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Journal Articles

Impacts of freeze-thaw processes and subsequent runoff on $$^{137}$$Cs washoff from bare land in Fukushima

Igarashi, Yasunori*; Onda, Yuichi*; Wakiyama, Yoshifumi*; Yoshimura, Kazuya; Kato, Hiroaki*; Kozuka, Shohei*; Manome, Ryo*

Science of the Total Environment, 769, p.144706_1 - 144706_9, 2021/05

 Times Cited Count:0 Percentile:0(Environmental Sciences)

Journal Articles

Speciation of cesium in tree tissues and its implication for uptake and translocation of radiocesium in tree bodies

Tanaka, Kazuya; Kanasashi, Tsutomu*; Takenaka, Chisato*; Takahashi, Yoshio*

Science of the Total Environment, 755(Part 2), p.142598_1 - 142598_8, 2021/02

 Times Cited Count:3 Percentile:83.41(Environmental Sciences)

In this study, we investigated coordination structures of Cs in $$^{133}$$Cs-doped bark, sapwood, heartwood, needle, and branch samples of trees collected in Fukushima by extended X-ray absorption fine structure (EXAFS) spectroscopy. We examined four representative tree species in Fukushima, ${it Cryptomeria japonica}$, ${it Pinus densiflora}$, ${it Quercus serrata}$, and ${it Eleutherococcus sciadophylloides}$. EXAFS spectra suggested that Cs was adsorbed as an outer-sphere complex on all parts of the four species, with electrostatic binding to negatively charged functional groups in components of tree tissues. These results were supported by extraction experiments where most of the sorbed Cs was desorbed from all parts of each tree species using 1 M CH$$_{3}$$COONH$$_{4}$$.

Journal Articles

Distribution and settling behavior of americium-241 in the tropical East Pacific

Kinoshita, Norikazu*; Nagaoka, Mika; Nakanishi, Takashi*

Science of the Total Environment, 753, p.142087_1 - 142087_10, 2021/01

 Times Cited Count:1 Percentile:65.97(Environmental Sciences)

The distribution of the anthropogenic radionuclide americium-241 ($$^{241}$$Am), a decay product of $$^{241}$$Pu discharged from atmospheric tests of nuclear weapons, was investigated to resolve its horizontal and vertical migration in the Tropical East Pacific. We analyzed $$^{241}$$Am concentrations in seawater samples collected in 2003. On comparing the $$^{241}$$Am concentrations with the previously determined concentrations of $$^{239+240}$$Pu in the same samples, the vertical profiles of $$^{241}$$Am were found to be similar to those of $$^{239+240}$$Pu. At some stations, the maximum concentration of $$^{241}$$Am occurred 100-200 m deeper than that of $$^{239+240}$$Pu. The $$^{241}$$Am/$$^{239+240}$$Pu ratios in the North Pacific and South Pacific were comparable to one another, and were typical of the ratio for the Pacific. The $$^{241}$$Am distribution was influenced by the water mass at depths below 400 m. The $$^{241}$$Am data support the view there is a current flowing at depths of 400-3000 m from the North Pacific through the equator to the South Pacific. In addition, the $$^{241}$$Am vertical profile was explained by using a box model that considers the decay of $$^{241}$$Pu and adsorption and scavenging by suspended particles. The different depths for the maximum concentrations of $$^{241}$$Am and $$^{239+240}$$Pu observed at some stations were well explained by the model and by the distribution of CaCO$$_{3}$$ particles. The residence time of $$^{241}$$Am in the Pacific was also estimated by using the model.

Journal Articles

A Unique high natural background radiation area; Dose assessment and perspectives

Hosoda, Masahiro*; Nugraha, E. D.*; Akata, Naofumi*; Yamada, Ryohei; Tamakuma, Yuki*; Sasaki, Michiya*; Kelleher, K.*; Yoshinaga, Shinji*; Suzuki, Takahito*; Rattanapongs, C. P.*; et al.

Science of the Total Environment, 750, p.142346_1 - 142346_11, 2021/01

 Times Cited Count:5 Percentile:96.3(Environmental Sciences)

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h$$^{-1}$$ and 1109 nGy h$$^{-1}$$. Indoor radon concentrations ranged from 124 Bq m$$^{-3}$$ to 1015 Bq m$$^{-3}$$. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m$$^{-3}$$ recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

Journal Articles

Reservoir sediments as a long-term source of dissolved radiocaesium in water system; a mass balance case study of an artificial reservoir in Fukushima, Japan

Funaki, Hironori; Sakuma, Kazuyuki; Nakanishi, Takahiro; Yoshimura, Kazuya; Katengeza, E. W.*

Science of the Total Environment, 743, p.140668_1 - 140668_9, 2020/11

 Times Cited Count:5 Percentile:39.03(Environmental Sciences)

Journal Articles

Key factors controlling radiocesium sorption and fixation in river sediments around the Fukushima Daiichi Nuclear Power Plant, 1; Insights from sediment properties and radiocesium distributions

Tachi, Yukio; Sato, Tomofumi*; Akagi, Yosuke*; Kawamura, Makoto*; Nakane, Hideji*; Terashima, Motoki; Fujiwara, Kenso; Iijima, Kazuki

Science of the Total Environment, 724, p.138098_1 - 138098_11, 2020/07

 Times Cited Count:5 Percentile:70.14(Environmental Sciences)

To understand and predict radiocesium transport behaviors in the environment, highly contaminated sediments from Ukedo and Odaka rivers around the Fukushima Daiichi Nuclear Power Plant were investigated systematically focusing on key factors controlling radiocesium sorption and fixation, including particle size, clay mineralogy and organic matter.

Journal Articles

Key factors controlling radiocesium sorption and fixation in river sediments around the Fukushima Daiichi Nuclear Power Plant, 2; Sorption and fixation behaviors and their relationship to sediment properties

Tachi, Yukio; Sato, Tomofumi*; Takeda, Chizuko*; Ishidera, Takamitsu; Fujiwara, Kenso; Iijima, Kazuki

Science of the Total Environment, 724, p.138097_1 - 138097_10, 2020/07

 Times Cited Count:2 Percentile:39.03(Environmental Sciences)

To understand and predict radiocesium transport behaviors in the environment, sorption and fixation behaviors of radiocesium on river sediments from Ukedo and Odaka rivers around the Fukushima Daiichi Nuclear Power Plant were investigated systematically focusing on Cs sorption and fixation mechanisms and their relationship with Cs concentrations and sediment properties including clay mineralogy and organic matter.

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:2 Percentile:39.03(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

Factors controlling dissolved $$^{137}$$Cs concentrations in east Japanese rivers

Tsuji, Hideki*; Ishii, Yumiko*; Shin, M.*; Taniguchi, Keisuke*; Arai, Hirotsugu*; Kurihara, Momo*; Yasutaka, Tetsuo*; Kuramoto, Takayuki*; Nakanishi, Takahiro; Lee, S*; et al.

Science of the Total Environment, 697, p.134093_1 - 134093_11, 2019/12

 Times Cited Count:8 Percentile:62.46(Environmental Sciences)

To investigate the main factors that control the dissolved radiocesium concentration in river water in the area affected by the Fukushima Daiichi nuclear power plant accident, the correlations between the dissolved $$^{137}$$Cs concentrations at 66 sites normalized to the average $$^{137}$$Cs inventories for the watersheds with the land use, soil components, topography, and water quality factors were assessed. We found that the topographic wetness index is significantly and positively correlated with the normalized dissolved $$^{137}$$Cs concentration. Similar positive correlations have been found for European rivers because wetland areas with boggy organic soils that weakly retain $$^{137}$$Cs are mainly found on plains. However, for small Japanese river watersheds, the building area ratio in the watershed strongly affected the dissolved $$^{137}$$Cs concentration.

Journal Articles

Nagasaki sediments reveal that long-term fate of plutonium is controlled by select organic matter moieties

Lin, P.*; Xu, C.*; Kaplan, D. I.*; Chen, H.*; Yeager, C. M.*; Xing, W.*; Sun, L.*; Schwehr, K. A.*; Yamazaki, Hideo*; Kokubu, Yoko; et al.

Science of the Total Environment, 678, p.409 - 418, 2019/08

 Times Cited Count:3 Percentile:20.11(Environmental Sciences)

Nagasaki sediments containing bomb-derived Pu provided a unique opportunity to explore the long term geochemical behavior of Pu. Through a combination of selective extractions and molecular characterization via electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry, we determined that 55 $$pm$$ 3% of the $$^{239,240}$$Pu was preferentially associated with more persistent organic matter compounds in Nagasaki sediments, particularly those natural organic matter (NOM) stabilized by Fe oxides. Other organic matter compounds served as a secondary sink of these $$^{239,240}$$Pu (31 $$pm$$ 2% on average), and less than 20% of the $$^{239,240}$$Pu was immobilized by inorganic mineral particles. While present long-term disposal and environmental remediation modeling assume that solubility limits and sorption to mineral surfaces control Pu subsurface mobility, our observations suggest that NOM undoubtedly plays an important role in sequestering Pu. Ignoring the role of NOM in controlling Pu fate and transport is not justified in most environmental systems.

Journal Articles

Altitudinal characteristics of atmospheric deposition of aerosols in mountainous regions; Lessons from the Fukushima Daiichi Nuclear Power Station accident

Sanada, Yukihisa; Katata, Genki*; Kaneyasu, Naoki*; Nakanishi, Chika*; Urabe, Yoshimi*; Nishizawa, Yukiyasu*

Science of the Total Environment, 618, p.881 - 890, 2018/03

 Times Cited Count:12 Percentile:59.27(Environmental Sciences)

Although the reconstruction of atmospheric deposition processes of radiocesium during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident is essential, the whole picture of the deposition mechanism in complex topography has not been well understood yet. To understand atmospheric deposition processes of aerosols over the complex mountainous topography, we analyzed altitudinal characteristics of radiocesium released during the accident. At five selected mountainous areas in the eastern Japan, altitudinal characters of air dose rate observed by our high-resolution airborne surveys after the accident was analyzed based on the results of three typical (dry, wet, and cloud water) deposition obtained from the latest atmospheric dispersion.

Journal Articles

Effect of topsoil removal and selective countermeasures on radiocesium accumulation in rice plants in Fukushima paddy field

Yang, B.*; Onda, Yuichi*; Omori, Yoshihiro*; Sekimoto, Hitoshi*; Fujiwara, Toru*; Wakiyama, Yoshifumi*; Yoshimura, Kazuya; Takahashi, Junko*; Sun, X.*

Science of the Total Environment, 603-604, p.49 - 56, 2017/12

 Times Cited Count:1 Percentile:5.42(Environmental Sciences)

Journal Articles

Modelling of marine radionuclide dispersion in IAEA MODARIA program; Lessons learnt from the Baltic Sea and Fukushima scenarios

Peri$'a$$~n$ez, R.*; Bezhenar, R.*; Brovchenko, I.*; Duffa, C.*; Iosjpe, M.*; Jung, K. T.*; Kobayashi, Takuya; Lamego, F.*; Maderich, V.*; Min, B. I.*; et al.

Science of the Total Environment, 569-570, p.594 - 602, 2016/11

 Times Cited Count:20 Percentile:66.41(Environmental Sciences)

State-of-the art dispersion models were applied to simulate $$^{137}$$Cs dispersion from Chernobyl Nuclear Power Plant disaster fallout in the Baltic Sea and from Fukushima Daiichi Nuclear Plant releases in the Pacific Ocean after the 2011 tsunami. Models were of different nature, from box to full three-dimensional models, and included water/sediment interactions. Agreement between models was very good in the Baltic. In the case of Fukushima, results from models could be considered to be in acceptable agreement only after a model harmonization process consisting of using exactly the same forcing (water circulation and parameters) in all models. It was found that the dynamics of the considered system (magnitude and variability of currents) was essential in obtaining a good agreement between models. The difficulties in developing operative models for decision-making support in these dynamic environments were highlighted.

Journal Articles

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

Ota, Masakazu; Nagai, Haruyasu; Koarashi, Jun

Science of the Total Environment, 551-552, p.590 - 604, 2016/05

 Times Cited Count:26 Percentile:75.78(Environmental Sciences)

A model for $$^{137}$$Cs transfer in forest was developed to assess behavior of Fukushima-derived $$^{137}$$Cs. The model simulation well reproduced observed 3 year migration of $$^{137}$$Cs in organic layer and mineral soil. Long-term predictions indicated that more than 90% of the deposited $$^{137}$$Cs remains in the top 5 cm soil till 30 years, suggesting that forest acts as a long-term reservoir of $$^{137}$$Cs with limited loss via groundwater pathway. Impacts of soil organic matter (SOM) on $$^{137}$$Cs dynamics were investigated by modifying parameters of $$^{137}$$Cs turnover. The results showed that SOM-induced reduction of $$^{137}$$Cs adsorption, slower fixation of $$^{137}$$Cs by clay and enhanced mobilization of the fixed $$^{137}$$Cs elevate soil-to-plant transfer of $$^{137}$$Cs by increasing fraction of dissolved $$^{137}$$Cs. A substantial proportion (27% $$sim$$ 73%) of $$^{137}$$Cs in these soils was delivered to horizons deeper than 5 cm decades later. These results suggested that SOM significantly influences behavior of $$^{137}$$Cs over long-term.

Journal Articles

Radioactive Cs in the estuary sediments near Fukushima Daiichi Nuclear Power Plant

Yamasaki, Shinya*; Imoto, Jumpei*; Furuki, Genki*; Ochiai, Asumi*; Onuki, Toshihiko; Sueki, Keisuke*; Namba, Kenji*; Ewing, R. C.*; Utsunomiya, Satoshi*

Science of the Total Environment, 551-552, p.155 - 162, 2016/05

 Times Cited Count:26 Percentile:75.78(Environmental Sciences)

Cesium-137 ($$^{137}$$Cs) of estuary sediment impacted by the FDNPP was measured. Increasing radioactivity was observed from surface to bottom. 90% of the $$^{137}$$Cs was strongly bound to clay minerals in the estuary sediments. These results suggest that $$^{137}$$Cs is being transported from contaminated paddy fields to the estuary.

Journal Articles

Speciation of iodine isotopes inside and outside of a contaminant plume at the Savannah River Site

Schwehr, K. A.*; Otosaka, Shigeyoshi; Merchel, S.*; Kaplan, D. I.*; Zhang, S.*; Xu, C.*; Li, H.-P.*; Ho, Y.-F.*; Yeager, C. M.*; Santschi, P. H.*; et al.

Science of the Total Environment, 497-498, p.671 - 678, 2014/11

 Times Cited Count:10 Percentile:36.54(Environmental Sciences)

A new, accurate and simple pH-dependent solvent extraction method combined with accelerator mass spectrometry (AMS) measurement for $$^{129}$$I/$$^{127}$$I isotopes and iodine speciation (iodide, iodate, and organo-I) quantification in liquids of any ionic strength has been developed. We then validated the AMS method for activity concentration measurements with a recently developed gas chromatography mass spectrometry method for $$^{129}$$I concentrations of 1 Bq/L or higher. This technique was applied to $$^{129}$$I-contaminated groundwater from the Savannah River Site, USA, and demonstrated changes of $$^{129}$$I and $$^{127}$$I concentrations and speciation along a pH, redox potential, and organic carbon gradient. The data suggest that $$^{129}$$I/$$^{127}$$I and species distribution is strongly pH dependent. The new method can now be applied to a wide range of chemically-diverse aquatic systems, including uncontaminated environments.

Journal Articles

Comparison of the vertical distributions of Fukushima nuclear accident radiocesium in soil before and after the first rainy season, with physicochemical and mineralogical interpretations

Matsunaga, Takeshi; Koarashi, Jun; Atarashi-Andoh, Mariko; Nagao, Seiya*; Sato, Tsutomu*; Nagai, Haruyasu

Science of the Total Environment, 447, p.301 - 314, 2013/03

 Times Cited Count:108 Percentile:96.09(Environmental Sciences)

The effect of intensive rainfall in the on distribution of Fukushima accident-derived $$^{137}$$Cs in soil was examined in Fukushima-city in post-rainy season and were compared with those in pre-rainy season. It is concluded that rainfall during the rainy season had a limited effect on $$^{137}$$Cs distribution in soil, indicating its overall immobility. Chemical extraction of $$^{137}$$Cs from selected soil samples indicated that $$^{137}$$Cs in soil was hardly water-soluble and extractable with 1M ammonium acetate. This supports the overall immobility of $$^{137}$$Cs in our soils. No direct relationship was obtained between the mineral composition and the $$^{137}$$Cs retention in upper soil layer. In contrast, positive correlations were found between the $$^{137}$$Cs extractability and soil properties such as pH, organic matter content, and finer-sized particle contents in the soils. These results suggest that the mineralogical effect may be masked by non-specific adsorption offered by physicochemical properties of the soils.

Journal Articles

Factors affecting vertical distribution of Fukushima accident-derived radiocesium in soil under different land-use conditions

Koarashi, Jun; Atarashi-Andoh, Mariko; Matsunaga, Takeshi; Sato, Tsutomu*; Nagao, Seiya*; Nagai, Haruyasu

Science of the Total Environment, 431, p.392 - 401, 2012/08

 Times Cited Count:129 Percentile:96.32(Environmental Sciences)

no abstracts in English

Journal Articles

Factors controlling mobility of $$^{127}$$I and $$^{129}$$I species in an acidic groundwater plume at the Savannah River Site

Otosaka, Shigeyoshi; Schwehr, K. A.*; Kaplan, D. I.*; Roberts, K. A.*; Zhang, S.*; Xu, C.*; Li, H.-P.*; Ho, Y.-F.*; Brinkmeyer, R.*; Yeager, C. M.*; et al.

Science of the Total Environment, 409(19), p.3857 - 3865, 2011/09

 Times Cited Count:50 Percentile:81.1(Environmental Sciences)

Spatial distributions of concentrations and speciation of radioiodine ($$^{129}$$I) and stable iodine ($$^{127}$$I) in groundwater in the vicinity of the F-area seepage basin at the U.S. Department Energy of Savannah River Site were investigated. $$^{129}$$I concentration in groundwater was 8.6 Bq/L immediately downstream of the seepage basin (well FSB-95DR), and decreased with distance from the infiltration basin. $$^{127}$$I concentration decreased similarly to that of $$^{129}$$I. Although there was no potential $$^{127}$$I source in wastes in the basin, $$^{127}$$I also showed a similar gradient to that of $$^{129}$$I. High concentrations of $$^{127}$$I or $$^{127}$$I were not detected in groundwater collected from wells located outside of the mixed waste plume of this area. The high iodide concentrations in groundwater near the basin were presumed to be caused by dissolution of iodide from soil due to gradually increasing of pH values in the last decade.

Journal Articles

Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas

Morita, Takami*; Niwa, Kentaro*; Fujimoto, Ken*; Kasai, Hiromi*; Yamada, Haruya*; Nishiuchi, Ko*; Sakamoto, Tatsuya*; Godo, Waichiro*; Taino, Seiya*; Hayashi, Yoshihiro*; et al.

Science of the Total Environment, 408(16), p.3443 - 3447, 2010/06

 Times Cited Count:12 Percentile:34.9(Environmental Sciences)

Iodine-131 ($$^{131}$$I) was detected in brown algae collected off the Japanese coast. The maximum measured specific activity of $$^{131}$$I in brown algae was 0.37$$pm$$0.010 Bq/kg-wet. Cesium-137 ($$^{137}$$Cs) was also detected in all brown algal samples used in this study. There was no correlation between specific activities of $$^{131}$$I and $$^{137}$$Cs in these seaweeds. Low specific activity and minimal variability of $$^{137}$$Cs in brown algae indicated that past nuclear weapon tests were the source of $$^{137}$$Cs. Although nuclear power facilities are known to be pollution sources of $$^{131}$$I, there was no relationship between the sites where $$^{131}$$I was detected and the locations of nuclear power facilities. Most of the sites where $$^{131}$$I was detected were near big cities with large populations. On the basis of the results, we suggest that the likely pollution source of $$^{131}$$I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.

22 (Records 1-20 displayed on this page)