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Satoh Y, Omori Y. Evaluating production rates of particulate organic hydrogen by marine phytoplankton for estimating phytoplanktonic productivity of organically bound tritium. WATER RESEARCH 2023; 245:120592. [PMID: 37703756 DOI: 10.1016/j.watres.2023.120592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/04/2023] [Accepted: 09/06/2023] [Indexed: 09/15/2023]
Abstract
To estimate the production potential of organically bound tritium (OBT) by phytoplankton from tritiated water in coastal areas adjacent to the Fukushima Daiichi Nuclear Power Plant (FDNPP), phytoplanktonic production rates of particulate organic hydrogen (POH) were evaluated in laboratory and field experiments using stable isotope tracers (2H and 13C). In the laboratory experiment, the production rate of POH was evaluated for five types of phytoplankton cultivated cultures (two diatoms, Haptophyceae, Chlorophyceae, and Cryptophyceae) at two temperatures (15 °C and 25 °C) and two 2H concentrations in the medium (1 and 5%). Additionally, the production rate of POH was especially focused on non-exchangeable POH (NE-POH) which is the chemical form of hydrogen connected tightly to organic matter. The production rates of NE-POH in the laboratory experiment varied (0.10 to 36 μmol L-1 d-1 μg-Chl a-1) with the productivity of particulate organic carbon, phytoplankton species, and temperature, with negligible influence of 2H concentrations. In the field experiment, in situ incubation of coastal seawater at water depths of 1 and 20 m with isotope tracers under light and dark conditions, respectively, was performed thrice (November 2021, May 2022, and October 2022) on the Pacific coastal ocean approximately 2 km from the land of northeast Japan. We observed variation in the production rate of POH (0.21 to 3.1 μmol L-1 d-1 μg-Chl a-1), which was theoretically explained by the data in the laboratory experiment. Using the phytoplanktonic production rate of POH obtained in this study, OBT production by phytoplankton and the subsequent accumulation potential of OBT in sediments in the coastal area adjacent to FDNPP were tentatively estimated, results of which suggested this potential to be small.
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Affiliation(s)
- Yuhi Satoh
- Department of Radioecology, Institute for Environmental Sciences (IES), 1-7 Rokkasho, Aomori 039-3212, Japan.
| | - Yuko Omori
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan
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Chen D, Nie B, Dong B, Yang D, Wu S, He J, Gu W, Wang D. Insights into near-surface distribution characteristics of multi-form tritium with consideration of atmospheric buoyancy and gravitational deposition. CHEMOSPHERE 2023; 312:137231. [PMID: 36375611 DOI: 10.1016/j.chemosphere.2022.137231] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/30/2022] [Accepted: 11/10/2022] [Indexed: 06/16/2023]
Abstract
Tritium contributes majority to the total airborne radioactive effluents from the nuclear facility because of its considerable production and difficulty in separation. Tritium inventory in the fusion reactor would reach an unprecedented magnitude which brings new safety concern. After being released into the atmosphere, inconsistent atmospheric dispersion behaviors might appear regarding different physicochemical forms such as gaseous state HT, gaseous-aerosol-droplet state HTO. In this study, atmospheric dispersion characteristics of multi-form tritium were investigated based on the computational fluid dynamics method validated by multi-fan type wind tunnel experiments. Species transport model and discrete phase model were used to describe atmospheric dispersion of gaseous and aerosol-droplet state tritium, respectively. Deposition velocity was predicted for gaseous and aerosol-droplet state tritium with different particle sizes. Conditions for describing the changes of particle diameter and its influencing on near-surface tritium distribution due to condensation were provided. The results show that buoyancy effect would strengthen along with the increasing gaseous tritium mass fraction in the airborne effluents. We also indicated that obvious gravitational deposition would appear once gaseous HTO was transformed into droplet state HTO with the particle diameter larger than 20 μm. Both the atmospheric buoyancy and deposition phenomenon would result in a quite different near-surface tritium distribution.
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Affiliation(s)
- Deyi Chen
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Baojie Nie
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
| | - Bing Dong
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Derui Yang
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Siyuan Wu
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Jinpeng He
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Weiguo Gu
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Dezhong Wang
- School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
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Tani T, Nagai M. RETENTION OF ORGANICALLY BOUND DEUTERIUM IN GRASS PLANTS EXPOSED TO HEAVY WATER VAPOUR AT DIFFERENT GROWTH STAGES. RADIATION PROTECTION DOSIMETRY 2022; 198:886-890. [PMID: 36083732 DOI: 10.1093/rpd/ncab192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/14/2021] [Accepted: 11/02/2021] [Indexed: 06/15/2023]
Abstract
Potted timothy grass plants were exposed to heavy water (HDO) vapour at seven different periods during the third growth of harvestable shoots (the part 5-cm above the ground surface), and the concentration of non-exchangeable organically bound deuterium (NE-OBD) was measured in harvestable shoots, stubbles and roots at the third harvest. The excess concentration of NE-OBD was obtained as an increase in the concentration of NE-OBD against the background level. On average, this value was 1.8- to 2.6-fold higher in the harvestable shoots than in the stubble for plants exposed to HDO vapour during the period when the harvestable shoots grew faster than the stubble. Our results suggest that the separation of harvestable shoots and stubble, both of which are generally combined as one part in studies on the metabolism of organically bound tritium (OBT) in grass, could contribute to a realistic evaluation of OBT transfer from timothy to livestock.
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Affiliation(s)
- Takashi Tani
- Department of Radioecology, Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho, Aomori 039-3212 Japan
| | - Masaru Nagai
- Department of Radioecology, Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho, Aomori 039-3212 Japan
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Yadav P, Le Dizès S. Intercomparison of model predictions of 14C concentrations in agricultural plants following acute exposures to airborne 14C. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2022; 248:106886. [PMID: 35472689 DOI: 10.1016/j.jenvrad.2022.106886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 03/24/2022] [Accepted: 04/07/2022] [Indexed: 06/14/2023]
Abstract
Carbon-14 (14C) is one of the main radionuclides released during normal operation by nuclear power plants, nuclear defense facilities and nuclear fuel reprocessing plants. It is mainly released in the form of carbon dioxide gas denoted 14CO2, which has the specificity of being incorporated into food webs via photosynthesis by primary producing organisms. In order to better assess the environmental and human impacts of 14CO2 under normal operating conditions - or after potential accidental releases - from nuclear facilities, it is necessary to improve our understanding and our predictions of the behaviour of this radionuclide along the human food chain. To achieve this goal, the International Atomic Energy Agency (IAEA) Environmental Modelling for Radiation Safety (EMRAS) model evaluation programme included the Tritium and 14C Working Group (TCWG) which dealt with the intercomparison exercises between several models of environmental transfer in the case of routine and accidental releases of these radionuclides into the environment, and their performance testing. The TOCATTA-χ model developed at IRSN is a dynamic compartment model with high temporal resolution, which simulates the transfer of 14C (and tritium) in grassland ecosystems exposed to gaseous 14CO2 (and HTO) from nuclear facilities under normal or accidental operating conditions. Following this work, IRSN proposed a related project to extend the application of the TOCATTA-χ model to 14C estimates in leafy vegetables, fruits and roots. This article deals with the application of the TOCATTA-χ model to a specific real-case scenario identified within the framework of the TCWG. The scenario provides experimental data and predicted results from models developed at the international level. Model-model and model-data intercomparison exercises were thus carried out to validate the evaluations of the TOCATTA-χ model. In addition, this paper discusses the parameterization of the TOCATTA-χ model for this scenario and the development of modules for 14C concentrations in potato tubers, based on the assumption that photosynthetic transfer occurs directly from leaves to tubers and depends mainly on the growth stage of the tubers. It is observed that the predictions of the TOCATTA-χ model for the concentrations of 14C in leaves and tubers are slightly better than the other models due to the modelling approaches adopted by TOCATTA-χ for the calculation of key ecophysiological processes that govern plant functioning. Overall, the TOCATTA-χ model reduces the Root Mean Square Error (RMSE) by a factor of less than 8 compared to other models. In addition, most of the predicted results of the TOCATTA-χ model better match the measurements and are within the measurement uncertainty limit, while a few are overestimated. This could be due to the high uncertainty associated with the experimentally measured 14C activities, which reflects the field variability in plant growth rate.
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Affiliation(s)
- Pratibha Yadav
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Reactor Safety Division, Bautzner Landstrasse 400, 01328, Dresden, Germany; Institut de Radioprotection et de Sûrete Nucleaire (IRSN), PSE-ENV/SRTE/LR2T, Laboratoire de Recherche sur les Transferts des radionucleides dans les écosystèmes Terrestres, CEN Cadarache, Saint Paul Lez Durance, 13115, France.
| | - Séverine Le Dizès
- Institut de Radioprotection et de Sûrete Nucleaire (IRSN), PSE-ENV/SRTE/LR2T, Laboratoire de Recherche sur les Transferts des radionucleides dans les écosystèmes Terrestres, CEN Cadarache, Saint Paul Lez Durance, 13115, France
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Satoh Y, Imada S, Tani T, Ishimine A, Arai R. Investigation of ratio of carbon to hydrogen (C/H ratio) in agricultural plants for further estimation of their productivity of organically bound tritium. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2022; 246:106845. [PMID: 35172229 DOI: 10.1016/j.jenvrad.2022.106845] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 02/08/2022] [Accepted: 02/10/2022] [Indexed: 06/14/2023]
Abstract
The carbon to hydrogen ratio (C/H ratio, w/w) in plants is a key factor in estimating the amount of hydrogen in the photosynthetic product. The amount of hydrogen calculated from photosynthetic model estimation associated with the C/H ratio is an essential parameter of the estimation model of productivity of organically bound tritium (OBT) by plants. To propose a sophisticated estimation model of OBT by agricultural plants, temporal changes in the C/H ratio of six plant species (Japanese radish, cabbage, orchard grass, paddy field rice, apple, and radish) during their cultivation were investigated for each plant part. The C/H ratio in the plants cultivated in the field and growth chamber generally exceeded 6, which is the value for the primary photosynthetic monosaccharides, such as glucose and fructose (both chemical formulae, C6H12O6). In the vegetative parts (e.g. Japanese radish leaves, cabbage leaves and roots, rice leaves and roots, and radish leaves and fine roots) the C/H ratio fluctuated irregularly or remained constant within an approximate range of 6.6-7.3 during cultivation. The C/H ratio in enlarged organs (e.g. Japanese radish root, rice ear, apple fruit, and radish main root) decreased continuously, approaching 6. These results suggest that the C/H ratio can be generally set as approximately 6.9 except for enlarged organs, in which the ratio may change over time during cultivation, within an approximate range of 6-7.
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Affiliation(s)
- Yuhi Satoh
- Department of Radioecology, Institute for Environmental Sciences (IES), 1-7 Rokkasho, Aomori, 039-3212, Japan.
| | - Shogo Imada
- Department of Radioecology, Institute for Environmental Sciences (IES), 1-7 Rokkasho, Aomori, 039-3212, Japan
| | - Takashi Tani
- Department of Radioecology, Institute for Environmental Sciences (IES), 1-7 Rokkasho, Aomori, 039-3212, Japan
| | - Akinobu Ishimine
- Department of Radioecology, Institute for Environmental Sciences (IES), 1-7 Rokkasho, Aomori, 039-3212, Japan
| | - Ryuji Arai
- Department of Radioecology, Institute for Environmental Sciences (IES), 1-7 Rokkasho, Aomori, 039-3212, Japan
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Renard H, Connan O, Le Dizes S, Solier L, Hébert D, Cazimajou O, Laguionie P, D M. Experimental measurements of the bacterial oxidation of HT in soils: Impact over a zone influenced by an industrial release of tritium in HT form. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2022; 242:106779. [PMID: 34847526 DOI: 10.1016/j.jenvrad.2021.106779] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 11/17/2021] [Accepted: 11/24/2021] [Indexed: 06/13/2023]
Abstract
Tritium is a radionuclide released to the atmosphere by nuclear industries in various forms, mainly HTO and to a lesser extent HT. However, some nuclear sites may emit predominantly HT in the atmosphere. The HT is oxidized to HTO essentially in the top cm of soils, and that the formed HTO is then possibly released into the atmosphere. HTO is an assimilable form by plants. Therefore, it is important to understand the environmental behaviour of HT. In this work, we adapt the bacterial oxidation model of HT in soils of Ota et al. (2007) by laboratory experiments on soils typical of western France, and we have in particular adapted the frequency factor A and the Michaelis-Menten enzymatic reaction parameter (Km) on the basis of an Arrhenius equation in function of the porosity of the soil. We then applied this model to the environment near the reprocessing plant of Orano la Hague (France), which emits a significant amount of HT. Based on the adapted model, and knowing the atmospheric variations of HTO and HT over the period 2013-2016, we estimated that the mean HTO activity in soil due to atmospheric HT reached 0.6 Bq.L-1 (with a peak value of 5 Bq.L-1) while the mean value with all sources taken into account is 6.2 Bq.L-1. Then, in an environment such as that surrounding the Orano La Hague plant, where near-field atmospheric HT activity is very high, the bacterial oxydation contribution to produce HTO in the soil can be considered as approximately 10%. The flux to the atmosphere from these source representing approximately. 1.5 Bq.m-2.d-1. If we consider an area of 2 km around the plant (i.e. 13 km2), we estimate 218 Bq.s-1 of HTO was released by the soil, representing less than 0.1% of the direct atmospheric release of HTO around the site. From this work, it appears clear that this secondary source term from the soil is insignificant at this specific site.
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Affiliation(s)
- H Renard
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LRC, BP 10, rue Max Pol Fouchet, 50130, Cherbourg-En-Cotentin, France
| | - O Connan
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LR2T, BP 3, 13115, Saint Paul Lez Durance, France.
| | - S Le Dizes
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LRC, BP 10, rue Max Pol Fouchet, 50130, Cherbourg-En-Cotentin, France
| | - L Solier
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LRC, BP 10, rue Max Pol Fouchet, 50130, Cherbourg-En-Cotentin, France
| | - D Hébert
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LRC, BP 10, rue Max Pol Fouchet, 50130, Cherbourg-En-Cotentin, France
| | - O Cazimajou
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LRC, BP 10, rue Max Pol Fouchet, 50130, Cherbourg-En-Cotentin, France
| | - P Laguionie
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LRC, BP 10, rue Max Pol Fouchet, 50130, Cherbourg-En-Cotentin, France
| | - Maro D
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE/LRC, BP 10, rue Max Pol Fouchet, 50130, Cherbourg-En-Cotentin, France
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Le Dizès S, Gonze MA. Behavior of 36Cl in agricultural soil-plant systems: A review of transfer processes and modelling approaches. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 196:82-90. [PMID: 30408682 DOI: 10.1016/j.jenvrad.2018.10.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 10/21/2018] [Indexed: 05/25/2023]
Abstract
This article aims to review up-to-date knowledge and data acquired on 36Cl transfers to terrestrial soil-plant systems, evaluate the existing modelling approaches and identify priorities for future model improvements. This update has revealed the existence of fairly recent studies, whose results could be used for improving the modelling approaches which have been developed over the last decade. The priority areas include the consideration of the dry deposition process and the transfer of both gaseous and aerosol 36Cl to plants. The consideration of secondary processes such as the synthesis/mineralization of organochlorines and plant biomass litterfall is not recognized as a priority issue when assessing the impact of gaseous discharges. It was also identified that additional experimental studies had to be conducted to improve the understanding of the processes governing stable Cl and 36Cl dynamics in other terrestrial ecosystems (field crops, vegetables, grass) than forest environments on which most of the reported knowledge and data are reviewed.
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Affiliation(s)
- S Le Dizès
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SRTE/LR2T, Laboratoire de Recherche sur les Transferts de Radionucléides dans les écosystèmes Terrestres, CEN Cadarache, 13115, Saint-Paul-Lez-Durance, France.
| | - M A Gonze
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SEREN/LEREN, Laboratoire d'expertise et d'étude en Radioprotection des Populations et de la Radioactivité dans l'environnement, CEN Cadarache, 13115, Saint-Paul-Lez-Durance, France
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Eyrolle F, Ducros L, Le Dizès S, Beaugelin-Seiller K, Charmasson S, Boyer P, Cossonnet C. An updated review on tritium in the environment. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2018; 181:128-137. [PMID: 29149670 DOI: 10.1016/j.jenvrad.2017.11.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 10/31/2017] [Accepted: 11/01/2017] [Indexed: 06/07/2023]
Abstract
Various studies indicated more or less recently that organically bound tritium (OBT) formed from gaseous or liquid tritium releases into the environment potentially accumulates in organisms contradicting hypotheses associated to methods used to assess the biological impact of tritium on humans (ASN, 2010). Increasing research works were then performed during the last decade in order to gain knowledge on this radionuclide expected to be increasingly released by nuclear installations in the near future within the environment. This review focusses on publications of the last decade. New unpublished observations revealing the presence of technogenic tritium in a sedimentary archive collected in the upper reaches of the Rhône river and findings from the Northwestern Mediterranean revealing in all likelihood the impact of terrigenous tritium inputs on OBT levels recorded in living organisms are also presented. Identifying and understanding the physicochemical forms of tritium and the processes leading to its persistence in environmental compartments would explain most observations regarding OBT concentrations in organisms and definitively excludes that tritium would "bio accumulate" within living organisms.
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Affiliation(s)
- Frédérique Eyrolle
- Institut de Radioprotection et de Sureté Nucléaire (IRSN), PSE-ENV, SRTE, BP 3, 13115 Saint-Paul-lez-Durance, France.
| | - Loïc Ducros
- Institut de Radioprotection et de Sureté Nucléaire (IRSN), PSE-ENV, SRTE, BP 3, 13115 Saint-Paul-lez-Durance, France
| | - Séverine Le Dizès
- Institut de Radioprotection et de Sureté Nucléaire (IRSN), PSE-ENV, SRTE, BP 3, 13115 Saint-Paul-lez-Durance, France
| | - Karine Beaugelin-Seiller
- Institut de Radioprotection et de Sureté Nucléaire (IRSN), PSE-ENV, SRTE, BP 3, 13115 Saint-Paul-lez-Durance, France
| | - Sabine Charmasson
- Institut de Radioprotection et de Sureté Nucléaire (IRSN), PSE-ENV, SRTE, BP 3, 13115 Saint-Paul-lez-Durance, France
| | - Patrick Boyer
- Institut de Radioprotection et de Sureté Nucléaire (IRSN), PSE-ENV, SRTE, BP 3, 13115 Saint-Paul-lez-Durance, France
| | - Catherine Cossonnet
- Institut de Radioprotection et de Sureté Nucléaire (IRSN), PSE-ENV, SAME, Bois des Rames, Bat 501, 91400 Orsay, France
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Ota M, Kwamena NOA, Mihok S, Korolevych V. Role of soil-to-leaf tritium transfer in controlling leaf tritium dynamics: Comparison of experimental garden and tritium-transfer model results. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2017; 178-179:212-231. [PMID: 28910625 DOI: 10.1016/j.jenvrad.2017.09.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 08/24/2017] [Accepted: 09/01/2017] [Indexed: 06/07/2023]
Abstract
Environmental transfer models assume that organically-bound tritium (OBT) is formed directly from tissue-free water tritium (TFWT) in environmental compartments. Nevertheless, studies in the literature have shown that measured OBT/HTO ratios in environmental samples are variable and generally higher than expected. The importance of soil-to-leaf HTO transfer pathway in controlling the leaf tritium dynamics is not well understood. A model inter-comparison of two tritium transfer models (CTEM-CLASS-TT and SOLVEG-II) was carried out with measured environmental samples from an experimental garden plot set up next to a tritium-processing facility. The garden plot received one of three different irrigation treatments - no external irrigation, irrigation with low tritium water and irrigation with high tritium water. The contrast between the results obtained with the different irrigation treatments provided insights into the impact of soil-to-leaf HTO transfer on the leaf tritium dynamics. Concentrations of TFWT and OBT in the garden plots that were not irrigated or irrigated with low tritium water were variable, responding to the arrival of the HTO-plume from the tritium-processing facility. In contrast, for the plants irrigated with high tritium water, the TFWT concentration remained elevated during the entire experimental period due to a continuous source of high HTO in the soil. Calculated concentrations of OBT in the leaves showed an initial increase followed by quasi-equilibration with the TFWT concentration. In this quasi-equilibrium state, concentrations of OBT remained elevated and unchanged despite the arrivals of the plume. These results from the model inter-comparison demonstrate that soil-to-leaf HTO transfer significantly affects tritium dynamics in leaves and thereby OBT/HTO ratio in the leaf regardless of the atmospheric HTO concentration, only if there is elevated HTO concentrations in the soil. The results of this work indicate that assessment models should be refined to consider the importance of soil-to-leaf HTO transfer to ensure that dose estimates are accurate and conservative.
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Affiliation(s)
- Masakazu Ota
- Research Group for Environmental Science, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 Japan.
| | - Nana-Owusua A Kwamena
- Canadian Nuclear Safety Commission, 280 Slater Street, PO Box 1046, Station B, Ottawa, Ontario K1P5S9, Canada
| | - Steve Mihok
- Canadian Nuclear Safety Commission, 280 Slater Street, PO Box 1046, Station B, Ottawa, Ontario K1P5S9, Canada
| | - Volodymyr Korolevych
- Environmental, Radiological and Chemical Sciences Division, STN51A, Canadian Nuclear Laboratories, Chalk River, Ontario, Canada
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