Potential risks of the residue from Samarco's mine dam burst (Bento Rodrigues, Brazil)

Effects of seasonal contaminant remobilization on the community trophic dynamics in a Brazilian tropical estuary

In tropical estuaries, wet seasons are responsible for the downstream transport of allochthonous material from the upper basin and flooded plains. Although allochthonous matter is commonly associated to nutrient and detritus input, pollutants are also transported throughout the basin or suspended from the river bottom via strong streamflow remobilization and rainfall dynamics. We assessed community and population trophic niche-based patterns using organisms' stable isotopes signatures in the wet and the dry seasons to test if estuarine trophic diversity is affected by remobilization of metal-contaminated material from a mining dam collapse that occurred in the Doce river basin, Brazil. Trophic depletion was detected community-wide and in a key consumer group (bottom-dwelling fishes) at the end of the wet season in the impacted Doce river estuary (DRE). Conversely, higher trophic diversity values were recorded in a well-preserved estuary used as control site. Stable isotopes mixing models indicated in the DRE that G. genidens, a predator fish species, presented poor-quality diet based on pollutant-tolerant tiny organisms, a finding that strongly contrasts from diet described in other, little-impacted Brazilian estuaries. Although wet seasons are expected to increase trophic, functional and taxonomic diversity in tropical estuaries, in the DRE the rainfall-driven dynamics poses a threat to the community due to the presence of ore tailings.

Mercury Concentrations in Four Marine Fishery Resources from Rio de Janeiro Coast, SW Atlantic, and Potential Human Health Risk Via Fish Consumption

Mercury (Hg) contamination has caused ecological and socioeconomic problems worldwide. One of the main Hg contamination routes by the human populations is through fish ingestion. Herein, we analyzed the total Hg concentrations (THg) in highly consumed marine fish species: Brazilian flathead Percophis brasiliensis, Atlantic bigeye Priacanthus arenatus, Stripped weakfish Cynoscion guatucupa, and Jamaica weakfish C. jamaicensis. The specimens were collected from fishing landings off the Rio de Janeiro, SW Atlantic. Additionally, we calculate the estimated weekly intakes (EWI) and the maximum amount of fish (MAF) that can be safely ingested, both based on the provisional tolerable weekly intake (PTWI). The highest THg concentrations were recorded in P. brasiliensis with a mean of 340.59 μg/kg (dry weight) and the lowest in P. arenatus (115.75 μg/kg). THg concentrations were positively related to the δ¹⁵N ratios indicating an increase in contamination with trophic level. All samples showed THg concentrations below the established limits by Brazilian and international regulation. Hg intake via human fish consumption does not exceed the PTWI. The EWI varied from 1.41% (P. arenatus size class I) to 11.52% (P. brasiliensis class II) of the PTWI, while the estimated EWI for "fish consumers" varied between 8.35 and 68.07% PTWI. The MAF estimated for an adult (70 kg) could safely consume between 1277.85 and 7075.50 g/week. This study is an important baseline for monitoring and future comparisons. Therefore, it is important to maintain monitoring of mercury levels in fish species in different marine regions, especially those species most consumed by humans.

Modeling the kinetics of potentially toxic elements desorption in sediment affected by a dam breakdown disaster in Doce River - Brazil

On November 5th, 2015, a mining dam spilled a huge plume of mining waste in the Doce River. Even though many studies have reported the environmental impact from the Doce River's tragedy, the transport of potentially toxic elements (PTE) by kinetic modeling to determine how long the basin takes to achieve the natural balance has not been described. Therefore, samples of sludge, sediment, and water were collected along the Doce River basin, to assess the elements' total leaching by kinetic modeling. The elements Fe, Al, Mn, Cu, Ag, Pb, Cd, and As were evaluated. An innovative mobilization factor (F_S/D) indicated that Mn²⁺, Ag⁺, and Cd²⁺ can be mobilized about 80, 89, and 57 times more than its initial concentration. Besides, in low pH, the Al and Pb ions can be mobilized. The desorption kinetics showed a lower rate constant (k) and higher initial desorption constant (h) for Mn²⁺ than Cd²⁺ and Ag⁺, suggesting both high- and low-affinity interaction sites for Mn²⁺. The exponential decay demonstrated that metals can leach for months or years. Thus, the long-lasting release of metals from mining tailing waste in concentrations that endanger the ecosystem and human health makes clear the need for long-term monitoring.

Phenolic compounds in surface water: methodology and occurrence in Doce River, Brazil

Phenolic compounds are widely spread in surface water, mainly in developing countries, where sewage and wastewater treatment are still reduced. Thus, this work quantified these pollutants in the Doce River analyzing the associated risk for the environment and human health. This river is in the state of Minas Gerais in Brazil and was recently impacted by the collapse of a mining dam that compromised the resilience of the entire watershed. For that purpose, a methodology for simultaneous identification and quantification of 17 different phenols was developed. It was possible to verify phenolic compounds' occurrence with concentration ranging from 0.13 to 24.16 µg·L^-1. 2-Nitrophenol and bisphenol A appeared in all samples analyzed. The analytical method was processed using solid-phase extraction (SPE) (C₁₈ cartridge), gas chromatography with FID, and mass spectrometry to define the analytes' retention time. For case validation, the selectivity, linearity, detection and quantification limits, sensitivity, precision, accuracy, resolution, matrix effect, and peak quality were assessed. Four different solvents were tested in the recovery-grade trials, which were dichloromethane, methanol, acetonitrile, and ethyl acetate. Among them, methanol had a better performance and was used throughout all analyses. The phenolic compounds had a recovery degree higher than 50% after SPE, regardless of the matrices.

Iron ore tailings as a source of nutrients to the coastal zone

The Fundão dam rupture was one of the largest environmental disasters worldwide and released millions of m³ of iron ore tailings into the Doce River basin in southeastern Brazil. Here we assessed the supply of dissolved nutrients associated to tailings in the Doce River estuary and its adjacent coastal zone. First, we observed an acute increase in dissolved silicates (From 16.26 μM to 175.47 μM) and nitrate (From 5.56 μM to 50.69 μM) in the estuary when compared to days prior to the event. Coastal marine ecosystems showed significant concentrations of nitrite (From 0.72 μM to 2.99 μM) and phosphate (From 0.09 μM to 2.30 μM) one year after the disaster, which we attribute mainly to nutrient recycling. The chronic effects include an increase in nutrient load to the coastal zone with a predominance of nitrogenous species, which may increase the limitation of phosphorus and silica to marine primary production.

Mechanical and permeation response characteristics of basalt fibre reinforced tailings to different reinforcement technologies: an experimental study

Tailings dam is a man-made hazard with high potential energy; dam failure would cause great losses to human lives and properties. However, the limitations of conventional reinforcement methods like geosynthetic make it easy to slide along the weak structural plane. In this paper, we innovatively added basalt fibre (BF) with different lengths (l) and contents (ω) into tailings to study its mechanical and permeation characteristics. The results indicate that BF can improve the shear strength (τ), cohesion (c) and compression index (Cc ) of tailings, but it has little effect on internal friction angle (φ). When l is constant, τ, c and Cc are positively correlated with ω. One notable phenomenon is that τ and c do not constantly increase with l when ω is constant, but obtain the maximum under the optimal length of 6 mm. Moreover, when ω > 0.6%, permeability coefficient (k) is greater than that of the original tailings and the sensitivity of c, φ, τ, Cc , k to fibre content is greater than that of length. The research results facilitate the understanding of BF reinforced tailings, and could serve as references for improving the safety of tailings dam and other artificial soil slopes or soil structures.

Application of remote sensing in environmental impact assessment: a case study of dam rupture in Brumadinho, Minas Gerais, Brazil

The collapse of mining tailing dams in Brumadinho, Minas Gerais, Brazil, that occurred in 2019 was one of the worst environmental and social disasters witnessed in the country. In this sense, monitoring any impacted areas both before and after the disaster is crucial to understand the actual scenario and problems of disaster management and environmental impact assessment. In order to find answers to that problem, the aim of this study was to identify and analyze the spatiality of the impacted area by rupture of the tailing dam of the Córrego do Feijão mine in Brumadinho, Minas Gerais, by using orbital remote sensing. Land use and land occupation, phytoplankton chlorophyll-a, water turbidity, total suspended solids on water, and carbon sequestration efficiency by vegetation (CO₂Flux) were estimated by orbital imagery from the Landsat-8/OLI and MSI/Sentinel-2 sensors in order to assess the environmental impacts generated by the disaster. Data were extracted from spectral models in which the variables that best demonstrated the land use variation over the years were sought. Mean comparison by t-test was performed to compare the time series analyzed, that is, before and after the disaster. Through the analysis of water quality, it was observed that the environmental impact was calamitous to natural resources, especially water from Córrego do Feijão.

Seven potential sources of arsenic pollution in Latin America and their environmental and health impacts

This review presents a holistic overview of the occurrence, mobilization, and pathways of arsenic (As) from predominantly geogenic sources into different near-surface environmental compartments, together with the respective reported or potential impacts on human health in Latin America. The main sources and pathways of As pollution in this region include: (i) volcanism and geothermalism: (a) volcanic rocks, fluids (e.g., gases) and ash, including large-scale transport of the latter through different mechanisms, (b) geothermal fluids and their exploitation; (ii) natural lixiviation and accelerated mobilization from (mostly sulfidic) metal ore deposits by mining and related activities; (iii) coal deposits and their exploitation; (iv) hydrocarbon reservoirs and co-produced water during exploitation; (v) solute and sediment transport through rivers to the sea; (vi) atmospheric As (dust and aerosol); and (vii) As exposure through geophagy and involuntary ingestion. The two most important and well-recognized sources and mechanisms for As release into the Latin American population's environments are: (i) volcanism and geothermalism, and (ii) strongly accelerated As release from geogenic sources by mining and related activities. Several new analyses from As-endemic areas of Latin America emphasize that As-related mortality and morbidity continue to rise even after decadal efforts towards lowering As exposure. Several public health regulatory institutions have classified As and its compounds as carcinogenic chemicals, as As uptake can affect several organ systems, viz. dermal, gastrointestinal, peptic, neurological, respiratory, reproductive, following exposure. Accordingly, ingesting large amounts of As can damage the stomach, kidneys, liver, heart, and nervous system; and, in severe cases, may cause death. Moreover, breathing air with high As levels can cause lung damage, shortness of breath, chest pain, and cough. Further, As compounds, being corrosive, can also cause skin lesions or damage eyes, and long-term exposure to As can lead to cancer development in several organs.

Chemical, physical, and biological attributes in soils affected by deposition of iron ore tailings from the Fundão Dam failure

Monitoring degraded areas is essential for evaluation of the quality of the rehabilitation process. In this study, we evaluate how the physical and chemical characteristics of the mixture of iron ore tailings with the soil have affected the soil microbial biomass and activity in areas along the Gualaxo do Norte River after the Fundão Dam disaster. Composite soil samples were collected from areas that were impacted (I) and not impacted (NI) by the tailings. The following attributes were evaluated: chemical element content; soil density, porosity, and texture; microbial biomass carbon; basal respiration; and enzyme activity and density of microbial groups (bacteria, actinobacteria, fungi, arbuscular mycorrhizae, phosphate solubilizers, cellulolytic microorganisms, nitrifiers, ammonifiers, and diazotrophs). According to result, the deposition of tailings increased the pH and the soil available P, Cr, Fe, and Mn content and reduced organic matter. The physical and biological attributes were negatively affected, with increases in the silt content and density of the soil, and reduction in macroporosity and in the microbial biomass and activity of the soil (respiration and enzymes) in the impacted area. However, the impacted areas exhibited greater densities of some microbial groups (cellulolytic microorganisms, nitrifiers, and diazotrophic bacteria). Modifications in the organic matter and silt content are the main attributes associated with deposition of the tailings that affected soil microbial biomass and microbial activity. This may affect erosive conditions and the functionality of the ecosystem, indicating an imbalance in this environment. In contrast, the higher density of some microbial groups in the impacted areas show the high rehabilitation potential of these areas.

Time-sequence development of metal(loid)s following the 2015 dam failure in the Doce river estuary, Brazil

In the context of the Doce river (Southeast Brazil) Fundão dam disaster in 2015, we monitored the changes in concentrations of metal(loid)s in water and sediment and their particulate and dissolved partitioning over time. Samples were collected before, during, and after the mine tailings arrival to the Doce river estuary (pre-impact: 12, 10, 3 and 1 day; acute stage: tailing day - TD and 1 day after - DA; chronic stage: 3 months and 1 year post-disaster). Our results show that metal(loid) concentrations significantly increased with time after the disaster and changed their chemical partitioning in the water. 35.2 mg Fe L^-1 and 14.4 mg Al L^-1 were observed in the total (unfiltered) water during the acute stage, while aqueous Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se and Zn concentrations all exceeded both Brazilian and international safe levels for water quality. The Al, Fe and Pb partitioning coefficient log (K_d) decrease in the acute stage could be related to the high colloid content in the tailings. We continued to observe high concentrations for Al, Ba, Cd, Cr, Cu, Fe, V and Zn mainly in the particulate fraction during the chronic stage. Furthermore, the Doce river estuary had been previously contaminated by As, Ba, Cr, Cu, Mn, Ni and Pb, with a further increase in sediment through the tailing release (e.g. 9-fold increase for Cr, from 3.61 ± 2.19 μg g^-1 in the pre-impact to 32.16 ± 20.94 μg·g^-1 in the chronic stage). Doce river sediments and original tailing samples were similar in metal(loid) composition for Al, As, Cd, Cr, Cu, Fe, V and Zn. As a result, these elements could be used as geochemical markers of the Fundão tailings and considering other key parameters to define a baseline for monitoring the impacts of this environmental disaster.

Complete Genome Sequence of Bacillus safensis Strain 3A, a Heavy Metal-Resistant Bacterium Isolated from Contaminated Estuarine Sediment in Brazil

Bacillus safensis 3A was isolated from a contaminated estuarine sediment sample with mine tailing from the Samarco dam disaster, which occurred in 2015 in Minas Gerais State, Brazil. We report here a draft genome sequence (3.6 Mb) of this bacterial strain. B. safensis exhibited strong resistance to heavy metals.

High levels of metals/metalloids in blood and urine of residents living in the area affected by the dam failing in Barra Longa, District, Brazil: A preliminary human biomonitoring study

Fundão mining tailings dam in Mariana District has collapsed in 2015 and caused the biggest environmental disaster in Brazil. Barra Longa District had its urban area invaded by toxic sludge and its population was extensively exposed to it. Blood and urine samples were collected from 11 residents, focused on investigating the presence of metals at the end of an exploratory health study in 507 inhabitants in 2016. Results have shown increased levels of aluminum, arsenic, cadmium, cooper, lead, manganese and nickel, and zinc defficiency in their body, as well as clinical outcomes.

Comparison of foliar spray and soil irrigation of biogenic CuO nanoparticles (NPs) on elemental uptake and accumulation in lettuce

Nanoparticles (NPs) can be used in several ways in agriculture, including increasing production rates and improving nutritional values in plants. The present study aims to clarify how biogenic copper oxide nanoparticles (CuO NPs) applied by two routes of exposure (foliar spray and soil irrigation) affect the elemental uptake by lettuce. In vivo experiments using lettuce (n = 4) were performed with CuO NPs in comparison with copper salt (CuSO4), considering a final mass added of 20 mg of CuO per plant. The elemental composition of roots was mostly affected by the soil irrigation exposure for both Cu forms (NPs and salt). Neither Cu form added by soil irrigation was translocated to leaves. Copper concentration in leaves was mainly affected by foliar spray exposure for both Cu forms (NPs and salt). All Cu forms through foliar spray were sequestered in the leaves and no translocation to roots was observed. Foliar spray of CuO NPs caused no visual damage in leaves, resulted in less disturbance of elemental composition, and improved dry weight, number of leaves, CO2 assimilation, and the levels of K, Na, S, Ag, Cd, Cr, Cu, and Zn in leaves without causing significant changes in daily intake of most elements, except for Cu. Although Cu concentration increased in leaves by foliar spray of CuO NPs, it remained safe for consumption.

Use of iron mine tailing as fillers to polyethylene

The iron mine tailings accumulation in dams is an environmental and economic problem. The composite based on high-density polyethylene/iron mine tailing production for the application of wood plastic and some items of domestic plastic industry can be a good alternative to reduce the rejects in the environment. This work presents the influence of the processing methodology in the mechanical, thermal and morphological properties of composites based on the high-density polyethylene/iron mine tailing. Four methodology processing by continuous and/or batch mixing were available. The iron mine tailing particles in the polymer matrix promoted an increase in mechanical strength and thermal stability. Besides, the particles acted as flame retardant. The iron mine tailing materials produced using batch mixing showed more significant modifications in the properties due to the better dispersion of the filler as shown by scanning electron microscopy.

Assessment of iron-rich tailings via portable X-ray fluorescence spectrometry: the Mariana dam disaster, southeast Brazil

On November 5, 2015, the Fundão dam collapsed and released > 60 million m³ of iron-rich mining sediments into the Doce river basin, covering >1000 ha of floodplain soils across ~80 km from the rupture. The characterization of alluvial mud covering and/or mixed with native soil is a priority for successful environmental rehabilitation. Portable X-ray fluorescence (pXRF) spectrometry was used to (1) assess the elemental composition of native soils and alluvial mud across impacted riparian areas; and 2) predict fertility properties of the mud and soils that are crucial for environmental rehabilitation and vegetation establishment (e.g., pH, available macro and micronutrients, cation exchange capacity, organic matter). Native soils and alluvial mud were sampled across impacted areas and analyzed via pXRF and conventional laboratory methods. Random forest (RF) regression was used to predict fertility properties using pXRF data for pooled soil and alluvial mud samples. Mud and native surrounding soils were clearly differentiated based on chemical properties determined via pXRF (mainly SiO₂, Al₂O₃, Fe₂O₃, TiO₂, and MnO). The pXRF data and RF models successfully predicted pH for pooled samples (R² = 0.80). Moderate predictions were obtained for soil organic matter (R² = 0.53) and cation exchange capacity (R² = 0.54). Considering the extent of impacted area and efforts required for successful environmental rehabilitation, the pXRF spectrometer showed great potential for screening impacted areas. It can assess total elemental composition, differentiate alluvial mud from native soils, and reasonably predict related fertility properties in pooled heterogeneous substrates (native soil + mud + river sediments).

On the effects of iron ore tailings micro/nanoparticles in embryonic and larval zebrafish (Danio rerio)

Iron ore tailings (IOT) represent a major problem in the mining industry worldwide due to large volumes of waste disposed in mine sites. IOT are exposed to the environment and subjected to wind and water dispersion, even under non-catastrophic scenarios as dam collapses, and the effects of these particles to the biota are still mostly unknown. This work aimed to prepare and to characterize a suspension containing the finest (micro/nano range) particles of IOT and to evaluate its effects on development and behavior of zebrafish (Danio rerio), at both embryonic and larval stages. IOT suspension comprised 37 mg L^-1 of a multi-mineral material mainly composed by hematite and quartz, in a size-range of 33-1400 nm. Regarding in vivo toxicological assays, no robust alterations were recorded in functional, morphological and behavioral end-points analyzed, although a significant adhesion of IOT particles on zebrafish chorion was observed, without a prejudice of embryo hatching. Under applied conditions, iron ore particles did not present harmful effects to the initial stages of zebrafish development, and the particle size range and potential interactions with SiO₂ content might be behind such effect.

Social injustice in environmental health: A call for fortitude

The objective of this short paper is to call upon the scientific community to channel its attention to the duty and heedfulness of social justice issues. While recognized for decades the impact of social injustice on public health and its disproportionate effects on poorer communities, little has been done to systematically address it. Here, we provide several examples pertinent to the health outcomes associated with social injustice and call upon the scientific community to attend to the issue and antagonize those who attempt to subvert science and its role in ensuring social justice in health.

Satellite evidence for pervasive water eutrophication in the Doce River reservoirs following the collapse of the Fundao dam in Brazil☆

One of the worst socio-environmental disasters to mark the history of Brazil and the world occurred in November 2015 and involved the mining sector. The collapse of the Fundao dam released approximately 43 million m³ of iron ore tailings, which moved downstream to reach the Doce River. This resulted in the contamination of water, soil, and sediments along the entire course of the river, which also affected its mouth in the Atlantic Ocean. Four years after the disaster, several socio-environmental problems continue to persist in the affected areas. In this context, the reservoirs built along the Doce River deserve special attention as they are artificial environments that are highly vulnerable to changes in water parameters. This study aims to determine water quality indicators of these reservoirs using remote sensing data and image processing methods, including semi-analytical algorithms, to comprehend the progress of eutrophication processes. Operational land imager/Landsat-8 data (from 2013 to 2019) were used to map the suspended particulate matter (SPM), euphotic zone (Z_eu) and chlorophyll-a (Chl-a) before and after the collapse. The results showed significant changes in SPM and Z_eu in the reservoirs after the collapse. Non-conformity of these parameters is observed even now, and they tend to intensify during rainy periods when resuspension processes of sediments occur. Moreover, there has been an increase in the eutrophication of reservoirs as noticed by the significant increase in Chl-a after the disaster, especially in January, July, and August.

Immediate and long-term impacts of one of the worst mining tailing dam failure worldwide (Bento Rodrigues, Minas Gerais, Brazil)

The rupture of Fundão Dam is considered one of the largest environmental disasters in Brazilian history and one of the largest in the world involving tailings dams. The present study analyzed the changes in metal concentrations in the dissolved, suspended particulate matter (SPM) and sediment in the period just after (15 days) and six months after the dam rupture, together with the biological and cytogenotoxic effects, from the collapse site until the Doce River mouth in the Atlantic Ocean. After the dam rupture, the tailings were mainly transported as SPM. After six months, with the deposition, there was a decrease in metal concentrations in dissolved and SPM and increased levels were observed in the sediment. Cr, Ni, Cd and Hg levels in sediment were higher than the threshold effects level (TEL/NOAA), especially six months after the dam rupture. The water induced immediate negative biological effects at different levels of the trophic chain, together with Al, Fe, Mn and Zn accumulation in fish muscle. Both water and sediment also showed cytotoxic, genotoxic and mutagenic effects. These data demonstrate the importance of long-term monitoring with abiotic and biotic parameters to clarify the impacts of mining tailings and can help to direct future monitoring programs.

Ecological risk assessment of trace metals in soils affected by mine tailings

Environmental impacts caused by mine dam ruptures or inappropriate tailing depositions represent a global concern. An ecological risk assessment was performed in 18 areas affected by the collapse of a major mining dam in southeastern Brazil, in two monitoring periods (2015 and 2018). In these areas, pedogeochemical surveys, and ecological risk levels were determinate. In addition, ecotoxicological assays with Proisotoma minuta (Collembola) were carried out in laboratory. Soil screening values indicated that all contaminated areas were above regional reference values for soil quality for at least one metal (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn), likewise exceeding threshold values for potential ecological and human health risks. In two monitoring years, significant ecotoxicity in the avoidance and reproduction of P. minuta (> 60 % and >80 %, respectively) were evidenced in most soils; and lethal responses in some areas like Córrego Novo, Governador Valadares and Tumiritinga. Results suggest changes in soil physical-chemical properties due to tailing deposition, thus affecting soil dwellers. This study can elucidate the use of appropriate tools to ecological risk assessments, helping to identify the priority areas for defining remediation and monitoring strategies.

Trace metals in Rio Doce sediments before and after the collapse of the Fundão iron ore tailing dam, Southeastern Brazil

The collapse of the Fundão Dam, in Southeastern Brazil, caused about 50 million m³ of iron ore tailings to sluice down the mountain to Rio Doce, in what is considered the greatest environmental disaster in Brazilian history. The fluvial system received an intense and sudden mudflow that was transported for more than 650 km, before reaching the Atlantic Ocean. Because the area was already impacted by the mineral activities in the region, it becomes essential to evaluate the environmental conditions before the disaster to correctly assess the disaster real damage. This study compares the concentration of trace metals in the sediments of the Rio Doce alluvial plain, before and after the dam collapse, as well as the newly deposited iron ore tailings that became part of the sedimentary framework. The data indicate that the fine particles deposited have since been incorporated into the sandy river sediments. The cadmium and arsenic contents in the sediments increased to levels above the National Environment Council thresholds. The comparison between the levels of trace metals in the situations before and after disaster shows that the mining mud is the source of cadmium while the arsenic was present before the environmental disaster, and its concentration increased due to sediment remobilization. The iron ore tailings deposited on the alluvial sediments also affected the physical parameters since the formed ferruginous crusts waterproofed the ground surface and may, gradually, release toxic metals when exposed to weathering and river reworking.

Do tailings from the Mariana, MG (Brazil), disaster affect the initial development of millet, maize, and sorghum?

The collapse of the Fundão dam in Mariana, MG, in 2015 resulted in the overflow of more than 50 million m³ of mud containing mine tailings, leaving a path of destruction and immeasurable social and environmental consequences. Tailings' chemical and physical assessments revealed the presence of some elements at levels higher than those allowed by Brazilian guidelines. The tailings also showed high density, which restricts vegetation recovery. Therefore, this study aimed to analyze the effects of mud containing mine tailings from the Fundão dam on the germination and initial growth and development of three plant species: millet, maize, and sorghum. These species were cultivated on substrates with five tailings proportions: 0 T (100% sand), 25 T (25% tailings + 75% sand); 50 T (50% tailings + 50% sand); 75 T (75% tailings + 25% sand); and 100 T (100% tailings). In experiment I, the germination and initial growth of seedlings (plants with 1 or none fully expanded leaf) in these substrates were evaluated. In experiment II, growth parameters, photosynthetic efficiency (gas exchange and chlorophyll a fluorescence), metal accumulation, and plant root morphology of the same species were evaluated at the three fully expanded leaves vegetative stage (V3). Overall, the germination of seedlings and the initial growth of the three species analyzed were not affected by the presence of tailings. However, in plants at the V3 stage, morphophysiology variations differed among species, given that their growth, biomass accumulation, and root dynamics were altered. Proportions of tailings in the substrate did not influence the absorption of iron or manganese by the studied plants. At the V3 stage, maize was the most tolerant, with a more robust root system, and showed fewer morphological changes and greater water use efficiency than the other studied species.

Contamination and oxidative stress biomarkers in estuarine fish following a mine tailing disaster

BACKGROUND

The Rio Doce estuary, in Brazil, was impacted by the deposition of iron mine tailings, caused by the collapse of a dam in 2015. Based on published baseline datasets, the estuary has been experiencing chronic trace metal contamination effects since 2017, with potential bioaccumulation in fishes and human health risks. As metal and metalloid concentrations in aquatic ecosystems pose severe threats to the aquatic biota, we hypothesized that the trace metals in estuarine sediments nearly two years after the disaster would lead to bioaccumulation in demersal fishes and result in the biosynthesis of metal-responsive proteins.

METHODS

We measured As, Cd, Cr, Cu, Fe, Mn, Pb, Se and Zn concentrations in sediment samples in August 2017 and compared to published baseline levels. Also, trace metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, Se and Zn) and protein (metallothionein and reduced glutathione) concentrations were quantified in the liver and muscle tissues of five fish species (Cathorops spixii, Genidens genidens, Eugerres brasilianus, Diapterus rhombeus and Mugil sp.) from the estuary, commonly used as food sources by local populations.

RESULTS

Our results revealed high trace metal concentrations in estuarine sediments, when compared to published baseline values for the same estuary. The demersal fish species C. spixii and G. genidens had the highest concentrations of As, Cr, Mn, Hg, and Se in both, hepatic and muscle, tissues. Trace metal bioaccumulation in fish was correlated with the biosynthesis of metallothionein and reduced glutathione in both, liver and muscle, tissues, suggesting active physiological responses to contamination sources. The trace metal concentrations determined in fish tissues were also present in the estuarine sediments at the time of this study. Some elements had concentrations above the maximum permissible limits for human consumption in fish muscles (e.g., As, Cr, Mn, Se and Zn), suggesting potential human health risks that require further studies. Our study supports the high biogeochemical mobility of toxic elements between sediments and the bottom-dwelling biota in estuarine ecosystems.

Doce River Estuary: Geochemical Changes Following the Largest Tailing Spill in South America

Accidents involving economic activities of great impact, such as mining, have caused massive environmental damage. In November 2015, the dam of Fundão, located in the city of Mariana, MG, broke and released 5 × 10⁷ m³ of tailings in the nearby ecosystems, including the Doce River. The physicochemical changes that occurred in the Doce River estuary were analyzed, as well as the trace metal concentrations, both 1 day before and 1 month after the disaster. The analyses of the collected samples (water and sediment) showed changes to the physicochemistry regarding dissolved oxygen, SPM, and temperature (p = 0.008, 0.001, 0.036, respectively). It also detected metals (Fe and Al) in the dissolved fraction beyond the limits recommended by the Brazilian legislation. There was an increase in the total concentrations of Fe and Cd in the sediment after the rupture of the dam and a change in mobile metals (Al, Cd, Cr, Cu, Fe, Ni, Pb, and Zn), with higher concentrations of mobile metals being found closer to the ocean (p = 0.06356). After the rupture of the dam, there was a change in the granulometric fraction of the sediment, which became composed mainly of silt and clay. All of the results showed a change on the Doce River estuary, caused by the arrival of the tailings, which can result in future harmful effects with the release of metals present in the sediment and adsorbed to the particles. The changes to the sediment, such as changes in the granulometric fraction, can have negative consequences for the benthic community.

Marine zooplankton dynamics after a major mining dam rupture in the Doce River, southeastern Brazil: Rapid response to a changing environment

Zooplankton were sampled five days after the tailings from the Samarco dam rupture reached the ocean in the coastal region at the mouth of the Doce River. This was one of the largest environmental disasters in Brazilian history, and the impacts on the marine biota are not yet fully understood. This study aimed to evaluate the zooplankton community short term responses to the metal enrichment after the tailings reached the coastal region in different scenarios. Our results showed an acute impact on the zooplankton community, which peaked in abundance (222,958.60 ind/m³) and decreased in diversity (H' = 1.23) near the river mouth. Two copepod species, Parvocalanus sp. and Oithona nana, composed up to 61% of the total abundance and they were correlated with concentrations of Fe, Pb, Cu and Zn in particulate fraction. These species feed opportunistically on nanophytoplankton, which dominated the autotroph community, possibly in response to the iron enrichment caused by the mud flow. A shift on zooplankton species composition was also observed. During the first three days, we found the presence of oceanic species in the 20 and 30 m isobaths during an incomplete upwelling event, which directly correlated with the presence of Calanoides carinatus. However, only three days later, following a cold front passage and consequent increase of water turbidity, those species were already absent, and the zooplankton community was significantly altered (PERMANOVA, df = 1, pseudo-F = 9.2247, p = .001). Zooplankton responded quickly to the environmental changes detected during our sampling period and proved to be key factors in costal monitoring, especially in dynamic oceanographic areas such as the Doce River coastal region.

Histological and molecular changes in gill and liver of fish (Astyanax lacustris Lütken, 1875) exposed to water from the Doce basin after the rupture of a mining tailings dam in Mariana, MG, Brazil

The effects of the rupture of a mining tailings dam were investigated using the gills and liver of Astyanax lacustris as a proxy for environmental quality. The fish were exposed for seven days to water sampled forming four groups: upstream of the dam rupture (P1), and 22 km (P2); 48 km (P3); and 70 km (P4) downstream from the dam rupture in the Doce River basin. The control group received dechlorinated tap water. The dissolved concentrations of metals were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). We evaluated the histology of the gills and liver, as well as, immunohistochemistry for HSP70 and Na⁺/K⁺ ATPase (NKA) in the gills, and for P-gp in liver. In all sites we observed a mix of metals, with higher concentrations of Mn, Cd, As, and Cu/Cr in P1, P2, P3, and P4, respectively. All treatments groups showed histological changes in gills and liver, with the highest amount of these alterations found in the P2 group. Disorganization of the secondary lamellae, epithelial lifting, and mitochondria-rich cells (MRC) were observed in the gills. The parenchyma of the liver was rather disorganized, and hepatocytes and nuclei showed hypertrophy, vacuolization and cytoplasmic degeneration. A higher immunoreaction of HSP70 in P2 when compared with the other groups and lower labeling of HSP70 in the P4 was registered. In P2 and P3, NKA-positive cells were observed with hypertrophy and disorganization. Morphometric analyses of the liver revealed that all treatment groups presented a lower immunolabeling of P-gp when compared with the control group. Thus, the experimental approach revealed that the water from Doce basin can promote histological alterations in fish's liver and gills, as well as modulation of disruption of ionic balance, cellular responses to stress, and cell detoxification pathways.

Remediation of a Riparian Site in the Brazilian Atlantic Forest Reached by Contaminated Tailings from the Collapsed Fundão Dam with Native Woody Species

The failure of the Fundão dam in Brazil spilled alkaline contaminated sediments (pH ~8) into the Doce River basin. The contaminated sediments had high levels of ether amine (6 mg/kg) and Na (54 mg/kg) in relation to those in preserved sites. In the present study, a riparian forest was established over contaminated sediment using 2 main remediation strategies: phytoremediation with species native to the Atlantic forest and previously selected for their tolerance to sediment toxicity, and physicochemical remediation by incorporating organic matter (OM) into the sediment. In the experimental site (ES), the tolerant native woody species were cultivated in 2 treatments: T1, scraping of the sediments and incorporation of the OM, and T2, nonmanaged sediment and superficial deposition of the OM. The results were compared with the findings from a degraded site (DS), which was reached by the contaminated sediments but lacked vegetation, and a preserved site (PS), which was composed of a fragment of preserved Atlantic forest. Six months after transplanting, the plants from T1 showed a better height growth performance and survival index in relation to those from T2. Furthermore, T1 showed a significant decline in the pH (to ~6) concomitant with a reduction in the ether amine and Na contents (to ~0.4 mg/kg and 23 mg/kg, respectively). There was an improvement in the soil fertility and total microbial biomass in both treatments, especially in T1. Therefore, the adopted phyto- and physicochemical remediation procedures are recommended to reclaim zones reached by dam tailings containing Na and ether amine. Integr Environ Assess Manag 2020;16:669-675. © 2020 SETAC.

Impacts of the Samarco Tailing Dam Collapse on Metals and Arsenic Concentration in Freshwater Fish Muscle from Doce River, Southeastern Brazil

On November 2015, Samarco tailings dam in Mariana, Minas Gerais, Brazil, collapsed, releasing 62 million tons of tailings that advanced through 668 km of the Doce River and adjacent floodplain. Although the collapse was the worst environmental disaster in Brazil, little is known about its consequences to aquatic biota. Here we evaluate the effects of the tailings mudflow on metal and As concentration in fish and how concentration correlates with water and fish characteristics. We quantified semitotal amounts of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in fish muscle tissue using inductively coupled plasma mass spectrometry (ICP-MS) in 255 individuals (34 species) sampled in unaffected and affected areas along the Doce River basin. Arsenic and Hg were higher in fish from affected sites, likely due to turbulent mixing of previously sedimented material by the giant tailings wave. Silver and Zn concentrations were higher in unaffected sites. Arsenic concentration in Geophagus brasiliensis decreased with increasing fish weight. Copper and Zn decreased with increasing fish weight considering the whole assembly of fish. The tailings mudflow increased water conductivity, and conductivity increased Al concentration in fish, so we expected a larger Al concentration in fishes from affected sites. However, the observed Al concentration in fishes from affected sites was lower than expected by water conductivity. Thus, the tailings mudflow reduced Al uptake or accumulation in fishes. Mercury decreased with increasing water conductivity in both unaffected and affected sites considering all species and in G. brasiliensis alone. Despite the relatively low concentration range of metals and As found in fish, fishes from sites affected by the Fe ore tailings mudflow showed higher As and Hg concentration, compared to fishes from unaffected sites. The higher As and Hg in affected sites require further detailed monitoring to ensure safeguards of human health by fishing activity along the Doce River. Integr Environ Assess Manag 2020;16:622-630. © 2020 SETAC.

Evaluation of Metals in Soil and Tissues of Economic-Interest Plants Grown in Sites Affected by the Fundão Dam Failure in Mariana, Brazil

The objective of this study was to evaluate the concentration of potentially toxic elements in Brachiaria decumbens, Stylosanthes guianensis, and Saccharum officinarum plants and soil samples in affected and unaffected areas by rupture of the Fundão dam, Brazil. Samples were collected in areas affected by residues from the Fundão dam (RAA1, RAA2, RAA3) and in an unaffected area (control). The material was analyzed for the composition of micronutrients and trace elements in soil and plants, as well as contamination factor (CF), accumulation factor, and translocation factor (TF). Overall, the results showed that soil and plant tissues had increased Fe, Mn, Cu, and Cr content and decreased Zn content in the affected areas, compared to the control. Leaves and roots of B. decumbens showed an increase in Fe content in affected areas, compared to the control, reaching a mean maximum value of 42 958 µg/g of roots of RAA2-collected plants. As a result, CF for Fe of B. decumbens was classified as very high and they presented low TF values. Furthermore, B. decumbens collected in affected areas showed an increase of Fe, Mn, Cu, and Cr in leaves, stems, and roots, whereas in Stylosanthes guianensis, there was an increase of Fe concentration in all tissues and Cr in leaves. Also, Saccharum officinarum showed the accumulation of Mn in the stem and Cu in leaves and stem. On the other hand, there was no contamination of plants by hazardous elements such as Pb, Cd, and As in the samples analyzed. In conclusion, increases in the content of Fe, Mn, Cu, and Cr were found in soil and several plant tissues of residue-affected areas, which could compromise plant growth and represent potential hazards arising from the biomagnification process in the food chain. Integr Environ Assess Manag 2020;16:596-607. © 2020 SETAC.

Possible contamination of the Abrolhos reefs by Fundao dam tailings, Brazil - New constraints based on satellite data

The Fundão dam, located in Mariana city, Minas Gerais State, southeastern Brazil, collapsed in November 2015, causing the discharge of over 50 million m³ of iron ore tailings in the Doce river basin. The mud generated by the disaster was composed of fine particulates (silt and clay), which are more sensitive to wind dispersion. Based on laboratory analyses and hydrodynamic modeling, early research postulates the hypothesis that the mud discharged in the ocean traveled 10,000 km up north and may have reached the Abrolhos coral reefs. This research aims to investigate further this hypothesis based on broad-scale remotely sensed data. Satellite images were used to estimate the suspended particulate matter (SPM) in the coastal zone before, during, and after the dam collapse. Results indicate that higher concentrations of SPM appeared during and post-collapse and were restricted to the coastal zone and its shallower regions, including beaches. However, we demonstrate that under exceptional circumstances the wind blew to the north, carrying fine particulate material and potentially-toxic metals derived from the iron ore tailings towards the northeastern Brazilian coastline and possibly the reefs of the Abrolhos Bank.

Influence of Fundão Tailings Dam Breach on Water Quality in the Doce River Watershed

The Fundão dam (Minas Gerais, Brazil) breach resulted in the transport and deposition of Fe mine tailings and debris for approximately 670 km along the Doce River watershed. Following the event, an extensive water quality monitoring program was implemented. The results generated by this program were used to assess the temporal and spatial impacts of the event on water quality. Data from several sampling sites situated along affected watercourses collected from 6 November 2015 to 27 September 2017 were evaluated. The sampling area was grouped into 4 zones delineated by hydropower plant dams located along the Doce River watershed and divided into 5 distinct time periods related to hydrological seasonality. Data were also compared to the Brazilian standards of water quality and available pre-event conditions. Principal component analysis followed by analysis of variance (ANOVA) tests were performed to evaluate the observed temporal and spatial trends and patterns. The results indicated that concentrations of 58 water quality parameters increased with the arrival of the tailings wave released by the breach, generally exceeding pre-event and regulatory levels. Persistent or seasonally recurring concentrations were observed for 30 water quality parameters. Concentrations of total and dissolved forms of Fe, Al, Mn, total P, total suspended solids, and turbidity tended to increase during the wet season and decrease during the dry season, this trend being more pronounced close to the dam. The water quality changes were more pronounced immediately after the arrival of the tailings wave, gradually decreasing over time and returning prebreach conditions, but fluctuated seasonally in response to the natural variation in river flow. Integr Environ Assess Manag 2020;16:583-595. © 2020 SETAC.

Tailings from Fundão Tragedy: Physical-Chemical Properties of the Material That Remains by Candonga Dam

In this work, samples of Fe mining tailings from the collapsed Fundão Dam, Brazil, which were retained by the Candonga hydroelectric power plant, were characterized by various techniques. Quartz, hematite, kaolinite, and goethite were identified as the main phases present. The composition, homogeneity, and relatively low (~1%) organic matter content indicate potential for usage of these tailings in civil constructions. The next step of this work is to investigate such applications. If their feasibility is confirmed, the goal is to use this material for construction in the areas affected by the Fundão Dam rupture. This use will lead to positive socio-environmental impacts in these regions, where tailings still need to be removed and damaged infrastructure needs to be repaired. Integr Environ Assess Manag 2020;16:636-642. © 2019 SETAC.

Adaption of microbial communities to the hostile environment in the Doce River after the collapse of two iron ore tailing dams

In November 2015, two iron ore tailing dams collapsed in the city of Mariana, Brazil. The dams' collapse generated a wave of approximately 50 million m³ of a mixture of mining waste and water. It was a major environmental tragedy in Brazilian history, which damaged rivers, and cities 660 km away in the Doce River basin until it reached the ocean coast. Shortly after the incident, several reports informed that the concentration of metals in the water was above acceptable legal limits under Brazilian laws. Here the microbial communities in samples of water, mud, foam, and rhizosphere of Eichhornia from Doce River were analyzed for 16S and 18S rRNA-based amplicon sequencing, along with microbial isolation, chemical and mineralogical analyses. Samples were collected one month and thirteen months after the collapse. Prokaryotic communities from mud shifted drastically over time (33% Bray-Curtis similarity), while water samples were more similar (63% Bray-Curtis similarity) in the same period. After 12 months, mud samples remained with high levels of heavy metals and a reduction in the diversity of microeukaryotes was detected. Amoebozoans increased in mud samples, reaching 49% of microeukaryote abundance, with Discosea and Lobosa groups being the most abundant. The microbial communities’ structure in mud samples changed adapting to the new environment condition. The characterization of microbial communities and metal-tolerant organisms from such impacted environments is essential for understanding the ecological consequences of massive anthropogenic impacts and strategies for the restoration of contaminated sites such as the Doce River.

Arsenic contamination assessment in Brazil - Past, present and future concerns: A historical and critical review

This paper presents a summary of some relevant documents published during the last decades regarding arsenic contamination in Brazil until December 2018, including scientific papers, reports and regulatory documents. Natural and anthropogenic arsenic sources were covered, excluding those related to agriculture. International "key" documents related to arsenic contamination were used to support the discussion and comparative analysis. This paper aims: (a) to summarize and discuss some available data (including Portuguese written documents) concerning arsenic contamination in Brazil, mainly geographical, geological, geochemical, environmental and health studies; (b) to critically review the published studies comparing their main findings; (c) to describe and compare ancient and recent contamination events; and (d) to highlight key knowledge gaps, and identify promising areas for future researches. The arsenic contamination scenario in Brazil results not only from mining. Natural or anthropogenic emissions caused by great magnitude phenomena as flooding, erosion, landslide and, water scarcity equally impact arsenic mobilization/immobilization equilibria. Our literature review demonstrates that arsenic contamination of soils, sediments and water sources is observed at least at three of the five geographically defined Brazilian regions (Northern, Southern and, Southeastern regions). Arsenic enriched soils, and waters naturally occur all around the country and anthropogenic activities have been the main contributory factor to the environmental contamination since the 18th Century. Geogenic materials (topsoil and mining tailings), and water samples could contain extremely high arsenic concentrations, i.e. 21,000 mg kg^-1 or 1,700,000 μg L^-1, respectively, have been found mainly at the "Iron Quadrangle". Moreover, if we consider both the Brazilian and international parameters, the health risks associated with the human exposition to arsenic are of significant concern. For those reasons, constant monitoring of As contaminated areas in Brazil is mandatory. Furthermore, it is necessary to learn from the mistakes made in the past in order to prevent or minimize future problems.

Marine Microbial Response to Heavy Metals: Mechanism, Implications and Future Prospect

Growing levels of pollution in marine environment has been a matter of serious concern in recent years. Increased levels of heavy metals due to improper waste disposal has led to serious repercussions. This has increased occurrences of heavy metals in marine fauna. Marine microbes are large influencers of nutrient cycling and productivity in oceans. Marine bacteria show altered metabolism as a strategy against metal induced stress. Understanding these strategies used to avoid toxic effects of heavy metals can help in devising novel biotechnological applications for ocean clean-up. Using biological tools for remediation has advantages as it does not involve harmful chemicals and it shows greater flexibility to environmental fluctuations. This review provides a comprehensive insight on marine microbial response to heavy metals and sheds light on existing knowledge about and paves for new avenues in research for bioremediation strategies.

Vermicompost improves maize, millet and sorghum growth in iron mine tailings

The Fundão dam was designed to store iron mine tailings in the region of Mariana, MG, Brazil. When it ruptured, the tailings overflowed. These tailings affected the soil due to the formation of a thick crust as a result of drying (compaction) and hindered the natural revegetation process. In this context, the use of organic fertilizers, including vermicompost, is method of reducing the physical limitations on root growth caused by soil properties and changing soil-metal interactions. For this reason, vermicompost was added to iron mine tailings, and its morphological and physiological effects on maize, millet and sorghum plants were studied. The experiment was conducted in a greenhouse using 6 dm³ pots. The plants were subjected to three treatments: mine tailings, mine tailings + vermicompost, and a reference soil. From the V3 stage onwards, biweekly growth, leaf gas exchange and chlorophyll fluorescence evaluations were performed. At the end of the experiment, dry biomass and metal, macro- and micronutrient contents were quantified, and the root morphology was evaluated. The tailings created physical limitations on root growth and had low nutrient content as well as high concentrations of chromium, iron and manganese. The addition of vermicompost favored increases in shoot and root dry biomass, increases in root length, volume, surface area and diameter, and the absorption of macro- and micronutrients, which was reflected in the growth of the studied species. In addition, vermicompost led to greater investment in thick and very thick roots, and in general, the plants showed no symptoms of metal toxicity. Considering the characteristics of the studied tailings, it can be concluded that vermicompost favors the growth of plant species and may be a viable method for beginning the recovery process in areas containing iron mine tailings.

Impact of mining activities on areas of environmental protection in the southwest of the Amazon: A GIS- and remote sensing-based assessment

The southwest Brazilian Amazon state of Rondônia has a relatively recent non-indigenous occupation, which subsequently develops a variety of human pressures and conflicts of interest presently identified in the region. Given such framework, it is worthwhile to note that there are 57 Conservation Units that must guarantee the biodiversity protection of Amazonia biome. However, due to the need for electricity and the international high demand for minerals, the highlighted scenario has dramatically changed in recent years. Official data from mining processes in the studied area demonstrated the existence of high interest for minerals, especially cassiterite and gold. Mining is indeed an essential activity for the nation mainly due to the generation of jobs and income. On the other hand, it produces several environmental and social impacts that vary accordingly to the peculiarities of the mining and with respect to the type of ore. Therefore, this research work investigated the concentration of mining projects in the state of Rondônia and complementarily evaluated the impact of such activities on areas of environmental protection. Landsat 8 OLI imageries were employed to map the diversity of land covers across the study area and also to evaluate the corresponding impact of mining activities. More than 500 processes have been identified within the Conservation Units. A significant part of the mining areas, covering about 26 km², was observed inside one of the three types of evaluated areas (Integral Protection Sustainable Use Conservation Units and Damping Zone), clearly showing the development of the illegal activity, as defined in terms of the National System of Conservation Units. If deforestation is considered in this analysis, the area increases to about 6110 km², representing more than 5.2% of the Conservation Units. In addition, we proposed the creation of the Mining Pressure Index (MPI), which allows classifying a Conservation Unit by the degree of pressure from mining activities. The proposed index revealed to be very efficient since it predicted high values over Conservation Units where it was expected a greater vulnerability. The index is a promising tool for public policy formulation and management of protected areas, as well as for enforcement action. The results provide a new horizon in terms of the perspective of importance and applicability of geotechnologies in the evaluation of environmental impacts, not restricted to mining activity.

Metal concentrations and biological effects from one of the largest mining disasters in the world (Brumadinho, Minas Gerais, Brazil)

The rupture of the Brumadinho mining tailings dam in Brazil is considered one of the largest mining disasters in the world, resulting in 244 deaths and 26 missing people, in addition to the environmental consequences. The present study aims to evaluate the concentrations of multiple elements and the biological effects on water and sediments of the Paraopeba River after the Brumadinho Dam rupture. The tailings are formed by fine particulate material with large amounts of Fe, Al, Mn, Ti, rare earth metals and toxic metals. In the water, the levels of Fe, Al, Mn, Zn, Cu, Pb, Cd and U were higher than those allowed by Brazilian legislation. In the sediments, Cr, Ni, Cu and Cd levels were higher than the established sediment quality guidelines (TEL-NOAA). The differences in metal concentrations in the water and sediments between the upstream and downstream sides of the dam illustrate the effect of the tailings in the Paraopeba River. Toxicological tests demonstrated that the water and sediments were toxic to different trophic levels, from algae to microcrustaceans and fish. The fish exposed to water and sediments containing mine ore also accumulated metals in muscle tissue. This evaluation emphasizes the necessity of long-term monitoring in the affected area.

Heavy metals in iron ore tailings and floodplain soils affected by the Samarco dam collapse in Brazil

In November 2015, the Fundão Dam collapsed releasing about 35 million m^-3 of iron ore tailings into the environment, which covered approximately 15 km² of floodplain soils. Four years later, there is still great concern and controversy regarding contamination by heavy metals in the affected areas. Thus, the present study sought to evaluate the heavy metal contents and its distribution in tailings and non-affected soils. Tailings samples were collected in the stretch between Bento Rodrigues and the Candonga hydroelectric plant, in addition to a sample inside the Fundão Dam. Non-affected soils and river sediments from the same region were also collected as a control group. The heavy metal contents in the tailings were lower than in non-affected samples from the same area, discarding the hypothesis of contamination by the tailings mud. The non-affected samples presented high levels of As, Ba, Co, Cr, Cu, Ni and Zn, with at least one sample exceeding the quality reference values (QRV's) established for Minas Gerais state, which indicated a scenario of pre-disaster contamination for the Doce River watershed. Most of the elements (As, Cr, Cu, Ni, V and Zn) were extracted in the residual fraction of the BCR sequential extraction, presenting low risk of release in nature. The health risk assessment for As estimated that all the non-affected soils and sediments from Gualaxo do Norte, Carmo and Doce rivers have carcinogenic risk higher than the acceptable value for children. From our results, it is more likely to conclude that the deposited tailings are not a time-bomb for heavy metals contamination in the region.

Effects of metal contamination on liver in two fish species from a highly impacted neotropical river: A case study of the Fundão dam, Brazil

Environmental disasters such as the rupturing of mine tailings dams are a major concern worldwide. In the present study, we assess the effects of the release of mine waste due to the rupture of the Fundão dam on two native fish species (Hoplias intermedius and Hypostomus affinis) from the Doce River basin. Two sampling sites were chosen: S1, a reference site, and S2, contaminated by mining waste. Water and sediment were collected to evaluate metals concentration. Adult fish were caught to analyse biological parameters, hepatic histopathology, and biomarkers of metal contamination. Compared to site S1, the concentration of manganese was statistically higher in water while lead, nickel, and arsenic were statistically higher in the sediment from site S2, and iron had no significant difference between sites. At site S1, fish of both species presented hepatic tissue with normal architecture. At site S2, hepatic alterations, such as cytoplasmic vacuolization and necrosis were frequently found in both species. Regarding the histopathological index, higher values were found in both species from site S2. The positive antibody reactions for cytochrome P450 1A (CYP1A) and metallothionein (MT) were statistically greater in site S2 for both species. The oxidative stress biomarkers, superoxide dismutase (SOD) and catalase (CAT) were statistically higher in H. intermedius from site S2, but only CAT was statistically greater in H. affinis at site S2. These results demonstrate that the release of mineral residues from the rupture of the Samarco mine dam is provoking hepatic damage in the fish from the Doce River besides inducing the expression of proteins and enzymes related to metal contamination.

Does Samarco's spilled mud impair the growth of native trees of the Atlantic Rainforest?

The failure of the Fundão dam, the largest environmental disaster in the world's mining sector, was responsible for releasing millions of cubic meters of iron ore tailings into the environment. It affected thousands of hectares of the Atlantic Forest domain, one of the biodiversity hotspots for conservation. Considering the urgency to restore the flora of the affected area, we evaluated the effects that iron ore tailings from the Fundão reservoir have on the germination and initial growth of tree species native to the Atlantic Forest in the Rio Doce basin. We demonstrated that the tailings do not affect the seed germination, but do negatively interfere with plant growth. Lower biomass production, height, leaf area, chlorophyll concentration and photosynthesis as well as high concentration of iron was observed in plants grown in the tailings. Thus, we investigated if these deleterious effects were due to the presence of potentially toxic metals or nutritional deficiency imposed by low fertility of the tailings. We concluded that reduced growth was a result of nutritional limitations due to low nutrient availability, low organic matter content and low cation exchange capacity of the tailings. This conclusion was further supported by the application of fertilization, which reversed the deleterious effect of the waste on the growth of plants, assuring physiological levels of iron and nutrients in the shoot. Thus, this strategy should be considered for in situ recovery projects aiming to improve the performance of native plants.

Geochemical evaluation of bottom sediments affected by historic mining and the rupture of the Fundão dam, Brazil

The rupture of the Fundão dam released about 39 million m³ of tailings into the Rio Doce/Brazil. The sediment load increase in the affected rivers has become a concern. As such, this article provides recent information about the region. In addition, based on past studies in the region, it shows the magnitude and dynamics of the environmental impacts caused by the rupture of the dam on the bottom sediments. Sediment samples in different seasonal periods were collected at eleven sampling stations located along the Gualaxo do Norte River, the first tributary of the Rio Doce affected by the environmental disaster. These sediments underwent physical, chemical, and granulometric analyses for their organic, metal, and semimetal content. The contamination factor and the enrichment factor of the samples also were calculated. To evaluate the anthropogenic contributions to sediment metal concentrations, reference values (regional background values) for the Gualaxo do Norte River were used. The results indicate that, in the sampling stations not affected by the disaster, the concentrations of the metals and semimetals reflect the geology of the Quadrilátero Ferrífero. However, in the area affected by the environmental disaster, there were changes in the chemical and physical properties of the bottom sediment, mainly in the concentrations of iron, organic matter, and fine sediment fractions. This was reflected in the contamination factors and enrichment factors calculated for the sediments of the sampling stations. Iron and manganese concentrations in sediments are much higher than other rivers in the world that are unaffected by mining activities. The observed changes in the bottom sediments of the river suggest a need for constant monitoring of the iron because the iron oxide minerals present in silt and clay have a high adsorption capacity. In the long term, these factors may contribute to the decrease of the quality of these sediments and consequently of the waters and biota present in these environments.

Physiological damages of Sargassum cymosum and Hypnea pseudomusciformis exposed to trace metals from mining tailing

The damages of Mariana's mining mud in the physiology of the brown algae Sargassum cymosum and its main epiphytic, the red algae Hypnea pseudomusciformis, were evaluated by controlled essays. Seaweeds were exposed to presence or absence of mud, isolated or in biological association, for 5 and 15 days. Measured parameters were growth rates, biochemical descriptors, and the chemical investigation of concentration and metal profile of the mud dissolved in seawater. Results showed that the highest values for metals were Al > Fe > Mn > Zn in both exposure periods. The mud also affected the growth rate with lethality in both isolated and associative treatments with H. pseudomusciformis after 15 days. According to our redundancy analysis (RDA), the profile and concentration of all metallic elements can induce different physiological responses of the organisms. We were able to observe a higher physiological adaptive ability of S. cymosum against the long-term presence of metals by the synthesis of phenolic compounds, while the deviation of metabolic routes in H. pseudomusciformis can be addressed as the main responsible for its lethality. Moreover, the presence of Hypnea in associative treatments reduces Sargassum's detoxification ability. The present results reinforce the importance of biological interaction studies in a context of physiological resilience against mining mud pollution and mutual influences of species over the individual ability to avoid oxidative stress.

Chronic trace metals effects of mine tailings on estuarine assemblages revealed by environmental DNA

Mine tailing disasters have occurred worldwide and contemporary release of tailings of large proportions raise concerns of the chronic impacts that trace metals may have on the aquatic biodiversity. Environmental metabarcoding (eDNA) offers an as yet poorly explored opportunity for biological monitoring of impacted aquatic ecosystems from mine tailings and contaminated sediments. eDNA has been increasingly recognized to be an effective method to detect previously unrecognized small-sized Metazoan taxa, but their ecological responses to environmental pollution has not been assessed by metabarcoding. Here, we evaluated chronic effects of trace metal contamination from sediment eDNA of the Rio Doce estuary, 1.7 years after the Samarco mine tailing disaster, which released over 40 million m3 of iron tailings in the Rio Doce river basin. We identified 123 new sequence variants environmental taxonomic units (eOTUs) of benthic taxa and an assemblage composition dominated by Nematoda, Crustacea and Platyhelminthes; typical of other estuarine ecosystems. We detected environmental filtering on the meiofaunal assemblages and multivariate analysis revealed strong influence of Fe contamination, supporting chronic impacts from mine tailing deposition in the estuary. This was in contrast to environmental filtering of meiofaunal assemblages of non-polluted estuaries. Here, we suggest that the eDNA metabarcoding technique provides an opportunity to fill up biodiversity gaps in coastal marine ecology and may become a valid method for long term monitoring studies in mine tailing disasters and estuarine ecosystems with high trace metals content.

Genotoxicity effects on Geophagus brasiliensis fish exposed to Doce River water after the environmental disaster in the city of Mariana, MG, Brazil

Abstract The Doce River basin has suffered the largest environmental accident ever occurred in Brazil with the influx of tailings from Fundão and Santarém, belonging to Samarco mining company, due to the disaster in Mariana. A spill between 50 and 60 million m3 of tailings was estimated by the company. According to Samarco, the wastewater was composed mainly of clay, silt and heavy metals like iron, copper and manganese. Thereby, the objective of the present study was evaluated the genotoxic damage in juvenile of Geophagus brasiliensis (Quoy e Gaimard, 1824) exposed to Doce river water before (DRWBA – Doce River water before acident) and after (DRWAA – Doce River water after acident) the influx of tailings from the Germano and Santarém Dam disasters in Mariana, MG, Brazil. For this, 24 individuals of the species G. brasiliensis (obtained on IFES/ALEGRE fish culture) were submitted to a bioassay with three treatments and eight replicates. The treatments were: 1) Control water (water from the urban water supply system, filtered with a 0.45 µm membrane), 2) DRBA and 3) DRAA. After 96 h, these fishes were anesthetized to remove blood for evaluation of genotoxic damage (micronucleus and comet). For the bioassay, a total of 80 L of The Doce River water were collected before the influx of tailings and after the influx and then submitted to metal quantification analysis. Fish exposed to DRWBA and DRWAA treatments showed a significant increase in both the number of erythrocyte micronuclei and the DNA damage index in relation to the control fish; however, they did not present any differences between the two treatments. The results demonstrate that the DRWBA treatment was already genotoxic for the fish, mainly due to dissolved Cu concentrations in the water. The DRWAA treatment probably presented genotoxicity due to the increase in the dissolved fraction and synergistic effects of several metals found in the tailings of the Mariana accident.