title: Vertical distribution and migration of global fallout Pu in forest soils in southwestern China.
abstract: Soil samples collected in southwestern China were analyzed for Pu isotopes. The (240)Pu/(239)Pu atom ratios were around 0.18, which indicated the dominant source of global fallout. Consistent sub-surface maximums followed by exponential decline of (239+240)Pu activities in the soil cores were observed. Most of the Pu has still remained in the 0-10 cm layers since its deposition. Convection velocities and dispersion coefficients for Pu migration in the soils were estimated by the convection-dispersion equation (CDE) model. The effective convection velocities and effective dispersion coefficients ranged from 0.05 to 0.11 cm/y and from 0.06 to 0.29 cm(2)/y, respectively. Other factors that control the vertical migration of Pu in soil besides precipitation, soil particle size distribution and organic matter were suggested. Long-term migration behaviors of Pu in the soils were simulated. The results provide the Pu background baseline for further environmental monitoring and source identification of non-global fallout Pu inputs in the future.
authors: State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China; Research Center of Radiation Protection, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage, Chiba 263-8555, Japan.
authors: Wenting
authors: W
authors: Bu
authors: Research Center of Radiation Protection, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage, Chiba 263-8555, Japan. Electronic address: jzheng@nirs.go.jp.
authors: Jian
authors: J
authors: Zheng
authors: State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China. Electronic address: qjguo@pku.edu.cn.
authors: Qiuju
authors: Q
authors: Guo
authors: Research Center of Radiation Protection, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage, Chiba 263-8555, Japan.
authors: Shigeo
authors: S
authors: Uchida
mesh_terms: D002681:China; D065928:Forests; D013058:Mass Spectrometry; D011005:Plutonium / Q000032:analysis*; D011834:Radiation Monitoring; D011847:Radioactive Fallout / Q000032:analysis*; D012990:Soil Pollutants, Radioactive / Q000032:analysis*
chemical_list: D011847:Radioactive Fallout; D012990:Soil Pollutants, Radioactive; D011005:Plutonium
keywords: CDE model; Downward migration; Pu isotopes; Soils; Southwestern China