Spatial-temporal variations of metals and arsenic in sediments from the Doce River after the Fundão Dam rupture and their bioaccumulation in Corbicula fluminea.

The rupture of the Fundão dam in Brazil released tons of mining tailings into the Doce River Basin (DRB). This investigation aimed to determine the bioaccumulation of metals in soft tissues of the bivalve Corbicula fluminea exposed to sediments collected in the DRB in four periods (just after, 1, 3, and 3.5 years after the dam rupture). In the exposure bioassays, the concentrations of Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in sediments and bivalve soft tissues were quantified. The concentration of some elements (As, Cd, Mn, and Al) in sediments exceeded the federal limits or regional backgrounds at some sampling sites, but their concentrations tended to decrease over time. However, higher concentrations of many elements were detected in the winter of 2019. Several elements were detected in C. fluminea soft tissues, but the bioaccumulation factors were generally low or not related to those elements associated with the ore tailings, evidencing that the bioavailability of metals to bivalves, in laboratory conditions, was limited. Integr Environ Assess Manag 2024;20:87-98. © 2023 SETAC.

Diazotrophic bacteria improve Hymenaea courbaril seedlings growth and survival in iron mine tailings.

One of the largest accidents with mine tailings happened in Brazil in 2015, with the rupture of the Fundão dam, and the physical characteristics of these tailings make it difficult to recover degraded areas. Hymenaea courbaril is a tree species native to Brazil that has low nutritional and water requirements, besides its capacity for survival in contaminated environments. In this study we hypothesized that inoculation with diazotrophs would improve the growth and physiology of H. courbaril in tailings, favoring the reforestation process aiming the recovery of the accident site. Every 20 days for 60 days, we investigated the morphophysiology of H. courbaril grown in iron mine tailings or soil, with the addition of nitrate (N-positive control), non-inoculation (negative control) or inoculation with native diazotrophic bacteria previously isolated from the tailings (UNIFENAS100-569; UNIFENAS100-654 and UNIFENAS100-638). We found that H. courbaril has survival capacity under mine tailings, with no growth alteration in the tailings, although there were signs of reduced ability for photoprotective responses. Inoculation with diazotrophic bacteria improved physiological aspects of H. courbaril and strain UNIFENAS100-638 was the most effective in favoring total growth of plants, net photosynthetic rate and root morphology under mine tailings. The survival capacity and growth of H. courbaril indicates the possibility of its use for reforestation in areas degraded by mine tailings. Further studies are necessary in field conditions and with a larger experimental period to more thoroughly understand H. courbaril tolerance.

Avaliação da reatividade ao ataque químico de resíduo oriundo da mineração da scheelita utilizado como agregado em argamassas cimentícias / Evaluation of reactivity to the chemical attack of waste from the mining of scheelite used as aggregate in cementitious mortars

RESUMO A mineração de scheelita, localizada em Currais Novos, Rio Grande do Norte, tem gerado grandes volumes de resíduos sólidos que são destinados inadequadamente aos sistemas ambientais, causando impactos ambientais negativos ao município. Uma das alternativas encontradas para destinar adequadamente esses resíduos é o uso em argamassas de matriz cimentícia. No entanto, não há estudos consistentes sobre a viabilidade técnica quanto aos ataques químicos e à influência na sua durabilidade. Nesse contexto, este trabalho teve como objetivo verificar se as argamassas confeccionadas com resíduos da mineração de scheelita em substituição total ao agregado convencional são suscetíveis ao ataque por sulfato de sódio. A caracterização física, química e mineralógica do resíduo foi realizada fazendo uso das seguintes técnicas: análise granulométrica por peneiramento; determinação da massa unitária; obtenção do teor de material pulverulento; espectrometria de fluorescência de raios X, e difração de raios X. A investigação da ocorrência do ataque por sulfato de sódio foi avaliada pela variação dimensional dos corpos de prova quando imersos em solução de sulfato de sódio, de acordo com a metodologia da Associação Brasileira de Normas Técnicas NBR 13583. Os resultados do traço 1:3 indicaram que os agregados oriundos dos resíduos da mineração de scheelita apresentaram comportamento reativo ao ataque por sulfato de sódio (expansão maior que 0,06%), bem como houve aumento da resistência à compressão simples em 4,74%. Portanto, embora tenha sido constatado que os corpos de prova incorporados com resíduos de scheelita tenham sido reativos ao sulfato, observou-se que não foram capazes de deteriorar mecanicamente os corpos de prova.

ABSTRACT The scheelite mining, located in Currais Novos, Rio Grande do Norte, has generated large volumes of solid waste that are inadequately destined for environmental systems, causing negative environmental impacts to the municipality. One of the alternatives to destination of these residues is the use in cementitious matrix mortars. However, there are no consistent studies on the technical feasibility of chemical attacks and influence on their durability. In this context, this work aimed to verify whether mortars made with scheelite mining residues in total substitution to conventional aggregate are susceptible to attack by sodium sulfate. The physical, chemical, and mineralogical characterization of the residue was carried out using the following techniques: sieve particle size analysis; determination of unit mass; obtaining the content of powdery material; X-ray fluorescence spectrometry, and X-ray diffraction. In the investigation of the occurrence of sodium sulfate attack was evaluated by the dimensional variation of the specimens when immersed in sodium sulfate solution, according to the methodology of Associação Brasileira de Normas Técnicas NBR 13583. The results of mixture 1:3 indicated that the aggregates from scheelite mining residues showed a reactive behavior to attack by sodium sulfate (expansion greater than 0.06%), as well as an increase in resistance to simple compression by 4.74%. Therefore, although it was found that specimens incorporated with scheelite residues were reactive to sulfate, it was observed that they were not able to mechanically deteriorate the specimens.

Surface composition and catalytic activity of an iron mining residue for simultaneous degradation of sulfonamide antibiotics.

Iron mining residue was evaluated as a potential catalyst for heterogeneous Fenton/photo-Fenton degradation of sulfonamide antibiotics. The residue contained 25% Fe2O3 and 8% CeO2, as determined by X-ray fluorescence spectroscopy, as well as other minor phases such as P2O5, SiO2, and TiO2. X-ray photoelectron spectroscopy analysis revealed a lower content of iron oxides on the surface, which restricted interaction of the residue with H2O2. Despite this limitation and the relatively low specific surface area (26 m2 g-1) of the crude iron mining residue (without any pretreatment), the material presented high catalytic activity for Fenton degradation of sulfonamide antibiotics. The degradation was strongly dependent on the initial pH, showing the highest efficiency at pH 2.5. For this condition, a concentration of sulfathiazole below the detection limit was obtained within 30 min, under black light irradiation and using 0.3 g L-1 residue, with low H2O2 consumption (0.2 mmol L-1). The residue also provided highly efficient sulfathiazole degradation in the dark, with the concentration of the antibiotic decreasing to an undetectable level after 45 min. Simultaneous degradation of two sulfonamide antibiotics revealed higher recalcitrance of sulfamethazine, compared to sulfathiazole, but the levels of both antibiotics decreased to below the detection limit after 45 min. The residue was very stable, since no significant concentration of soluble iron was detected after the degradation process. Furthermore, high catalytic activity was maintained during up to five cycles, showing the potential of this material for use as a low-cost and environmentally compliant catalyst in Fenton processes.

Organic residues and biochar to immobilize potentially toxic elements in soil from a gold mine in the Amazon.

Waste from gold mining (Au) is a threat to the ecosystem and human health because it contains high levels of potentially toxic elements (PTEs). Organic waste and biochar can be used to recover contaminated soils from mining areas because they have the potential to immobilize PTEs and improve soil fertility, enabling revegetation. The objective of this study was to investigate the efficiency with which organic residues and biochar immobilize PTEs in a multicontaminated soil of a small-scale Au mine in the state of Pará. The soil from a gold mining area was mixed with different proportions (v/v) of coffee ground residues (Bcoffee), Brazil nut tegument residues (BN), açai palm stone residues (A), and Brazil nuts biochar residues to determine which treatment is best for immobilizing PTEs. The treatments with the addition of BN and A resulted in low pH and high contents of organic matter (OM) and phosphor (P) The BN increased the available levels of Ba and reduced the available levels of Ni. The addition of coffee ground residues and biochar increased the uptake of Ba, Pb, and Ni in lettuce plants compared to treatments with BN and A. Plants grown with A showed higher dry matter yield and lower absorption and translocation of PTEs. Thus, the addition of BN and A residues in PTE phytostabilization programs in PTE-multicontaminated soils is a potential possibility.

Fractionation and mobility of thallium in areas impacted by mining-metallurgical activities: Identification of a water-soluble Tl(I) fraction.

Mining and metallurgy generate residues that may contain thallium (Tl), a highly toxic metal, for which it is currently not feasible to determine its geochemical speciation through X-ray absorption spectroscopy due to a combination of very low contents and the interference of accompanying high arsenic contents. Therefore, fractionation studies in residues and soils are required to analyze the mobility and bioavailability of this metal, which in turn provide information to infer its speciation. For this purpose, in this work a modification of the BCR procedure was applied to residues and contaminated soils from three mining zones of Mexico and two mining zones of Spain, spanning samples with acidic to alkaline pH values. The Tl extraction procedure consisted of the following fractions: (1) water-extractable, (2) easily exchangeable and associated to carbonates, associated to (3) poorly-crystalline and (4) crystalline Fe and Mn oxyhydroxides, and (5) associated to organic matter and sulfides; and finally a residual fraction as associated to refractory primary and other secondary minerals. The extracted contents were analyzed by Inductively-Coupled Plasma with Mass Spectrometry. Surprisingly, water-soluble, in Tl(I) oxidation state, was detected in most areas, regardless of the pH, a fact that has not been reported before in these environments, and alerts to potential health risks not previously identified. Most of the samples from a metallurgy area showed high levels of Tl in non-residual fractions and a strong correlation was obtained between extracted Mn and Tl in the third fraction, suggesting its association to poorly crystalline manganese oxides. In the majority of samples from purely mining environments, most of the Tl was found in the residual fraction, most probably bound to alumino-silicate minerals. The remaining Tl fractions were extracted mainly associated to the reducible mineral fractions, and in one case also in the oxidizable fraction (presumably associated to sulfides). Capsule: Soluble Tl(I) was found in all soil samples contaminated with either mining or metallurgical wastes. Additionally, in those affected by metallurgical wastes a very strong Tl-Mn correlation was found.