Water and Sediment Quality in the Coastal Zone Around the Mouth of Doce River After the Fundão Tailings Dam Failure

Abstract

Fundão dam (Minas Gerais, Brazil) breached on 5 November 2015, releasing 50 million m³ of Fe ore tailings and dam materials into the upper Doce River system. The tailings travelled 670 km along the river system to the ocean. Starting on 17 November 2015, 6 days before the tailings reached the Doce River mouth, a water quality monitoring program with a daily sampling schedule was implemented by Samarco Mineração S.A. (Samarco) to assess the impacts on marine water and sediment quality. Between November 2015 and August 2017 water and sediment quality were monitored at 28 locations offshore from the Doce River mouth. The sampling areas were grouped by hydrological and metocean season (i.e., rainy and dry seasons and wave and wind climates), distance from the river mouth (<5 km, >5 km and within a Marine Protected Area), and water depth. The data were compared to the Brazilian water quality standards and prebreach conditions. Statistical tests were conducted to evaluate temporal and spatial trends and patterns. For the water quality parameters of relevance (total suspended solids, turbidity, total and dissolved Fe, Al, and Mn), pulses of concentration increases were observed right after the arrival of the plume in the coastal zone and during the subsequent rainy seasons. Exceedances of prebreach conditions were more frequent closer to the Doce River mouth. During the dry season, concentrations tended to decrease, reaching prebreach levels for a number of parameters, with small short‐term pulses associated with metocean factors. For sediment quality parameters of relevance (particle size, Fe, Al, and Mn), Fe was the only one that clearly resulted from the dam breach, which was mediated by river influence and oceanographic factors affecting particle size distribution. Results indicated that the Fundão dam failure did affect water and sediment quality in the Atlantic Ocean, with greater impacts closer to the river mouth and immediately after the arrival of the tailings plume, with concentrations gradually returning to preevent levels over time. Integr Environ Assess Manag 2020;16:643–654. © 2020 SETAC

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

“…The great magnitude of the disaster made it practically impossible to establish control sampling sites, because the entire estuary was highly impacted by the mining tailings. However, evidence indicates increased trace metal contamination in the estuarine sediments, associated with the tailings arrival in November 2015 and subsequent negative effects on both benthic and fish assemblages ( De Oliveira Gomes et al, 2017 ; Queiroz et al, 2018 ; Andrades et al, 2020 ; Richard et al, 2020 ). In August 2017, sediment trace metal concentrations were still significantly above baseline levels in the estuary, with measurable effects on benthic assemblages ( Bernardino et al, 2019 ).…”

“…As a result, the tailings exhibit high potential for element mobility, especially for Al, As, Ba, Fe, Mn, Pb and Sr, which may be potentially bound to Fe oxides ( Segura et al, 2016 ). Once the tailings reached the estuary, in November 2015, fine sediments containing high concentrations of some elements were immediately deposited on the bottom, raising ecological concerns regarding the long term risks to the estuarine and coastal ecosystems ( De Oliveira Gomes et al, 2017 ; Queiroz et al, 2018 ; Richard et al, 2020 ). The tailings initially impacted benthic and fish assemblages in the Rio Doce estuary ( De Oliveira Gomes et al, 2017 ; Andrades et al, 2020 ).…”

Manganese: The overlooked contaminant in the world largest mine tailings dam collapse

“…Thus, Fe oxyhydroxides from the tailings were subjected to a biogeochemical environment highly favorable towards Fe III reduction to Fe II and its subsequent solubilization ( Cummings et al, 2000 ; Xia et al, 2019 ). In estuaries, the fate of solubilized Fe II following dissimilatory Fe reduction may vary, for instance as precipitation of poorly crystalline Fe oxyhydroxide, uptake by plants, or removal from the estuary into the ocean ( Canfield and Kristensen, 2005 ; Johnston et al, 2011 ; da Richard et al, 2020 ). The significant decrease in total Fe in soils collected in 2017 ( r < 0.001; Fig.…”

Dissimilatory Iron-Reducing Microorganisms Are Present and Active in the Sediments of the Doce River and Tributaries Impacted by Iron Mine Tailings from the Collapsed Fundão Dam (Mariana, MG, Brazil)

“…DNA from known DIRM genera, such as Geobacter and Geothrix, was found in sediments of the Doce River and its tributary the Carmo River after the Fundão Dam burst [93,94], but it was not shown if they were actively reducing Fe(III) minerals in the river sediments. Although the bottom sediments of the Gualaxo do Norte River stretch impacted by tailings showed very small TOC values [54], the downstream Doce River is impacted by the discharge of untreated sewage [59,60]. Jardim et al [59] estimated that untreated sewage of approximately 870,000 people was discharged into the Doce River mainstream and tributaries, contributing an estimated 8 tons of organic N and 2.2 tons of organic P per day to the watershed, which led to eutrophication and recurrent cyanobacterial blooms before dam burst [59].…”

“…The Doce River watershed was highly impacted by untreated sewage from at least 870,000 people, which increased the organic and nutrient loads in water and sediments and led to frequent cyanobacterial blooms before dam burst [59]. After dam burst, the presence of high levels of thermotolerant coliforms and DO (dissolved oxygen) below 5 mg/L at several points along the river indicates that discharge of large amounts of untreated sewage is still occurring in the watershed [60]. Here, we extend this rationale to the sediments of the entire Doce River as well as affected tributaries, pointing to the risk of extensive dissolution of iron oxides in the river sediments by DIRMs, releasing trace metals and impairing water quality.…”