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1.
Nat Commun ; 12(1): 823, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33547296

RESUMO

We present an application of multi-isotopic fingerprints (i.e., 236U/238U, 233U/236U, 236U/129I and 129I/127I) for the discovery of previously unrecognized sources of anthropogenic radioactivity. Our data indicate a source of reactor 236U in the Baltic Sea in addition to inputs from the two European reprocessing plants and global fallout. This additional reactor 236U may come from unreported discharges from Swedish nuclear research facilities as supported by high 236U levels in sediment nearby Studsvik, or from accidental leakages of spent nuclear fuel disposed on the Baltic seafloor, either reported or unreported. Such leakages would indicate problems with the radiological safety of seafloor disposal, and may be accompanied by releases of other radionuclides. The results demonstrate the high sensitivity of multi-isotopic tracer systems, especially the 233U/236U signature, to distinguish environmental emissions of unrevealed radioactive releases for nuclear safeguards, emergency preparedness and environmental tracer studies.


Assuntos
Radioisótopos/análise , Água do Mar/análise , Urânio/análise , Poluentes Radioativos da Água/análise , Países Bálticos , Humanos , Cinza Radioativa/análise , Suécia
2.
J Environ Radioact ; 229-230: 106530, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33482539

RESUMO

The Acacia auriculiformis is a tree common in tropical Asian countries, capable of growing in many different soil types, so it could be used for biomonitoring for high natural radionuclide areas in tropical and subtropical climates. The transfer factor (TF) of radionuclides from soil to A. auriculiformis in eight uranium and rare earth element (REE) mining areas of North Vietnam was investigated. The activity concentrations 226Ra, 238U, 137Cs, 228Ra, and 40K in both soil and A. auriculiformis showed considerable variation. The TFs of these radionuclides also varied in a wide range. In most of the eight areas, the highest TF was observed for 137Cs and 228Ra. While the TFs for 226Ra and 238U were smallest. In addition, the TFs for radionuclides near REE mines were similar to those observed near uranium mines. The TFs for A. auriculiformis were within the ranges of TF reported for other plants, except for 137Cs.


Assuntos
Acacia , Monitoramento de Radiação , Poluentes Radioativos do Solo , Urânio , Solo , Poluentes Radioativos do Solo/análise , Árvores , Urânio/análise , Vietnã
3.
J Environ Radioact ; 229-230: 106538, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33485191

RESUMO

Transfer factors of radium 226(226Ra), lead 210(210Pb), polonium 210 (210Po), uranium 238 (238U) and thorium 234(234Th) from five different agricultural soils in Syria to coriander, parsley and mint were investigated in a pot culture experiment. Geometric means of transfer factors (TF)were226Ra (0.13),210Pb(0.03), 210Po (0.02) and 238U (1.76) were within worldwide values, while TF values for 234Th (1.35) were higher than those recorded globally. The available transfer factor (ATF) values ranged between 0.03 and 1.45, 0.33 and 3.2, 0.10 and 3.36, 1.30 and 16.2 and 1.0 and 6.95 for226Ra,210Pb,210Po, 238U and 234Th, respectively. However, it is worth mentioning that the data from pot experiments may not represent field conditions. Liquid/solid partition coefficients (Kd)of 226Ra, U, 210Pb and 210Po for55 soils representing the dominant types of soils in Syria were also determined. Geometric means of Kd values ranged from 280 to1200, 750 to1600, 350to 4800 and 100-120 L kg-1 for 226Ra, 238U, 210Pb and 210Po, respectively at pH = 4.0, and from 200 to 6700, 670 to 2400, 150 to 2100 and 100 to 160Lkg-1at pH = 5.5, and from 370 to 790, 130 to 550, 60 to 330 and370 to 920Lkg-1at pH = 7.0. The effects of soil mineral content, CEC, ECE, pH and soluble ions on the Kd values were investigated. In general, there were logarithmic relationships between the activity concentrations in soil and the Kd values (R2 ranged from 0.59 to 1.00 at pH 4.0). There were no relationships between the Kd values and soil pH.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos do Solo , Urânio , Radioisótopos/análise , Solo , Poluentes Radioativos do Solo/análise , Síria , Fator de Transferência , Urânio/análise
4.
J Environ Radioact ; 229-230: 106539, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33493873

RESUMO

Sequential extraction tests were used to study partitioning of U in the bottom sediments of two reservoirs that have been used for the temporary storage of nuclear waste at the "Mining and Chemical Combine" (Zheleznogorsk, Krasnoyarsk region, Russia). Various sequential extraction protocols were applied to the bottom sediment samples and the results compared with those obtained for laboratory-prepared simulated samples with different speciation and partitioning, e.g., U(VI) sorbed onto various inorganic minerals and organic matter, as well as uranium oxides. The distributions of uranium in fractions extracted from simulated and actual contaminated samples were compared to shed light on the speciation of U in the bottom sediments. X-ray absorption spectroscopy, X-ray diffraction, and scanning electron microscopy were also used to analyze the partitioning of U in contaminated sediments. We also compared the results obtained using the spectroscopic and microscopic techniques, as well as sequential extraction.


Assuntos
Monitoramento de Radiação , Urânio , Poluentes Radioativos da Água , Sedimentos Geológicos , Federação Russa , Urânio/análise
5.
Arch Environ Contam Toxicol ; 80(1): 308-318, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33398396

RESUMO

The presence of radioactive elements in groundwater results in high health risks on surrounding populations. Hence, a study was conducted in central Tamil Nadu, South India, to measure the radon levels in groundwater and determine the associated health risk. The study was conducted along the lithological contact of hard rock and sedimentary formation. The concentrations of uranium (U) varied from 0.28 to 84.65 µg/L, and the radioactivity of radon (Rn) varied from 258 to 7072 Bq/m3 in the collected groundwater samples. The spatial distribution of Rn in the study area showed that higher values were identified along the central and northern regions of the study area. The data also indicate that granitic and gneissic rocks are the major contributors to Rn in groundwater through U-enriched lithological zones. The radon levels in all samples were below the maximum concentration level, prescribed by Environmental Protection Agency. The effective dose levels for ingestion and inhalation were calculated according to parameters introduced by UNSCEAR and were found to be lesser (0.235-6.453 µSvy-1) than the recommended limit. Hence, the regional groundwater in the study area does not pose any health risks to consumers. The spatial distribution of Rn's effective dose level indicates the higher values were mainly in the central and northern portion of the study area consist of gneissic, quarzitic, and granitic rocks. The present study showed that Rn concentrations in groundwater depend on the lithology, structural attributes, the existence of uranium minerals in rocks, and the redox conditions. The results of this study provide information on the spatial distribution of Rn in the groundwater and its potential health risk in central Tamil Nadu, India. It is anticipated that these data will help policymakers to develop plans for management of drinking water resources in the region.


Assuntos
Água Subterrânea/química , Monitoramento de Radiação/métodos , Radônio/análise , Poluentes Radioativos da Água/análise , Sedimentos Geológicos/química , Índia , Urânio/análise
6.
Environ Monit Assess ; 193(2): 87, 2021 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-33501571

RESUMO

The Al Aziziah area is built on volcanic and granitic rocks. The igneous rocks always contain a high amount of naturally radioactive elements such as uranium, thorium and potassium, which produce gamma rays causing environmental hazards when exceeding the permissible limit. Radon gas is a result from the decomposition of uranium/thorium leaks into enclosed areas (e.g. homes or offices). This leakage is controlled by many conditions, and one of them is the underlining rock type. To work on such an environmental study, a gamma ray spectrometer survey was used. The uranium, thorium and potassium contents, as well as their ratios and the total radiation, were determined and mapped. The radiation dose rate was calculated and mapped in mSv/y and nGy/h units. The radiation contamination of groundwater is detected from the contour map of the dose rate over the artificial drainage lines of rains and floods which move this water to the groundwater wells. The main results are as follows: granitic rocks show an average dose rate of about 2.4 mSv/y, while the deposits of these rocks have an average dose rate of 1.2 mSv/y. A low average dose is recorded over the basalt. The average radiation dose recorded in the study area is 1.08 mSv/y, while its range is from 0.001 to 4.41 mSv/y. The estimated effective doses within the Al Aziziah area and vicinity area were higher than 1 mSv/y, which is the public exposure limit, and lower than the occupational exposure limit of 20 mSv/y. We recommend ventilating homes and offices in these places on an ongoing basis and constant radon measuring in closed places.


Assuntos
Monitoramento de Radiação , Radônio , Urânio , Doses de Radiação , Radônio/análise , Arábia Saudita , Tório/análise , Urânio/análise
7.
Bull Environ Contam Toxicol ; 106(2): 385-392, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33388830

RESUMO

This study aims to synthesize and characterize an economical and ecological adsorbent with high adsorption capacity. For this purpose, the peanut shells (Pistacia vera L.) were modified chemically. After the synthesis of activated carbon (AC), the optimum conditions for enrichment steps were performed using parameters: pH and contact time for uranium in the model solutions. The measurements were carried out by inductively coupled plasma-mass spectrometry (ICP-MS). From the shapes of the BET isotherms, the AC obtained exhibits type I. The study indicated that the surface area and total pore volume of the AC were found to be 679.9 m2 g-1 and 0.31 cc g-1, respectively. The adsorption capacity was found to be 260 mg g-1. The optimum pH was found to be 6.0 for enrichment using the AC obtained by sulfuric acid as a chemical-modifier. The optimized method was applied to enrichment of U at ppb levels in the model solutions.


Assuntos
Carvão Vegetal , Urânio , Adsorção , Arachis , Concentração de Íons de Hidrogênio , Cinética , Urânio/análise
8.
Chemosphere ; 263: 127909, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32822937

RESUMO

236U has attracted more attention as an environmental tracer in recent years. However, in-depth study of 236U in terrestrial environments is still rare in China. Data on 236U and 137Cs concentrations in soil and road dust samples collected from Beijing and Zhangjiakou, China were obtained to demonstrate the background and distinct characteristics of anthropogenic 236U and 137Cs. 236U and 137Cs were detected in the range of (1.10-7.90) × 107 atoms g-1 and below the method limits of detection to 5.30 Bq kg-1. A clear characteristic was observed in road dust, where 236U concentrations increased with decreasing of sample particle size. Soil samples showed an irregular characteristic, but the highest 236U concentrations were observed in particle size fraction of <0.053 mm in both samples. This phenomenon was caused by U chemical properties, higher specific surface areas and organic compounds in fine particles. Anthropogenic radionuclides fingerprint characteristics in <0.053 mm samples were specially discussed. 236U/238U atom ratios were detected in the range of (0.627-3.38) × 10-8. A weak correlation between anthropogenic 236U and natural U isotopes were observed. The intermediate correlation between 236U and 137Cs indicated somewhat distinct migration behavior of these two radionuclides in soil after release to the environment. The released amount of 236U from global fallout during the period of atmospheric nuclear weapons testing was roughly estimated to be 1300 ± 448 kg. These results could be used as fingerprint information for anthropogenic 236U migration behavior and tracer application in environment.


Assuntos
Radioisótopos de Césio/análise , Monitoramento de Radiação , Poluentes Radioativos do Solo/análise , Urânio/análise , Pequim , China , Poeira/análise , Compostos Orgânicos , Tamanho da Partícula , Solo/química
9.
Chemosphere ; 263: 127908, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32835973

RESUMO

The effects of breccia pipe uranium mining in the Grand Canyon watershed (Arizona) on ecological and cultural resources are largely unknown. We characterized the exposure of biota to uranium and co-occurring ore body elements during active ore production and at a site where ore production had recently concluded. Our results indicate that biota have taken up uranium and other elements (e.g., arsenic, cadmium, copper, molybdenum, uranium) from exposure to ore and surficial contamination, like blowing dust. Results indicate the potential for prolonged exposure to elements and radionuclides upon conclusion of active ore production. Mean radium-226 in deer mice was up to 4 times greater than uranium-234 and uranium-238 in those same samples; this may indicate a potential for, but does not necessarily imply, radium-226 toxicity. Soil screening benchmarks for uranium and molybdenum and other toxicity thresholds for arsenic, copper, selenium, uranium (e.g., growth effects) were exceeded in vegetation, invertebrates, and rodents (Peromyscus spp., Thomomys bottae, Tamias dorsalis, Dipodomys deserti). However, the prevalence and severity of microscopic lesions in rodent tissues (as direct evidence of biological effects of uptake and exposure) could not be definitively linked to mining. Our data indicate that land managers might consider factors like species, seasonal changes in environmental concentrations, and bioavailability, when determining mine permitting and remediation in the Grand Canyon watershed. Ultimately, our results will be useful for site-specific ecological risk analysis and can support future decisions regarding the mineral extraction withdrawal in the Grand Canyon watershed and elsewhere.


Assuntos
Exposição à Radiação , Poluentes Radioativos da Água/toxicidade , Animais , Arsênico/análise , Cádmio/análise , Cobre/análise , Invertebrados , Camundongos , Mineração , Monitoramento de Radiação , Radioisótopos/análise , Rádio (Elemento) , Roedores , Selênio/análise , Solo , Urânio/análise
10.
Environ Sci Process Impacts ; 23(1): 73-85, 2021 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-33325952

RESUMO

We investigated the mechanisms of uranium (U) uptake by Tamarix (salt cedars) growing along the Rio Paguate, which flows throughout the Jackpile mine near Pueblo de Laguna, New Mexico. Tamarix were selected for this study due to the detection of U in the roots and shoots of field collected plants (0.6-58.9 mg kg-1), presenting an average bioconcentration factor greater than 1. Synchrotron-based micro X-ray fluorescence analyses of plant roots collected from the field indicate that the accumulation of U occurs in the cortex of the root. The mechanisms for U accumulation in the roots of Tamarix were further investigated in controlled-laboratory experiments where living roots of field plants were macerated for 24 h or 2 weeks in a solution containing 100 µM U. The U concentration in the solution decreased 36-59% after 24 h, and 49-65% in two weeks. Microscopic and spectroscopic analyses detected U precipitation in the root cell walls near the xylems of the roots, confirming the initial results from the field samples. High-resolution TEM was used to study the U fate inside the root cells, and needle-like U-P nanocrystals, with diameter <7 nm, were found entrapped inside vacuoles in cells. EXAFS shell-by-shell fitting suggest that U is associated with carbon functional groups. The preferable binding of U to the root cell walls may explain the U retention in the roots of Tamarix, followed by U-P crystal precipitation, and pinocytotic active transport and cellular entrapment. This process resulted in a limited translocation of U to the shoots in Tamarix plants. This study contributes to better understanding of the physicochemical mechanisms affecting the U uptake and accumulation by plants growing near contaminated sites.


Assuntos
Nanopartículas , Tamaricaceae , Urânio , New Mexico , Fósforo , Raízes de Plantas/química , Urânio/análise
11.
J Environ Radioact ; 228: 106511, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33341752

RESUMO

Corrosion process was investigated of depleted uranium (DU) ammunition fragments buried for three years in aerobic soils continuously irrigated with water. The continuing corrosion process was triggered through formation of soluble uranyl oxyhydrate phases such as metaschoepite and becquerelite, which were identified by micro-Raman and X-ray diffraction spectroscopy. The soil was not amended by phosphates and, therefore, no uranyl phosphates were found as corrosion products on the DU surfaces by X-ray photoelectron spectroscopy. A speciation modelling at high temporal sequence (chronospeciation approach) indicated that the abundant Fe oxyhydroxides in the soil immobilized the U(IV) released through DU corrosion. During the first two years, therefore, only <10 mg of U(VI) was thus found in the leachates from the soil columns, even though >3 g of DU had been corroded. However, the degree of this immobilization was found to be controlled by the amount of dissolved inorganic and organic carbon (DIC and DOC) in the soil pore water providing for U(VI) complexation competing with surface complexation by the Fe hydroxides. The chronospeciation approach applied is useful to improve our understanding and ability to predict the long-term fate of U(VI) and the mechanisms controlling U(VI) mobility in soil contaminated with DU shells.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos do Solo , Urânio , Corrosão , Solo , Poluentes Radioativos do Solo/análise , Urânio/análise
12.
Mar Environ Res ; 163: 105221, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33341237

RESUMO

Uranium (U) mining is an aquatic environmental concern because most of these harmful compounds are discharged into freshwater, reaching the saline environment as the final destination of this contaminated water. Carbonates are present in ocean waters and are essential for benthic organisms, however they may influence the U-induced toxicity. Thus, the aim of this study was to compare the toxicity of uranium nitrate (UN) and uranium acetate (UA) in Artemia salina (AS), which is one of the leading representatives of the marine biota. The cultures of AS (instar II) maintained in artificial seawater containing CaCO3 were exposed for 24 h to different concentrations of U compounds. The results showed that AS were more sensitive to UN (LC50 ≈ 15 µM) when compared with UA (LC50 ≈ 245 µM) indicating higher toxicity of this U compound. Calculated U speciation indicated that Ca2UO2(CO3)3 and (UO2)2CO3(OH)3- complexes predominated under our experimental conditions. The immobilization/lethality was observed after 9 h of exposure for both U compounds. However, only UN caused a significant decrease (≈40%) in the acetylcholinesterase (AChE) activity when compared with control. In order to observe preliminary toxicity effects, we evaluated oxidative stress parameters, such as catalase (CAT) activity, TBARS formation, radical species (RS) generation and cell membrane injury and/or apoptosis (CMI). In this study, we demonstrate that U compounds caused a significant decrease in CAT activity. Similarly, we also observed that UN increased TBARS levels in AS at concentrations 5 times lower than AU (10 µM and 50 µM, respectively). Furthermore, RS generation and CMI were enhanced only on AS treated with UN. Overall, the effects observed here were remarkably significant in AS exposed to UN when compared with AU. In this study, we showed different profiles of toxicity for both U compounds, contributing significantly to the current and scarce understanding of the aquatic ecotoxicity of this heavy metal.


Assuntos
Compostos de Urânio , Urânio , Animais , Artemia , Água Doce , Água do Mar , Urânio/análise , Urânio/toxicidade
13.
Chemosphere ; 254: 126859, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957279

RESUMO

Understanding the long-term fate, stability, and bioavailability of uranium (U) in the environment is important for the management of nuclear legacy sites and radioactive wastes. Analysis of U behavior at natural analogue sites permits evaluation of U biogeochemistry under conditions more representative of long-term equilibrium. Here, we have used bulk geochemical and microbial community analysis of soils, coupled with X-ray absorption spectroscopy and µ-focus X-ray fluorescence mapping, to gain a mechanistic understanding of the fate of U transported into an organic-rich soil from a pitchblende vein at the UK Needle's Eye Natural Analogue site. U is highly enriched in the Needle's Eye soils (∼1600 mg kg-1). We show that this enrichment is largely controlled by U(VI) complexation with soil organic matter and not U(VI) bioreduction. Instead, organic-associated U(VI) seems to remain stable under microbially-mediated Fe(III)-reducing conditions. U(IV) (as non-crystalline U(IV)) was only observed at greater depths at the site (>25 cm); the soil here was comparatively mineral-rich, organic-poor, and sulfate-reducing/methanogenic. Furthermore, nanocrystalline UO2, an alternative product of U(VI) reduction in soils, was not observed at the site, and U did not appear to be associated with Fe-bearing minerals. Organic-rich soils appear to have the potential to impede U groundwater transport, irrespective of ambient redox conditions.


Assuntos
Água Subterrânea/química , Resíduos Radioativos/análise , Solo/química , Urânio/análise , Poluentes Radioativos da Água/análise , Compostos Férricos , Microbiologia do Solo , Urânio/química , Compostos de Urânio/análise , Espectroscopia por Absorção de Raios X
14.
Chemosphere ; 254: 126898, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957293

RESUMO

The utilization of Microcystis biomass is an urgent issue in the mitigation of cyanobacterial bloom. In this study, Microcystis-derived biochar (MB) and Fe3O4-modified biochar (Fe3O4/MB) were fabricated for the U(VI) elimination. The results showed that U(VI) sorption process by either MB or Fe3O4/MB was pH-dependent and ionic strength-independent. The maximum sorption capacity of MB was higher than that of Fe3O4/MB. According to the analysis of X-ray photoelectron spectroscopy, U(VI) sorption on both MB and Fe3O4/MB was mainly ascribed to the surface complexation between U(VI) and oxygen-containing functional groups on the surface of MB. Fe3O4 particles on the surface of MB didn't provide extra active sites for the sorption of U(VI), but it enabled the adsorbent to be magnetically separated. Five consecutive sorption/desorption cycles verified the good reusability of Fe3O4/MB in this study. Therefore, the investigation is not only meaningful for the utilization of nuisance biomass from cyanobacterial blooms, but also provides novel adsorbents for the U(VI) removal from aqueous solutions.


Assuntos
Carvão Vegetal/química , Eutrofização , Óxido Ferroso-Férrico/química , Microcystis/química , Urânio/análise , Poluentes Radioativos da Água/análise , Purificação da Água/métodos , Adsorção , Biomassa , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Modelos Teóricos , Concentração Osmolar
15.
J Environ Radioact ; 222: 106338, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32836144

RESUMO

The European Atlas of Natural Radiation, recently published, contains a collection of maps of Europe showing the levels of natural sources of radiation. Among the lacunae of the Atlas are maps of U, Th and K concentrations in rocks due to lack of European-wide geochemical surveys of bedrock units. The objective of this paper is to investigate the usability of scattered geochemical data of rock samples for large-scale mapping of U, Th and K concentrations in geological units. For this purpose, geochemical data were compiled from literature sources to produce a geochemical database (LIT database) that includes 2817 entries of U, Th and K concentrations measured in rock samples of geological units outcropping in Portugal. Given the methodical heterogeneity within LIT database, the influence of the geochemical analysis techniques was assessed through a three-way analysis of variance (ANOVA) using geological units, geochemical analysis techniques and loss on ignition (LOI) as categorical variables. The percentage of variation explained by geological factors was large (>35%), while the percentage of variation explained by the geochemical analysis techniques and LOI was generally lower than 5%. The geological factors were the main source of variability in the data, followed by the error component which can be assumed to represent the true spatial variability of geochemical concentrations. The pairwise comparison of the least square (LS) means computed through the ANOVA for each geochemical analysis technique indicates that LIT database can be considered consistent within itself, thus, reliable. In order to validate the usability of literature data the terrestrial gamma dose rate (TGDR) calculated from LIT database (TGDRcalc) was compared to the TGDR displayed in the Radiometric Map of Portugal (TGDRobs). The correlation between TGDRcalc and TGDRobs was highly significant (p < 0.001) and the results of a paired sample t-test and Wilcoxon median tests indicate that the differences between the arithmetic means of TGDRcalc and TGDRobs were not statistically significant (p = 0.126 and p = 0.14, respectively). Distributions of TGDRcalc and TGDRobs were seemingly equal according to the Kolmogorov-Smirnov and Anderson-Darling tests. Although, systematic discrepancies between TGDRcalc and TGDRobs were observed for sedimentary rocks, the compatibility of the RMP and LIT databases can be considered acceptable, which implies that the estimation of the contents of terrestrial radionuclides using literature data for large-scale mapping of U, Th and K contents in geological units is reasonable.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos do Solo , Tório , Urânio , Europa (Continente) , Portugal , Potássio , Poluentes Radioativos do Solo/análise , Tório/análise , Urânio/análise
16.
J Environ Radioact ; 222: 106362, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32858445

RESUMO

A general approach is presented to derive probabilistic radionuclide distribution coefficients (Kd) in soils from a Kd dataset. The main aim was to derive informed estimates with a low inherent uncertainty by restricting the Kd value data to subsets based on key soil factors and the experimental approach used to calculate the Kd value (e.g., sorption and desorption tests). As an example, the general approach was applied to uranium (U) Kd values that are part of a critically reviewed dataset containing more than 5000 soil Kd entries for 83 elements and an additional 2000 entries of Kd data for 75 elements gathered from a selection of other, non-soil, geological materials. The overall soil U Kd dataset included 196 values spanning a range of four orders of magnitude (1-67,000 L kg-1), with additional 50 entries for other geological materials. Whereas the effect of the experimental approach could be disregarded, major factors in decreasing U Kd variability were pH and organic matter content (OM). Limitation in the number of entries made it difficult to use texture information (sand, silt, clay) to further decrease U Kd variability. The integrated combination of pH + OM permitted some soil groups to have U Kd confidence intervals as narrow as two orders of magnitude. Specifically for U Kd, data in the Mineral (< 20% OM) and Organic (≥ 20% OM) partial datasets were significantly different. Analogue data from geological materials other than soils, such as subsoil, till and gyttja (a lacustrine mud having elevated organic matter (OM) contents), were also statistically evaluated to determine whether they could be used to fill U Kd data gaps. It was shown that U Kd from subsoils and tills, but not gyttjas, could be used to enhance soil U Kd datasets. Selection of probabilistic Kd values for risk modelling can be made more reliably and with less uncertainty by using appropriate geochemical data representative of the study site to narrow the wide range of potential Kd values.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos do Solo , Poluentes do Solo , Urânio , Adsorção , Argila , Solo , Poluentes Radioativos do Solo/análise , Urânio/análise
17.
Sci Total Environ ; 747: 141295, 2020 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-32777513

RESUMO

Uranium mining and milling activities raise environmental concerns due to the release of radioactive and other toxic elements. Their long-term management thus requires a knowledge of past events coupled with a good understanding of the geochemical mechanisms regulating the mobility of residual radionuclides. This article presents the results on the traces of anthropic activity linked to previous uranium (U) mining activities in the vicinity of the Rophin tailings storage site (Puy de Dôme, France). Several complementary approaches were developed based on a study of the site's history and records, as well as on a radiological and chemical characterization of soil cores and a dendrochronology. Gamma survey measurements of the wetland downstream of the Rophin site revealed a level of 1050 nSv.h-1. Soil cores extracted in the wetland showed U concentrations of up to 1855 mg.kg-1, which appears to be associated with the presence of a whitish silt loam (WSL) soil layer located below an organic topsoil layer. Records, corroborated by prior aerial photographs and analyses of 137Cs and 14C activities, suggest the discharge of U mineral particles while the site was being operated. Moreover, lead isotope ratios indicate that contamination in the WSL layer can be discriminated by a larger contribution of radiogenic lead to total lead. The dendroanalysis correlate U emissions from Rophin with the site's history. Oak tree rings located downstream of the site contain uranium concentrations ten times higher than values measured on unaffected trees. Moreover, the highest U concentrations were recorded not only for the operating period, but more surprisingly for the recent site renovations as well. This integrated approach corroborates that U mineral particles were initially transported as mineral particles in Rophin's watershed and that a majority of the deposited uranium appears to have been trapped in the topsoil layer, with high organic matter content.


Assuntos
Monitoramento de Radiação , Urânio , França , Mineração , Solo , Urânio/análise
18.
Environ Monit Assess ; 192(9): 564, 2020 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-32757090

RESUMO

The inventories and the possible mechanisms behind the relative deficiency of both radium and uranium release processes within an elevated gamma-anomalous rock were investigated. A field survey was performed on the highest radioactive anomalous zone that was recorded at Jabal Al Alam (20° 13' 10.06″ N and 44° 14' 32.13″), with the ferruginous sandstone, iron oxide band, and iron concretions (with uranium content and reaching up to1500 ppm). The chemical analyses and the laboratory's gamma-ray spectrometric measurements demonstrated high uranium levels in the analyzed rock samples of the Wajid Sandstone (up to 1000 ppm). The borehole geophysical logs further confirmed that the radioactive anomalies are attributed to the sandstone sequence of the Wajid Formation that is often found associated with elevated concentrations of uranium. The groundwater samples taken from the wells tapping the Wajid aquifer showed uranium concentrations ranging from 0.01 to 5.5 ppb (µg/L). The average 226Ra in groundwater samples was 0.2 Bq L-1. The majority of the 226Ra and 228Ra activities were below the lower limit of detection (LLD). The radiochemical analyses of water samples from the Wajid aquifer display low concentrations of both uranium and 226Ra, with relation to uranium content in host rocks. This was attributed to the fact that uranium is susceptible to form iron oxide complexes, causing them to precipitate in a more stable form. Furthermore, iron oxides coat the sand grains of the Wajid Formation and accordingly might act as a foundation for re-adsorption for both uranium and radium, resulting in their relative deficiency in the surrounding water. The coating might also act as a physical barrier resulting in hindrance of the recoil nuclei due to its significant thickness (several orders of magnitude) compared with that of the average (120 nm) whole alpha-recoil track (ART). The coating layer thickness was determined via scanning electron microscopy (SEM) and was found to be up to 180 µm.


Assuntos
Água Subterrânea , Monitoramento de Radiação , Rádio (Elemento)/análise , Urânio/análise , Poluentes Radioativos da Água/análise , Monitoramento Ambiental , Cromatografia Gasosa-Espectrometria de Massas , Arábia Saudita
19.
Arch Microbiol ; 202(10): 2711-2726, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32728830

RESUMO

In recent years, bioremediation is considered as an efficient method to remove the pollutants from the industrial wastewater. In this study, quantitative gene expressions (Real-time RT-PCR) of mtr gene cluster (mtrA, mtrB, mtrC, mtrD, mtrE, mtrF and omcA) in five different uranium concentrations (0.1, 0.25, 0.5, 1 and 2 mM) were performed with ICP and microscopic live cell counting analysis under anaerobic condition, by Shewanella RCRI7 as a native bacterium. The results indicated that the amount of uranium removal and live-cell counting were decreased in the higher uranium concentrations (1 and 2 mM), due to the uranium toxicity, suggesting 0.5 mM as the optimum uranium concentration for Shewanella RCRI7 resistance. The expression of mtrCED and omcA genes presented increasing trend in the lower uranium concentrations (0.1, 0.25 and 0.5 mM) and a decreasing trend in 1 and 2 mM, while mtrABF, presented an inverse pattern, proving the alternative role of mtrF for mtrC and omcA, as the substantial multiheme cytochromes in Extracellular Electron Transfer (EET) pathway. These data are a proof of these gene vital roles in the EET pathway, proposing them for genetic engineering toward EET optimization, as the certain pathway in heavy metal bioremediation process.


Assuntos
Biodegradação Ambiental , Proteínas de Membrana Transportadoras/genética , Shewanella/genética , Shewanella/metabolismo , Urânio/análise , Poluentes Químicos da Água/análise , Proteínas da Membrana Bacteriana Externa/genética , Grupo dos Citocromos c/genética , Transporte de Elétrons/genética , Família Multigênica/genética , Oxirredução , Águas Residuárias/química , Poluição da Água/análise
20.
Environ Sci Pollut Res Int ; 27(31): 38901-38915, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32638303

RESUMO

The spatial and vertical distributions of radon and uranium are evaluated in relation to the hydrogeology, geomorphology, and hydrochemistry of southwest Punjab. Radon activity of the groundwater ranges from 580 to 3633 Bq/m3 (shallow groundwater 580 to 2438 Bq/m3 and deep groundwater 964 to 3633 Bq/m3), and uranium concentration varies from 24.4 to 253 µg/L (shallow groundwater 24.4 to 253 µg/L and deep groundwater 27.6 to 76.3 µg/L). Shallow groundwater shows higher U concentration compared with deeper ones, which can be attributed to the presence of dissolved oxygen (DO) and NO3- as oxidants and HCO3- as stabilizing agent in shallow zone. Unlike uranium, the radon activities were found to be similar in both shallow and deep groundwater. Rnexcess over secular equilibrium was used to confirm the possibility of additional sources of radon, such as secondary minerals present in the subsurface. Surface manifestations show significant influence on radon and uranium distributions in the shallow zone but not in deep zone due to limited hydraulic connectivity. Depth profiles and correlations of radon and uranium with trace elements and hydrochemical parameters indicate that groundwater exhibits different redox characteristics in shallow (younger and oxidizing) and deep zones (older and reducing). The present study provides critical information that can be helpful for planning sustainable groundwater development in this region and other similar regions without contaminating the relatively safer deep aquifers.


Assuntos
Água Subterrânea , Radônio/análise , Urânio/análise , Poluentes Radioativos da Água/análise , Índia
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