Natural attenuation processes in AMD context by mineralogical control: iron oxyhydroxides, oxyhydroxysulfates, and efflorescent sulfates

Acid mine drainage (AMD) is a common problem associated with the weathering of metal sulfide wastes in abandoned mining areas, which can be rich in toxic metals and metalloids. Oxidative dissolution of these minerals may negatively affect the soils and water reservoirs nearby. The formation of secondary mineral phases such as iron oxyhydroxides, oxyhydroxysulfates, and efflorescent sulfates may be a natural attenuation process in these areas because these minerals can scavenge potentially toxic elements. Typically formed by the evaporation (efflorescent salts) or precipitation (ochreous iron-rich oxyhydroxides) these minerals are highly soluble and reactive. Therefore, their characterization and inventory are particularly important for predicting the cycles of retention/contamination or accumulation zones of potential toxic elements (PTE) and acidity in mining contaminated systems. The abandoned mines of Valdarcas and São Domingos were selected for the present study due to their AMD signature and occurrence of some of these secondary minerals. Valdarcas (north of Portugal) is a W-mine associated with a skarn deposit with sulfides that has already been rehabilitated. However, the AMD problems remain in the watercourse that receives leachates from the waste dumps. São Domingos is a Cu-mine composed of massive sulfide deposits that belong to the Iberian Pyrite Belt (south of Portugal). This mining area, which is presently under remediation process, is highly contaminated and AMD is a longlasting problem. The samples collected in these mining areas were characterized by their morphology, size, mineralogy, and chemical composition using different techniques: binocular microscopy, SEM-EDS, TEM, BET, DRX, FTIR, and XPS. In Valdarcas mine area, typical ochreous phases such as schwertmannite and goethite were identified as the dominant secondary phases. These brownish-yellow ferric amorphous and poorly crystalline minerals with high surface area (125 mg2 /m) can remove PTE via adsorption processes, contributing to their retention in the mining environment. In contrast, at São Domingos, efflorescent sulfate salts are more abundant. Melanterite and copiapite were the prevailing salts identified. With different morphologies, these minerals are highly soluble and therefore play a relevant key in the retention/mobilization cycles of hazardous contaminants, such as arsenic (As). This integrative methodologic approach, based on the use of several techniques, allowed a complete characterization of these minerals. In addition to composition, the surface properties that are relevant for the adsorption ability, were also obtained. Therefore, the study revealed a diversity of behaviors for the identified phases, suggesting various roles in increasing the resilience of the contaminated systems

Aerodynamics of a wheelchair sprinter racing at the 100m world record pace by CFD

The aim of this study was to analyze aerodynamics in a racing position of a wheelchair-racing sprinter, at the world record speed. The athlete and wheelchair were scanned at the beginning of the propulsive phase position (hands near the handrims at 12h) for the 3D model acquisition. Numerical simulation was run on Fluent, having as output the pressure, viscosity and total drag force, and respective coefficients of drag at the world record speed in T-52 category. Total drag was 7.56N and coefficient of drag was 1.65. This work helped on getting a deeper insight about the aerodynamic profile of a wheelchair-racing athlete, at a 100m world record speed.info:eu-repo/semantics/publishedVersio

Geoenvironmental study of gold mining tailings in a circular economy context: Santa Barbara, Minas Gerais, Brazil

We characterized the tailings from the Santa Barbara tailings dam, which is located in Minas Gerais, southeastern Brazil, to: (i) identify its chemical, mineralogical, and metallurgical properties, and (ii) perform an environmental evaluation of the water at the surface of the tailings facility. The potential recovery of elements such as Sb, As, and Au was also considered for potential tailings reuse. The water was alkaline, with maximum pH values of ≈ 10, and contained potentially toxic elements, such as Sb (up to 0.500 mg/L), As (up to 0.080 mg/L), and Cu (up to 20 mg/L). Gold enrichment areas were found in the tailings dam, with concentrations up to 0.5 g/t. Alignment exists among tailings management, demand for critical raw materials, and increased interest in the processing of low-grade ores and mining waste, which is important in the context of the circular economy. They suggest that valorisation of tailings, although challenging, can be achieved by economic recovery of the more valuable metals.This work was funded the Fundação para a Ciência e a Tecnologia (FCT) through projects UIDB/04683/2020, UIDP/04683/2020, Nano-MINENV 029259 (PTDC/CTAAMB/29259/2017), and by AngloGold Ashanti Brazil

X-DLVO interactions between Nanocolloidal Magnetic Particles : the quantitative interpretation of the pH-dependent phase diagram of EDL-MF

The phase behavior of acidic samples of EDL-MF based on cobalt ferrite nanoparticles with controlled mean sizes was investigated at constant temperature and in absence of magnetic field. By monitoring the anoparticle charge by pH adjustments, we constructed an experimental pH-dependent phase diagram for all samples that revealed sol, gel thixotropic or coagulated phases in different pH regions. Then, by using an extended DLVO potential we analyzed quantitatively the observed phase diagram in function of pH and nanoparticle mean size

Copiapite group: occurrence and properties in mining contamination scenarios

O grupo copiapite apresentou uma ampla gama de composições químicas, permitindo a identificação de várias fases minerais (por exemplo, aluminocopiapite e magnesiocopiapite). Esses minerais, normalmente observados em ambientes mineiros, são formados a partir da precipitação e evaporação da drenagem ácida da mina. Nessas áreas, a copiapite tem sido estudada para compreender a sua capacidade de adsorção de alguns elementos potencialmente tóxicos. O presente trabalho visa caracterizar amostras minerais de copiapite, utilizando diferentes técnicas, para entender a sua morfologia, composição mineralógica e química, bem como o seu papel ambiental

Desempenho funcional de crianças com paralisiacerebral diparéticas e hemiparéicas

The definition ideal of cerebral palsy (PC) is to associate the functional performance with topographical characteristics and alterations of tonus. However, most of the bibliography describes this pathology and its consequences, when they evaluate the functional performance and doesn´t consider the existing differences in these types or uses only one type of PC. In literature, only one bibliography was differentiate the self-care between diplegic and hemiplegic. Evaluating the relation of the functional performance of children with diplegic and hemiplegic P.C. Transversal study with children of three to seven years old who have diplegic and hemiplegic spastics P.C., in both the sexes, and did under physitherapy. Children who didn’t walk and/or had any cognitive deficit were excluded from the research. Guardians were interviewed using part I (functional performance in the areas of self-care and mobility) of the Pediatric Evaluation of Disability Inventory (PEDI), as well as questionnaire with personal datas of the children. The program BioEstat 4,0 was used, statistical test Mann-Whitney, to verification of the association purpose. α 0,05 was used as statistics inference. The sample was composed for 40 children, 22 diplegic and 18 hemiplegic. The feminine sex participation (53%) was the biggest and carried through treatment associated with the physitherapy (88%). The self-care area (p=0,16) didn´t present difference between the groups, however, mobility, (p=0,02) suggests that the hemiplegic group had a better functional performance. The hemiplegic had better mobility that the diplegic, while in the self-care it was not observed statistic difference between the groups.Na Paralisia Cerebral (PC), o ideal é associar o desempenho funcional com características topográficas e alterações de tônus. Entretanto, grande parte da bibliografia descreve apenas a doença e suas conseqüências, e, quando se avalia o desempenho funcional, não se consideram as diferenças existentes nos tipos de PC ou se utiliza apenas um tipo. Na literatura, foi encontrada apenas uma referência bibliográfica que diferencia diparéticos e hemiparéticos quanto ao seu autocuidado, e nenhuma que compare a mobilidade entre eles. Este trabalho teve por objetivo avaliar a relação do desempenho funcional de crianças com PC diparéticas e hemiparéticas. Para tanto, fez-se um estudo transversal com portadores de PC diparéticos e hemiparéticos espásticos, de ambos os sexos, de três a sete anos, que estavam realizando fisioterapia. Excluíram-se crianças que não andavam e (ou) com déficit cognitivo. Foram realizadas entrevistas com cuidadores, utilizando-se a parte 1 (desempenho funcional nas áreas de autocuidado e mobilidade) do Inventário de Avaliação Pediátrica de Incapacidade (PEDI), assim como um questionário com dados pessoais das crianças. Utilizou-se programa BioEstat 4.0, e o teste estatístico Mann-Whitney, para verificação da associação proposta. Aceitou-se α 0,05 como inferência estatística. A amostra foi composta de 40 crianças, 22 diparéticas e 18 hemiparéticas. A maioria era do sexo feminino (53%) e realizava tratamento associado à fisioterapia (88%). A área de autocuidado (p=0,16) não apresentou diferença entre os grupos. Todavia mobilidade, (p=0,02) sugere que o grupo hemiparético possui melhor desempenho funcional. Concluiu-se que os hemiparéticos possuem melhor mobilidade que os diparéticos, enquanto que, no autocuidado, não se observou diferença estatística entre os grupos

Impact of soil moisture on crop yields over Brazilian semiarid

The objective of this work was to investigate the relationship between soil water content and rainfall with rice, beans, cassava and corn yields in the semiarid region of Northeast Brazil. Precipitation and modeled soil water content were compared to yields recorded at the county levels in this region. The results were also integrated over the area of the nine States that lie within the officially recognized region of semiarid climate in Brazil. The influence of water balance components was quantified by calculating their correlation coefficient with yields of the different crop species over the municipalities of the region. It was found that rainfall had higher correlation to crop yields over most of the region, while soil water content had lower values of correlation. This result is consistent with the fact that average root depth is 40 cm, lower than the layer of soil used in the model used to estimate soil water content (100 cm). Plants respond better to the precipitation in the top layers of soil, while the water storage in the deep layer of soil might be important only in other temporal and spatial scales of the hydrological cycle.Peer ReviewedPostprint (published version

Cryopreservation and characterization of canine preantral follicles

The aim of this study was to define the population, morphological and ultrastructural characteristics of bitch preantral follicles (PAFs) and to compare the effects on the morphology of PAF of two cryopreservation techniques - slow freezing (SF) and vitrification (V) - of bitches' ovarian tissue. The average population (number per ovary) of PAFs was 48,541 ± 18,366, where 94.25% were primordial (45,145 ± 16,076). The average diameter of the primordial follicles was 27.5 ± 4.2 μm. The overall percentage of morphologically normal PAFs was 93.66 ± 6.81% for the control group, 86.16 ± 11.05% after SF and 68.14 ± 12.75% after V. The percentage of normal primordial follicles was 96.69 ± 4.72% in control, 89.51 ± 10.39% in SF and 75.32 ± 9.23% in V. There was no significant difference in the overall percentage of normal PAFs among SF and the control. However, slow frozen follicles presented ultrastructural damage, while vitrified primordial and primary follicles were well preserved. In conclusion, although slow freezing seemed to be a good preserving method, vitrification was more effective than slow freezing in preserving the ultrastructure of primordial and primary follicles of bitches