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Rare earth elements (REE) can be found in expressive contents in different secondary sources, such as acid mine drainage (AMD). This work evaluated separation of light and heavy rare earth elements (REE) from an acid mine drainage (AMD) generated in a former uranium mine in Brazil by using ion exchange. This AMD presents pH 3.50, total REE content of 97 mg L−1 and 1.3 g L−1 of sulfate and was used in the REE loading experiments. Loading experiments were carried out in columns using a commercial strong acid cation (SAC) exchange resin. Elution was performed with 0.01 mol L−1 NH4EDTA in systems with one, two and three columns. Regarding the loading step, the resin presented a total loading capacity of 0.58 mmol g−1. The resin proved to be more selective for light REE with adsorption efficiency of 78% and 48% for heavy REE. Regarding elution, high efficiencies between 90 and 100% were achieved for REE. The final REE solution is approximately 10 times more concentrated in the liquor related to the acid mine water. Better fractionation results were achieved for the system with three columns. Although the complete separation of the REE into pure elements was not possible, two distinct fractions of heavy and light REE could be obtained, and La was completely separated from the other REE. In order to improve fractionation and separate the REE into individual ones, the concentrated fractions can proceed to subsequent ion exchange systems. [ABSTRACT FROM AUTHOR]

In Santa Quitéria City, part of the population uses surface water for potation. These waters do not undergo any treatment before consumption. As the region has a deposit of uranium, assessing water quality becomes important. In the present study, the uranium activity concentration (AC) in becquerels per liter was determined in water samples from six points. Univariate statistics showed differences between the soluble and the particulate fraction (soluble AC > particulate AC). The particulate fraction showed no variation in AC among the six points. On the other hand, the soluble fraction and the total fraction presented different ACs between them. The multivariate statistics allowed to separate the soluble from the particulate fraction of the points. The same tools applied to the total fraction made it possible to differentiate the sampling points, grouping them ((#1, #2); (#3, #4), and (#5, #6)). The maximum mean value of AC found was 0.177 Bq∙L−1, corresponding to 25% of the chemical toxicity limit (0.72 Bq∙L−1). The maximum mean dose rate, 2.25 µSv∙year−1, is lower than the considered negligible dose rate (> 10 µSv∙year−1). The excess lifetime cancer risk was 10−6, two orders of magnitude smaller than the threshold considered for taking action. The assessment parameters used in this work indicate that the risk due to the uranium intake by the local population is negligible. [ABSTRACT FROM AUTHOR]

The new coronavirus pandemic (2019-nCoV) arrived in Brazil in February 2020, where the worsening led to social isolation. The population started to remain entirely in their homes, mainly the elderly, children, and adolescents. The study aimed to determine the impact of radioecological dosimetry within the residences located in the municipality from Espinharas, Paraíba, Brazil, where one of the main uranium deposits in Brazil occurs. A scintillator-type gamma spectrometer with a combined NaI (Tl) and BGO probe, at 1.0 m from the soil surface, was used. A total occupation factor for the pandemic period was considered. The dose-response for the three months ranged from 0.55 to 1.70 mSv, with an average of 0.68 mSv, which characterises an increase of 25% when compared to the same period of the retrospective study in 2014. In the period of one year, the dosimetric response can vary between 2.22 and 6.80 mSv/y, with an average of 2.73 mSv/y. The work portrays the importance of a database for future affirmative actions and the determination of different radiometric conditions in an environment already considered to have a high level of natural radioactivity. The study also provides definitions of extreme exposure conditions and correlations with public health parameters. [ABSTRACT FROM AUTHOR]

Dams are built to contain water or mining tailings and provide several benefits to society. The safety and stability of these structures are essential since eventual accidents can generate catastrophic damage. The main cause of ruptures is associated with abnormal seepage, which can progress to an internal erosion process. To assess the stability and safety of dams, periodic inspections are carried out, which typically include visual inspections and geotechnical instrumentation. Some geophysical methods have the potential to assist conventional geotechnical instrumentation using non-destructive and rapid acquisition investigations. The present study applied a finite element forward modeling to evaluate the percolation conditions and water stability in an earth dam of a decommissioned uranium mine in Brazil. The dam is the final structure of the contention system of mine water treatment. The electrical resistivity data were acquired using electrical resistivity tomography (ERT) and Schlumberger array. The results were presented from the inversion of data in 3D models. The data were processed by open-source software (modeling and inversion of geophysical data). The results indicate the presence of water in the vertical filter located in the crest area. The different levels of investigation indicated water infiltration in the rock mass of the dam foundation. These results are supported by structural surveys carried out in the area that indicate a fracturing pattern in the rock mass of the mine area. The results of the study were satisfactory for the desired purposes and demonstrate that geophysical methods constitute an important complementary tool for the geotechnical monitoring dams. [ABSTRACT FROM AUTHOR]

The Osamu Utsumi mine was the first to economically mine uranium ore in Brazil. During its operation, a river valley was buried for the construction of the waste rock pile. The original stream was diverted to the northwest side of the pile and has since flowed into a diversion channel devoid of basal waterproofing, while an acid mine drainage (AMD) source flows at the base of this waste rock pile. This research aims to evaluate the possible relationship between water infiltration of the diversion channel and the AMD resurgence at the base of the pile using electrical resistivity tomography and induced polarization. 2D inversion models and pseudo-3D maps allowed the recognition of low resistivity zones (< 100 Ω·m) with high chargeability areas (10 mV/V). Some of these low-resistivity areas have been interpreted as infiltration zones in segments of the diversion channel into the pile, and in one of them, the flow intercepts a high chargeability area interpreted as a sulfide-rich zone that is expected to contribute to AMD at the base of the pile. Understanding the hydrogeochemical process will help select effective actions to mitigate the generation of AMD at the mine, which is currently in the decommissioning phase. [ABSTRACT FROM AUTHOR]

The Ore Treatment Unit was a uranium mining company that is currently being decommissioned. The local rainfall index makes it necessary to release effluents into the environment. After releasing, the wastewater is available for unrestricted use. Current study aims to use national and international recommendations to assess the radiological potability of released effluents at one of the three points of company's interface with the environment. Twenty-four samples of water were collected and activity concentrations (AC) were obtained by gross alpha count, gross beta count, and for arsenazo spectrophotometry. Statistical analysis techniques were applied to the data with the purpose of understanding the results for the soluble, particulate, and total fractions. The mean AC for effluents were 3.580, 0.082, 0.103, 0.063, and 0.090 Bq L−1 for Unat, 226Ra, 210Pb, 232Th, and 228Ra, respectively, for the total fraction. The analysis of variance pointed to Unat as a critical radionuclide, since it presented more than 90% of the total AC released into the environment. Pearson's R2 pointed to soluble fraction as a major contributor to the total AC released. The guidance level proposed by WHO was used to assess the radiological potability of the effluents. The results obtained indicated the need for trigger other analyses. Committed effective dose was estimated due to the unrestricted use of effluents and the value obtained, 0.23 mSv year−1, was below the maximum allowed limit. Finally, the radiotoxicity of the released effluent was evaluated and the value obtained was ~ 50% of the maximum allowed limit. In conclusion, the present study showed that the level of radioactivity released into the environment by the Ore Treatment Unit does not present a radiological risk to the surrounding population. [ABSTRACT FROM AUTHOR]

A hydrogeological analysis was conducted of aquifer systems within a sulfide-rich tailings pile and underlying rocks at a uranium mine to understand the generation and transport of AMD. A geophysical investigation was carried out along seven transects spaced 30 m apart using electrical resistivity tomography and a Wenner-Schlumberger array. The results were used as input to 2D and pseudo-3D models of resistivity and chargeability parameters. The geophysical results and models contrasted unaffected saturated zones and zones impacted by AMD, in addition to three areas within the tailings with a high sulfide content. The tailings and underlying fractured bedrock aquifer are hydrologically connected, which promotes the exchange of mine-influenced water into the regional aquifer. Releases from the site's tailings and other wastes can severely affect regional groundwater. [ABSTRACT FROM AUTHOR]

The current work addresses the study of the recovery of rare earth elements (REE) from acid mine water by using cationic exchange resin. The acid water was obtained from a closed uranium mine in Brazil. Ion exchange experiments were carried out in batch with three different resins at 25 ± 0.5°C and pH values 1.4, 2.4 and 3.4 (natural). Data were adjusted to the Langmuir equation in order to calculate the maximum loading capacity (qmax) of the resins. The results of qmax for individual REE revealed that the resins present higher loading for La in detriment to the other REE. The Dowex 50WX8 and Lewatit MDS 200 H resins demonstrated favourable sorption profiles to REE, evidenced by values of equilibrium factor (RL) and higher values of the Langmuir constants (b). The separation factors ( α H R E E L R E E ) indicates that resins are more selective for light REE at all pH studied. The selectivity of the resins for the REE can be described as light REE > heavy REE. The pH 1.4 and 3.4 are more favourable for the recovery of REE. [ABSTRACT FROM AUTHOR]

A mine in an area of naturally occurring radioactive materials (NORM), characterized by acid mine drainage, generates effluents with natural radionuclide concentrations, usually above the limits authorized by the regulator. The plant exploiting NORM controls the water quality and discharges it into the aquatic environment after meeting technical requirements. Downstream, water usage is unrestricted. In order to reach activity concentrations in the released effluents below the authorized values, the facility applies a chemical treatment to the effluent. Then, to ensure the effectiveness of the treatment, the facility performs sampling of treated effluent and determines the activity concentration of natural radionuclides (Unat, 226Ra, and 210Pb from the uranium series and 232Th and 228Ra from the thorium series). In the current study, the proportion and distribution of these radionuclides between the soluble and particulate fractions were determined. The measured activity concentrations were compared with the values proposed by the World Health Organization and Brazilian legislation, as well as other authorities, as regards the potable use from the radioprotection point of view. It was observed that the radionuclides are not in secular equilibrium. The fractions contribute differently to the total release of radionuclide, and there is no linear relationship between the fractions. The average activity concentrations did not result in radiological restrictions to water use, and the committed effective dose due to ingestion was estimated at 0.06 mSv y−1. Therefore, there is no radiological restriction to water use, since the dose which was found was below the constraint value for the public. [ABSTRACT FROM AUTHOR]

Airborne geophysics provides one of the most relevant data for uranium exploration. However, the application of radiometric surveys is decreasing considerably as the depth of exploration is increasing. Notwithstanding, there is still a large potential for radiometric data, especially using recent data processing techniques such as machine learning methods. In this work, we propose a new method to detect uranium anomalies through regression using the Random Forest machine learning algorithm (RF). The RF regression allows combining airborne geophysical data to predict the expected uranium content, which represents the uranium content generated by environmental effects such as lithology and pedogenesis. Therefore, the deviation (Ud) between the measured uranium and the expected uranium represents the secondary effects such as weathering, soil alteration, hydrothermal alteration or mineralisation process. We evaluated the relevance of the geophysical parameters proposed by previous authors in the prediction of the expected uranium (thorium, thorium potassium ratio, uranium potassium ratio, and Total Gradient Amplitude). Randomly selecting only 10% of the database as training data, we estimate the expected uranium with an R2 = 0.99 concerning the measured uranium. To assess the reliability of the Ud anomalies, we employed the proposed methodology in the Carajás Mineral Province (CMP), Brazil. In the CPM, the Ud anomalies showed a clear correlation with the several Iron Oxide Copper–Gold deposits (IOCG) and some IOCG-related and granite-related prospects. In situ measurements with a portable gamma-ray spectrometer in the Salobo mine supported the uranium anomalies. The Ud map also highlighted contrasts within granites that correlate with previously reported granitic facies. Therefore, the Ud map generated by RF regression is useful in setting exploration targets for conventional and unconventional uranium resources, as well as in high-detail granitic facies mapping. [ABSTRACT FROM AUTHOR]

Penicillium piscarium can be indicated as promising in the treatment of sites contaminated with uranium. Thus, this research aimed to analyze the P. piscarium dead biomass in uranium biosorption. This fungus was previously isolated from a highly contaminated uranium mine located in Brazil. Biosorption tests were carried out at pH 3.5 and 5.5 in solutions contaminated with concentrations of 1 to 100 mg/L of uranium nitrate. Our results showed that the dead biomass of P. piscarium was able to remove between 93.2 and 97.5% uranium from solutions at pH 3.5, at the end of the experiment, the pH of the solution increased to values above 5.6. Regarding the experiments carried out in solutions with pH 5.5, the dead biomass of the fungus was also able to remove between 38 and 92% uranium from the solution, at the end of the experiment, the pH of the solution increased to levels above 6.5. The analysis of electron microscopy, Energy‐dispersive spectroscopy, and X‐ray fluorescence demonstrated the high concentration of uranium precipitated on the surface of the fungal biomass. These results were impressive and demonstrate that the dead biomass of P. piscarium can be an important alternative to conventional processes for treating water contaminated with heavy metals, and we hope that these ecofriendly, inexpensive, and effective technologies be encouraged for the safe discharge of water from industrial activities. [ABSTRACT FROM AUTHOR]

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This study presents a hydrogeological characterization that fills knowledge gaps in an area where a complex geological scenario connects two fractured (granite/metamorphic rocks and diabase) and one porous (sedimentary rocks) aquifer systems. Previous groundwater studies from the four local deep supply wells suggested the sedimentary aquifer as the source of uranium (∼60 μg/L) in one of the wells. Despite the water extraction interruption from this well, this finding needed to be supported by evidence provided by the geological and structural characteristics of the aquifers. Data collected through video inspection, caliper, optical (OPTV), and acoustic borehole televiewers (ATV) revealed the predominance of the crystalline aquifer in the area. As recorded by video inspection, the well's borehole with high U intersects the crystalline rocks at several open fractures and presents the highest gamma radiation values. Therefore, we infer that the origin of dissolved U is the weathering of primary minerals locally occurring in those rocks. The U leaching and complexation as calcium-uranyl-carbonates favors its solubility in that specific aqueous medium, as shown by hydrogeochemical modeling using PHREEQC. Additionally, the major ions and trace elements concentrations allow the division of the wells into two groups: a) two with higher U concentrations, influenced by the granite/metamorphic aquifer and possibly longer residence times, and b) the other two wells with lower U concentrations, higher nitrate concentrations, influenced by the diabase aquifer, possibly have younger residence times. • The crystalline aquifer is the local source of dissolved U in the groundwater. • The occurrence of U-bearing minerals was inferred by gamma radiation measurements. • Uranyl and calcium carbonates are the prevailing U species in the groundwater. [ABSTRACT FROM AUTHOR]

The Ore Treatment Unit (in Portuguese Unidade de Tratamento de Minérios - UTM) located in Caldas, MG, Brazil is a disabled uranium mine. Environmental conditions generate acid drainage leaching metals and radionuclides from the waste rock pile. This drainage is treated to remove the heavy metals and radionuclides, before allowing the release of the effluent to the environment. To validate the treatment, samples of the released effluents were collected at the interface of the installation with the environment. Sampling was carried out from 2010 to 2015, and the activity concentration (AC, in Bq·l −1 ) of uranium in the liquid effluent was analyzed by arzenazo UV-Vis spectrophotometry of the soluble and particulate fractions, and of the sum of both fractions. Descriptive statistics, Z test and Pearson R 2 correlation among the fractions were performed. Then, the data were organized by year and both ANOVA and Tukey test were carried out to group the means by magnitude of AC. The annual mean ranged from 0.02 Bq·l −1 in 2015 to 0.11 Bq·l −1 in 2010. The soluble fraction showed a higher AC mean when compared to the mean of the particulate fraction and no correlation of the data could be observed. Concerning the magnitude of the release, the ANOVA associated with the Tukey test, identified three groups of annual means (AC 2010 > AC 2011 = AC 2012 = AC 2013 = AC 2014 > AC 2015 ). The mean values of uranium release at the interface installation-environment checking point (point 014) were within the Authorized Annual Limit (AAL) set by the regulator (0.2 Bq·l −1 ) indicating compliance of treatment with the licensing established for the unit. Finally, the data showed a decreasing tendency of U release. [ABSTRACT FROM AUTHOR]

To understand the mechanisms and origin of ore deposits, it is essential to know their age. However, the processes responsible for ore formation do not always leave a geochronological record, with hydrothermal processes often either not affecting zircon or causing only partial resetting. The Lagoa Real uranium province hosts the most important U resource in Brazil. The U mineralization is hosted by Na-rich rocks known as albitite, which also contain variable amounts of garnet, clinopyroxene, biotite, amphibole, magnetite and titanite. These rocks are presumed to be the result of hydrothermal alteration of the Lagoa Real intrusive suite, a group of A-type granitic rocks emplaced between 1740 and 1720 Ma. Despite the economic importance of these rocks, determining the age of metasomatism and U mineralization has been extremely difficult, with previous attempts using a variety of methods and targeting the whole rock, titanite, uraninite, heavy-mineral concentrates and zircon, yielding a wide variety of ages in the range of 1.5 to 0.9 Ga. This study is the first to directly date metasomatic minerals (garnet and titanite) with the in situ U–Pb dating method. Garnet and titanite from an unmineralized sample gave U–Pb ages of ca. 545 Ma and ca. 520 Ma, respectively. U–Pb dating of zircon from two other unmineralized samples yielded ages of 1740–1720 Ma, interpreted as igneous ages. Electron-microprobe dating of uraninite from mineralized samples produced ages of 530–520 Ma. Altogether, these results suggest that both metasomatism and U mineralization occurred as a result of fluids associated with the gravitational collapse phase (ca. 530–480 Ma) of the Araçuaí–West Congo orogen. This study illustrates the utility of U–Pb dating of andradite garnet for determining the age of mineralization related to metasomatism. • Zircon of the metasomatic rocks records age of ca. 1740 Ma similarly with the São Timóteo granite crystallization age. • Andradite in situ U–Pb geochronology suggests hydrothermal and U- mineralization events at 545 ± 3 Ma. • Titanite in situ U–Pb geochronology suggests hydrothermal and U- mineralization events at 521 ± 11 Ma. • Uraninite in situ EMPA geochronology suggests U-mineralization between 530 and 520 Ma. [ABSTRACT FROM AUTHOR]

This study aimed at assessing the incorporation of radionuclides in animals in the proximity of the uranium mine in Caetité, Brazil. In 2014, samples of bovine and equine teeth and skull bones were collected and their contents of natural and artificial isotopes were assessed using nuclear spectrometry techniques. Gamma ray emission from 226,228 Ra and 40 K isotopes was determined using high-purity germanium (HPGe) spectrometry, 90 Sr radioactivity was measured with liquid scintillation, and 234,238 U, 232,230,228 Th, 210 Po and 239+240 Pu radioactivity was assessed with alpha-spectrometry. Prior to the measurements, sample dissolutions and isotope separations were performed. Our results indicate a high 228 Th isotope content in the skull bones and the teeth of animals, up to 179 Bq per kg of ash. The 226 Ra and 228 Ra concentrations were slightly lower. Activity concentrations of other isotopes were significantly lower or below the detection limit. We could not identify sources of technologically enhanced levels of 228 Ra in the area we investigated; therefore we suggest that their origin is natural. [ABSTRACT FROM AUTHOR]

Sited in the Poços de Caldas Plateau, in south-eastern Brazil, the Uranium Mining and Milling Facilities (UMMF) of Caldas are in the process of decommissioning. The main environmental problem in this site is the generation of acid mine drainage (AMD) in the tailings dam, open pit and waste rock piles. The aim of this work is to evaluate, by hydrochemical studies, the influence of acidic effluents from the Caldas UMMF, on the hydrochemistry of surface water along three watersheds: Consulta Brook, Soberbo Creek and Taquari River. Twelve sampling stations were established to carry out the investigation. Two of them were located at effluent retention ponds. Sampling was performed in the rainy and dry seasons of 2011, and the measured parameters were Eh, pH, EC (electrical conductivity), SO, HCO, Cl, Na, K, Ca, Mg and Fe. The results have shown that iron is not a main constituent of the ionic composition of the local AMD. It could also be observed that acidic effluents were being discharged from retention ponds into the watercourses, causing a pronounced increase of the sulfate and calcium concentrations downstream. To trace the AMD migration the (SO/HCO)/(Na + K/Ca) ratio was used. A detailed investigation of the near-surface groundwater is recommended downstream of the effluent ponds sites to evaluate the need for mitigating actions such as constructing hydraulic barriers. The present article shows that using simple techniques, such as Eh-pH and Piper diagrams, it is possible to depict the AMD fluvial migration pattern, which is an important information both to the authority responsible incumbent upon the remediation of the site, and to the affected interested parties who inhabit the impacted region. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the environmental waste management of the Heap-Leach Uranium Production Facility of Caetité located in a semi-arid region in Brazil. A comparison is made with the first uranium production site of the country located in Poços de Caldas. It is demonstrated that differences in the operational process along with different environmental conditions can lead to different impacts. In the present case groundwater is the potential most sensitive environmental medium despite the well-established consensus in the literature that radon and aerosol emissions may turn-out to be the most relevant environmental aspects of an installation located at this type of region. Most of the 226Ra content in the ore remains in the leached ore that is deposited with the waste rock. A lack in appropriate prediction of the hydrological balance has been causing unanticipated emissions of liquid effluents into the environment. Chemical treatment of this effluent may be needed. Contamination of groundwater in the short term by the waste ponds is not to be expected but it can be a relevant issue in the long term. As a consequence, careful closure schemes will need to be put in place. Finally, the overall costs with remediation in the Caetité production center are lower than those observed at the Poços de Caldas mining site. [Copyright &y& Elsevier]

Uranium mining and processing at Lagoa Real (Bahia, Brazil) started in 2000. Hydrogeochemical monitoring carried out from 1999 to 2001 revealed generally good quality of the water resources outside and inside the mineralized area. No chemical contamination in waters for domestic uses was observed. Hydrochemical characteristics did not vary significantly after 1 year of U exploitation, as compared to premining conditions. Due to the short time of mining, the results cannot exclude future variations in water quality. Leaching experiments helped to describe processes of ore and waste degradation. Sulfate was identified as an indicator for different types of contamination. Potential hazards related to local climate (hot rainy season) were identified. They indicate that tailings derived from the ore processing, destabilized by sulfuric acid attack, may induce acidification and salinization in the surrounding environment. Another potential source of environmental impact could be linked to local radium-rich mineralization, originating radon emission. [ABSTRACT FROM AUTHOR]

The Lagoa Real uranium (U) province, referred to as Lagoa Real, is located in the state of Bahia, north-eastern Brazil. Lagoa Real has ∼112,000 metric tonnes and average grade of 2700 ppm of U 3 O 8 , being one of the largest U deposits in the world and the largest in Brazil. Despite its economic and strategic importance, there are gaps in the geological knowledge of the Lagoa Real U deposits. One of them is the lack of extensive whole-rock chemical data sets. Here, we present whole-rock chemical analyses for major and trace elements, including the rare-earth elements (REE), from barren country rocks to uraniferous ore shoot, systematically sampled from an exploratory drill hole. The chemical data indicate that albitite rocks, with and without uraniferous mineralisation, cannot result from sodic syenitic magmatism, as proposed by recent studies. Petrographical and geochemical evidence supports the previously suggested concept that the Lagoa Real albitite rocks resulted from sodic metasomatism of the granitic country rock, known as the São Timóteo granite. Their ore-mineral assemblages and geochemical characteristics are similar to albitite-hosted U deposits worldwide. [ABSTRACT FROM AUTHOR]

It is important to understand the environmental fate and potential risks posed by metals and metalloids around mines and in legacy mining areas. In order to assess the bioavailable concentrations of several potentially toxic elements (PTEs: As, Pb, Cd, Ni, Cu, Cr, Mn, Zn, Ba, U) and rare earth elements (REEs: La to Lu), a multi-method evaluation of their concentrations/fractionation/speciation in soils was related to their biouptake in corn, for a region surrounding a legacy U mine in Brazil. Chemical fractions of the PTE and REE in soils were determined using the BCR (Community Bureau of Reference) sequential extraction procedure; a single extraction with Ca(NO 3) 2 and the diffusion gradient in thin films (DGT) technique. All techniques were better correlated to the metals accumulated by the crops as compared to total metal concentrations. Ba, Cu, Mn and Zn were shown to have high mobility and high bioaccumulation factors in the corn. Concentrations of U, As, Cd, and Pb were above threshold concentrations and strongly correlated, suggesting that they had a similar anthropogenic source. Geospatial modeling agreed with results from principal component analysis, indicating multiple sources for the contamination. Results highlighted the need for multi-method approaches when evaluating the long-term risks posed by PTEs and REEs in agricultural soils. Image 1 • Potentially toxic elements and REE are accumulated by plants in a U mining area. • Chemical extractions and DGT correlated well with the metal bioavailability. • Geospatial modeling, PCA and FA indicated multiple sources of soil contamination. [ABSTRACT FROM AUTHOR]

The Osamu Utsumi uranium mine occupies a 20 km2 area in the city of Caldas, which is located in the state of Minas Gerais, Brazil. Since mining activities ended at Osamu Utsumi 24 years ago, the surrounding area has become contaminated by acid effluents containing high concentrations of uranium. Thus, the aim of this study was to assess the uranium bioremediation capacity of 57 fungi isolated from the mine area. In tolerance tests, 38% (22) of the fungal isolates were considered tolerant to uranium, including 10 Penicillium species. At a uranium concentration of 2000 mg L−1 48 fungi did not exhibit mycelial growth index inhibition. Minimal inhibitory concentration (MIC) analysis showed growth of 25 fungi above a uranium concentration of 8000 mg L−1. At high uranium concentrations, some fungi (i.e., Talaromyces amestolkiae and Penicillium citrinum) showed morphological changes and pigment (melanin) production. Among the fungal isolates, those considered to be more tolerant to uranium were isolated from soil and sediment samples containing higher concentrations of heavy metal. When comparing the results of resistance/tolerance tests with those for uranium biosorption capacity, we concluded that the fungi isolated from the Osamu Utsumi mine with the best potential for uranium bioremediation were Gongronella butleri , Penicillium piscarium , Penicillium citrinum , Penicillium ludwigii , and Talaromyces amestolkiae. Biosorption tests with live fungal biomass showed that 11 species had a high potential for uranium uptake from contaminated water. • Fifty seven fungi were isolated from the uranium mine area. • In tolerance tests, 38% of the fungal isolates were tolerant to uranium. • The majority of tolerant fungi were isolated from soil samples. • Some fungi showed morphological changes and pigment (melanin) production. • Biosorption tests showed species with high potential for uranium uptake from water. [ABSTRACT FROM AUTHOR]