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Vertical migration of 137Cs in the South Caspian soil
Published online by Cambridge University Press: 26 September 2012
Abstract
In order to study the vertical migration of anthropogenic 137Cs, soil inventories of this radionuclide were measured in two regions selected on the basis of a previous comprehensive survey in the northern Iranian province of Guilan located in the South Caspian region. Ten sampl ing stations were randomly chosen in these regions and split-level sampling was carried out to a depth of 30 cm. Sample analysis was performed using a HPGe detector system. In situ gamma measurements in both regions were als o carried out with the aid of a portable germanium spectrometer. The experimental data were then compared with the solution of the convection-dispersion equation (CDE) with the proper initial and boundary conditions to evaluate initial deposition as well as transport parameter values. The solution, including the effects of both considered sources, i.e. global fallout and Chernobyl releases, fits the measured data well. The effective convection velocity and dispersion coefficients of 137Cs lie in the range of 0-0.25 cm·y-1 and 0.32-0.75 cm2·y-1, respectively, indicating a very slow migrat ion rate in the area. Most of the deposited 137Cs still remained in the top 10-cm layer. Moreover, the fitted depth profiles were then employed to correct the surface activities of 137Cs estimated by in situ measurements.
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- © EDP Sciences, 2012
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