Changes in flocculation patterns of cohesive sediments after an iron ore mining dam failure

Grilo, Caroline Fiório; Quaresma, Valéria da Silva; Amorim, G.F.L.; Bastos, Alex Cardoso

doi:10.1016/j.margeo.2018.03.004

Cited by 26 publications

(11 citation statements)

References 48 publications

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“…Previous monitoring shows that the process of remobilization is normal for this area and this material could be transported further due to its smaller granulometry. On the other hand, changes in sediment composition and size, as in the mining tailing material, will result in changes in the flocculation process and settling behavior, making them more likely to be dispersed by currents and waves and to reach greater distances [44].…”

Section: Discussionmentioning

confidence: 99%

Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

et al. 2020

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The world's largest rhodolith beds have been reported from the Brazilian continental shelf. Highly biodiverse beds are located in Southeast Brazil, but ecological aspects of these beds remain unknown. Despite their ecological importance, rhodolith beds (RBs) have recently been subjected to a severe threat, when more than 35 million cubic meters of mining residues slid down a mountainside on 5 November 2015, after a collapse of a gigantic dam upstream (the Mariana disaster), causing a huge impact on the Doce River. Our aim is to assess rhodolith beds and adjacent coralline formations on the Doce River Shelf (DRS) after the dam collapse. This paper describes the distribution, abundance, vitality, size and shape, as well as unmapped bryozoan rich sediment formations in this area, serving as baseline knowledge for environmental monitoring. Four distinct biogenic sea bottom habitats (bryozoan bottoms, rhodolith beds, carbonate concretions, and reefs) were recognized at different depth ranges with distribution indicated to be mostly related to the local sedimentary regime. Mud sediments dominated the seafloor up to 35 m depth. On the mid shelf, bryozoan bottoms were recorded from 35 to 45 m depth. Crustose coralline algae (CCA) occurring as rhodoliths and carbonate concretions extend over 1953 km 2 in the mid and outer shelf. Rhodolith beds predominate in these areas, totaling 1521 km 2 of sea bottom and were more abundant at depths between 45 and 65 m, occupying an extensive area south of the Doce River mouth. Northward, rhodolith beds are less abundant or absent likely due to the long-term deposition of fine sediments in this region. Carbonate concretions and reefs covered by CCA occupy sparse areas on the outer shelf (65-105 m depth). Differences in rhodolith features recorded, including coverage, density and size, may be related to the Doce River sedimentation and related factors (e.g., hydrodynamics, depth, and light). However, since there are no previous detailed studies on RBs along the DRS, we could not assess the impact of sedimentation of dam wastes on RBs' abundance and density. In any case, these are valuable results for the further monitoring of long-term effects. Considering that the growth of these rhodoliths is relatively slow, and that they are affected by the sedimentation from the Doce River, the implementation of a management and conservation plan for this area is necessary in order to preserve this ecosystem.

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Section: Discussionmentioning

confidence: 99%

Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

et al. 2020

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“…The peak of turbidity, reduction of DO and the deposit of ore tailings in the Rio Doce are believed to be the main causes of mass mortality of fish observed in the Rio Doce after the disaster (ANA, 2016a). After the rupture, iron ore tailings were deposited along the Rio Doce channel, changing its hydrology and coating substrates with ferric oxide flocs (Grilo et al, 2018). However, contrary to our expectations, no significant variation in those parameters was observed.…”

Section: Discussionmentioning

confidence: 99%

“…The disaster left 19 people dead, hundreds homeless, and directly affected the health and livelihoods of thousands of people (Escobar, 2015). The spill produced ferric oxide flocs on channel substrates, silted the Rio Doce channel, contaminated the river with metals (Hatje et al, 2017) and produced a massive fish kill (Grilo et al, 2018; Neves et al, 2016). It also destroyed 457 ha of Atlantic Forest, a global biodiversity hotspot (Myers et al, 2000; Omachi et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Influences of multiple anthropogenic disturbances coupled with a tailings dam rupture on spatiotemporal variation in fish assemblages of a tropical river

et al. 2022

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The Mariana disaster, resulting from the rupture of the Fundão tailings storage facility (TSF) in 2015, was a large‐scale environmental disaster that drastically affected the entire channel of the Rio Doce, southeastern Brazil. The disaster produced substantial channel siltation, increased turbidity, riparian damage and a massive fish kill. However, the Rio Doce basin has a long history of environmental degradation, including hydroelectric dams. The latter are major threats to the ichthyofauna because they affect flow regimes, trap sediments and large wood, select generalist species, impair fish migrations and favour non‐native invasive species. In this study, we analysed the effects of the rupture as well as impacts from the construction of a run‐of‐the‐river hydroelectric dam on native and non‐native fish abundances, and species richness and composition in the middle Rio Doce. To do this, we examined fish survey data collected before and after each disturbance upriver of the reservoir, in the reservoir area and downriver of the dam. The data were separated into three temporal intervals: free‐flowing river, post‐filling reservoir and post‐TSF disaster. To assess temporal changes in native and non‐native fish species richness, we used a rarefaction method and tested it with two‐way ANOVA, which also was used to compare fish abundances. To test temporal changes in fish assemblage composition we used a PERMANOVA test. We observed no significant differences in total native or non‐native species richness as a result of the dam or the disaster. However, we did observe increased non‐native individual abundances after the TSF rupture as well as native individual abundances, depending on the location studied. The assemblage composition also changed after dam construction and the TSF rupture, except for the upriver reach after dam construction. We conclude that both the dam and the TSF rupture affected fish assemblages, favouring increased non‐native abundances, and also changed fish assemblage composition. Our results suggest that a century of landscape and riverscape pressures had extirpated the sensitive fishes from the Rio Doce before the TSF rupture. We conclude that multiple long‐term chronic disturbances can be as harmful to aquatic biota as the acute effects of a major environmental disaster.

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“…This is also in agreement with changes to flocculation processes that were demonstrated by settling experiments performed with mud sediment fraction (<63 μ m) from the continental shelf before and after the disaster. The post‐disaster decrease in the settling velocity of fine flocs was suggested to be a result of changes of the sediment composition, like the presence of porous Fe oxide goethite (Grilo et al 2018). In addition, adsorptive characterization of tailings from the Fundão dam was consistent with a monolayer model with low adsorption capacity and low interaction among adjacent molecules (Almeida et al 2018) which means that this material was probably less prone to processes of flocculation.…”

Section: Discussionmentioning

confidence: 99%

“…The transport of tailings mud from the river to the coastal sea in the acute stage of the disaster occurred as a massive loading of sediment/tailings highly enriched with Fe (44.3%; Pereira et al 2008) of finer grain size compared to pre-disaster conditions (Gomes et al 2017). This modified sediment deposited on the continental shelf remains fluid and subject to resuspension by high winds/waves dynamics (Rudorff et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Coastal waters contamination by mining tailings: What triggers the stability of iron in the dissolved and soluble fractions?

Longhini

Mahieu

Sá

et al. 2020

Limnology & Oceanography

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The solubility of iron (Fe) in seawater is greatly enhanced by complexation with organic ligands, predominantly occurring as humic substances (HS) in coastal areas. Mining exploitation is believed to change the natural biogeochemical cycle of Fe in coastal waters, even though its impacts on the physical and chemical speciation of the Fe fractions are not known. Here we show that dissolved and soluble Fe concentrations in coastal waters affected by a mining catastrophe (Fundão dam, Southeast Brazil) remain very high, even almost 3 years later, with concentrations of dissolved Fe up to 2.8 μM (0.45 μm filtration) or 700 nM (0.22 μm filtration), and soluble Fe (0.02 μm) up to 40 nM. Levels of humic substances can only explain the binding of 2% and 10% (median values) of dissolved Fe (0.22 μm) and soluble Fe concentrations, respectively, which shows that processes other than complexation with humic substances are at play to maintain such high dissolved Fe concentrations. We hypothesize that the colloidal phase that dominates the dissolved Fe fraction occurs as Fe(III) oxyhydroxides while the soluble fraction is comprised of Fe(III) complexes with amine compounds (widely used in the ore extraction process). Mass balance of dissolved Fe in the water column suggests that sediment resuspension on the continental shelf is by far the dominant process delivering dissolved Fe to coastal and shelf waters. Estimates of dissolved Fe yearly fluxes highlight the sheer magnitude of this catastrophe that might provide a non-negligible amount of dissolved Fe to the open ocean.

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Changes in flocculation patterns of cohesive sediments after an iron ore mining dam failure

Cited by 26 publications

References 48 publications

Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

Influences of multiple anthropogenic disturbances coupled with a tailings dam rupture on spatiotemporal variation in fish assemblages of a tropical river

Coastal waters contamination by mining tailings: What triggers the stability of iron in the dissolved and soluble fractions?

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