Sorption of ~(125)I-, ~(137)Cs~+, ~(85)Sr~(2+) and ~(152,154)Eu~(3+) during their transport in undisturbed vertical and horizontal soil cores under dynamic flow conditions

摘要

Transport and sorption of ~(125)I-, ~(137)Cs+, ~(85)Sr~(2+) and ~(152,154)Eu~(3+) in undisturbed soil cores have been studied under dynamic conditions. Radionuclides were dissolved in synthetic groundwater (SGW) of 0.015 mol/dm~3 ionic strength, pH 8.4 and redox potential E_h = 145 mV. The soil samples were taken vertically and horizontally from the river bed at 5-100 cm depths, about 120 m southward of the Dukovany Low and Medium Level Radioactive Waste Repository. The respective water-soluble carriers in the 10~(-6) mol/dm~3 concentration were added into the SGW prior to the experiments. The soil cores of 9 cm height and 3.8 cm in diameter were placed into columns made of 150 cm~3 PE injection syringes of suitable dimensions. The SGW was introduced into columns from the Mariotte's bottle through a glass manifolds to supply the soil columns by gravity flow at a constant flow-rate about 1.2 cm~3/h. Into the water stream, radioactive nuclides were added individually in a form of a short pulse in 0.1 cm~3 of demineralized water. In the case of ~(125)I~- transport, retardation and hydrodynamic dispersion coefficients were determined, using an integral form of a simple advection-dispersion equation. For each radionuclides, sorption and desorption data have been obtained, evaluated and the results were compared mutually. Residual distributions of the sorbed cationic radionuclides along the soil columns were also presented.