Food web structure of fish communities of Doce River, 5 years after the Fundão dam failure.

The rupture of the Fundão dam is considered the largest mining failure in history, which had a particularly detrimental impact on fish populations, as the mud from the ore tailings significantly altered the water quality and habitat of Doce River basin. This study aimed to assess the trophic structure of fish communities in areas impacted and not impacted by the dam rupture in the Doce River basin. To evaluate the food web structure, community-wide trophic niche, and trophic positions of fish, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were utilized across ten sites (seven impacted and three control). In general, fish appeared to assimilate resources such as invertebrates, algae, and periphyton, although the importance of each resource varied among sites. The site closest to the dam rupture exhibited a more simplified trophic structure compared to the control sites and those nearer the river mouth. In this site, most fish species occupied a similar trophic position. Trophic niches also exhibited the greatest dissimilarity between the site closest to the dam failure and those farther away from it, with an expansion of trophic niche breadth observed with an increase in the distance from the dam rupture. Our study provided valuable insights into the trophic structure of fish communities within the Doce River basin, shedding light on the trophic ecology of the 59 fish species investigated. We also emphasize the importance of our study for future assessments of ore tailings dam failure disasters and evaluating the effectiveness of mitigation measures for Doce River basin recovery.

Are fish assemblages recovering after the huge disaster of mining tailing dam collapse in Mariana (Brazil-MG)?

The Doce River basin is located in the Brazilian states of Minas Gerais (MG) and Espírito Santo (ES). Anthropogenic expansion throughout the twentieth century heavily modified the bioecological configuration of the region, which was worsened in November 2015 by the collapse of the Fundão tailing dam in Mariana municipality (MG). Local ichthyofauna suffered a loss of environmental quality, which served as an alert to the possible decline of native species and transformation of fish assemblages. Through a systematic literature review, the present study aimed to investigate the recovery stage of fish assemblage after the disaster. To accomplish this, we selected 14 documents reporting species lists and fish distributions in the area principally affected by the disaster. Data collected about fish assemblage (presence/absence) were spatially (upper, middle, and lower sections) and temporally (pre- and post-disaster) arranged, followed by non-metric multidimensional scaling (NMDS) analysis to assess similarity. We applied the Analysis of Similarities (ANOSIM) non-parametric test to confirm statistically significant differences between groups. We complemented the study by searching for the main bioecological characteristics of the most frequent species raised among the selected documents. NMDS showed differences in the similarity of fish assemblages among the three spatial sections, as confirmed by ANOSIM (p < 0.05), but no differences for the temporal component were observed. Nevertheless, we detected a trend based on continental fish assemblage transformation, as determined by the presence of many non-native species in the post-disaster period, suggesting the better resilience of these species over that of native species. The missing of many native species previously easily collected, mainly from the families Characidae, Loricariidae, and Trichomycteridae, suggested the system moving toward a new condition, probably worsened than the previous one. The ichthyofauna of the estuarine environment, on the contrary, seems to have recovered faster than ichthyofauna from the continental environment.

Impacts of mining pollution on coastal ecosystems: is fish body condition a reliable indicator?

Identifying reliable biological indicators is fundamental to efficiently assess human impacts on biodiversity and to monitor the outcomes of management actions. This study investigates whether body condition is an appropriate indicator of putative effects from iron ore mining tailings on marine fishes, focusing on the world's largest mining disaster - known as the Mariana disaster, in Brazil. Eight species were used to test the hypothesis that individuals inhabiting an area severely impacted by tailings have reduced body condition in comparison to those in control areas near (<60 km) and distant (>120 km) from the impact site. Contrary to our prediction, no significant difference in condition was detected between the impacted area and both near and distant controls in seven of the eight species. The results indicate that body condition, as measured by the scaled mass index, has limited applicability as indicator of impact from mining pollution on the fishes analysed. Hypotheses that could explain our findings are proposed, including nutrient provisioning from continental drainage that could indirectly influence fish condition and compensate for the deleterious effects of mining pollution.

The Fundão dam failure: Iron ore tailing impact on marine benthic macrofauna.

The Fundão dam failure, the worst environmental disaster in Brazilian history, launched 50 million m3 of iron ore tailings mud through the Doce River, reaching the Atlantic Ocean. Generally, mine tailings increase the sediment inflow, leading to mud burial of epibenthic macrofauna, and the raise of metal(oid)s concentration causing macrofauna long-term changes. After almost four years, tailings mud was still spreading on the Doce River Shelf, while impacts on marine macrofauna were still unknown. Herein, the IMS index (a tracer of Fundão dam tailings mud), sediment variables, organic pollutants, and metal(oid)s were integrated to uncover the drives of macrofauna structure from Costas da Algas to Abrolhos bank MPAs. Tailings mud was present only in Doce River Mouth and Degredo, organic pollutants and metal(oid)s above safety levels were concentrated in those same areas. Tailings mud (IMS index) drastically reduced species richness and diversity, favoring the abundance of opportunistic species. Mud, IMS index and Al, Ba, and V, metal(oid)s linked to dam failure, structured macrofauna composition in this impacted area, dominated by resistant groups as Nuculidae, Spionidae, and Magelonidae. Conversely, an opposite pattern was found for further and deeper sites with high CaCO3 content and total nitrogen that also showed large grain size, in areas known to harbour biogenic structures, sustaining a macrofauna composition distinct from the impacted areas, dominated by Syllidae and Crassatellidae, sensitives to impacts. Macrofauna composition was most structured by sediment variables, followed by the intersection between metal(oid)s-IMS and Mud, both gradients acting almost entirely on a broad spatial scale. Benthic macrofauna at the Doce River Shelf is still impacted by Fundão dam tailings mud, even after almost four years of the disaster, and may continue to, since the influx of tailings does not stop, and sediment resuspension is a recurrent source for those impacts.

Variability in nearshore fish biodiversity indicators after a mining disaster in eastern Brazil.

The rupture of the Fundão mining dam (Doce river basin, Brazil) caused a wide range of negative impacts. Yet, assemblage-level implications to estuarine and coastal fishes remain unclear, partly due to the lack of pre-disaster information. Based on monthly otter trawl surveys, we analyzed spatial and seasonal variability in univariate (total biomass, biomass of species vulnerable to exploitation, rarefied richness and evenness) and multivariate (species composition and trophic composition) indicators of fish biodiversity in the Doce river delta, eastern Brazil. We determined the independent and interactive effects of environmental, seasonal and spatial variables on species composition to test whether environmental alterations provoked by mine tailings could affect assemblage's organization. Most indicators present idiosyncratic spatiotemporal patterns, suggesting they have complementary roles in revealing changes in fish biodiversity. Environmental variables, including those affected by the Fundão dam collapse such as turbidity, dissolved oxygen and pH, were much more important than seasonal and spatial predictors in explaining the variation in fish species composition. These findings highlight the potential from mine tailings to disrupt local ichthyofauna and indicate a preponderant role of environmental conditions in assemblage structuring. Given the lack of data prior to rupture, our results may be used as a baseline against which to assess temporal trends in fish biodiversity relative to changes detected in less disturbed estuarine and coastal assemblages.

Mine tailings in a redox-active environment: Iron geochemistry and potential environmental consequences.

Iron (Fe) oxyhydroxides provide many functions in soils, mainly owing to their large surface area and high surface charge density. The reactivity of Fe oxyhydroxides is function of their mineralogical characteristics (e.g., crystallinity degree and crystal size). Detailed studies of these features are essential for predicting the stability and reactivity of these minerals within soil and sediments. The present study aimed to evaluate geochemical changes in Fe-rich tailings after the world's largest mining disaster in SE Brazil (in 2015) and to predict the potential environmental implications for the estuary. The mineralogical characteristics of the tailings were studied at three different times (2015, 2107, and 2019) to assess how an active redox environment affects Fe oxyhydroxides and to estimate the time frame within which significant changes occur. The study findings indicate a large decrease in the Fe oxyhydroxides crystallinity, which were initially composed (93%) of highly crystalline Fe oxyhydroxides (i.e., goethite and hematite) and 6.7% of poorly crystalline Fe oxyhydroxides (i.e., lepidocrocite and ferrihydrite). Within 4 years the mineralogical features of Fe oxyhydroxides had shifted, and in 2019 poorly crystalline Fe oxyhydroxides represented 47% of the Fe forms. Scanning electron microscope micrographs and the mean crystal size evidenced a decrease in particle size from 109 nm to 49 nm for goethite in the d111 direction. The changes in mean crystal size increased the reactivity of Fe oxyhydroxides, resulting in a greater number of interactions with cationic and anionic species. The decreased crystallinity and increased reactivity led to the compounds being more susceptible to reductive dissolution. Overall, the findings show that the decrease in crystallinity along with higher susceptibility to reductive dissolution of Fe oxyhydroxides can affect the fate of environmentally detrimental elements (e.g., phosphorus and trace metals) thereby increasing the concentration of these pollutants in estuarine soils and waters.

Conceptual model to analyze the effects caused by technological disaster on the physical-chemical state of the lower Doce River waters, Brazil.

Research has shown the effort to develop conceptual models that relate anthropic stressors to changes in aquatic environment state. Several of these models come from the structure Drivers, Pressures, State, Impact and Response (DPSIR), which has been used since the 1990s. However, there is a lack of conceptual models that consider in its structure the connection between the damages caused in the aquatic environment and technological disasters. This research develops a general conceptual model based on the DPSIR structure incorporating technological disasters. Based on the general conceptual model guidelines and the methodological procedure associated with it, a model was developed to assess the Lower Doce River waters' state, by considering Fundão's iron-ore dam failure scenario, which took place in November 2015, in the municipality of Mariana, state of Minas Gerais, Brazil. The relevant aspects of this adaptation of the DPSIR structure were: I) it considers the combined effect of drivers and pressures that already existed in the study area with those originated from the technological disaster; and II) the causal relationships among elements of the model were explicited through a systemic conceptual map, allowing a more holistic and integrated view of the problem. The application of the conceptual model to Doce River's scenario before the disaster allowed us to verify that a set of environmental pressures was already acting in a way to stress it, making the river vulnerable. For the post-disaster scenario, it was possible to determine that the already existing vulnerability condition, caused by urbanization, agriculture1 and mining, had been intensified by adding new pressures due to the tailings dam failure.

Metal accumulation induces oxidative stress and alters carbonic anhydrase activity in corals and symbionts from the largest reef complex in the South Atlantic ocean.

We evaluated the influence of metal accumulation on the oxidative status [lipid peroxidation (LPO) and total antioxidant capacity (TAC)] and carbonic anhydrase (CA) activity in host and symbionts of the coral Mussismilia harttii and the hydrocoral Millepora alcicornis collected in Abrolhos Reef Banks (Northeast Brazil), potentially impacted by a major mine dam rupture. Considering metal levels measured in reefs worldwide, Abrolhos corals had higher Fe and Mn levels than expected for preserved offshore reefs. Increasing concentrations of arsenic (As), chromium (Cr) and manganese (Mn) drove inhibition of CA and increased oxidative damage in the hydrocoral M. alcicornis. The impairment of enzymatic activity in the symbiotic algae of M. alcicornis may be related to the oxidative stress condition. The hydrocoral M. alcicornis was more affected by metals than the coral M. harttii, which did not show the expected CA inhibition after metal exposure. Our results suggest that CA activity can be applied as a complementary biomarker to evaluate the physiological impacts of environmental metal contamination in reefs. Also, the metal levels and biochemical biomarkers reported in the present study may provide reference data to monitor the health of reefs impacted by a relevant dam rupture.

Mining Dam Failures in Brazil: Comparing Legal Post-Disaster Decisions.

Mining dam failures have increased worldwide since the 1980s. Two large mining dam failures occurred recently in Mariana and Brumadinho, both in the state of Minas Gerais, Brazil. We hypothesize that there were significant differences in legal post-disaster decisions. The aim of this article is to understand the similarities and differences of post-disaster actions and controversies in Mariana and Brumadinho. We reviewed 686 news reports about court decisions and settlement agreements from the websites of state and federal courts and judicial institutions. After classifying the reports using an adapted protocol from a media health observatory, we conducted a thematic analysis. Our analysis suggests that there were significant differences in legal post-disaster decisions in the cases of Mariana and Brumadinho. In Mariana, there was privatization of post-disaster management, with the creation of the Renova Foundation, a mediated indemnity program, lack of access to information for those affected, and uncertainties in health and resettlement issues. In Brumadinho, there was faster implementation of the recovery and compensation measures, faster recognition of affected parties, and stronger participation of the population since the first hearings. Even though there were particularities in post-disaster management, the ultimate goal of the corporations responsible for the disasters was to protect their profits.

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.

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.

O objetivo deste estudo foi avaliar a concentração de elementos potencialmente tóxicos em plantas de Brachiaria decumbens, Stylosanthes guianensis e Saccharum officinarum e amostras de solos em áreas afetadas e não afetadas pelo rompimento da barragem de Fundão. As amostras foram coletadas em áreas afetadas por resíduos da barragem de Fundão (RAA1, RAA2, RAA3) e em uma área não afetada (controle). O material foi analisado quanto à composição de micronutrientes e elementos-traço no solo e plantas, além de fatores de contaminação (CF), bioacumulação e translocação (TF). No geral, os resultados mostraram que o solo e as plantas apresentaram maiores teores de Fe, Mn, Cu e Cr e menores teores de Zn nas áreas afetadas em comparação ao controle. Folhas e raízes de B. decumbens apresentaram aumento no teor de Fe nas áreas afetadas em relação ao controle, atingindo o valor máximo médio de 42.958 µg/g nas raízes de plantas coletadas em RAA2. Como resultado, CF para Fe de B. decumbens foi classificado como muito alto, mas com baixos valores de TF. Além disso, B. decumbens coletadas nas áreas afetadas apresentaram aumento de Fe, Mn, Cu e Cr nas folhas, caules e raízes, enquanto que em Stylosanthes guianensis houve aumento da concentração de Fe em todos as partes das plantas e Cr nas folhas. Saccharum officinarum também apresentou acúmulo de Mn no caule e Cu nas folhas e caule. Por outro lado, não há contaminação das plantas por elementos perigosos como Pb, Cd e As nas amostras analisadas. Concluindo, foram encontrados aumentos nos teores de Fe, Mn, Cu e Cr no solo e em vários tecidos vegetais, o que pode comprometer o crescimento das plantas e representar riscos potenciais decorrentes do processo de biomagnificação na cadeia alimentar. Integr Environ Assess Manag 2020;16:596-607.

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.

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.

Neste trabalho, amostras do rejeito de mineração de ferro, proveniente do rompimento da barragem de Fundão e retidas pela usina hidroelétrica de Candonga, foram caracterizadas por diversas técnicas. Quartzo, hematita, caulinita e ghoetita foram identificadas como as principais fases presentes no rejeito. A composição, homogeneidade e teor de matéria orgânica relativamente baixo, cerca de 1%, indicam uso potencial deste material em construção civil. O próximo passo deste trabalho é investigar tais aplicações. Se a viabilidade for confirmada, o objetivo é utilizar esse material para obras nas áreas afetadas pelo rompimento da barragem de Fundão. Isso contribuirá para reduzir os impactos socioambientais nessas regiões, as quais ainda necessitam da remoção do rejeito e de reparos na infraestrutura danificada. Integr Environ Assess Manag 2020;16:636-642.

Comportamento legislativo e financiamento eleitoral: o caso do desastre da samarco / Legislative behavior and electoral financing: the samarco disaster case / Comportamiento legislativo y financiamiento electoral: el caso de desastre de samarco / Comportement législatif et financement électoral: le cas de la catastrophe de samarco

O presente estudo centra-se na ocorrência dos desastres socioambientais, que estão intimamente relacionados às decisões administrativas e à priorização de resultados econômico-financeiros feitas pelos tomadores de decisão das grandes empresas. O objetivo do artigo é analisar o comportamento dos deputados estaduais do Espírito Santo em um momento crítico, qual seja, o desastre da barragem de Mariana, provocado pela Samarco/Vale/BHP. Busca-se, especificamente, apresentar um panorama geral da produção legislativa, e observar de que maneira o comportamento destes parlamentares pode estar associado às doações de campanha realizadas pelo grupo empresarial causador do desastre. Foram analisadas as 25 proposições apresentadas pelos deputados acerca do caso em análise, entre os anos de 2015 e 2019. Os resultados encontrados sugerem relação entre comportamento legislativo e financiamento de campanha. Os políticos financiados buscaram, sobretudo, interromper as investigações e solicitar o retorno das atividades da Samarco.

This research focuses on the occurrence of socio-environmental disasters, which are closely related to administrative decisions and the prioritization of economic and financial results made by decision makers of large companies. The purpose of the paper is to analyze the behavior of state representatives of Espírito Santo in a critical moment, namely the Mariana dam disaster, caused by Samarco / Vale / BHP. Specifically, it seeks to present an overview of legislative production, and to observe how the behavior of these parliamentarians may be associated with campaign donations made by the business group that caused the disaster. We analyzed the 25 propositions presented by the deputies about the case under analysis, between 2015 and 2019. The results suggest a relationship between legislative behavior and campaign financing. The funded politicians sought, above all, to interrupt the investigations and to request the return of Samarco's activities.

El presente estudio se centra en la ocurrencia de desastres socioambientales, que están estrechamente relacionados con las decisiones administrativas y la priorización de los resultados económicos y financieros realizados por los tomadores de decisiones de las grandes empresas. El propósito del paper es analizar el comportamiento de los representantes estatales de Espírito Santo en un momento crítico, a saber, el desastre de la presa Mariana, causado por Samarco / Vale / BHP. Específicamente, busca presentar una visión general de la producción legislativa y observar cómo el comportamiento de estos parlamentarios puede estar asociado con las donaciones de campaña realizadas por el grupo empresarial que causó el desastre. Analizamos las 25 propuestas presentadas por los diputados sobre el caso bajo análisis, entre 2015 y 2019. Los resultados sugieren una relación entre el comportamiento legislativo y el financiamiento de campañas. Los políticos financiados buscaron, sobre todo, interrumpir las investigaciones y solicitar el regreso de las actividades de Samarco.

Cette étude se concentre sur la survenue de catastrophes socio-environnementales, étroitement liées aux décisions administratives et à la hiérarchisation des résultats économiques et financiers des décideurs des grandes entreprises. L'objectif de l'article est d'analyser le comportement des représentants de l'État d'Espírito Santo à un moment critique, à savoir la catastrophe du barrage de Mariana, causée par Samarco / Vale / BHP. Plus précisément, il cherche à présenter un aperçu de la production législative et à observer comment le comportement de ces parlementaires peut être associé aux dons de campagne effectués par le groupe d'entreprises qui a causé la catastrophe. Nous avons analysé les 25 propositions présentées par les députés sur le cas sous analyse, entre 2015 et 2019. Les résultats suggèrent une relation entre le comportement législatif et le financement des campagnes. Les politiciens financés ont surtout cherché à interrompre les enquêtes et à demander le retour des activités de Samarco.

Mineral Waste Containing High Levels of Iron from an Environmental Disaster (Bento Rodrigues, Mariana, Brazil) is Associated with Higher Titers of Enteric Viruses.

Although the effects of heavy metals on the behavior, including infectivity, of bacteria have been studied, little information is available about their effects on enteric viruses. We report an investigation of effects on the biosynthesis of human adenoviruses (HAdV) and hepatitis A (HAV) of waters contaminated with mineral waste following an environmental disaster in Mariana City, Minas Gerais State, Brazil. The study area was affected on November 5, 2015, by 60 million m3 of mud (containing very high concentrations of iron salts) from a mining reservoir (Fundão), reaching the Gualaxo do Norte River (sites evaluated in this study), the "Rio Doce" River and finally the Atlantic Ocean. We found substantial counts of infectious HAdV and HAV (by qPCR) in all sampled sites from Gualaxo do Norte River, indicating poor basic sanitation in this area. The effects of iron on viral infection processes were evaluated using HAdV-2 and HAV-175, as DNA and RNA enteric virus models, respectively, propagated in the laboratory and exposed to this contaminated water. Experiments in field and laboratory scales found that the numbers of plaque forming units (PFU) of HAdV and HAV were significantly higher in contaminated water with high iron concentrations than in waters with low iron concentration (< 20 µg/L of iron). These findings indicate that iron can potentiate enteric virus infectivity, posing a potential risk to human and animal health, particularly during pollution disasters such as that described here in Mariana, Brazil.

Influence of the residue from an iron mining dam in the growth of two macrophyte species.

On November 5th, 2015 the worst environmental disaster in Brazil spilled 60 million m3 of iron mining residue into Gualaxo do Norte River (Minas Gerais State), an affluent of the highest River Basin of the Brazilian Southeast (Doce River Basin), reaching the Atlantic Ocean. To assess the impact of the iron residue on the aquatic plant metabolism, we performed macrophyte growth experiments under controlled light and temperature conditions using two species (Egeria densa and Chara sp.). The plants' growth data were fitted in a kinetic model to obtain the biomass yields (K) and growth rates (µ). Turbidity and electrical conductivity of the water were measured over time. Both plants showed the highest growth rates in the contaminated condition (0.056 d-1 for E. densa and 0.45 d-1 for Chara sp.) and the biomass increased in the short-term (≈20 days). The control condition (i.e. no impacted water) supported the biomass increasing over time and the development of vegetative buddings with high daily rates (1.75 cm d-1 for E. densa and 0.13 cm d-1 for Chara sp). Turbidity showed a sharp decrease in 48 h and had no effects in the plants growth in the contaminated condition. The contamination affected the plants' yields in the long-term affecting the biomass development. This study provides preliminary information about the ecological consequences of a mining dam rupture aiming to collaborate with monitoring and risk assessments.

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

On November 5th, 2015, Samarco's iron mine dam - called Fundão - spilled 50-60 million m3 of mud into Gualaxo do Norte, a river that belongs to Rio Doce Basin. Approximately 15 km2 were flooded along the rivers Gualaxo do Norte, Carmo and Doce, reaching the Atlantic Ocean on November 22nd, 2015. Six days after, our group collected mud, soil and water samples in Bento Rodrigues (Minas Gerais, Brazil), which was the first impacted area. Overall, the results, water samples - potable and surface water from river - presented chemical elements concentration according to Brazilian environmental legislations, except silver concentration in surface water that ranged from 1.5 to 1087 µg L-1. In addition, water mud-containing presented Fe and Mn concentrations approximately 4-fold higher than the maximum limit for water bodies quality assessment, according to Brazilian laws. Mud particle size ranged from 1 to 200 µm. SEM-EDS spot provided us some semi quantitative data. Leaching/extraction tests suggested that Ba, Pb, As, Sr, Fe, Mn and Al have high potential mobilization from mud to water. Low microbial diversity in mud samples compared to background soil samples. Toxicological bioassays (HepG2 and Allium cepa) indicated potential risks of cytotoxicity and DNA damage in mud and soil samples used in both assays. The present study provides preliminary information aiming to collaborate to the development of future works for monitoring and risk assessment.