EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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4 resultados
Resultados da Pesquisa
Item Análise comparativa de metodologias de determinação de valores de referência para sedimentos de corrente.(2019) Costa, Raphael de Vicq Ferreira da; Leão, Lucas Pereira; Leite, Mariangela Garcia Praça; Nalini Júnior, Hermínio AriasA definição de valores de referência em séries de dados geoquímicos tem sido um dos principais desafios nos estudos relativos à geoquímica ambiental. Antigas metodologias eram fundamentadas em parâmetros estatísticos, na construção de tabelas, gráficos e histogramas. Contudo, estas técnicas não definem estes valores de maneira correta ou apresentam valores muito diferentes para a mesma região. Desta forma, o presente trabalho testou diferentes metodologias de determinação de valores de referência para sedimentos de corrente: média +2 desvio padrão, mediana +2 MAD, boxplot UIF, análise fractal, análise espacial com a interpolação pelo modelo IDW e as metodologias associadas, o que foi feito na região do Quadrilátero Ferrífero – Brasil, conhecida mundialmente por sua diversidade de minérios e tipos litológicos. Os resultados indicam que as técnicas mais antigas de determinação de valores de referência, notadamente a “Média + 2x desvio padrão e a Mediana + 2x MAD” demonstraram não serem efetivas para a separação das anomalias, pois superestimam ou subestimam a faixa de referência, podendo causar erros consideráveis quando são discutidos aspectos relativos à legislação ambiental. Já as metodologias “Análise fractal” e “Boxplot UIF” apresentaram, para a grande maioria dos elementos, valores bem próximos, confirmando que o intervalo de referência está correto e, demonstrando que ambas são as mais adequadas para ambientes geológicos complexos. Contudo, foram verificados para alguns elementos (Cu, Fe, Pb e Ti) valores discrepantes de 30 a 46 % entre as metodologias. No entanto, sempre que ocorreram divergências, os valores obtidos via Análise fractal demonstraram ser mais condizentes com a distribuição espacial dos elementos, além de ter apresentado os outliers em locais onde notadamente são observados litotipos ricos no elemento e impactos ambientais capazes de disponibilizá-lo para o meio.Item Pollen storage by stingless bees as an environmental marker for metal contamination : spatial and temporal distribution of metal elements.(2018) Nascimento, Nathália de Oliveira; Nalini Júnior, Hermínio Arias; Oliveira, Fernanda Ataide de; Abreu, Adriana Trópia de; Antonini, YasmineSince the middle of the 20th century, human activities have led to overall ecosystem contamination and to major modifications in landscape structure and composition. Mining activities represent a major source of environmental contamination by metal residues. The objective of our study was to evaluate the presence of heavy metals and other elements on stingless bee pollen, and compare them to samples of Suspended Particulate Material (SPM) in five points a Mineral Province, in Brazil. More than 50 elements were identified by ICP-OES and ICP-MS, after microwave digestion. Overall, we found a strong relation among elements present on pollen and SPM. Samples from the four areas exhibited higher levels of minerals compared to the reference site. Mineral levels varied widely within the two seasonal periods. Some elements, like Pb, Cd, As, Cu, Zn, and Fe were found at levels considered potentially toxic to human health. Pollen stored by stingless bees was a successful bioindicator, and demonstrated the value of quantitative ecological information for detecting air pollution.Item Geochemical mapping of potentially hazardous elements in surface waters and stream sediments of the Quadrilátero Ferrífero, Brazil.(2018) Costa, Raphael de Vicq Ferreira da; Matschullat, Jörg; Leite, Mariangela Garcia Praça; Nalini Júnior, Hermínio Arias; Leão, Lucas PereiraGeochemical mapping and the determination of baseline concentrations of potentially hazardous elements in the environment receive increasing attention. The need to know regional geochemical background data as well as the spatial allocation of areas with anomalous element concentrations and chances to identify their major sources motivate the interest. Here, results from a geochemical mapping exercise and derived related baseline values are presented. 541 stream sediment and surface waters samples have been collected across the Iron Quadrangle (IQ), Brazil, with a density of 1 sample per 13 km2. Geochemical maps were compiled using the inverse distance weighted (lDW) interpolation method. “Normal” background concentrations were distinguished from anomalies with the separation-by-concentrationrange technique, where positive anomalies were defined by the “boxplot” Upper Inner Fence (UIF) rule. The results demonstrate that more than 70% of the IQ area shows geogenic background concentration ranges for the elements studied. About 20% of the area represent positive anomalies, likely related to both near surface rock types and to human interference. Distinct anthropogenic anomalies, notably from mining activities are identified in 5– 10% of all samples. This first sampling in the IQ allows delineation of the role of lithology on the elemental composition of stream sediments, and to establish baseline values for the main river basins – thus pinpointing localities, cities and fluvial basins that are exposed to environmental risks and need to be protected.Item Arsenic speciation in plant samples from the Iron Quadrangle, Minas Gerais, Brazil.(2005) Daus, Birgit; Wennrich, Rainer; Morgenstern, Peter; Weiß, Holger; Palmieri, Helena Eugênia Leonhardt; Nalini Júnior, Hermínio Arias; Leonel, Liliam Viana; Monteiro, Roberto Pellacani Guedes; Moreira, Rubens MartinsSeveral plants, especially ferns, have been shown to tolerate and accumulate high arsenic concentrations in soils. The leaves and roots of the ferns Pteris vittata (Chinese brake) and Pityrogramma calomelanos as well as a medical plant (Baccharis trimera) were sampled together with their associated soils in a region impacted by ore mining, the Iron Quadrangle in Brazil, where arsenic concentrations in the soils vary sharply (6–900 mgg 1). The bioaccumulation factors were found to be low compared to the literature data, which can be explained by the low water-soluble fraction of arsenic in soil. The arsenic species in the plants were mainly arsenite. In comparison to the rhizoid samples, the concentrations of arsenic were higher in the leaves of the fern samples. The medical plant behaved differently. The bioaccumulation factor was low (0.7), and trimethylarsine oxide was detected as the third arsenic species beside arsenite and arsenate in both the roots and the leaves.