RESUMEN
Retention or trapping of cesium, one of the radiologically important fission products, in the nuclear reactor becomes a great concern as the occurrence may affect radioactivity in the long term or its environmental fate. Herein the chemical compound of cesium that had been largely trapped on the nuclear reactor structural material of (calcium silicate) thermal insulator in a simulated nuclear accident condition was investigated. A combined pre- and post-water dissolution analysis through infrared (IR) spectroscopy and optical emission spectroscopy (OES) was explored to resolve the characterization difficulty encountered in conventional X-ray diffraction analysis reported in the previous works. This method allowed us to identify for the first time the related large amount of water-soluble cesium in the calcium silicate material after a high-temperature chemical reaction as cesium metasilicate (Cs2SiO3). It was evidenced by similar vibrational characteristics of the material to that in the synthesized Cs2SiO3 as well as based on the dissolved Cs and Si in the leaching water having a molar ratio of 2.16 ± 0.33. The corresponding 79-98% of the retained cesium in calcium silicate materials in the case study of 700 and 800 °C reactions was of this compound, emphasizing its significance once formed. Thermodynamic considerations further corroborated the higher stability of Cs2SiO3 in the cesium-calcium silicate reaction than other cesium silicates such as Cs2Si4O9, Cs2Si2O5, or Cs6Si2O7. This clearly poses a high environmental risk due to the volatility of cesium metasilicate as it may spread out further through the water leak path from a damaged nuclear reactor.
Asunto(s)
Compuestos de Calcio , Cesio , Silicatos , Silicatos/química , Compuestos de Calcio/química , Cesio/química , Cesio/análisis , Difracción de Rayos X , Radioisótopos de Cesio/análisis , Radioisótopos de Cesio/química , Liberación de Radiactividad PeligrosaRESUMEN
Radioactive nuclides cesium (Cs) and strontium (Sr) possess long half-lives, with 135Cs at approximately 2.3 million years and 87Sr at about 49 billion years. Their persistent accumulation can result in long-lasting radioactive contamination of soil ecosystems. This study employed geo-accumulation index (Igeo), pollution load index (PLI), potential ecological risk index (PEPI), health risk assessment model (HRA), and Monte Carlo simulation to evaluate the pollution and health risks of Cs and Sr in the surface soil of different functional areas in a typical mining city in China. Positive matrix factorization (PMF) model was used to elucidate the potential sources of Cs and Sr and the respective contribution rates of natural and anthropogenic sources. The findings indicate that soils in the mining area exhibited significantly higher levels of Cs and Sr pollution compared to smelting factory area, agricultural area, and urban residential area. Strontium did not pose a potential ecological risk in any studied functional area. The non-carcinogenic health risk of Sr to the human body in the study area was relatively low. Because of the lack of parameters for Cs, the potential ecological and human health risks of Cs was not calculated. The primary source of Cs in the soil was identified as the parent material from which the soil developed, while Sr mainly originated from associated contamination caused by mining activities. This research provides data for the control of Cs and Sr pollution in the surface soil of mining city.
Asunto(s)
Radioisótopos de Cesio , Minería , Contaminantes Radiactivos del Suelo , Medición de Riesgo , China , Contaminantes Radiactivos del Suelo/análisis , Radioisótopos de Cesio/análisis , Humanos , Radioisótopos de Estroncio/análisis , Cesio/análisis , Ciudades , Suelo/química , Método de Montecarlo , Monitoreo de RadiaciónRESUMEN
Effective, post-accidental management needs an accurate understanding of the biogeochemical behavior of radionuclides in surface environments at a regional scale. Studies on stable isotopes (element homologs) can improve this knowledge. This work focuses on the biogeochemical behavior of stable cesium (Cs) along a major European fluvial-estuarine system, the Gironde Estuary (SW France). We present results obtained from (i) a long-term monitoring (2014-2017) of dissolved (Csd) and particulate (Csp) Cs concentrations at five sites along the freshwater continuum of the Garonne watershed, (ii) Csd and Csp concentrations during four oceanographic campaigns at contrasting hydrological conditions along longitudinal profiles of the estuarine system, (iii) a 24 h cycle of Csp at the estuary mouth, and (iv) a historical trend of Cs bioconcentration in wild oysters at the estuary mouth (RNO/ROCCH, 1984-2017). In addition, we model the partitioning of Cs within the estuarine environment for clay mineral interactions via PhreeqC. At fluvial sites, we observe a geogenic dependence of the Csp and a seasonal variability of Csd, with a downstream increase of the solid-liquid partitioning (log10 Kd values from 3.64 to 6.75 L kg-1) for suspended particulate matter (SPM) < 200 mg L-1. Along the estuarine salinity gradients, Cs shows a non-conservative behavior where fresh SPM (defined as Cs-depleted particles recently put in contact with Csd) act as a Cs sink during both flood and low discharge (drought) conditions. This sorption behavior was explained by the geochemical model, highlighting the relevance of ionic strength, water and SPM residence times. However, at high salinities, the overall log10 Kd value decreases from 6.02 to 5.20 for SPM â¼300-350 mg L-1 due to the Csd oceanic endmember. Despite wild oysters showing low bioconcentration factors (â¼1220 L kg-1) at the estuary mouth, they are sensitive organisms to Cs fluxes.
Asunto(s)
Cesio , Monitoreo del Ambiente , Estuarios , Animales , Cesio/análisis , Francia , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismo , Agua Dulce/química , Ostreidae/metabolismo , Ostreidae/química , Ríos/químicaRESUMEN
The migration and retention of radioactive contaminants such as 137Cesium (137Cs) in various environmental media pose significant long-term storage challenges for nuclear waste. The distribution coefficient (Kd) is a critical parameter for assessing the mobility of radioactive contaminants and is influenced by various environmental conditions. This study presents machine-learning models based on the Japan Atomic Energy Agency Sorption Database (JAEA-SDB) to predict the Kd values for Cs in solid phase groups. We used three different machine learning models: random forest (RF), artificial neural network (ANN), and convolutional neural network (CNN). The models were trained on 14 input variables from the JAEA-SDB, including factors such as the Cs concentration, solid-phase properties, and solution conditions, which were preprocessed by normalization and log-transformation. The performances of the models were evaluated using the coefficient of determination (R2) and root mean squared error (RMSE). The RF, ANN, and CNN models achieved R2 values greater than 0.97, 0.86, and 0.88, respectively. We also analyzed the variable importance of RF using an out-of-bag (OOB) and a CNN with an attention module. Our results showed that the environmental media, initial radionuclide concentration, solid phase properties, and solution conditions were significant variables for Kd prediction. Our models accurately predict Kd values for different environmental conditions and can assess the environmental risk by analyzing the behavior of radionuclides in solid phase groups. The results of this study can improve safety analyses and long-term risk assessments related to waste disposal and prevent potential hazards and sources of contamination in the surrounding environment.
Asunto(s)
Cesio , Residuos Radiactivos , Cesio/análisis , Radioisótopos de Cesio/análisis , Residuos Radiactivos/análisis , JapónRESUMEN
To understand the relationship between the radioactive cesium (Cs) concentration in muscle of Japanese flounder Paralichthys olivaceus and the species' biological characteristics (size, sex, and age) under conditions of ecological equilibrium (i.e., distributed among ecosystem components over sufficient time, and with nearly constant ratios of Cs concentration in organisms to the concentration in water) as existed before the accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS), Japan, in 2011, we examined stable Cs, as it is thought to exist in equilibrium in the environment and behave similarly to radioactive Cs in aquatic animals. The concentration of stable Cs in 241 P. olivaceus (range 216-782 mm total length [TL]) collected in Sendai Bay, approximately 90 km north of the FDNPS, in June-July 2015 was expressed as an exponential function with size as an independent variable; the results show the concentration of stable Cs doubled with an increase in TL of 442 mm. Next, to evaluate the cause of the size-dependent change in stable Cs concentration, we examined 909 individuals (200-770 mm TL) collected in September 2013-July 2015 to determine their feeding habit based on size. Analysis of the frequency of occurrence of prey organisms in stomach contents showed that sand lance Ammodytes japonicus (55-180 mm standard length [SL]) was the most consistently consumed across size classes. Analysis on a wet-mass basis showed that A. japonicus and anchovy Engraulis japonicus (65-130 mm SL) were the main food of P. olivaceus sized 200-599 mm TL, whereas chub mackerel Scomber japonicus (120-230 mm SL) and two species of flatfishes (180-205 mm SL) were abundant in the diet of P. olivaceus sized ≥600 mm TL. All these prey items were presumed to have similar concentrations of stable Cs. Based on the above, the effect of diet on the relationship between stable Cs in muscle and fish size was considered negligible. That the diet of P. olivaceus largely did not change with size was also confirmed by C and N stable isotope ratios in P. olivaceus and their prey species. Therefore, the Cs-size relationship is probably determined by changes in the balance between the rate of Cs intake from food and seawater and the excretion rate during growth, both of which change as functions of body mass. Values of stable Cs concentrations among environmental components and animals appear to be a valid indicator for understanding the radioactive Cs distribution in the marine environment and aquatic animals under the equilibrium state, as existed before the 2011 nuclear accident.
Asunto(s)
Peces Planos , Lenguado , Accidente Nuclear de Fukushima , Animales , Tamaño Corporal , Cesio/análisis , Radioisótopos de Cesio/análisis , Dieta/veterinaria , Ecosistema , Japón , Masculino , FemeninoRESUMEN
We sought to explore the association between heavy metal exposure and coronary heart disease (CHD) based on data from the US National Health and Nutrition Examination Survey (NHANES, 2003-2018). In the analyses, participants were all aged > 20 and had participated in heavy metal sub-tests with valid CHD status. The Mann-Kendall test was employed to assess the trends in heavy metals' exposure and the trends in CHD prevalence over 16 years. Spearman's rank correlation coefficient and a logistics regression (LR) model were used to estimate the association between heavy metals and CHD prevalence. 42,749 participants were included in our analyses, 1802 of whom had a CHD diagnosis. Total arsenic, dimethylarsonic acid, monomethylarsonic acid, barium, cadmium, lead, and antimony in urine, and cadmium, lead, and total mercury in blood all showed a substantial decreasing exposure level tendency over the 16 years (all Pfor trend < 0.05). CHD prevalence varied from 3.53 to 5.23% between 2003 and 2018. The correlation between 15 heavy metals and CHD ranges from - 0.238 to 0.910. There was also a significant positive correlation between total arsenic, monomethylarsonic acid, and thallium in urine and CHD by data release cycles (all P < 0.05). The cesium in urine showed a negative correlation with CHD (P < 0.05). We found that exposure trends of total arsenic, dimethylarsonic acid, monomethylarsonic acid, barium, cadmium, lead, and antimony in urine and blood decreased. CHD prevalence fluctuated, however. Moreover, total arsenic, monomethylarsonic acid, and thallium in urine all showed positive relationships with CHD, while cesium in urine showed a negative relationship with CHD.
Asunto(s)
Arsénico , Enfermedad Coronaria , Metales Pesados , Adulto , Humanos , Cadmio/análisis , Encuestas Nutricionales , Arsénico/toxicidad , Arsénico/análisis , Antimonio/análisis , Bario/análisis , Talio/análisis , Prevalencia , Exposición a Riesgos Ambientales/análisis , Metales Pesados/análisis , Cesio/análisis , Enfermedad Coronaria/inducido químicamente , Enfermedad Coronaria/epidemiologíaRESUMEN
The overuse of chelating soil washing agents for removal of heavy metal can release soil nutrients and negatively affect organisms. Therefore, developing novel washing agents that can overcome these shortcomings is necessary. In this study, we tested potassium as a main solute of novel washing agent for cesium-contaminated field soil, owing to the physicochemical similarities between potassium and cesium. Response surface methodology was combined with a four-factor, three-level Box-Behnken design to determine the superlative washing conditions of the potassium-based solution for the removal of cesium from the soil. The parameters that were considered were the following: potassium concentration, liquid-to-soil ratio, washing time, and pH. Twenty-seven sets of experiments were conducted using the Box-Behnken design, and a second-order polynomial regression equation model was obtained from the results. Analysis of variance proved the significance and goodness of fit of the derived model. Three-dimensional response surface plots displayed the results of each parameter and their reciprocal interactions. The washing conditions that achieved the highest cesium removal efficiency (81.3%) in field soil contaminated at 1.47 mg/kg were determined to be the following: a potassium concentration of 1 M, a liquid-to-soil ratio of 20, washing time of 2 h, and a pH of 2.
Asunto(s)
Restauración y Remediación Ambiental , Metales Pesados , Contaminantes del Suelo , Potasio , Suelo/química , Contaminantes del Suelo/análisis , Metales Pesados/análisis , Quelantes/química , Cesio/análisisRESUMEN
The environmental behavior of radioactive cesium (RCs) in contaminated areas is generally governed by soil and sediment components and natural weathering conditions. In this study, desorption tests and spectroscopic approaches were used to explore the interaction between the weathering of micaceous minerals (i.e., biotite and phlogopite) and the adsorption of Cs+ and the critical role of weathering in the environmental behavior of RCs. Results showed that the reaction sequence between weathering and Cs+ adsorption significantly affected the surface species of Cs+ and the structure of biotite and phlogopite. Regardless of whether it occurred before, after, or during Cs+ adsorption, weathering generated more high-affinity adsorption sites, namely, interlayer sites (ITs) and frayed edge sites (FESs), to different extents, and then facilitated the uptake of Cs+ at FESs and ITs on micaceous minerals in a poorly exchangeable state. Cs+ stabilized the micaceous mineral structure once it was absorbed within collapsed interlayers by hindering cation exchange and preventing further destruction during weathering. As important weathering factors, high temperature and Ca2+ content promoted the binding of Cs+ in the interlayers of biotite and phlogopite by enhancing interlayer cation exchange. These findings are beneficial for a better understanding of the environmental behaviors of RCs in the hydrosphere and pedosphere.
Asunto(s)
Radioisótopos de Cesio , Cesio , Adsorción , Cesio/análisis , Minerales/química , Silicatos de AluminioRESUMEN
The presence of anthropogenic radioisotopes in the environment may be due to inappropriate discards, nuclear tests and accidents, which requires and justifies constant monitoring to ensure the safety of nuclear applications. The radiometric analysis is a necessary condition for exporting sugar for world consumption. The investigation of 134Cs and 137Cs in a sugar matrix is required to predict radiometric anomalies. This work aimed to standardise a semi-empirical radiometric model to characterise and quantify caesium isotopes in sugar. The research was carried out with high-resolution gamma spectrometry, a non-destructive method. The results were applied to the analysis of different types of sugar for export. The models allowed us to determine with excellent resolution the minimum quantifiable activities of 0.74 Bq kg-1 and 0.48 Bq kg-1 for 134Cs and 137Cs, respectively, which are lower than 600 Bq kg-1, reference values adopted by the EU for isotopes in food.
Asunto(s)
Monitoreo de Radiación , Azúcares , Azúcares/análisis , Monitoreo de Radiación/métodos , Radioisótopos de Cesio/análisis , Cesio/análisisRESUMEN
To date, radiocesium (137Cs) has been considered stable in the form of pollucite mineralized through high-temperature heat treatment. This study presented a possibility through experimental results that the entire medium exists as amorphous aluminosilicate at a relatively low temperature, but cesium is partially and preferentially converted from a composite adsorbent into pollucite. Cesium lowers the eutectic point within the system and initiates the nucleation of pollucite prior to other elements. We confirmed that the partial mineral phase of cesium showed the same chemical stability as when the entire medium was converted to pollucite. X-ray absorption spectroscopy provided direct evidence for this phenomenon; also, the stability results of radioactive cesium shown through a series of sintering experiments supported the conclusion. This method can be applied as a method to immobilize radioactive cesium under relatively mild temperature conditions of atmospheric pressure, while eliminating the problem of diffusion due to its volatilization.
Asunto(s)
Radioisótopos de Cesio , Cesio , Cesio/análisis , Cesio/química , Silicatos de AluminioRESUMEN
This study aimed to evaluate the applicability of non-destructive radioactivity measurement equipments for screening radio-cesium in whole foods without sample preparation procedures. Wild mushrooms and bamboo shoots were collected and studied using five different non-destructive radioactivity devices, and activity concentration was determined by conventional gamma-ray spectrometry using a Ge-detector. Linear regression analyses of activity concentrations were conducted and prediction intervals determined as uncertainties. Overall, non-destructive radioactivity measurement devices found to be suitable for screening radioactive cesium contamination in foods with an effective screening level.
Asunto(s)
Contaminación Radiactiva de Alimentos , Accidente Nuclear de Fukushima , Radiactividad , Radioisótopos de Cesio/análisis , Contaminación Radiactiva de Alimentos/análisis , Cesio/análisisRESUMEN
This paper addresses the modelling of cesium sorption in non-equilibrium and nonlinear conditions with a two-site model. Compared to the classical Kd approach, the proposed model better reproduced the breakthrough curves observed during continuous-flow stirred tank reactor experiments conducted on two contrasted soils. Fitted parameters suggested contrasted conditions of cesium sorption between 1) equilibrium sites, with low affinity and high sorption capacity comparable to CEC and 2) non-equilibrium sites, with a fast sorption rate (half-time of 0.2-0.3 h), a slow desorption rate (half-time of 3-9 days) and a very low sorption capacity (0.02-0.04% of CEC). Comparison of EK sites densities with sorption capacities derived from the literature suggests that the EK equilibrium and kinetic sites might correspond to ion exchange and surface complexation of soil clay minerals respectively. This work stresses the limits of the Kd model to predict 137Cs sorption in reactive transport conditions and supports an alternative non-equilibrium nonlinear approach.
Asunto(s)
Monitoreo de Radiación , Contaminantes del Suelo , Suelo , Adsorción , Cesio/análisisRESUMEN
Cesium-137 (137Cs) is one of the radioactive substances that was released into the environment as a result of the Fukushima nuclear disaster. Radiocesium exposure is of great concern due to its potential environmental implications. However, research on 137Cs removal using algae is still limited. This is the first report to describe the kinetic properties of 137Cs uptake by Vacuoliviride crystalliferum in the presence and absence of potassium. In this work, we studied the kinetic properties of 137Cs uptake using a freshwater microalga, V. crystalliferum (NIES 2860). We also analyzed the effects of temperature, light, and potassium (K) on the 137Cs uptake. Results showed that V. crystalliferum can remove up to 90% of 157 nM 137Cs within an hour. At 20 °C, the removal increased by up to 96%, compared to less than 10% at 5 °C. However, the removal was inhibited by nearly 90% in the dark compared to the removal in the light, implying that V. crystalliferum cells require energy to accumulate 137Cs. In the inhibition assay, K concentrations ranged from 0 to 500 µM and the inhibitory constant (Ki) for K was determined to be 16.7 µM. While in the uptake assay without potassium (- K), the Michaelis constant (Km) for Cs was 45 nM and increased to 283 nM by the addition of 20 µM potassium (+ K), indicating that V. crystalliferum had a high affinity for 137Cs. In addition, the maximum uptake velocity (Vmax) also increased from 6.75 to 21.10 nmol (mg Chl h)-1, implying the existence of Cs active transport system. In conclusion, V. crystalliferum is capable of removing radioactive 137Cs from the environment and the removal was favorable at both normal temperature and in the light.
Asunto(s)
Accidente Nuclear de Fukushima , Microalgas , Monitoreo de Radiación , Radioisótopos de Cesio/análisis , Cesio/análisis , Potasio/análisis , JapónRESUMEN
The Fukushima Daiichi Nuclear Power Plant accident led to contamination with radioactive cesium in an extensive environment in Japan in 2011. We evaluated the concentration of radioactive cesium in the skeletal muscles of 22 wild boars and the expression of IFN-γ, TLR3, and CyclinG1 in the small intestine and compared them with those of wild boar samples collected from Hyogo prefecture. The average 137Cs radioactivity concentration in wild boars in the ex-evacuation zone was 470 Bq/kg. Most of samples still showed radioactivity concentration that exceeded the regulatory limit for foods, but the dose remarkably decreased compared with samples just after the accident. IFN-γ expression was significantly higher in wild boars in the ex-evacuation zone than in samples from Hyogo prefecture. TLR3 expression was also upregulated. CyclinG1 expression also tended to be high. Hence, wild boars might have received some effects of low-dose radiation, and immune cells were activated to some extent. However, pathological examination revealed no inflammatory cell infiltration or pathological damage in the small intestine of wild boars in the ex-evacuation area. Long-term monitoring would be necessary, but we consider that the living body responds appropriately to a stimulus from a contaminated environment.
Asunto(s)
Contaminación Radiactiva de Alimentos , Accidente Nuclear de Fukushima , Monitoreo de Radiación , Porcinos , Animales , Contaminación Radiactiva de Alimentos/análisis , Sus scrofa/genética , Receptor Toll-Like 3/análisis , Radioisótopos de Cesio/análisis , Cesio/análisis , Expresión Génica , Dosis de Radiación , Japón , Plantas de Energía NuclearRESUMEN
The sorption characteristics of Eu(III) and Cs(I) removal from aqueous solution were estimated using phalaris seeds peel powder (PSP), a novel biosorbent that is economical and low-cost. Batch equilibrium experiments were carried out to investigate the effects of contact time, initial metal concentration, media pH, and interference ions on the sorption of Eu(III) and Cs(I). PSP powder characterization via Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG/DSC), X-ray diffraction (XRD), and scanning electron microscope (SEM) revealed some changes before and after the adsorption process. This indicates that most likely, adsorption has taken place between the metal ions and the adsorbents in the aqueous solution. The obtained results show that Eu(III) has a higher selectivity than Cs(I). The kinetics of the adsorption of Eu3+ and Cs+ have been discussed. It was shown that the second-order kinetic equation could describe the sorption and was found to be the best fitted model (R2 = 0.999) for two metal ions. Langmuir and, Dubinin-Radushkevich (D-R), isotherm were found to best fit (R2 = 0.99) in this study. The separation factor (RL) value of less than 1.0 indicates that the biosorption of both metal ions on PSP is favorable. Thermodynamic parameters, such as ΔHo, ΔGo, and ΔSo, have been calculated by using the thermodynamic equilibrium coefficient obtained at different temperatures. The obtained results indicated the endothermic nature of the sorption process for both metal ions onto PSP. PSP powder has the potential to be used as a low-cost biosorbent for the removal of Eu(III) and Cs(I) from wastewater, according to the findings.
Asunto(s)
Phalaris , Contaminantes Químicos del Agua , Cinética , Europio/análisis , Polvos , Concentración de Iones de Hidrógeno , Adsorción , Agua/análisis , Iones , Termodinámica , Cesio/análisis , Espectroscopía Infrarroja por Transformada de Fourier , Semillas/química , Contaminantes Químicos del Agua/análisisRESUMEN
The TEPCO Fukushima Daiichi Nuclear Power Plant accident that occurred in March 2011 resulted in the release of radioactive caesium into the environment. The radioactive caesium has been detected in the Tama River watershed. Previous investigations have shown that the concentration of radioactive caesium in sediment was relatively high in the Nogawa River. In this study, the relationship between the concentration of radioactive caesium in the sediment and the sediment characteristics was investigated. We found that 137Cs concentration in the tributary sediment has difficulty migrating downstream, while exhibiting a strong correlation with the amount of organic matter and a correlation with the clay, silt layer. Based on the results, we inferred that 137Cs is deposited together with the organic matter and clay, silt layer in the sediment and migrates at a slower pace than that in the mainstem.
Asunto(s)
Accidente Nuclear de Fukushima , Monitoreo de Radiación , Contaminantes Radiactivos del Suelo , Contaminantes Radiactivos del Agua , Cesio/análisis , Radioisótopos de Cesio/análisis , Arcilla , Sedimentos Geológicos , Japón , Contaminantes Radiactivos del Suelo/análisis , Contaminantes Radiactivos del Agua/análisisRESUMEN
Radiocaesium is released into the environment by accidents in nuclear facilities. One of the major issues related with this is the assessment and reduction of internal exposure of crops grown in contaminated soil. To solve this, we developed a method of inhibiting Cs absorption by plant roots. In the presence of potassium concentrations >100 µM, Cs absorption occurs mainly via voltage-insensitive cation channels (VICC). Since the transport activity of VICC was inhibited by calcium at millimolar concentrations, we hypothesised that Ca would effectively inhibit Cs absorption. We grew Arabidopsis and rice plants in the presence of Cs and Ca in the nanomolar and millimolar range and measured Cs concentrations in the plants using inductively coupled plasma mass spectrometry. The results showed that the Cs concentration in both plants decreased with increasing Ca concentration in the medium. This suggests that Ca has an inhibitory effect on Cs absorption.
Asunto(s)
Arabidopsis , Calcio , Cesio/análisis , Radioisótopos de Cesio/análisis , Raíces de Plantas , Plantas , Potasio/análisisRESUMEN
This study is concerned with the sorption of 137Cs and/or 90Sr from low-level radioactive waste using tin(IV) vanadate (SnV) sorbent fabricated by the precipitation technique. The structure and properties of SnV were studied using different analytical tools such as X-ray diffraction, X-ray fluorescence, Fourier-transform infrared, and scanning electron microscopy. Batch technique was used to investigate the sorption behavior of SnV towards 137Cs and/or 90Sr considering the influence of independent parameters including pH of the solution, contact time, and initial metal ions concentrations in simulation studies using the γ emitting isotopes 134Cs and 85Sr as representatives of 137Cs and 90Sr, respectively. The sorption efficiency values of 70.3% and 92.2% were respectively obtained for 134Cs and 85Sr at optimum conditions (pH = 6, Ci = 100 mg/L, and time = 120 min). The amount sorbed (mg/g) increases by increasing pH and temperatures. The pseudo-2nd-order kinetic is a reaction command. Isotherm is more relevant to a Langmuir at different reaction temperatures. The sorption process was endothermic and spontaneous. The adsorption efficiency of the composite material was studied in removing both cesium and strontium nuclides from real low-level radioactive waste. This study showed that the new material can be used as a promising material to retain 137Cs and 90Sr from real radioactive waste.
Asunto(s)
Residuos Radiactivos , Adsorción , Cesio/análisis , Radioisótopos de Cesio , Cinética , Residuos Radiactivos/análisis , Estroncio/química , Radioisótopos de Estroncio , Estaño , VanadatosRESUMEN
Cesium (Cs+) enters environments largely because of global release into the environment from weapons testing and accidents such as Fukushima Daiichi and Chernobyl nuclear waste. Even at low concentrations, Cs+ is highly toxic to ecological receptors because of its physicochemical similarity to macronutrient potassium (K+). We investigated the uptake and accumulation of Cs+ by Arthrobacter globiformis strain 151B in reference to three similar alkali metal cations rubidium (Rb+), sodium (Na+), and potassium (K+). The impact of hexavalent chromium (Cr+6) as a co-contaminant was also evaluated. A. globiformis 151B accumulated Cs+ and Cr6+ in a time-dependent fashion. In contrast, the uptake and accumulation of Rb+ did not exhibit any trends. An exposure to Cs+, Rb+, and Cr+6 triggered a drastic increase in K+ and Na+ uptake by the bacterial cells. That was followed by the efflux of K+ and Na+, suggesting a Cs+ "substitution." Two-dimensional gel-electrophoresis of bacterial cell proteomes with the following mass-spectrometry of differentially expressed bands revealed that incubation of bacterial cells with Cs+ induced changes in the expression of proteins involved in the maintenance of cellular homeostasis and reactive oxygen species removal. The ability of A. globiformis 151B to mediate the uptake and accumulation of cesium and hexavalent chromium suggests that it possesses wide-range bioremediation potential.