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Updated: Apr 27, 2026

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films
Published on: November 9, 2015
Vertical distribution and migration of global fallout Pu in forest soils in southwestern China
Wenting Bu1, Jian Zheng2, Qiuju Guo3
1State 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.
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.
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