Publications by authors named "Yasunori Mahara"

Iodine-129, which is a promising tracer for dating old groundwater, has been used as a tracer for deep upwelling groundwater. The nuclide is expected to be one of the key factors for site selection for high-level radioactive waste disposal, which is a global societal issue. The pre-anthropogenic I/I ratio for marine iodine is (1.

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We investigated the tritium concentration in commercial modern DO reagents frequently used in nuclear magnetic resonance analysis for analytical chemistry and in environmental tracer testing. The concentration of tritium in 11 DO and 1 HO reagents ranged from 61 Bq/L (5 × 10 TU) to 2.5 × 10 Bq/L (2 × 10 TU) in order of magnitude.

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The opportunity to measure the concentrations of H and Cl released by the Fukushima nuclear accident in 2011 directly in rain was lost in the early stage of the accident. We have, however, been able to reconstruct the deposition record of atmospheric H and Cl following the accident using a bore hole that was drilled in 2014 at Koriyama at a distance of 60 km from the accident. The contributions of H and Cl from the accident are 1.

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Although 10 years have passed since Japan's Fukushima nuclear accident, the future radiation risk from Cs contamination of wood via root uptake is a serious concern. We estimated the depth at which the roots of evergreen coniferous sugi (Cryptomeria japonica) and broadleaf deciduous konara (Quercus serrata) trees actively take up soil water by using positive δD values from the artificial DO tracer and seasonal changes in the δO values of soil water as a natural environmental tracer. We compared the tracer concentration changes in xylem sap with those in the soil water and ascertained that both tree species primarily took up water from a depth of 20 cm, though with mixing of water from other depths.

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Large areas of forests were radioactively contaminated by the Fukushima nuclear accident of 2011, and forest decontamination is now an important problem in Japan. However, whether trees absorb radioactive fallout from soil via the roots or directly from the atmosphere through the bark and leaves is unclear. We measured the uptake of radiocesium by trees in forests heavily contaminated by the Fukushima nuclear accident.

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We measured (134)Cs and (137)Cs in the surface soil of the Kanto loam in the eastern Tokyo metropolitan area and the Nishiyama loam in Nagasaki, Japan. The observed (137)Cs deposition in the Kanto loam from the Fukushima nuclear power plant (NPP) accident ranged from 4.0 to 77 kBq m(-2), which corresponds to 0.

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We measured the concentrations of (131)I, (134)Cs, and (137)Cs released from the Fukushima nuclear accident in soil and rainwater samples collected March 30-31, 2011, in Ibaraki Prefecture, Kanto district, bordering Fukushima Prefecture to the south. Column experiments revealed that all (131)I in rainwater samples was adsorbed onto an anion-exchange resin. However, 30% of (131)I was not retained by the resin after it passed through a soil layer, suggesting that a portion of (131)I became bound to organic matter from the soil.

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