Simple Methods for Estimating the Migration Rate of Excess 210Pb in Undisturbed Soil.

概要

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Two simple methods were developed to calculate migration rates of excess radioactive 210Pb from undisturbed soil profiles. The migration of excess 210Pb was described by one-dimensional differential equation with decay term under steady state. One method (method 1) assumes a constant migration rate of excess 210Pb in the ground. This assumption gives resultantly the constant initial concentration of excess 210Pb per unit bulk volume at the ground surface. The other method (method 2) assumes that the migration flux of 210Pb through the ground decreases only by radioactive decay. The latter method can estimate the travel time of 210Pb from the ground surface to any horizon of interest.Undisturbed soil samples were taken at Kyoto City, Japan. 210Pb and 226Ra contents were analyzed to get an excess 210Pb profile in the ground. Each method was applied to the observed profile. The resultant migration rate was respectively found to be 0.70 and 0.25-1.00mm/y for methods 1 and 2. These results could be applied well to evaluate the stable Pb migration through the ground.
日本保健物理学会の論文