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  • Author or Editor: Š. Palágyi x
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Abstract  

The vertical distribution of85Sr and137Cs in undisturbed single-contaminated agricultural soils have been studied during their irrigation with wet atmospheric precipitation in dependence on time under laboratory conditions for about one year. The soil samples were collected from several localities in the environment of nuclear power plants at Dukovany and Jaslovské Bohunice using a special auger. The samples were placed into polyethylene columns of 9 cm in diameter and 20 cm in height. The activity of radionuclides in soil profiles after their separation into single layers were counted by Ge(Li) semiconductor gamma-spectrometry. Based on the exponential depth distribution of radionuclides, the values of their migration parameters as relaxation depth, migration rate and retardation factor were calculated. The influence of the permanent grass cover and of the applied zeolite on the migration parameters of these radionuclides was also investigated.

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Abstract  

Sorption of radionuclides on homogenized soils (under 2.5 mm grain size) from synthetic groundwater of 8·10−3M ionic strength and pH 8.5 has been studied under dynamic (flow) and static (batch) conditions. The corresponding water-soluble compounds, as carriers in the 10−6 mol/dm3 concentration, were added into the SGW prior to the experiments. Soil samples were taken from several locations around the environment of the High Level Waste Storage Facility at Nuclear Research Institute Řež plc in 5–100 cm depth. The dynamic experiments were carried out in columns made of PP+PE injection syringes of 17.8 cm length and 2.1 cm in diameter. A multi-head peristaltic pump was used for pumping the water upward through the columns at a seepage velocity of about 0.06 cm/min in average. The radioactive nuclides were added into the water stream individually in a form of a short pulse in 0.1 cm3 of demineralized water. Dynamic desorption experiments were performed with the same experimental arrangement using a mixture of 10−2N H2SO4 and 10−2N HNO3 in a volume ratio of 2: 1. Retardation, distribution and hydrodynamic dispersion coefficients during transport of radionuclides were determined by the evaluation of the integral form of a simple advection-dispersion equation, used for fitting experimental data and modeling the theoretical sorption breakthrough and desorption displacement curves. The static experiments were realized in 100 cm3 plastic bottles stirring 5 g of soil samples with SGW occasionally in a soil to SGW ratio of 1: 10 (m/V). Kinetic parameters including equilibrium sorption activity, activity transfer rate constants and sorption half-times were also determined. The results of dynamic experiments were compared with static sorption experiments.

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Abstract  

The sorption of cadmium labeled with 109Cd in nitrate form, from aqueous solutions in different horizons of some arable and forest soils was studied under static (batch) conditions. Before sorption, a method of sequential soil treatment was applied, which consist in the consecutive removal of individual soil components by the use of appropriate reagents and procedures. Three sorption isotherms were tested. Kinetic studies showed that the sorption of cadmium is rather rapid and it can be well described by a Freundlich or a linear isotherm, whereas the closeness of Langmuir isotherm to the experimental results is lower. From the different sorption isotherms, it would also be possible to estimate the effect of individual components on the sorption of cadmium in soils. It was found that the untreated soils exhibit the highest sorption and the sorption decreases in the order of untreated > acetate treated > water treated > peroxide treated > dithionite treated soil. Sorption of cadmium increases with the depth of the studied soils disregarding their chemical treatment.

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Abstract  

The vertical migration of 85Sr, 137Cs and 131I in some arable and undisturbed single-contaminated soils was studied by gamma-spectrometry measurements under lysimetric laboratory conditions during irrigation of the soil profiles with wet atmospheric precipitation for about one year, except 131I. A new simple exponential compartment (box) model was derived, which makes it possible to calculate the migration rate constants and migration rates in the individual soil layers (vertical sections) as well as the total vertical migration rate constants and total vertical migration rates of radionuclides in the bulk soil horizon. The relaxation times of radionuclides in respective soil horizons can also be evaluated.

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Abstract  

A method has been developed for the determination of113mCd from fallout in large-volume environmental water samples. In the analytical procedure a known amount of cadmium carrier is added to the sample and the cadmium is preconcentrated as insoluble hydroxide by coprecipitation with ferric hydroxide. The separated cadmium is purified from other interfering elements by an anion—exchange procedure. Finally, cadmium is coprecipitated with copper sulfide, and the radioactivity of113mCd is measured in a lowbackground, gas-flow proportional beta counter. The cadmium recovery is established by determining the amount of Cd in the precipitate using an energy dispersive x-ray fluorescence spectrometer. For a 24hr counting period a lower limit of detection around 50μBq113mCd/1 of sample has been attained. Samples of Lake Michigan water were analyzed: the concentration of113mCd in 1980 was 177±5 μBq/l.

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Abstract  

A simple method for rapid determination of131I in soil is described. The method is based on the specific separation and concentration of radioiodine from the soil extract with a liquid anion exchanger and measuring its radioactivity with liquid scintillation counting. The131I from soil is extracted with aqueous solution of sodium hydroxide. The method permits the determination of131I with a lower limit of detection less than 0.1 Bq/10 g of soil.

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Abstract  

The method is based on the resiliency of the open-cell polyurethane foam filling used in a pulsing bed column. A liquid anion exchanger containing I2 has been used as a hydrophobic organic phase immobilized in the polyurethane foam matrix. Forced flow of the mobile phase during successive pulsing of the column bed results in high preconcentration factors with practically quantitative separation yields. The pulsated column technique may also be conveniently automated. It can be utilized most advantageously for the rapid determination of low activity radioiodine in environmental waters mainly in routine field analysis.

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Abstract  

Polyether type polyurethane foams (PU) are regular stacks of solid quasi-spherical membranes produced by the reaction of polyisocyanates with polyols of polyether nature in the presence of a catalyst and a blowing agent. Contrary to conventional membrane separations, where a solid membrane is merely a differentially separating agent, or a transport medium, PU foams, apart from separation and preconcentration, also retain, i.e., sorb the species on, or in the membranes. Therefore, PU foam membranes can be considered to act as true sorbents. The membrane properties of PU foam sorbents offer unique advantages over conventional bulk type granular sorbents in rapid, versatile and effective separations and preconcentrations of different compounds from fluid samples. Unloaded PU foam sorbents have received considerable attention in the separation of different trace inorganic species.

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Abstract  

Theoretical separation efficiencies in one-stage static and multistage dynamic models of liquid-liquid extraction have been studied mathematically. By the use of the iterative numerical method the maximum difference between separation efficiencies in these two models, as well as the absolute values of the respective separation efficiencies were calculated at this maximum. The maximum difference between multistage and one-stage separation efficiencies amounts to 20.36%, when the respective separation efficiencies are about 91.89% and 71.56%.

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Abstract  

Transport and sorption of water-soluble 85Sr2+ and 125I in the columns with beds of crushed crystalline rocks from synthetic groundwater has been studied under dynamic flow conditions. Samples of crystalline rocks: diorite-I, diorite-II, gabbro, granite and tonalite, having the grain size between 0.25 and 0.80 mm, were used. Plastic syringes of 8.8 cm length and 2.1 cm in diameter were applied as columns. The synthetic groundwater was pumped downward through the columns with a seepage velocity of about 0.2 cm/min and the given radioactive nuclide was added into the water stream individually in a form of a short pulse. In case of 85Sr, desorption from diorite-I was also studied using an artificial acid rainfall and then, the longitudinal distribution of the residual 85Sr activity along the bed was measured. Retardation, distribution and hydrodynamic dispersion coefficients were determined by the evaluation of respective breakthrough curves. A corrected integral form of a simple advection–dispersion equation was derived and used for fitting the experimental data. The K d-parameters resulting from dynamic experiments were also compared with the results of static sorption experiments.

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