Iron ore tailings as a source of nutrients to the coastal zone

Utilization of High-Silicon Iron Ore Tailings for 4N8 High-Purity Quartz Powder Production via Two-Stage Acid Leaching

This study investigates the process mechanisms for preparing 4N8 high-purity quartz powder from high-silicon iron ore tailings. Silicon concentrate obtained by wet high-intensity magnetic separation was used as the raw material, with impurities removed through a two-stage acid leaching process. The effects of acid concentration, temperature, time, and liquid-solid ratio on impurity removal were examined. Thermodynamic analysis shows that HF enhances the dissolution of Fe and Al impurities. In the first stage, response surface optimization determined the optimal conditions: acid concentration of 11.69 mol/L, temperature of 99.5 °C, and reaction time of 6.3 h, yielding SiO2 purity of 99.949%. Kinetic analysis indicates Fe leaching is controlled by a chemical reaction (activation energy: 66.69 kJ/mol), while Al leaching is limited by internal diffusion (activation energy: 13.64 kJ/mol). The second-stage leaching, conducted at 10 mol/L acid concentration, 250 °C, and a liquid-solid ratio of 5:1 for 9 h, further reduced impurities. The final 4N8 high-purity quartz powder was obtained through fine grinding and high-temperature treatment. These findings provide theoretical guidance for the high-value utilization of iron ore tailings in applications such as semiconductors and photovoltaics.

Checklist of marine macroalgae in two contiguous Marine Protected Areas in the south-western Atlantic

Background

The Costa das Algas Environmental Protection Area (EPA) and the Santa Cruz Wildlife Refuge (WR), located in the Espírito Santo Continental Shelf, Brazil, are outstanding marine protected areas due to their high biodiversity, particularly of macroalgae. Together, these two relatively small protected areas (1,150 and 177 km2, respectively) harbour about a quarter of all macroalgal species recorded in Brazil.The checklist presented herein updates the algal flora of these two protected areas with data obtained until 2019. Two hundred and sixty-five macroalgal taxa were recorded, most of which with vouchers. Checklists based on the collections of each protected area were published on: "Catálogo de Plantas das Unidades de Conservação do Brasil" (https://catalogo-ucs-brasil.jbrj.gov.br/).

New information

Besides specimens collected between 2018 and 2019, the algal flora presented herein includes previous records from different Brazilian herbaria (e.g., SP, SPF, ALCB). Herbaria records may include species that do not occur in intertidal reefs (e.g., Laminaria). Overall, 249 macroalgal taxa and one marine angiosperm were recorded in the Costa das Algas EPA (87 new records) and 136 macroalgal taxa and one marine angiosperm in the Santa Cruz WR (46 new records). All taxa are native to Brazil and nine are endemic to Brazil. Our results provide a taxonomic foundation to support management, long-term monitoring and conservation in these protected areas.

Polycyclic aromatic hydrocarbons in estuarine sediments as a consequence of the mine tailings remobilization and transport in the Rio Doce basin

The Fundão dam failure in 2015 severely impaired the economy, the lives of riverine communities, and the aquatic ecosystems of the Rio Doce basin in southeast Brazil. Several contaminants, including polycyclic aromatic hydrocarbons (PAHs), were transported downstream, deposited in the estuary, and released into the Atlantic Ocean. The high concentration of PAHs in estuarine sediments may pose ecological risks and deleterious effects to benthic organisms, so here we aimed at determining the source and fate of these compounds before and after the tailings' arrival. The mean concentration of the analyzed Σ16PAHs increased from 34.05 µg kg-1 in the prefailure period to 751.77 µg kg-1 one year after the arrival of the tailing. The classification of the sediment quality changed from low to moderate contamination. Our results suggest that there was PAHs remobilization by mine tailings along the Rio Doce basin. The target analytes exhibited mostly a pyrolytic profile from fossil fuel and biomass burning. In addition to other contaminants deposited in the estuary after the arrival of the tailings, this study revealed that the profile change of PAHs in the estuary region is a consequence of the mud's erosive power. Integr Environ Assess Manag 2024;20:169-178. © 2023 SETAC.

Fish biodiversity of a tropical estuary under severe anthropic pressure (Doce River, Brazil)

Abstract The Doce River has undergone severe changes over the last centuries (e.g., flow regulation, pollution, habitat and species loss). Here, we present the first comprehensive fish biodiversity assessment of the Doce River estuary and a summary of the main impacts and their drivers for the whole river since the early 18th century. Carangiformes, Siluriformes and Eupercaria incertae sedis were the most representative orders for the 115 species recorded. Most species are native (87.8%), euryhaline/peripheral (80%) and zoobenthivorous (33.9%). Threatened (Paragenidens grandoculis, Genidens barbus, and Lutjanus cyanopterus) and near threatened (Cynoscion acoupa, Dormitator maculatus, Lutjanus jocu, Lutjanus synagris, and Mugil liza) species are peripheral. Thirteen species are exotic at the country (Butis koilomatodon, Coptodon rendalli, and Oreochromis niloticus) or the basin level (e.g., Pygocentrus nattereri and Salminus brasiliensis). The catfish Cathorops cf. arenatus is reported for the first time on the eastern coast of Brazil and Paragenidens grandoculis, considered extinct in the Doce River, was discovered in the estuary.

Benthic bioturbation: A canary in the mine for the retention and release of metals from estuarine sediments

After the largest mining tailings spill in Brazil, the Rio Doce estuarine ecosystem was severely impacted by metal contamination. In a 28-day laboratory experiment, we examined the effects of the polychaeta Laeonereis sp. on fluxes of oxygen and metal across the sediment-water interface. The density-dependent effect of Laeonereis sp. in the oxygen and metal fluxes was tested at low and high (74 and 222 ind m^-2, respectively) densities, and compared with defaunated controls. The higher worm density had an amplified effect on the oxygen flux, sediment uptake of Al and Mn, and Fe oxidation compared with the control, but no significant effects on other metals (Ba, Cd, Co, Cr, Cu, Ni, and Zn). Higher worm density increased the oxidation of Fe phases, but no effect in the solid phase of other metals. Consequently, Laeonereis sp. bioturbation prevents the reduction of Fe phases and the release of metal-bound-contaminants to estuarine systems.