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| Author(s): |
Amanda Duim Ferreira
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2024-03-01 |
| Examining board members: |
Tiago Osorio Ferreira;
Owen William Duckworth;
Dean Louis Ralph Hesterberg
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| Advisor: | Tiago Osorio Ferreira |
| Abstract | |
The \"Mariana Disaster,\" one of the world\'s largest environmental disasters, released over 50 million m3 of iron ore mine tailings (Fe) into the Rio Doce Basin. The mine tailings reached the estuary in the municipality of Linhares, Espírito Santo. Estuarine soils are strongly influenced by redox fluctuations, which control the dynamics of Fe, a primary component of the tailings. Additionally, Fe plays a significant role in the dynamics of potentially toxic elements (PTEs). In this context, this study aimed to: i) investigate the biogeochemical controls on the dynamics of Fe and PTEs in estuarine soils; ii) determine potential risks associated with consuming food produced in areas impacted by tailings; iii) identify suitable plant species for Fe and PTEs phytoremediation; iv) study strategies to enhance phytoremediation efficiency. To achieve these objectives, soils and plants from the Rio Doce estuary were sampled in 2019, 2020, and 2021, and four laboratory experiments and one field experiment were conducted. Seasonal controls on Fe biogeochemistry in Rio Doce estuarine soils were observed. The dissolution of Fe oxides during the transition from the rainy to dry seasons resulted in a substantial Fe loss, leading to a notable increase in the availability of PTEs (Mn, Cr, Cu, Ni, and Pb), posing elevated environmental risks, especially during the dry season. Data modeling for two dry seasons (2019 and 2021) and one wet season (2020) revealed that climatic factors (i.e., accumulated precipitation) accounted for 48% of PTEs bioavailability in soils. Regarding soil physical and chemical parameters, pH and organic matter content were the primary controllers, explaining 29% of PTEs bioavailability. Geochemical factors, specifically short-crystallinity iron oxides (e.g., ferrihydrite and lepidocrocite), accounted for 23% of PTEs bioavailability. Risk analysis associated with consuming food from the Rio Doce estuary indicated that the association between PTEs and Fe oxides, often reducing PTEs bioavailability, may not be efficient in redox- active environments like estuarine soils. Concentrations of Cd, Cr, Cu, Ni, and Pb exceeded limit values in edible parts (i.e., fruits and tubers) of all studied crops. However, daily intake rates (ADI) for these elements remained below internationally established tolerable daily intake levels. The total hazard index (THI), estimating the probability of adverse effects of PTEs on health, indicated potential health risks for children consuming bananas from the estuary. For adults, there was low risk for both fruit and tuber consumption of the studied crops. Given the identified risks, there is a need to reduce Fe and PTE concentrations in the estuary. For this, we tested different remediation techniques: i) chemical remediation through pyritization induction; ii) bioremediation; iii) assisted phytoremediation. The survey of species in the estuary revealed that the macrophyte Typha domingensis exhibited the highest potential for phytoextraction, extracting high amounts of Fe (3.7 tons year1), Mn (75.7 tons year1), Cr (169.7 kg year1), and Ni (107.8 kg year1). This potential correlated with the lower rhizospheric soil pH (4.73) and the prevalence of short-range ordered Fe oxides (i.e., ferrihydrite and lepidocrocite), which are more susceptible to dissolution. Although the plant species Hibiscus tilliaceus showed potential for Cu and Pb phytostabilization, other strategies were tested for these PTEs remediation. The use of agricultural gypsum (CaSO4) as a sulfate source for chemical remediation resulted in increased dissolution rates of iron oxides, elevated concentrations of Fe2+, and sulfides (HS and H2) in the solution, leading to enhanced Pb pyritization (+40%) and reduced bioavailable Pb in the soil. When agricultural gypsum was combined with the application of a microbial consortium (Azospirillum sp., Pseudomonas sp., Saccharomyces sp., and Rhizobium sp.), significant decreases in Fe and Mn associated with oxides contents and increased bioavailable concentrations of these elements were observed in the soils. The microbial consortium also reduced total Cr (-85%), Cd (-61%), Cu (-49%), and Pb (-55%) contents in the iron ore mining tailings and increased concentrations of Fe, Mn, Cd, Cr, and Pb in the solution, which could be useful for assisted phytoremediation strategies. In addition, there was a reduction in solution concentrations for Cu, indicating potential Cu biosorption by microbial biomass. Fertilization, either alone or combined with chelating agents and microbial consortium, induced significant geochemical changes in iron mine tailings (decreased pH and Eh, increased total and dissolved organic carbon, increased bioavailable Fe), resulting in higher Fe extractions by T. domingensis plants. Thus, this study demonstrates that remediation of areas affected by mine tailings can be achieved using native plant species. This research introduces a novel approach to Fe and PTEs phytoremediation by modulating Fe geochemistry in mine tailings to enhance bioremediation using non-hyperaccumulator plants and beneficial microorganisms. (AU) | |
| FAPESP's process: | 19/14800-5 - Estuarine plants and their control in metals biogeochemistry in soils impacted by the `Mariana disaster´ |
| Grantee: | Amanda Duim Ferreira |
| Support Opportunities: | Scholarships in Brazil - Doctorate |