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

Author(s)

Queiroz, Hermano M. ^[1] ; Ying, Samantha C. ^{[2, 3]} ; Abernathy, Macon ^[3] ; Barcellos, Diego ^[1] ; Gabriel, Fabricio A. ^[4] ; Otero, Xose L. ^[5] ; Nobrega, Gabriel N. ^[6] ; Bernardino, Angelo F. ^[4] ; Ferreira, Tiago O. ^[1]

Affiliation

^[1] Univ Sao Paulo ESALQ USP, Luiz de Queiroz Coll Agr, Ave Padua Dias 11, BR-13418900 Piracicaba, SP - Brazil

^[2] Univ Calif Riverside, Dept Environm Sci, Riverside, CA 92521 - USA

^[3] Univ Calif Riverside, Environm Toxicol Grad Program, Riverside, CA 92521 - USA

^[4] Univ Fed Espirito Santo, Dept Oceanog, Grp Ecol Benton, BR-29075910 Vitoria, ES - Brazil

^[5] Univ Santiago Compostela, Fac Biol, CRETUS, Dept Edaphol & Agr Chem, Campus Sur, Santiago De Compostela 15782 - Spain

^[6] Fed Fluminense Univ, Dept Geochem, Grad Program Earth Sci Geochem, Niteroi, RJ - Brazil

• Document type: Journal article
• Source: Environment International; v. 146, JAN 2021.
• Web of Science Citations: 0

Abstract

Manganese (Mn) is an abundant element in terrestrial and coastal ecosystems and an essential micronutrient in the metabolic processes of plants and animals. Mn is generally not considered a potentially toxic element due to its low content in both soil and water. However, in coastal ecosystems, the Mn dynamic (commonly associated with the Fe cycle) is mostly controlled by redox processes. Here, we assessed the potential contamination of the Rio Doce estuary (SE Brazil) by Mn after the world's largest mine tailings dam collapse, potentially resulting in chronic exposure to local wildlife and humans. Estuarine soils, water, and fish were collected and analyzed seven days after the arrival of the tailings in 2015 and again two years after the dam collapse in 2017. Using a suite of solid-phase analyses including X-ray absorption spectroscopy and sequential extractions, our results indicated that a large quantity of Mn-II arrived in the estuary in 2015 bound to Fe oxyhydroxides. Over time, dissolved Mn and Fe were released from soils when Fe-III oxyhydroxides underwent reductive dissolution. Due to seasonal redox oscillations, both Fe and Mn were then re-oxidized to Fe-III, Mn-III, and Mn-IV and re-precipitated as poorly crystalline Fe oxyhydroxides and poorly crystalline Mn oxides. In 2017, redox conditions (Eh: -47 +/- 83 mV; pH: 6.7 +/- 0.5) favorable to both Fe and Mn reduction led to an increase (similar to 880%) of dissolved Mn (average for 2015: 66 +/- 130 mu g L-1; 2017: 582 +/- 626 mu g L-1) in water and a decrease (similar to 75%, 2015: 547 +/- 498 mg kg(-1); 2017: 135 +/- 80 mg kg(-1)) in the total Mn content in soils. The crystalline Fe oxyhydroxides content significantly decreased while the fraction of poorly ordered Fe oxides increased in the soils limiting the role of Fe in Mn retention. The high concentration of dissolved Mn found within the estuary two years after the arrival of mine tailings indicates a possible chronic contamination scenario, which is supported by the high levels of Mn in two species of fish living in the estuary. Our work suggests a high risk to estuarine biota and human health due to the rapid Fe and Mn biogeochemical dynamic within the impacted estuary. (AU)

• FAPESP's process: 18/08408-2 - Comparative studies of the mineral transformation of iron oxide nanoparticles in mine-tailing affected sediments and soils and their impacts on mobilization and fixation of heavy metals under two contrasting redox environments
• Grantee: Tiago Osório Ferreira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/04259-2 - Iron biogeochemistry and its control on dynamics of trace metals in the soils of Doce River estuary after the "Mariana disaster"
• Grantee: Hermano Melo Queiroz
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 19/19987-6 - Soils and plants of the Rio Doce estuary controlling the biogeochemistry of iron and metals in response to the Mariana (MG) disaster
• Grantee: Tiago Osório Ferreira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/17413-2 - Redox processes controlling Fe oxide-associated metals dynamics in rio Doce estuary sediments after the Mariana dam disaster
• Grantee: Hermano Melo Queiroz
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 19/02855-0 - Redox fluctuations, iron and heavy metals dynamics in soils from Rio Doce estuary after the "Mariana (MG) disaster": an experimental approach
• Grantee: Diego Barcellos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral