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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

Impacts of anthropogenic source from the nuclear fuel reprocessing plants on global atmospheric iodine-129 cycle; A Model analysis

Kadowaki, Masanao; Katata, Genki*; Terada, Hiroaki; Suzuki, Takashi; Hasegawa, Hidenao*; Akata, Naofumi*; Kakiuchi, Hideki*

Atmospheric Environment, 184, p.278 - 291, 2018/07

 Times Cited Count:8 Percentile:49.71(Environmental Sciences)

The long-lived radioactive iodine ($$^{129}$$I) is a useful geochemical tracer in the atmospheric environment. We recently observed clear seasonal trends in air concentration and deposition of $$^{129}$$I in Japan. Using these data, we developed a global atmospheric $$^{129}$$I transport model to reveal key processes for the global atmospheric $$^{129}$$I cycle. The model generally reproduced the observed seasonal change in air concentration and deposition of $$^{129}$$I in Japan, and the global distribution of $$^{129}$$I concentration in rain as presented in past literature. Numerical experiments changing the intensity of anthropogenic and natural sources were conducted to quantify the impact of anthropogenic sources on the global $$^{129}$$I cycle. The results indicated that the atmospheric $$^{129}$$I from the anthropogenic sources was deposited in winter and can be accumulated mainly in the northern part of Eurasia. In contrast, the atmospheric $$^{129}$$I from the natural sources dominated the deposition in summer. These results suggested that the re-emission process of $$^{129}$$I from the Earth's surface may be important as a secondary impact of $$^{129}$$I in the global-scaled environment. Furthermore, although wet deposition dominated the total deposition in the Northern hemisphere, dry deposition regionally and seasonally contributed to the total deposition over arctic and northern part of Eurasia in winter, suggesting that the dry deposition may play a key role in the seasonal change of $$^{129}$$I deposition in the Northern hemisphere high latitudes.

Oral presentation

Development of a global transport model for airborne iodine-129 including atmospheric photolysis and gas-particle conversion processes

Kadowaki, Masanao; Katata, Genki*; Terada, Hiroaki; Suzuki, Takashi; Hasegawa, Hidenao*; Akata, Naofumi*; Kakiuchi, Hideki*

no journal, , 

Iodine-129 ($$^{129}$$I) has been shown as a useful isotope for dating of water, tracing of marine sediments and investigating the geochemical cycle of iodine. Main sources of atmospheric $$^{129}$$I are volatilization from ocean and discharge from nuclear fuel reprocessing facilities. Although released $$^{129}$$I is globally transported in the atmosphere and deposited to the Earth's surface, spatial and temporal distributions of atmospheric $$^{129}$$I are still not well understood. In this study, we developed an atmospheric global transport model of $$^{129}$$I which includes the processes such as advection and turbulent diffusion, dry and wet deposition, discharge from nuclear fuel reprocessing facility, volatilization from ocean and atmospheric chemical reactions (atmospheric photolysis and gas-particle conversion). Input meteorological fields of three-dimensional components of wind, air temperature, atmospheric pressure, and turbulent diffusion coefficient were calculated using WRF (Weather Research and Forecasting) with ERA-Interim dataset. The simulation period was set to be from 1 Jan 2006 to 31 Dec 2010. For model validation, we used air concentration and deposition of gaseous and particulate forms of $$^{129}$$I measured at Rokkasho in Japan from 2006 to 2010 and past measurements of $$^{129}$$I concentration in rain water in Europe, Asia, and North America. The model successfully reproduced the seasonal variations of measured air concentration and deposition of $$^{129}$$I at Rokkasho as maximum and minimum values during the wintertime and summertime, respectively. Furthermore, spatial patterns of simulated $$^{129}$$I concentration in globe were similar to those of measurements. In the presentation, key factors in controlling the spatiotemporal distribution of airborne $$^{129}$$I and its cycle in the atmosphere suggested by model results will be discussed.

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