Experimental and modeling studies of radiocesium retention in soils

A two-compartment model was used to describe the irreversible sorption behavior of ¹³⁷Cs on frayed edge sites (FES) of finite capacity in soils in Hong Kong reservoir. The sorption rate was assumed to depend on factors like the fractional water activity concentration, the difference between the activity concentration of ¹³⁷Cs in aqueous phase and that in particulate phase, and the number of available sorption sites. By varying the exponents of the different factors, very good fitting was obtained between experimental data and theory. A relationship between the number of available frayed edge sites and the mass of soil was proposed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sorption of radiocesium on soils in the presence of electrolytes

The influence of background electrolytes (KCl, NH₄Cl, CTABr) in different concentrations on the sorption ability of radiocesium by measuring the distribution coefficient has been studied. Sorption isotherms of cesium for characterization of soil sorption ability were used. Sorption of cesium depends on its concentration and at least three different sorption sites are active in the sorption process. In the case of low cesium concentration, two very selective sites with high distribution coefficients are responsible for the sorption. With increasing cesium concentration in the aqueous phase, distribution coefficient is decreasing. Frayed edge sites of illite in soil and exchangeable potassium are probably responsible for nonlinear isotherms at low cesium concentrations. From sorption isotherms and determination of potassium by activation analysis, it was found that the capacity of very selective sites for different concentrations of background electrolyte was up to 7 mmol·kg^–1.     

Geographical and vertical distribution of radiocesium levels in coniferous forest soils in Izmir

Preliminary picture of ¹³⁷Cs radioactivity levels in forested areas in and around Izmir is illustrated. Both activity concentrations and activity depositions of ¹³⁷Cs in soil samples were determined. Their values varied from 8.29±0.27 to 445±3.16 Bq.kg⁻¹ (d.w.) and 0.63±0.01 to 11.6±0.08 kBq.m^–2 (d.w.), respectively. It was found that while activity deposition of ¹³⁷Cs is normally distributed, activity concentration of ¹³⁷Cs is log-normally distributed in forest soils and the activity deposition is less variable than the activity concentration. Cesium-137 activities in soils increase with increasing elevation, annual average rainfall and soil organic matter.     

Migration of radiocesium in a zeolite-solution system

Some properties of natural zeolite from Zaloka gorica, Slovenia, Yugoslavia were investigated to establish its applicability in solidification and for storage purposes of radioactive waste. It was found that this material is a rather good sorber for cesium, with a capacity of about 0.6 meq g^–1. The migration rate of Cs⁺ in a system ion exchanger-aqueous solution was investigated and correlated with the sorption behaviour of cesium in a system. The leaching rate of cesium from concrete containing zeolite was measured.     

Chernobyl-derived radiocesium in some pharmaceutical plants

The cesium rarioactivity (owing to¹³⁴Cs and¹³⁷Cs) in a number of wild plants of phamaceutical interest harvested in Transylvania was followed during the 1986–1994 period. The data give information on major pathways of vegetable organism contamination through lives from fallout and resuspention and by root uptake from contaminated soil.     

Sorption and desorption experiments using stable cesium: considerations for radiocesium retention by fresh plant residues in Fukushima forest soils

Journal of Radioanalytical and Nuclear Chemistry - We conducted sorption experiments with stable cesium (133Cs) solution in different organic matter samples, aiming to understand the sorption of...     

Chernobyl-derived radiocesium in mosses in the Black Sea area

Radiocesium (¹³⁴Cs and¹³⁷Cs) activity levels in mosses from the Black Sea area, northern Turkey, are reported following the Chernobyl accident during the period of 1989–1991. The cesium radionuclides were detected and measured in all the samples but other longlived radionuclides such as¹⁴⁴Ce and¹⁰⁶Ru were measured in only one sample. The present data support the fact that radioactivity monitoring in mosses can be useful to determine the lasting effect of radioactive contamination.     

Fukushima-derived radiocesium in the western North Pacific in 2014

Journal of Radioanalytical and Nuclear Chemistry - In 2014, we measured activity concentration of radiocesium in the western North Pacific Ocean. In the north of Kuroshio Front high activity...     

Behavior of radiocesium in atmospheric arerosol and fallout in Prague

Radiocesium in ground layer atmospheric aerosol and fallout in Prague has been examined. After a decline in 1986–1988, controlled by a sum of two negative exponentials,¹³⁷Cs aerosol concentration reached a constant level based on an equilibrium between its deposition and resuspension. Deposition velocity was compared to that of⁷Be and²²⁶Ra. It confirmed the supposed source of¹³⁷Cs as resuspension from the ground. Resuspension factor of the order of magnitude of 10^–9 was determined, reminding similar values found earlier in Prague as well as those found in Munich. It also agrees well with the USAEC resuspension model. Solubility of¹³⁷Cs was measured in combined wet and dry fallout. The average undissolved fraction of¹³⁷Cs was found to be about 70% which can be explained by the conditions of the¹³⁷Cs aerosol formation in Chernobyl.     

Long-term monitoring of radiocesium deposition near the Fukushima Dai-ichi nuclear power plant: effect of interception of radiocesium on vegetables

In this study, gross alpha and beta radioactivity in food crops and surface soil collected from Ho Chi Minh City, Vietnam were measured. Based on the annual effective dose from ingestion of food crops, the degree of risk to human health was estimated. We found out that the obtained values of the dose do not exceed the WHO recommended level (290 µSv year^?1). The estimated soil-to-plant transfer factors for gross alpha (TF_α) and beta (TF_β) for food crops were also presented. It was found that TF_α varied in the range from 0.009 ± 0.005 to 0.99 ± 0.06, TF_β varied in the range from 2.26 ± 0.10 to 10.87 ± 0.53 and the maximum values of transfer factors were found in the root of ipomoea batatas.     

Isolation of radiocesium from a fission product mixture

A method of¹³⁷Cs isolation from strongly, acidic solutions of fission products is described, in which vanadyl ferrocyanide is used as a selective ion exchanger for cesium. The effects of the acidity of medium and the carrier concentration on the quantitative yield of separation have been studied and convenient conditions have been found for¹³⁷Cs isolation from the solution of fission products formed after irradiating uranium with neutrons.     

Factors affecting interaction of radiocesium with freshwater solids

The paper aims at the analysis of principal factors affecting the interaction of radiocesium with freshwater solids, important for the migration of radiocesium in rivers. Uptake of radiocesium by bottom sediments and suspended solids from small streams was studied as a function of pH and composition of aqueous phase, of the concentration of cesium in water and of the composition of freshwater solids, using laboratory model experiments. pH had negligible effect on the uptake in the pH range 5–9, the uptake decreased at pH values less than 3–5 depending on the nature and concentration of the solids. Addition of cations suppressed the uptake in the order K⁺>Na⁺>Ca²⁺, the suppression began at 0.001, 0.01 and 0.1 mol.dm^?3 concentration, respectively. Increase in cesium concentration in water caused a decrease of radiocesium uptake, but at very low concentrations of cesium combined with higher concentration of sediment (2g·dm^?3) the uptake was independent of cesium concentration. Removal of carbonates, oxidic coatings and organic matter from a sediment did not affect the sorption properties of the sediment. The nature of the effects found confirms that cesium is sorbed mainly by clay components of freshwater solids. Results obtained are compared with literature data and conclusions are drawn on the importance of the factors studied for modelling of radiocesium migration in rivers.     

Factors affecting interaction of radiocesium with freshwater solids

The paper aims at the analysis of principal factors affecting the interaction of radiocesium with freshwater solids, important for the migration of radiocesium in rivers. Uptake and release of radiocesium by bottom sediment and suspended solids from a small stream were studied as a function of contact time during the uptake and releases, of concentration of the solid phases and of temperature, using laboratory model experiments. Kinetics of the uptake were found to be singificantly affected by temperature and concentration of the solid phase. The kinetics and the concentration effect can be quantitatively described using kinetic model of two parallel or consecutive reactions. Kinetic parameters for the model were determined. Distribution coefficient K_d is independent of sediment concentration in the range of 20–70 mg·dm^?3 but passes through a maximum at higher concentration values. Release of radiocesium adsorbed on the freshwater solids was found to be quite rapid and a simple kinetics of the release from freshwater solids was observed. The amount released decreased with increasing contact time of radiocesium with solid phase. Quantitative evaluation of the release revealed partial irreversibility of radiocesium uptake on the solids studied. Results obtained are compared with literature data and conclusions are drawn on the importance of the factors studied for modeling of radiocesium migration in rivers.     

Uptake of radiocesium and alkali metals by mushrooms

Various mushrooms and soils were analyzed for alkali metals and for radiocesium. The obtained concentration factors of the nonradioactive Cs for mushrooms are not significantly different from that for vascular plants, whereas in the case of radiocesium the values found were orders of magnitude higher. The different behaviour of natural and radioactive cesium may be due to their disequilibrium in the ecosystems. The irradiation of man due to ingestion of contaminated mushrooms cannot cause a significant health risk.     

Sorption-desorption of radiocesium on various sorbents in presence of humic acid

In general, the amount of radiocesium sorbed by the five sorbents with 0.01 mol·dm^–3 NaCl was in order zeolite > NiFeCN–SiO₂ > montmorillonite > aerogel > silica gel. Addition of humic acid solution to the sorbents depressed the sorption of cesium by all sorbents, except for NiFeCN–SiO₂ was not seen, with the greatest effect showing to the aerogel. The presence of humic acid resulted in an enhanced desorption of cesium from zeolite, NiFeCN–SiO₂ and to a lesser extent from montmorillonite and silica gel. The order of cesium retention following desorption for both sorbent and sorbent/humic-acid mixtures was zeolit > NiFeCN–SiO₂ > montmorillonite > silica gel. The presence of humic acid resulted in decreasing of distribution coefficient values for both sorption and desorption processes.     

Investigation of radiocesium biokinetics in Manila clam (Ruditapes philippinarum)

This study was carried out to better understand the biokinetics of radiocesium in clams living in sediment. The accumulation and depuration kinetics of ¹³⁴Cs were investigated in the Manila clam (Ruditapes philippinarum) under controlled laboratory conditions. The concentration factor was found to be 3.0 for ¹³⁴Cs in the whole body; however, the concentration factor in the soft part of the clams (12) was significantly higher than those in the whole body and shell (0.80). The depuration kinetics of the radionuclide were described by a two-component exponential model for the whole body. The biological half-lives in the fast and slow components were found to be 0.63 and 22.1 days, respectively. The depuration kinetics for ¹³⁴Cs in the soft parts were described by a single-component exponential model with a resultant the biological half-life of 18.0 days.     

Rapid determination method of radiocesium in sea water by cesium-selective resin

A rapid and precise method of determining radiocesium corresponding to 5 mrem/y, the Japan AEC's guideline, was proposed. The development and practical performance of cesium-selective resin and the determination method was described in this paper. The resin was prepared by the formation of ammonium molybdophosphate in the structure of Amberlite XAD-7 resin. It took only 3 hours to carry out all the procedures the authors proposed. This value represents 1/10∼1/2 of the time of conventional method. The concentration of¹³⁷Cs and¹³⁴Cs in sea water was determined to be 0.13∼0.16 pCi/1 and less than 7.1·10⁻² pCi/1, respectively.     

Fat tissue is not a reservoir for radiocesium in wild boars

Meat of wild boars is not only known for high ¹³⁷Cs activity concentrations but also for the remarkable constancy of these levels. Even decades after the Chernobyl accident, the ¹³⁷Cs levels in wild boar meat in Central Europe have not declined but even partly increased. In the present study, we investigated an unusual hypothesis for this very unusual phenomenon: may the boars’ fat tissue act as a reservoir for radiocesium? We investigated fat and muscle tissues of four wild boars in Western Germany and found that the ¹³⁷Cs concentrations in fat were in the range of 10–30% of the respective activities in muscle tissue. Hence, the hypothesis was refuted.

     

Use of the inorganic hexacyanoferrate sorbents for analysis of radiocesium in aqueous samples

Journal of Radioanalytical and Nuclear Chemistry - Application of two inorganic hexacyanoferrate sorbents (T-35 and NPF-HTD) for radiochemical analysis of 137Cs in various water samples was...