Behavior Of 90Sr Research Articles

Application and Experimental Substantiation of the Radioecological Model for Prediction in Behavior 90Sr in Cultivated Soil-Crop System: A Case Study of Two Experimental Agricultural Fields.

The radioactive fission product 90Sr has a sufficient half-life (28.8 years) to be detected long after its appearance in the environment. After its uptake into the soil-edible plant system, it enters the food chain and represents a potential source of contamination that threatens human health. Due to these facts, tracking the distribution of the artificial radionuclide 90Sr in the soil-edible plant system is a subject of intense research. The tracking of the 90Sr radionuclide distribution in the soil profile, as well as in the crops on the long-term experimental fields was carried out using beta radiation spectrometry. The radiochemical analytical method was used to analyze the 90Sr content in cultivated soil and crops. The conducted study focused on the experimental substantiation of the developed model for predicting the behavior of 90Sr in the cultivated soil-crop system. The results of using the applied radioecological model for the transfer of 90Sr from the soil to the above-ground part of crops showed a relatively good agreement with the experimentally determined values of the soil-crop transfer factor, which indicates that the used model can be successfully applied for the prediction of the behavior of 90Sr in the soil-soil solution-crop system.

Study on advection–dispersion behavior for simulation of 3H, 99Tc, and 90Sr transport in crushed sandstone of column experiments

Abstract In order to establish a universal and safety-compliant post-closure safety assessment technique, it is necessary to develop appropriate models to explain the migration behavior of radioactive materials within the rock system. Advection-dispersion experiments (ADE) have proven successful in designing transport models through a calibration/validation process of breakthrough curves (BTCs). In the present investigation, we employed a dynamic column device to examine the transport of Tritium (3H), Technetium-99 (99Tc), and Strontium-90 (90Sr) in crushed sandstone. Non-reactive transport experiments utilizing conservative tracers enabled us to determine the transport parameters, including retardation factors (R) and dispersivity (α). Our study focused on investigating the surface complexation model (SCM) using an additive approach coupled with the advection-dispersion equation to simulate the reactive transport behavior of 90Sr. The results affirm the robustness of our chosen thermodynamic database and modeling approach, emphasizing the criticality of accurately modeling and predicting reactive transport behavior in porous media.

Analysing the behaviour of 90Sr and stable Sr in highly weathered soils: Soil to plant transfer factor and geochemical partitioning

Public concerns over environmental protection have increased after Fukushima accident. The soil-plant transfer factor (Fv) is a critical parameter for environmental risk assessment. 137Cs Fv values determined in acid Brazilian soils could be two orders of magnitude higher than Fv values measured in soils affected by the Chernobyl accident. This paper studied the behaviour of 90Sr in Brazilian soils where very few 90Sr Fv data is available. All classes of studied soils (Ferralsol, Acrisol and Nitisol) showed that more than 80% of total 90Sr in soils remains potentially mobile, mainly at the bioavailable phase, more than 2 years after soil contamination in an experiment conducted in lysimeters. Higher 90Sr Fv for maize and cabbage was observed in the acid soils with low content of exchangeable Ca, lower Fv values occurred at Nitisol, the subtropical soil type. It seems that the behaviour of 90Sr in these soils are mainly controlled by ionic competition mechanisms occurring for root uptake and sorption sites, with stable Sr and major nutrients (Ca, Mg and K). The mineralogy also seems to play a relevant role, since goethite rich clay soil presented 90Sr Fv values higher one or two orders of magnitude than 90Sr Fv values observed at clayed soil goethite rich with trace of vermiculite, for all studied crops. The high rate of 90Sr migration down the soil profiles observed for the studied soils during the 2 first years after contamination suggests a high rate of transfer to groundwater, even transfer to leafy crop group can be also a relevant pathway. In the present study, maize, among other plant species, presented the lowest Fv values, even when compared with maize cultivated in temperate soil. Our results suggest that stable Sr may not be a very good analogue of 90Sr for determining plant Fv values: geometric mean of stable Sr Fv for maize was Fvmaize = 6.3E-1 ± 2.1E0 (n = 8) and for 90Sr was Fvmaize = 1.8E-2 ± 2.5E0 (n = 16), geometric mean of stable Sr Fv for cabbage was Fvcabbage = 1.4E0 ± 3.9E0 (n = 17) and for 90Sr was Fvcabbage = 7.9E-1 ± 4.4E0 (n = 18).

Fresh Groundwater Discharge as a Major Source of 90Sr into the Coastal Ocean.

The behavior and source of 90Sr in the coastal ocean remain uncertain. Here, we investigated the distributions of 90Sr in coastal fresh groundwater, river water, pore water, and seawater in three bays along the southeastern coast of China between 2019 and 2021 and evaluated the potential of submarine groundwater discharge (SGD) as a source of coastal 90Sr. The 90Sr activity in coastal fresh groundwater was higher than that in river water and seawater, while the 90Sr activity in pore water was comparable to that in adjacent seawater. In addition, nonconservative mixing behavior of 90Sr along the salinity gradient between river water and seawater was observed. These observations indicated that fresh SGD may serve as an additional source of 90Sr in coastal seawater. Combining our groundwater 90Sr data with the reported fresh SGD flux data, the estimated fresh SGD-derived 90Sr fluxes into the three bays were comparable to or even higher than those supplied by riverine sources. These results revealed that fresh SGD is a major but overlooked source of 90Sr in the coastal ocean. This subterranean pathway for transport of 90Sr to the coastal ocean should be considered in the monitoring and risk assessment of coastal areas, especially those near nuclear facilities.

Effect of seawater intrusion on radioactive strontium (90Sr) sorption and transport at nuclear power plants

Abstract Batch sorption and column experiments were conducted to investigate and compare sorption and transport behavior of 90Sr on the assumption of seawater intrusion at nuclear power plants. Batch sorption experiments were carried out on fractured rocks and bedrocks using synthetic groundwater and seawater both spiked with 90Sr. In general, higher 90Sr sorption occurred on fractured rock samples than on bedrocks, because of the presence of weathered secondary minerals (iron oxide and clay) on fractured rock surfaces. However, one particular bedrock sample (WSP-B) which has higher porosity and carbon amount than fractured rock samples also showed the higher 90Sr sorption than its comparable fractured rocks. For all batch sorption studies, 90Sr sorption distribution coefficient, K d decreased from groundwater to seawater environment due to the higher ionic strength of seawater (6.4×10−1–7.7×10−1 M) compared to groundwater (4.0×10−3–6.0×10−3 M). The three different ionic strength solutions were used in column experiments, and the results showed that transport behavior of Sr through a fractured rock had similar sorption trend to batch sorption results. The highest mobility (or least retardation) for Sr was found for 100% seawater solution compared to the highest retardation (or least mobility) for 100% groundwater solution. These sorption and transport data of Sr on solid materials contacted with various ionic strength solutions corroborate empirically defensible information for assessment of radioactive contamination in groundwater below the NPP sites located nearby shores. In addition, the experimental data will be incorporated to improve transport models of 90Sr in the subsurface environment for severe nuclear accidents.

Long-term behavior of 90Sr and 137Cs in the environment: Case studies in Switzerland

We present long-term records of the 137Cs and 90Sr activity concentrations in soil, grass and milk from two lowland and two alpine pastures of Switzerland. The data is used for better understanding the long-term behavior of these radionuclides in the environment. Transfer factors between compartments are used as qualitative indicators of the magnitude of transfer and as a way to compare different elements (e.g. Cs and Sr) in similar conditions. The long-term behavior was quantified by means of the effective half-life which integrates all processes that cause a decrease of activity in a given medium such as leaching, fixation, erosion and radioactive decay. Our study shows that 90Sr is more likely transferred from alpine soil to grass than 137Cs. This is explained by a stronger fixation of Cs in the soils. We observed higher transfers of 90Sr to grass in soils with lower Ca concentrations, and vice versa. In contrast, the transfer of 137Cs to grass was not affected by the variations of the K content in the soil. We provide evidence that shows that 137Cs, after intake by dairy cattle, is more likely transferred to milk than 90Sr. However, as the 90Sr and Ca transfers to milk are influenced by parameters/processes that were not taken into account in our study, our result cannot be entirely validated. The effective half-lives of 137Cs and 90Sr in soil, grass and milk corresponded with previous estimates in alpine soils. We have found that processes other than radioactive decay are responsible for a major decrease of the 90Sr activity in soil. For 137Cs, on the other hand, radioactive decay is among the most relevant process. Our data shows to be of interest in studying the trends of behavior of radionuclides in alpine regions.

Impact of environmental conditions on the sorption behavior of radionuclide 90Sr(II) on Na-montmorillonite

Clay minerals have been studied extensively due to their strong sorption and complexation ability toward various environmental pollutants. In this study, the sorption of 90Sr(II) on Na-montmorillonite was studied as a function of various environmental conditions such as pH, ionic strength, humic acid (HA) and temperature. The results indicated that the sorption of 90Sr(II) on Na-montmorillonite was strongly dependent on pH and ionic strength. The experimental data of 90Sr(II) sorption was simulated by the diffuse-layer model (DLM) well with the aid of Visual Minteq 3.0. At low pH, the sorption of 90Sr(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on Na-montmorillonite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of HA enhanced 90Sr(II) sorption at pH<7.0 but decreased 90Sr(II) sorption at pH>7.0. Langmuir and Freundlich models were used to simulate the sorption isotherms of 90Sr(II) at three different temperatures of 303, 318 and 333K. The thermodynamic parameters (ΔH, ΔS and ΔG) calculated from the temperature-dependent sorption isotherms indicated that the sorption of 90Sr(II) on Na-montmorillonite was an endothermic and spontaneous process. The thermodynamic parameters calculated from temperature-dependent sorption data were crucial to understand the interaction behavior of 90Sr(II) with Na-montmorillonite.

The state of Lake Ladoga pollution by global 90Sr, 137Cs, and 239,240Pu

The state of radioactive pollution of Lake Ladoga has been studied. The purification half-life of lake water from 90Sr was found to be 21.7 year. The ratio of 90Sr storage in lake water volume to its storage in silts (0–10 cm layer) was 2: 1. Lake water purification from global 137Cs was slower than that from 137Cs originating from Chernobyl emergency emission because of the chronic supplement of global 137Cs reserve by atmospheric fallouts. The behavior of 90Sr, 137Cs, and 239,240Pu in bed soils was in agreement with the geochemical nature of the elements. By the distribution of 239, 240Pu in bed soils, the sedimentation of substances of non-radiation nature was estimated at 0.3 and 0.5 mm/year at denting and flat relief, respectively.

Effect of liming on the behaviour of 90Sr and 137Cs in a lake ecosystem

Liming of lakes is considered one possible remedial action to reduce the accumulation of radionuclides into fish in the case of a radiological accident. These responses were tested in field conditions in a small acidified lake that was divided into two parts: one limed with CaCO 3 and the other half left as an unlimed control. The transfer of 90Sr from water into fish decreased on average by 50% during the first year after liming. However, at the same time the 90Sr concentration in water increased, reaching a maximum within 6 months after liming. Approximately 50% more 90Sr was detected in water in the limed part of the lake than on control side during the first year. 90Sr was most probably released from the sediment as the Ca concentration and pH of the water increased. As a result of these two processes, which counterbalanced each other (increased release of 90Sr into water from sediment and decreased transfer of 90Sr from water into fish), the 90Sr concentration in fish did not notably differ between the limed and control sides of the lake. Liming may only be suitable as a remedial action if carried out immediately after a radiological accident, before significant amounts of radionuclides have been deposited in lake sediments. In the case of 137Cs, the effect of liming was less pronounced. 137Cs activity concentration in water increased in the first year by 20% and uptake by fish decreased by 20%.

Transfer of 90Sr into fish in Finnish lakes

The long-term behavior of 90Sr was investigated from 1987 to 1997 in fifteen lakes in southern and central Finland following the 1986 Chernobyl accident. Both water and fish samples (perch, pike, vendace) were analyzed. 90Sr stays long in the freshwater ecosystem; the observed half-lives during the study period were generally around 10 years in water and even longer in fish. One lake exhibited very different behavior for 90Sr, with elevated levels in fish and water and very short observed half-life in fish, less than 2 years. Concentration factors of 90Sr in fish (Bqkg −1 f.w. in fish/Bqkg −1 in water) among the studied lakes significantly correlated with both the Ca concentration and electrical conductivity of the water. More 90Sr was transferred into fish in lakes with a low electrical conductivity and a low Ca concentration. Among other water parameters evaluated were pH, color, total nitrogen, and phosphorus.

Application of mathematical modelling techniques for evaluation of radionucleide accumulation levels in biota

In the majority of the cases associated with radioactive contamination of the environment, forest and lake ecosystems as natural filters and radionuclide storages relate to critical ecosystems. These two types of natural ecosystems as well as meadow prevail in the areas where NPP are located. To solve the entire complex of radioecological problems, the authors have developed the models for 137Cs and 90Sr migration in forest ecosystems that take into account the transformation processes of 137Cs and 90Sr in a soil-litter system, age- and season-specific dynamics for the tree layer and seasonal biomass changes in the understory, as well as radionuclide entering into food chains. A mathematical model for the migration of varied kinds of admixtures is developed and enhanced on the pattern of the 90Sr, 106Ru, 125Sb, 137Cs, 144Ce radioactive micro-admixture in lake ecosystems. The model takes into account the fact that micro-admixture withdraws out of the water both as a result of molecular/ ion-exchanging sorption on the boundary of the bottom sediments/ water layer and as a result of the detritus-forming process. When describing a vertical radionuclide migration in bottom sediments through a diffusion equation, the increase in the bottom sediment layer is considered. The authors have developed the mathematical models describing a long-term behavior of 90Sr and 137Cs in meadow ecosystems and taking into account basic processes that define the 90Sr and 137Cs biological accessibility for root absorption as well as the transformation processes in soil. For the assessment of biological effects of a radiation factor on the biota, a complex of dosimeter models is developed to evaluate the internal/ external doses to biota taking into account different geometry of the exposure source of ionizing radiation. The represented mathematical models were successfully used during an environmental expertise performed for a number of Russian NPP and also when assessing environmental effects from the implementation of countermeasures in the Mayak facility region, as well as the effects of radioactive contamination in the Bryansk Region resulted from the Chernobyl accident. The complex of mathematical migration and dosimeter models developed by the authors may be used to solve theoretical or applied radioecological issues with regard to the investigation of radionuclide behavior peculiarities in different ecosystems, as well as the evaluation of radiation impacts on organisms, populations or entire ecosystems. Besides, the models can be parameterized for specific forest/ water/ meadow ecosystems in varied situations associated with nuclear pollution of environment.

Comparative migration behaviour of 90Sr, 239+240Pu and 241Am in mineral and organic soils of France

The vertical migration of 90Sr, 239+240Pu and 241Am has been studied in two types of soils in France (acid forest soil in the Vosges Mountains and organic-rich alkaline wetland in the Mercantour area). In order to interpret the different migration behaviour of radionuclides, the combination of two approaches are proposed – a statistical study of the evolution of radionuclide ratios ( 241Am/ 239+240Pu, 90Sr/ 239+240Pu) with depth and a calculation of the radionuclide migration rates. Migration behaviour of 90Sr, 239+240Pu and 241Am is significantly different in the Vosges and Mercantour soils. In the Mercantour soil 241Am was found to be less mobile than 239+240Pu. In both profiles 90Sr is more mobile than 239+240Pu. The high sand content (55–60%) and weathering processes of cations in the Vosges soil are thought to be responsible for the larger migration rates of radionuclides in depth, while the high organic matter content (>70%) of Mercantour soil is thought to be responsible for the stronger retention of 241Am in the first 10 cm of the soil.

Ecological half-lives of 90Sr and 137Cs in terrestrial and aquatic ecosystems

This paper describes the long-term behaviour of 90Sr and 137Cs in foods, feeds and a variety of environmental media. The long-term behaviour is quantified by means of the ecological half-life which integrates all processes that cause a decrease of activity in a given medium such as leaching, fixation and erosion. A large number of long-term time series of concentrations of radiocaesium and radiostrontium in these media have been identified and re-evaluated using a standardised statistical procedure to establish reference data sets of ecological half-lives. By example of undisturbed soils and marine water bodies it is shown that the ecological half-life concept is questionable if the distribution of the radionuclide of interest within the medium studied is non-uniform and if mixing and transport processes within this medium, therefore, are of considerable importance during the time period of observation.

Quantitative assessment of the long term behaviour of 90Sr in Lake Uruskul, Southern Urals, Russia

The present paper is aimed at assessing the long term behaviour of 90Sr migration from water to bottom sediments of Lake Uruskul, Southern Urals, Russia. The lake was contaminated following the nuclear accident at the Mayak nuclear complex in 1957 (the Kyshtym accident). Some transfer parameters relevant to the behaviour of 90Sr in the water–sediment system were evaluated: a) the radionuclide migration velocity from the water column to the bottom sediment, b) the radionuclide migration rate from bottom sediment to water, and c) the radionuclide migration rate from bottom sediment to deep sediment. The estimated values of the above parameters were 6.4×10 −8 m s −1, 5.7×10 −10 s −1 and 5.2×10 −10 s −1, respectively. These values were compared with data obtained for some Italian lakes contaminated by 90Sr after the nuclear weapons tests fallout. The relatively low radionuclide migration from water to sediment of these lakes is reflected by the values of the ratio migration velocity/migration rate from sediment to water (4 m and 12 m) that are significantly lower than the corresponding value in the Russian lake (112 m). The peculiar hydrochemical conditions of Lake Uruskul (high pH, high mineralisation, etc.) are considered to be responsible for the high radionuclide migration from water to sediment.

Characterization of the Mobilities of Selected Actinides and Fission/Activation Products in Laboratory Columns Containing Subsurface Material from the Snake River Plain

Laboratory column tests were performed to characterize the mobilities of 60Co, 90Sr, 137Cs, 233U, 239Pu, and 241Am in a basalt sample and a composite of sedimentary interbed from the Snake River Plain at the Idaho National Engineering and Environmental Laboratory. The radionuclides were spiked into a synthetic groundwater (pH 8, ionic strength = 0.004 M) and introduced into the columns (D = 2.6 cm, L = 15.2 cm) as finite steps with a width of 1 pore volume followed by unspiked synthetic groundwater. The effluent concentrations were measured continuously for up to 200 pore volumes. Hydrogen-3 was used as a nonreactive tracer in all of the experiments to monitor for channeling. In the basalt sample, the behavior of 90Sr, 137Cs, and 233U was quite different from that of 60Co, 239Pu, and 241Am. The column effluent curves for the former were characterized by single peaks containing, within the limits of experimental uncertainty, all of the activity in the spike. The mobilities were ordered as follows: 233U ([overbar]R = 5.6) > 90Sr ([overbar]R = 29) > 137Cs ([overbar]R = 79). The curves for the other radionuclides were characterized by two or three fractions, each having a distinctly different mobility. Cobalt-60 had high- ([overbar]R = < 3), intermediate- ([overbar]R = 34), and low- (R > 200) mobility fractions. Although a majority of the 239Pu and 241Am had low mobility (R > 200), there were high-mobility (R < 3) fractions of each (17 to 29% for 239Pu and 7 to 12% for 241Am). In sedimentary interbed, mobilities were generally much lower than in basalt. Uranium-233 was the only radionuclide with 100% recovery within 200 displaced pore volumes, and it had a retardation factor of 30. However, high-mobility fractions were observed for 60Co (1 to 4%) and 239Pu (1.1 to 2.4%). These results could have important implications with respect to transport modeling. If the multiple-mobility fractions observed here are also present in the field, transport predictions based on classical modeling approaches that incorporate mobilities from batch sorption experiments are likely to be in error.

MINERALOGICAL AND HYDROCHEMICAL EFFECTS ON ADSORPTION REMOVAL OF CESIUM-137 AND STRONTIUM-90 BY KAOLINITE

Adsorption characteristics of the nuclides onto kaolinite were investigated by batch experiment under various pH conditions and concentrations of groundwater cations (Ca2+, Mg2+, K+ and Na+) and anions (HCO3 −, CO3 2− and SO4 2−). Adsorption removal of 137Cs and 90Sr by kaolinite greatly increased as the concentration of groundwater cations increased from 10−5 to 10−1M. In contrast, the pH exerted a small effect on the adsorption of 137Cs and 90Sr onto kaolinite. The zeta potential of kaolinite particles showed a negative increase of amphoteric surface charge with increasing pH. The adsorption behavior of 90Sr was also highly dependent on the concentration of bicarbonate. The thermodynamic saturation index indicated that bicarbonate exerts great effect on strontium adsorption by the precipitation of a strontianite (SrCO3) and a change in pH.

Plutonium, 241Am, 90Sr, and 137Cs concentrations in some Antarctic matrices.

A radioecological survey in Antarctica shows that the 239 + 240Pu, 238Pu, 241Am, 90Sr, and 137Cs activities were detectable in nearly all the samples. The activity level of 239 + 240Pu, 241Am, and 137Cs in antarctic sediments was about 5-20 times lower than in the northern Adriatic Sea sediments, but the 238Pu activities were relatively high. It was interesting to note that the 90Sr concentrations in all the sediments tended to be low, which could be the result of the easier exchangeable behavior of 90Sr in water. High concentrations were detected in mosses and lichens and their activity levels were comparable to those in central Italy. The radionuclide ratio analyses show that the major part of 239 + 240Pu, 241Am, 90Sr, and 137Cs was a result of nuclear weapon tests. The higher 241Am/239 + 240Pu ratio was observed and it could perhaps be the result of fallout of nuclear weapon tests prior to 1962. The 238Pu/239 + 240Pu ratio in the antarctic matrices was about seven times higher than in the Northern hemisphere and it could be inferred that the major part of 238Pu was originating from the SNAP-9A satellite accident.

Modeling the potential role of a forest ecosystem in phytostabilization and phytoextraction of 90Sr at a contaminated watershed

The behavior of 90Sr at forest sites in the White Oak Creek watershed, near Oak Ridge, Tennessee, was simulated with a simple, site-specific, multicompartment model that linked biomass and element cycling dynamics. The model was used to predict the role of forest cover in mitigating hydrologic losses of 90Sr from contaminated soils (i.e. phytostabilization) under conditions where contaminant transport is governed mainly by shallow subsurface flow. The model was also used to predict the removal of 90Sr from soil (i.e. phytoextraction) through the growth and harvest of short rotation woody crops over a period of 30 years. Simulations with the model indicated that (1) forest preservation on the watershed is a form of phytostabilization because forest cover helps to minimize hydrologic losses of 90Sr and (2) an attempt to significantly reduce amounts of 90Sr in soil through phytoextraction would be unsuccessful. Over a period of 30 years, and under various management strategies, the model predicted that <15% of the 90Sr initially present in soil at a contaminated site was lost through hydrologic transport and <53% was lost by radioactive decay. Phytostabilization may be important in the management of radioactive land when issues like waste minimization and pollution prevention affect the selection of technologies to be used in environmental restoration.

Predicting the long term behaviour of 90Sr in lacustrine systems by a collective model

This paper describes a model for predicting the behaviour of 90Sr in lakes. The model, which accounts for the mass balances of the contaminant in water, includes the processes of radionuclide migration through the lacustrine abiotic components and from the drainage area. It is applied to seven Italian lakes contaminated by 90Sr due to nuclear weapon tests in the atmosphere over past decades. The results of the sensitivity and uncertainty analyses are described. The uncertainty of the model is less than a factor of 1.5 around the predicted values (68% confidence levels) over a period of more than 40 years. The model makes use of `collective parameters' which summarise, in single quantities, complex sets of competing processes occurring in the lacustrine environment. Such parameters are scantily variable and uncertain despite the large range of lake characteristics. Therefore, the model may be successfully applied to a variety of different environmental situations as a generic tool for evaluating the concentration of the radionuclide in water. The values of the most important migration parameters are the following: migration velocity from water to sediment is 1.2×10 −7 m s −1 (deep lakes) and 3.5×10 −7 m s −1 (shallow lakes); migration rate from sediment to lake water is 3.0×10 −8 s −1; transfer coefficient from drainage area to lake is 0.2 m −1.

Behavior of90Sr and137Cs in floodplain soils of the techa and iset' rivers

Behavior of90Sr and137Cs in floodplain soils of the techa and iset' rivers