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Soils and plants of the Rio Doce estuary controlling the biogeochemistry of iron and metals in response to the Mariana (MG) disaster

Grant number: 19/19987-6
Support type:Regular Research Grants
Duration: August 01, 2020 - July 31, 2022
Field of knowledge:Agronomical Sciences - Agronomy - Soil Science
Principal Investigator:Tiago Osório Ferreira
Grantee:Tiago Osório Ferreira
Home Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
Assoc. researchers: Angelo Fraga Bernardino ; Diego Barcellos ; Fernando Dini Andreote ; Gabriel Nuto Nóbrega ; Xose Luis Otero

Abstract

Soils and plants at the Rio Doce estuary were impacted by mine tailings derived upstream from the collapse of the Fundão Dam in Mariana (MG) in 2015, which is considered one of the largest environmental disasters worldwide. The mine tailings consist predominantly of iron (Fe) oxides, which may undergo oxidation and reduction (redox) processes given the physical-chemical fluctuating conditions of estuarine soils. Iron reduction may release adsorbed trace metals (such as cobalt, lead, nickel, and zinc), which may become bioavailable for organisms, with potential environmental and anthropic contaminations. Phosphorus (P) is another element that is bound to iron minerals and may also be released during iron reduction, posing potential eutrophication risks in soil-water of estuarine/terrestrial/marine ecosystems. Furthermore, the pollutants that can be potentially released from the iron mine tailings may impact the estuarine plants, although some of them are capable of (phyto)accumulate metals, favoring natural phytoremediation of contaminated environments. For instance, previous studies demonstrated that Typha domingensis is capable of accumulate metals within the plant tissues. Therefore, the present project have the following objectives: (i) characterize and quantify trace metals, iron, phosphorus, and the mineralogy of the estuarine soils at Rio Doce; (ii) quantify the release and bioavailability of metals (Cu, Cr, Co, Mn, Ni, Pb e Zn) due to iron reduction processes, by incubating estuarine soils under laboratory conditions; (iii) quantify trace metals within roots, shoots, leaves, and fruits, as well as the biomass production for the estuarine plants; and (iv) evaluate the potential for the plant species Hibiscus tiliaceus and Typha domingensis to accumulate the bioavailable iron and metal forms from soils, and the potential plant physiological harms. To achieve our objectives, we aim to quantify Fe, P, and metals (Mn, Zn, Cu, Cr, Co, Ni e Pb) contents in soils using an ICP-OES, and to conduct sequential fractionation of Fe, P, and metals in soils. We will conduct a laboratory incubation using estuarine soils under three distinct redox treatments (redox fluctuation, constantly oxic, and constantly anoxic), and measure iron species (FeII e FeIII), the amount of bioavailable metals, as well as total and dissolved organic C contents. Plant tissue extractions will provide the content of metals translocated and bioaccumulated by plants. Extracellular enzymatic microbial analysis will provide metal concentrations at the rhizospheric and non-rhizospheric soils. Thus, our project is targeting a comprehensive and integrated understanding of ecosystems processes at the Rio Doce estuary, including a detail physical-chemical characterization of soils and plants, and to prove basis and assessment for future mitigation procedures at this contaminated area. (AU)