Has the Rio Doce "time bomb" been defused? Using a weight-of-evidence approach to determine sediment quality.

The Fundão mine tailings dam rupture of 2015, in the Rio Doce basin, Brazil, resulted in the deposition of tailings downstream of the dam. It has yet to be determined if metals associated with the tailings have contributed toxicity to organisms, burying a time bomb that could be ticking. Currently the data on toxicity to benthic and aquatic organisms have not been assessed sufficiently to allow an informed assessment using an approach based on weight-of-evidence. This study was conducted to ascertain if sediments at "hot spots" that received Fundão tailings reflected elevated concentrations of metals and if these concentrations were sufficient to result in toxicity to freshwater organisms. The lines-of-evidence considered included assessing metals concentrations in relation to sediment quality criteria, establishing biogeochemical characterizations, completing an evaluation of potential metal release upon resuspension to provide information on bioavailability, and identifying acute and chronic toxicity effects using sensitive native species for waters (water flea, Daphnia similis) and sediments (burrowing midge larvae, Chironomus sancticaroli). Only porewater concentrations of iron and manganese exceeded Brazilian surface water criteria, whereas most trace elements exhibited no enrichment or elevated environmental indexes. The concentrations of bioavailable metals were assessed to be low, and metal concentrations did not increase in the overlying water upon resuspension; rather, they decreased through time. Toxicity testing in resuspended waters and bulk sediments resulted in no acute or chronic toxicity to either benthic or aquatic species. The low metal bioavailability and absence of toxicity of the tailings-enriched sediments was attributed to the strong binding and rapid removal of potentially toxic metal ions caused by oxyhydroxides and particles in the presence of iron-rich particulates. The findings of these sediment hot-spot studies indicate the Fundão dam release of tailings more than six years ago is not causing the current release of toxic concentrations of metals into the freshwaters of the Rio Doce. Integr Environ Assess Manag 2024;20:148-158. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Scientometric analysis on the review research evolution of tailings dam failure disasters.

As the most severe damage form of tailings ponds, dam failure causes a serious threat and damage to the surrounding lives and environment. Therefore, based on the systematic collection and consultation of relevant data at home and abroad, the literature source analysis on tailings dam failure disasters is conducted using the CiteSpace scientometric tool. The research on tailings dam failure disasters can be classified into two stages: the preliminary germination stage and rapid development stage. Based on the scientometric knowledge map, the research hotspots of tailings dam failure disasters are analyzed and summarized as three main research directions: environmental impact, risk assessment, and mechanical behavior. With the maturity of the research on ecological problems caused by tailings leakage, ecological restoration has also gradually become a hot research topic. Through the analysis of keyword bursts and co-cited bursts, the research frontier of tailings dam break disaster is explored. "Risk management," "real-time monitoring," and "tailings characteristic" represent the current research frontier. Among them, risk management is burst for the longest time and is expected to be a very important research direction in the future. Finally, a tailings pond risk management and control suggestion is proposed with risk management as the core, emphasizing risk monitor, and combined with dynamic risk control, which provides a foundation for the construction of tailings dam safety management and dynamic monitoring systems.

Tailings dams: Assessing the long-term erosional stability of valley fill designs.

Tailings is a generic term for waste material from the extraction and processing of minerals and frequently contain mineral and chemical residues. They are usually highly erodible and transportable via fluvial processes. Tailings are commonly stored in 'tailings dams' and such dams are a feature of many mine sites. As they impound water and sediment, tailings dams can be at risk from both catastrophic and gradual failure, especially if unmanaged. A fundamental question for their management is, can tailings dams ever be walk-away structures? Catastrophic failure occurs when there is a large scale rapid structural failure of the dam wall suddenly releasing large volumes of water and sediment. However, over time, there will the increased risk of gradual failure by the slow infilling of the dam and the erosion of the dam wall. Failure can occur where water overtops the dam wall and then incises through the wall due to a loss of freeboard in the dam, a situation which is more likely in legacy tailings dams where they have been filled, vegetated and abandoned. Here, firstly, a computer based landscape evolution model (CAESAR-Lisflood) is employed to assess a hypothetical tailings dam failure by erosion. Secondly, using an idealised example, it is demonstrated that given average climate conditions a dam can be sufficiently robust to last centuries. Thirdly, and longer term it is demonstrated that the tailings can be contained if (a) maintenance is conducted to increase the dam wall height over time or (b) a more robust dam wall is constructed to manage extreme events. However, erosion and infill will continue to reduce the integrity of any structure over time. Therefore, it is highly likely that tailings dams will require continued monitoring and maintenance. The method outlined provides a new tool for assessing any tailings facility for its erosional stability.

Effect of simulated earthquake loading on radon exhalation from uranium tailings dam.

Uranium tailings sand will continuously release radon-222. When the external condition changes, the exhalation of radon will also change. Thus, radon is being recommended as a tracer for dam damage assessment. When an earthquake is simulated on the uranium tailings dam with a shaking table test and the change in radon concentration is measured, it is observed that the earthquake causes micro-fissures in the uranium tailings dam, which aggregate to form fractures. During the process, the radon concentration will climb dramatically, as will the radon exhalation rate. To verify that the radon monitoring date is accurate, the acceleration response, surface displacement, and interior displacement are all monitored. The results show that radon can be utilized as a tracer to evaluate uranium tailings dam damage.

Numerical Simulation of Tailings Flow from Dam Failure over Complex Terrain.

A tailings dam failure can lead to disastrous impacts on people's livelihood and the surrounding ecological environment. Due to interactions among water, tailings and ground, the mechanism of a tailings flow is more complicated than that of a flood flow. In this paper, the tailings flow is regarded as a homogeneous and incompressible non-Newtonian fluid. Its rheological properties were studied through rheological tests conforming to the Bingham model. The rheological parameters were further used in a Computational Fluid Dynamics (CFD) simulation over complex terrain to explore the tailings flow characteristics. The method was validated with experimental results of a non-Newtonian dam-break flow from literature. The flow characteristics, including flow velocity, runout distance, inundation area and depth, were analyzed in the case of the Dagangding tailings dam. The results showed that the downstream railway and village would not be affected in a conservative scenario. Finally, the effects of two measures for preventing tailings flow hazards were discussed. Setting the check dam and planting grasses and trees can effectively mitigate the damage of tailings flow.

An integrated study of the plankton community after four years of Fundão dam disaster.

Mining activities can affect the environment either by the tailings releasing or dams failures. The impact of the tailings can last decades and cause chronic effects due to their toxicity. The Fundão dam collapse, a relevant environmental disaster, occurred in November 2015 in Southeastern Brazil. Tailing rich in metals reached the Doce River and arrived in the Atlantic Ocean. Previous studies revealed the acute impact of the tailings in the marine planktonic community near the Doce River mouth. The current study aims to characterize the structure of planktonic assemblages in the impacted area after four years of the disaster. Sampling occurred in November 2018, January, April, and July 2019 at 32 stations located at the marine coastal area near the Doce River mouth. Our study detected high metal concentrations in the surface waters during January 2019, when the lowest diversity and abundance of phytoplankton, lowest zooplankton diversity, and low ichthyoplankton abundance were recorded. The zooplanktonic community was structured by environmental parameters and ichthyoplankton assemblages in November 2018, January and April 2019. Nutrients and metals, mainly iron from the tailing carried by the Doce River waters to the marine environment changed the plankton community, confirming the impact of the Fundão Dam collapse in the coastal area near the Doce River mouth. The phytoplankton community, influenced by the nutrients and to a lesser extent metals concentrations, was not decisive in the zooplankton community structure. The environmental variability was driven by the meteoceanographic conditions and the Doce River flow. There was a high correlation between the zooplanktonic community and ichthyoplanktonic assemblage and the environmental factors and metals. These relations indicate the impact of the tailings from the collapse of the Fundão Dam on these communities, even after four years of the Mariana disaster.

Metáforas da lama: multimodalidade e argumentação em discursos sobre sustentabilidade e rompimento de barragens de rejeitos de minério de ferro / Metaphors of the mud: multimodality and argumentation in discourses about sustainability and the rupture of tailings dams of iron ore

As barragens de rejeito de minério de ferro fazem parte do processo de mineração no Brasil. Trata-se de uma técnica antiga envolvendo diversas tecnologias para torná-la mais segura. A constante vigília e cuidado sobre essas estruturas tornaram-se uma rotina frequente das mineradoras para evitar possíveis rupturas dessas barragens. Após o rompimento da barragem de rejeitos de minério em Brumadinho-MG e Mariana-MG muitos discursos com elementos metafóricos acerca da sustentabilidade e a prática de uso de barragens de rejeitos foram sustentados por uma intencionalidade discursiva voltada para a crítica social. O objetivo deste estudo é identificar e analisar o uso de metáforas conceptuais presentes como elementos multimodais na argumentação textual, numa perspectiva sociocognitiva e interacional da linguagem. Para isso, adota-se uma pesquisa expo-facto. O viés teórico da intencionalidade discursiva na linha de Searle; o caráter de modelos mentais, representações sociais e conhecimento sociocultural tal com prevê Van Dijk, a visão sociosemiótica de Geeraerts para compreender como argumentação por meio do campo imagético das charges é construída e sustentada socialmente e o dialogismo na perspectiva de Meyer a partir da argumentação. Nessa perspectiva sociocognitiva e interacional, o texto é pensado como uma construção linguístico-discursiva na qual a intencionalidade está relacionada com os modelos mentais resultantes de representações construídas a partir da experiencia do sujeito em sociedade e das práticas interacionais. Nesse contexto, o texto contempla uma gama de operações cognitivas interligadas como direciona Marscuschi. Constitui-se um corpus de charges publicadas na mídia brasileira, orientadas para a temática do rompimento de barragens de rejeitos de minério de ferro para a análise do aparecimento de metáforas conceptuais. Conclui-se que as metáforas se constituem recursos multimodais na orientação argumentativa e revelam metáforas do medo e da lama envolvendo um discurso do horror sobre a tragédia das cidades de Brumadinho e Mariana.

Iron ore tailings dams are part of the mining process in Brazil. It is an old technique involving several technologies to make it more secure. Constant vigilance and care about these structures have become a frequent routine for mining companies to avoid possible failures of these dams. After the collapse of the ore tailings dam in Brumadinho (MG) and Mariana (MG) cities, many discourses with metaphorical elements about sustainability and the practice of using tailings dams were supported by a discursive intentionality focused on social criticism. The aim of this study is to identify and analyze the use of conceptual metaphors present as multimodal elements in textual argumentation, in a sociocognitive and interactional perspective of language. For this, it is adopted from expo-facto research. The theoretical bias of discursive intentionality along the lines of Searle; the character of mental models, social representations,and sociocultural knowledge as predicted by Van Dijk, the sociosemiotic vision of Geeraerts (2016) to understand how argumentation through the imagery field of cartoons is constructed and socially supported and dialogism in perspective of Meyer from the argumentation. In this sociocognitive and interactional perspective, the text is thought of as a linguistic-discursive construction in which intentionality is related to mental models resulting from representations built from the subject's experience in society and interactional practices. In this context, the text contemplates a range of interconnected cognitive operations as directed by Marscuschi. A corpus of cartoons published in the Brazilian media is constituted, oriented to the theme of breaking up iron ore tailings dams for the analysis of the appearance of conceptual metaphors. It is concluded that metaphors are multimodal resources in the argumentative orientation and reveal metaphors offear and mud involving a horror speech about the tragedy of the cities of Brumadinho and Mariana.