Bauxite Research Articles

Verification of the sampling procedure for radioactivity analysis of waste and industrial material.

In accordance with ISO/IEC 17025:2017, the testing laboratory needs to verify its ability to properly perform methods. For radiological testing, the sampling does not affect the results directly, but it has to ensure that sample adequately represents the tested material. To verify the procedure, a sampling of red mud and bauxite ore was conducted. All samples were measured in identical geometry by HPGe spectrometer. The counting rates per unit mass in the recorded spectra were compared. For each measurement series, the mean and standard deviations of respected peaks were calculated, as well as average and standard deviation of all series. The obtained results of each individual series were considered satisfactory, i.e. sampling procedure ensures the representativeness of the bulk material, if it is within ± two standard deviations of the average of the mean values.

Impact of Bauxite Mining on Soil Chemical Properties at Several Depths

Bauxite is one of the mining commodities that have high economic value as a contributor to the country’s foreign exchange with a potential of 349.61 million tons. The potential for bauxite is large enough to cause soil damage at the beginning of mining because to get bauxite ore, it has to move the layer of soil above it. Soil damaged by the bauxite mining process was improve with reclamation activities, which is one of the PT ANTAM obligations after the extraction of bauxite ore is complete. The soil in the reclamation area after bauxite mining has some very low soil chemical properties, for example the nutrient content of N, K, Ca, Mg and Na. In addition, the cation exchange capacity is very low, each ranging from 2.56 - 5.82 Cmol(+).kg−1, while base saturation is between 6.53 – 12.45%. Soil pH values ranged from 4.32 to 5.11 which was classified as very acidic to acidic. There is a tendency in the deeper soil layers some soil properties to decrease, such as pH, CEC, base saturation and C-organic content.

Effects of Dosage and Type of GGBS on the Mechanical Properties of a Hybrid Red-Mud Geopolymer

Bayer red mud (RM) is made from aluminum ore using the Bayer process and is considered an industrial waste. The storage of unused RM can cause environmental and geological problems. Although several studies have focused on RM geopolymers, the amount of RM consumed by these synthetic geopolymers is small (usually <50%). Therefore, in this study, a hybrid geopolymer material with more than 90% RM content was developed and made it possible to apply in engineering construction. The consumption of a considerable amount of RM would reduce the massive accumulation of RM and address the shortage of natural construction materials. Experiments were conducted with ground granulated blast-furnace slag (GGBS) as the activator. Two different active GGBSs were selected to stabilize the RM by geopolymerization. The effects of dosage and type of GGBS on the mechanical properties of RM were investigated by conducting unconfined compression tests and disintegration and compression experiments. The experimental results indicated that the type and dosage of GGBS had a significant effect on the mechanical behavior of RM. Based on the unconfined compressive strength (UCS) values and the results of the disintegration and compression experiments, the optimal RM-GGBS mixed geopolymer was determined by orthogonal analysis. Microscopic analysis showed that under optimal conditions, the amorphous phase participated in the geopolymerization process, forming an amorphous geopolymer that improved the mechanical properties of RM.

Genetic mechanism of super-large karst bauxite in the northern North China Craton: Constrained by diaspore in-situ compositional analysis and pyrite sulfur isotopic compositions

>5 billion tons of karstic bauxites were formed during the Late Carboniferous in the North China Craton (NCC). However, the metallogenic mechanism of bauxite is still obscure due to the unclear formation process of the main ore mineral, diaspore. We conducted geological, mineralogical, δ34Spyrite, and in-situ diaspore trace element analyses on the Baode-Xingxian large bauxite deposit in the northern NCC, aiming to clarify the diaspore-forming mechanism and explore the genesis of bauxite. Generally, bauxites in northern NCC contains three layers from bottom to top: Fe-bearing claystone, bauxite ore, and claystone. The bauxite ore is mainly diaspore, kaolinite, and illite; the Fe-bearing claystone is illite and berthierine; and the claystone is primarily kaolinite. The broadly distributed high positive δ34Spyrite values (10‰–40‰) indicate that bauxites in the northern NCC formed in shallow-water environments. Total 216 diaspore grains have similar trace element compositions, and are obviously enriched in Cr, V, Re and U, but not in Mo, indicating that diaspore was formed in the subreduced facies. Diaspore with Fe/Al up to 4 mol% has slightly large cells, indicated that small-scale larger ions, Fe, entered the diaspore lattice to form Fe-diaspore. The favorable temperature and water activity of Fe-diaspore precipitation is similar to that of Al-hematite+ boehmite. We thus propose a probable diaspore formation mechanism: the small scale of Fe for Al substitution in the diaspore lattice and stabilize it to induce Fe-diaspore formation. Fe-diaspore is metastable with respect to diaspore and tends to convert into it during the diagenesis process.

Trade network characteristics, competitive patterns, and potential risk shock propagation in global aluminum ore trade

Aluminum is an essential strategic mineral resource. The geographical space distribution characteristics make the aluminum ore trade relationship more complicated. This paper analyzes the evolution characteristics, spatial migration, and trade competition of aluminum ore trade from 2011 to 2020. This paper constructs the aluminum supply risk propagation network Aluminum Supply Risk Spread Network to analyze the propagation path, impact scope, and potential impact of different risk outbreak sources. The results show that a few countries control more aluminum ore resources, and the trade community and center of trade gravity have changed significantly. Trade competition gradually intensifies, mainly concentrated in Asia and Europe. When supply risk occurs, the threat spreads rapidly. This paper selects four major trading countries Brazil, Guinea, Australia, and China, as risk outbreak countries. Risk outbreak mainly shows three typical characteristics. Meanwhile, indirect infections account for a large proportion, and China plays an essential role in trade. Finally, based on these findings, some suggestions to maintain the stability of the aluminum resource trade and improve its ability to resist risks for China.

New Polymer Composites with Aluminum Phosphates as Hybrid Flame Retardants.

Polymeric aluminum organophosphates are a class of nanostructured aluminum-based compounds that can be considered organic and inorganic hybrid materials. Aluminum phosphates have attracted considerable interest due to their ability to enhance composite materials' mechanical characteristics, lightweight, and thermal properties. Extensive studies have shown the potential of aluminum organophosphates as a component in the development of fire-retardant materials. Aluminum-organophosphorus hybrid (APH) materials have been prepared by reacting aluminum oxide hydroxide (boehmite) with alkyl and aryl phosphoric acids and used to prepare composites with epoxy resin. Boehmite is an aluminum oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminum ore bauxite. In this work, the composites based on epoxy resin Epidian 601 and commercial curing agent IDA were obtained. Pure boehmite and APH hybrids were added as flame retardants. FTIR and TGA analysis showed that obtained APH possesses a hybrid structure, high thermostability, and various morphologies. These new APH were incorporated into epoxy resin. The infrared spectroscopy confirmed the structure of hybrids and composites. Pyrolysis combustion flow calorimetry (PCFC) and cone calorimeter analyses were performed to assess the flame retardant properties of the composites. The results showed that the incorporation of 17 wt% APH allows a reduction of heat release rate but to a limited extent in comparison to pure boehmite, which is due to the different decomposition mechanisms of both boehmite and hybrids. The cone calorimetry test showed that residue contents correspond quite well to the mineral fraction from boehmite only. The hybrid APHs appear no more efficient than pure boehmite because the mineral fraction in APH is reduced while phosphate fraction cannot promote significant charring.

Characterisation of stabilised red mud waste material for road infrastructure

Red mud is an industrial waste material generated during the extraction of aluminium metal from bauxite ore. It is deposited in a slurry form into the dam which is called the tailing dam near the industry. It is occupying large costly land without uses. Its production is about 9 million tons/year in India. To investigate its potential application in road infrastructure, it was collected from M/s Vedanta Ltd. Lanjhigarh, Odisha. Basic geotechnical characterisation of red mud was carried out in the laboratory. To improve its geotechnical properties, it was stabilised with cement in the range of 3 to 9 % to investigate their potential application in subbase and base layers of road infrastructure. Compressive and durability characteristics of stabilised red mud were also studied. A laboratory study concluded that red mud is a fine-grained silt-size material. Other geotechnical properties are similar to conventional silty soil viz. dry density, and shear strength. Unconfined compressive strength and durability characteristics indicated the suitability of cement-stabilised red mud for the construction of subbase and base layers of road infrastructure as per Indian road congress guidelines. Application of red mud will lead to the sustainable development of road infrastructure and will reduce environmental pollution.

MODELLING MICROWAVES IN BAUXITE

AbstractSending microwaves through bauxite ore allows almost continuous measurement of moisture content during offload by conveyor belt from a ship. Data and results from a microwave analyser were brought to a European Study Group with Industry at the University of Limerick, with the over-arching question of whether the results are accurate enough. The analyser equipment uses linear regression against phase shifts and signal attenuation to infer moisture content in real time. Simple initial modelling conducted during the Study Group supports this use of linear regression for phase shift data. However, that work also revealed striking and puzzling differences between model and attenuation data.We present an improved model that allows for multiple reflections of travelling microwaves within the bauxite and in the air above it. Our new model uses four differential equations to describe how electric fields change with distance in each of four layers. By solving these equations and taking reflections into account, we can accurately predict what the receiving antenna will pick up.Our new solution provides much-improved matches to data from the microwave analyser, and indicates the deleterious effects of reflections. Modelled signal strength behaviour features a highly undesirable noninvertible dependence on bauxite mixture permittivity.Practical measures that might be expected to reduce the effects of microwave reflections and improve the accuracy of microwave analyser results are suggested based on our improved model solution. This modelling approach and these results are anticipated to extend to the analysis of moisture content during transport on conveyor belts of other ores, slurries, coal, grains and pharmaceutical powders, especially when the depth of the conveyed material is variable.

Upgraded Analytical Protocols in Bauxite Refining Industry Using Composite Sampling Approach to Minimize Laboratory Analysis Load

The laboratories in the bauxite processing industry are always under a heavy workload of sample collection, analysis, and compilation of the results. After size reduction from grinding mills, the samples of bauxite are collected after intervals of 3 to 4 hours. Large bauxite processing industries producing 1 million tons of pure aluminium can have three grinding mills. Thus, the total number of samples to be tested in one day reaches a figure of 18 to 24. The sample of bauxite ore coming from the grinding mill is tested for its particle size and composition. For testing the composition, the bauxite ore sample is first prepared by fusing it with X-ray flux. Then the sample is sent for X-ray fluorescence analysis. Afterwards, the crucibles are washed in ultrasonic baths to be used for the next testing. The whole procedure takes about 2 - 3 hours. With a large number of samples reaching the laboratory, the chances of error in composition analysis increase. In this study, we have used a composite sampling methodology to reduce the number of samples reaching the laboratory without compromising their validity. The results of the average composition of fifteen samples were measured against composite samples. The mean of difference was calculated. The standard deviation and paired t-test values were evaluated against predetermined critical values obtained using a two-tailed test. It was found from the results that paired test-t values were much lower than the critical values thus validating the composition attained through composite sampling. The composite sampling approach not only reduced the number of samples but also the chemicals used in the laboratory. The objective of improved analytical protocol to reduce the number of samples reaching the laboratory was successfully achieved without compromising the quality of analytical results.

Radiological and X-Ray Diffraction Characterization of Bauxite and Rutile Ore Contaminated Environment in Kanam and Wase Mineral Exploration Sites, Plateau State-Nigeria

Radiological and X-Ray Diffraction Characterization of Bauxite and Rutile Ore Contaminated Environment in Kanam and Wase Mineral Exploration Sites, Plateau State-Nigeria

Mineralogical Study of Bauxite of Kenco Area, Landak District, West Kalimantan Province, Indonesia

Indonesia is a country with a tropical climate that allows for high levels of weathering. Bauxite is the result of weathering rocks that have high aluminum content, low iron content, and little quartz content. The formation of bauxite deposits is controlled by source rock which is rich in Al element, tropical climatic conditions, and geomorphological conditions that allow the formation of the accumulation of weathered source rock products. The altered silicate minerals due to weathering result in the silica element being released from the crystal bonds and some iron are released so that the aluminum element is concentrated as a residual precipitate. X-ray diffraction (XRD) analysis on 16 bauxite samples which are estimated to represent the overburden horizon, bauxite ore horizon, clay horizon, and source rock to establish the mineral composition of bauxite. Mineral groups in the overburden horizon, bauxite ore horizon, and clay horizon are alumina, iron, titanium, silicates, carbonates, sulfides, and sulfates, while mineral groups in source rock are iron, titanium, silicate, sulfide, and sulfate. The type of bauxite in the study area is gibbsite bauxite based on the dominant appearance frequency of gibbsite compared to mineral corundum as an alumina group.

Mechanical properties of pavement quality concrete with aluminium industry waste as a binder

Utilizing industrial marginal materials in the production of concrete makes it economical by reducing the cost of cement and reduces the environmental risk associated with Ordinary Portland Cement (OPC) production. Aluminium Dross (AD) is an industrial by-product from aluminium industry obtained during resmelting of aluminium ore in the furnace at high temperatures. Dumping of this waste in landfill makes it difficult to facilitate large area required and causes nuisance to the surrounding environment. Also, it is required to minimize the use of Ordinary Portland Cement (OPC) due to higher energy consumption involved in its production. AD is pre-treated and tested by Toxicity Characteristic Leaching Procedure (TCLP) to check its leachability. In this study, mechanical properties of concrete along with flexural fatigue behaviour are discussed with respect to partial replacement of AD for OPC. Strength properties of concrete at 15% AD replacement is comparable with that of control concrete. Scanning Electron Microscope (SEM) image of the concrete mix with 15% AD is taken to observe minor voids in comparison with the SEM image of normal concrete mix. Flexural fatigue behaviour is evaluated at varying stress levels and found that the concrete with 15% AD is satisfying the requirements to be used as Pavement Quality Concrete.

U-Pb detrital zircon ages and Hf isotope from Sardinia and Adria Cretaceous bauxite (Italy): Constraints on the Alpine Tethys paleogeography and tectonic evolution

Bauxite deposits in Italy mainly distribute in Sardinia and Adria regions within Cretaceous carbonate sequences. Parental affinity of Italian bauxite deposits has long been a controversial problem. At least four potential sources have been proposed: (1) Cretaceous debris and autochthonous marlstones; (2) alluvial sheets from the weathered Variscan basement; (3) weathering materials from North Africa and (4) Cretaceous bimodal volcanism in the Dinaric and Carpatho-Balkan orogenic belts. In this study, a total of 374 detrital zircon U-Pb ages and 86 Hf isotope values have been acquired from Cretaceous bauxites of Sardinia and Adria regions. Combining with the published geochemical data, provenances of Cretaceous bauxite deposits in Sardinia and Adria regions have been discussed. In bauxite deposits of Sardinia, dominant Early Paleozoic aged zircon grains (main age peaks at 291 – 295 Ma, 454 – 465 Ma, and 582 – 639 Ma) and their various Hf isotope compositions (εHf(t) = +9.61 to −5.66) indicate a parental affinity of Variscan metasedimentary basement. As a contrast, bauxite deposits in Adria show abundant Jurassic – Cretaceous (93 – 178 Ma) zircon grains with negative εHf(t) values (-13.75 to −4.61), demonstrating significant supply from coeval volcanic materials. Cretaceous bauxite samples from Sardinia and Adria shed light on paleogeographic restoration and tectonic evolution of Alpine Tethys. Began in Early Cretaceous, Sardinia was affected by uplift due to the subduction between Ligurian oceanic crust and the Iberia plate. The Mesozoic carbonate sequence were eroded and the underlying Variscan basement was exposed in the area from Sardinia to the Massif Meridional, provided weathering materials for bauxitization. Late Cretaceous witnessed the further NNE-trending subduction of the Adria Plate to the West Vardar oceanic plate, where calcalkaline igneous rocks and volcanic ashes from Dinarides supplied windborne weathering materials to carbonate platforms in Adria. Particularly, provenance difference between the bauxite of central-southern Apennine and Sardinian reveals that the hosting carbonate sequence in Apennine was not located on the Sardinia shelf before the Cenozoic tectonism in the south Mediterranean realm. Diversity of provenances in bauxite deposits from Sardinia and Adria may cause differences in geochemical composition and further influence qualities of bauxite ore in two regions.

Metallogenic process of Permian Taiping karstic bauxite deposit in Youjiang Basin, China

More than 1 billion tons of bauxite was formed on the karstic surface of the Permian Maokou Formation limestone in the western Guangxi area of Youjiang Basin (YB). However, its formation mechanism is still a matter of debate. In this study, the Taiping bauxite deposit, a representative large deposit in this area, was selected to carry out detailed mineral microanalysis and pyrite sulfur isotope analysis to further understand the metallogenic process of bauxite in this region. Taiping bauxite contains two layers: the lower bauxite layer and the upper claystone layer. Bauxite ore was mainly composed of diaspore, pyrite, anatase, kaolinite, minor pyrophyllite, parisite, and bastnäsite. Small amounts of detrital moissanite, native boron, and zircon were also found in the ore. The claystone was dominated by kaolinite, diaspore, pyrite, and chlorite. The occurrence of detrital zircon, moissanite, and native boron suggests that they were most likely derived from volcanic ash or lava, further confirming the contribution of volcanoes. The mineral assemblages of diaspore, pyrite, anatase, parisite, and bastnäsite in the bauxite ore indicate alkaline and reducing depositional environments. The extensive development of ovoid microorganisms and the significant negative δ34S values of pyrite (−42.80 ‰ to −12.54 ‰) indicate that microorganisms were involved in the formation of bauxite. This view was further confirmed by the wide development of fine pyrite (∼1 μm) cemented by cryptocrystalline diaspore in the ore. Extensive volcanism promotes the weathering of parent rocks, releasing Al3+, Fe3+, Ti4+, and REE3+ ions into the weathering system. Under strongly acidic and oxidizing conditions in the upper part of the weathering profile, these ions can migrate downward until they reach an alkaline and reducing environment on the carbonate surface. A large amount of diaspore, pyrite, anatase, parisite, and bastnäsite was formed near the karstic surface with the participation of microorganisms. Epigenetic modifications were also evident in the widespread development of kaolinite and pyrophyllite formed by the silicification of diaspore.

Phase equilibria and thermodynamic assessment of the Al2O3-SiO2-Sc2O3 system

Sustainable utilization of Sc2O3 in the bauxite ore residues has recently attracted significant interest in industries and research community. However, few thermodynamic and experimental data has been reported for Sc2O3 systems, which greatly limits the sustainable utilization of Sc2O3 in the bauxite ore residues. This study was carried out to develop an understanding of the phase equilibria of the Al2O3-SiO2-Sc2O3 ternary system and furnish essential information for the recovery of Sc2O3 from the bauxite ore residues. Therefore, a combined thermodynamic assessment and experimental investigation were performed for the Al2O3-SiO2-Sc2O3 ternary system. The phase equilibria of the ternary system based on Al2O3-SiO2-Sc2O3 was established at 1773 K and 1873 K using a thermodynamic equilibrium experiment. The obtained experimental results and findings from a systemic literature survey were utilized for the thermodynamic assessment to arrive at a thermodynamic data set pertaining to the Al2O3-SiO2-Sc2O3 system. Based on the thermodynamic data obtained in the study, isothermal sections at 1773 K and 1873 K were computed, and subsequently, a comparison was made with the available experimental data. The theoretical calculations corroborated quite well with the experimental findings, thereby demonstrating that the current thermodynamic data is credible and self-consistent.

Production of Micron-Sized Particles of Bauxite by Circulating Pulverization Experiment

A novel process involving the production of micron-sized particles of bauxite by circulating pulverization experiment is proposed. This method is through high-pressure gas infiltration, uniform and equal stress loading, and overcoming tensile strength between particles, which is different from the traditional ball milling based on overcoming compressive or shear strength. The circulating pulverization experiment is designed so that the coarse particles larger than 147 μm need to be repulverized or added to the new bauxite ores and repulverized under the same experimental conditions. The results of the first group of circulating experiments show that the proportion of particles less than 147 μm increases from 27% to 91%, which reveals that the coarse particles larger than 147 μm can be repowdered. The results of the second group of circulating experiments show that the powdering efficiency of particles larger than 147 μm is almost equivalent to the raw ore, and the proportion of particles less than 147 μm after four circulating pulverization experiments can reach 64.5%. The result is crucial for actual production because coarse particles will fill in the raw ore and be repulverized together, which can ensure continuous production and stable pulverization efficiency. Economic analysis reveals that the power consumption of the circulating pulverization experiment is estimated at 0.028$ per ton.

Investigation of Radiological and Chemical Contents of Bauxite Ore Extracted in Turkey.

In this study, which consists of two parts, the radiological and chemical content of bauxite ore was investigated. Gamma-ray spectrometry was used in the first part of the study to determine the activity concentrations of natural radionuclides in samples taken from bauxite deposits in Turkey. The measured activity concentrations of 226Ra, 232Th, and 40K varied from 12.1 ± 2.5 to 132.6 ± 11.4 Bq kg-1 with a mean of 78.4 ± 8.3 Bq kg-1, 6.5 ± 0.5 to 97.3 ± 9.9 Bq kg-1 with a mean of 64.5 ± 5.9 Bq kg-1, and 5.1 ± 0.0 to 356.4 ± 40.1 Bq kg-1 with a mean of 52.6 ± 5 Bq kg-1, respectively. The calculated mean radium equivalent activity value is 177.4 Bq kg-1, the mean gamma dose rate absorbed in the air is 78.8 nGy h-1, the mean corresponding annual effective dose value is 96.6 μSv y-1, and the mean lifetime risk of cancer is 3.85 × 10-4. The chemical content of the bauxite samples was determined in the second part of the study using X-ray fluorescence spectrometry (XRF). For which sectors in the industry the existing bauxite deposits in Turkey can be used was investigated based on this information.

Removal of organic compounds from Bayer liquor by oxidation with sodium nitrate

Large amounts of organic-containing bauxite ores are used during alumina production. Here, based on sulfur removal by NaNO3 oxidation during actual production, we propose a method involving NaNO3 wet oxidation to remove organic matter during bauxite dissolution. The effects of different dosages of NaNO3, oxidation temperatures, and oxidation times on the organic carbon removal efficiency, sodium oxalate concentration, and sodium humate concentration were studied. The organic carbon removal efficiency was 85.2% under the most suitable conditions (5% NaNO3 and 13% CaO relative to the mass of bauxite; oxidation temperature of 260 °C; oxidation time of 60 min). The oxidation and removal of sodium humate were high, but those of sodium oxalate were poor. The red mud obtained under the optimal conditions was analyzed.

Application of Volume Uncertainty for Resource Classification: A Case Study on the Rondon Do Pará Bauxite Deposit, Brazil

This study illustrates the application of conditional simulations to calculate the uncertainty associated with the thickness of bauxite ores. The bauxite deposit of Rondon do Pará in northern Pará State, Brazil, is characterized by a well-defined lateritic profile, with the ore being composed of two sequential horizons: massive bauxite and ferruginous bauxite. This study used ore thickness data from 1.005 drillholes with different grid spacing. Drillhole intervals of both types of bauxite ore were accumulated, converting the database from 3D to 2D. Sequential Gaussian simulation produced probability maps calculated from certain confidence intervals, which permits obtaining the uncertainty associated with estimates in thickness. Results show that in portions with the same regular drillhole spacing there are different ranges of uncertainty and variability, which could be useful to support resource classification, associating different confidence intervals to resource classes. This analysis could also guide the drilling program for resource conversion in order to optimize costs, indicating areas where there is greater uncertainty and would need to be densified. The incorporation of this information into the resource model could be very helpful for supporting subsequent studies of economic evaluation and risk analyses with respect to this type of deposit or similarly in mineral exploration.

Distribution of metals in different environmental compartments and oxidative stress biomarkers in Bryconops caudomaculatus (Osteichthyes: Characiformes) from a bauxite mining area in the Eastern Amazon

The Eastern Amazon is rich in bauxite ore. The extraction and processing of bauxite lead to the mobilization of Aluminum (Al) and other metals in environmental. We evaluated the metals (Al, Mn, Ba, and Cr) concentration in tissue, water, and sediment associated with antioxidant and oxidative damage responses in Bryconops caudomaculatus. The samplings were done in two hydrological periods (post-rain and post-dry periods) and at three points, located at two rivers: one in the surroundings of the mining area (P1) and other inside the mining area, upstream (P2), and downstream (P3). Defense antioxidant system biomarkers analyzed were total antioxidant capacity (ACAP) and glutathione-S-transferase (GST) activity. As an oxidative damage biomarker, the lipoperoxidation (LPO) was evaluated. Metals concentrations in the water and sediment were higher in the post-rain period compared to post-dry period. The water samples were acidic, with dissolved Al concentrations above the values established by local legislation at all points. In the gills, the metals accumulation was higher in fish from in the surrounding and upstream sites, and in the liver, was higher in fish from downstream site. Fish from the surrounding had increased antioxidant defenses, with higher ACAP in all tissues and higher GST in the gills. Consequently, they had lower levels of LPO. Fish from the mining area had decreased antioxidant defenses, with lower ACAP in all tissues and lower GST in the gills. Consequently, they had higher levels of LPO, indicating oxidative stress. The fish muscle was not responsive to GST and LPO at all sites. We conclude that the oxidative stress observed in the gills and liver of B. caudomaculatus from the area modified by the mining activity reflected the local anthropogenic impact status.