releases of $$^{129}$$I from Rokkasho reprocessing plant during 2007 to investigate the importance of each $$^{129}$$I-transfer pathway. The model calculation revealed that contamination of leaves of wild bamboo grasses was mostly caused by foliar adsorption of $$^{129}$$I (81%) induced via wet deposition of $$^{129}$$I. Wet deposition of $$^{129}$$I was the main $$^{129}$$I-input to the soil, ten-fold the dry deposition of $$^{129}$$I$$_{2}$$; however, the deposition of $$^{129}$$I during 2007 was only 2% of the model-assumed $$^{129}$$I that pre-existed in the soil; indicating the importance of long-term accumulation of $$^{129}$$I in soils. The model calculation also revealed that root uptake of $$^{129}$$I, not methylation, control the long-term turnover of soil $$^{129}$$I.

Journal Articles

Reconstruction of residents' thyroid equivalent doses from internal radionuclides after the Fukushima Daiichi Nuclear Power Station accident

Oba, Takashi*; Ishikawa, Tetsuo*; Nagai, Haruyasu; Tokonami, Shinji*; Hasegawa, Arifumi*; Suzuki, Gen*

Scientific Reports (Internet), 10(1), p.3639_1 - 3639_11, 2020/02

 Times Cited Count:1

Internal doses of residents after the Fukushima Daiichi Nuclear Power Station accident have been reconstructed. In total 896 behaviour records in the Fukushima Health Management Survey were analysed to estimate thyroid doses via inhalation, using a spatiotemporal radionuclides concentration database constructed by atmospheric dispersion simulations. After a decontamination factor for sheltering and a modifying factor for the dose coefficient were applied, estimated thyroid doses were close to those estimated on the basis of direct thyroid measurement. The median and 95th percentile of thyroid doses of 1-year-old children ranged from 1.2 to 15 mSv and from 7.5 to 30 mSv, respectively.

Journal Articles

Radioactive cesium contamination of arthropods and earthworms after the Fukushima Daiichi Nuclear Power Plant Accident

Tanaka, Sota; Adachi, Taro*; Takahashi, Tomoyuki*; Takahashi, Sentaro*

Low-Dose Radiation Effects on Animals and Ecosystems; Long-Term Study on the Fukushima Nuclear Accident, p.43 - 52, 2020/00

To understand the behavior of radiocesium in terrestrial invertebrates, chronological changes in the concentration of radiocesium in arthropods and earthworms from different trophic levels were investigated after the Fukushima Daiichi Nuclear Power Plant accident. The median radiocesium concentrations in the rice grasshopper, Oxya yezoensis, and the Emma field cricket, Teleogryllus emma, were 0.46 and 0.15 Bq/g fw in 2012, respectively, which dropped continuously to 0.05 and 0.01 Bq/g fw in 2016. In contrast, no significant reduction in radiocesium concentration was observed in the Joro Spider, Nephila clavata, in which the concentration was 0.31 Bq/g fw in 2012 and remained at 0.14 Bq/g fw in 2016. The comparison of radiocesium concentrations at each trophic level showed that the amount in detritivorous earthworms was 85 times higher than in herbivorous grasshoppers. This suggests that detritus food web could be a primary pathway of radiocesium through food webs.

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