DEGEO - Departamento de Geologia

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8

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Adsorption of gaseous elemental mercury on soils : influence of chemical and/or mineralogical characteristics.
(2019) Montoya, Juan Andres; Lena, Jorge Carvalho de; Windmoeller, Claudia Carvalhinho
Gaseous elemental Hg is stable enough to be transported over long distances. Some of the most important sources of Hg in the atmosphere are artisanal gold mining activities and forest fires. Both of these sources are particularly prevalent in the Amazonia region. Information regarding the capacity of soils for retaining Hg transported by the atmosphere is very important for understanding the metal cycle in the environment. The aim of this work was to study gaseous elemental Hg adsorption in soils with different physical and chemical characteristics. For this purpose, soils from different regions in Brazil and Colombia influenced or possibly influenced by gold mining activities and forest fires were studied. Hg adsorption tests were conducted by exposing soil samples to a gaseous elemental Hg atmosphere for 144 h. The total Hg concentration (THg) and Hg oxidation states were monitored using a direct Hg analyzer. Sample characterization analyses were performed. THg values obtained before the adsorption tests were 43–413 and 144–590 µg kg−1 for grain size fractions below 2 and 0.063 mm, respectively. The predominant species found was Hg2+, with abundance levels from 68% to 99%. The results show a wide range of enhanced Hg retention capacities among the samples, ranging from 13 to 2236 times the initial concentration, and the speciation results demonstrate a decrease in the oxidized species range, from 21% to 78%. The statistical analysis indicated the importance of Mn-bearing minerals for the processes of adsorption/oxidation of gaseous elemental Hg in soils. These results contribute to the elucidation of the processes that occur with Hg at the soil/atmosphere interface and may help to explain the high concentrations of Hg found in Amazonian soils where no gold mining activities are practiced.
Application of multivariate statistic of U, Th and Pb concentrations and Pb Isotopic signatures in the assessment of geogenic and anthropogenic sources in a U-mineralized area.
(2019) Vecchia, Adriana Monica Dalla; Lena, Jorge Carvalho de; Ladeira, Ana Cláudia Queiroz
This work presents a Principal Component Analysis (PCA) study using Pbi- sotope signatures and U, Th and Pb concentrations from groundwater, sedi- ments and rocks (granites and orthogneisses) of the Complex of Lagoa Real (Bahia, Brazil). This area is naturally enriched in U and Th, with the occur- rence of Pb derived from the radioactive decay of the elements (238U, 235U and 232Th) in the form of their stable isotopes 206Pb, 207Pb and 208Pb in addition to the natural isotope 204Pb. Sampling was carried out in the rainy season (De- cember to January) and the points were selected according to regional hy- drology and geology. Thirty samples were analyzed: 12 of groundwater (AP) and 18 of sediments (S). The results show that the use of isotopic ratios allows discrimination between geogenic and anthropogenic samples. This informa- tion is not obtained using only the analysis of concentration data. Statistically, the isotopic data of Pb stand out as an efficient tool in the characterization of sources in the scenario investigated, allowing an effective environmental monitoring and a better management of the mining activities.
Determination of methylmercury in sediment and cyanobacteria samples : method validation and application to methylation investigation.
(2018) Mendes, Louise Aparecida; Franco, Maione Wittig; Barbosa, Francisco Antônio Rodrigues; Carvalho, Paula Iannarelli Aires de; Lena, Jorge Carvalho de; Windmöller, Cláudia Carvalhinho
The aim of this work was to validate two methods for methylmercury (CH3Hg+) determination in sediments and cyanobacteria and their application to the Hg methylation study of planktonic organisms in water from a contaminated site in Brazil. Analytical methods for the determination of CH3Hg+ include many steps, and the necessity of adaptation to different matrices is very common and not always easy. In addition, these adaptations require new optimization and validation, which are found in a few articles using the matrix sediments but in none with planktonic organisms. The methods presented here were based on the extraction of CH3Hg+ from these matrices, derivatization, trapping, thermal desorption, GC separation, pyrolysis and detection by AFS (GC-pyro-AFS). The results showed good linearity (0.994) in the range of 0 to 400 pg CH3Hg+ with a repeatability of 3%, an intermediate precision of 8%, a recovery in spiked sample tests in the range of 93 to 129%, and detection limits of 0.04 mg kg 1 for sediments and 1.3 mg kg 1 for cyanobacteria. Certified reference materials showed good recoveries. The method for the cyanobacteria matrix was used for the Hg2+ methylation assay with cultures of cyanobacteria and microalgae isolated from water samples collected in an ancient Hg-contaminated gold mining area in Brazil. The production of CH3Hg+ was detected only in the culture of the microalga Stichococcus species (0.23% of total Hg), indicating its participation in the biotransformation of Hg. The methods can be used as important tools in routine analysis and/or studies of the biogeochemical cycle of Hg.
Speciation and quantification of Hg in sediments contaminated by artisanal gold mining in the Gualaxo do Norte River, Minas Gerais, SE, Brazil.
(2018) Rhodes, Valdilene da Penha; Lena, Jorge Carvalho de; Santolin, Camila Vidal Alves; Pinto, Thais da Silva; Mendes, Louise Aparecida; Windmöller, Cláudia Carvalhinho
The Iron Quadrangle in SE Brazil was, in the eighteenth century, one of the most important Au producing regions of Brazil. In this region, gold is produced, even today, by artisanal methods that use Hg to increase the extraction efficiency with no control of Hg release to water systems and the atmosphere. In this context, the Gualaxo do Norte River is of particularinterest; its springs are located in the Doce River basin, an important Brazilian basin that supplies water for 3.5 million people. The main goal of this work was to quantify and speciate the Hg in the sediments of the Gualaxo do Norte River using a direct mercury analyzer and gas chromatography-pyrolysis-atomic fluorescence detection system. Statistical analyses consisted of principal component analysis, aiming to assess interactions among elements and species and to group the variables in factors affecting the properties of sediment. The results show that total Hg (THg) and methylmercury (CH3Hg+) concentrations in samples ranged from 209 to 1207 μg kg−1 and from 0.07 to 1.00 μg kg−1, respectively (methylation percentages from 0.01 to 0.27%). Thermal desorption analysis showed that mercury is mainly present in the oxidized form, and correlation analyses pointed to a relationship between THg and MnO, indicating that manganese can oxidize and/or adsorb Hg. Together, MO and CH3Hg+ are important parameters in the third principal component, indicating the influence of OM on the methylation process. This first investigation on Hg methylation in this small-scale gold mining area points to the possibility of Hg bioaccumulation and to the need of better understanding the biogeochemical cycle of Hg in this area. Samples were collected in 2012, prior to the 2015 Fundão Dam disaster. The results are also a record of the characteristics of the sediment prior to that event.
Quantification of methylmercury and geochemistry of mercury in sediments from a contaminated area of Descoberto (MG), Brazil.
(2016) Mendes, Louise Aparecida; Lena, Jorge Carvalho de; Valle, Cláudia Magalhães do; Fleming, Peter Marshall; Windmoller, Cláudia Carvalhinho
In 2002, metallic Hg was found buried in a rural area of Descoberto city, Brazil. The origin of the Hg was a gold mining explotation plant established nearly one century ago. Although a number of studies have been conducted in order to assess the contamination of the area, none of them investigated the presence of methylated Hg in the hydric system. In this work methylmercury (CH3Hgþ) was determined using gas chromatography-pyrolysis-atomic fluorescence detection (CG-pyro-AFS) in material from rain sedimentation boxes and stream sediments near the contaminated area. Total Hg concentration (HgT) along with the chemical speciation by thermo-desorption were performed. HgT in material from the sedimentation boxes was found to be very high, up to 41,580 mg kg 1, even in the rainy season, when in general HgT were much lower than in dry season. The samples from the Grama and Rico streams show a range of HgT from 5.8 to 266 mg kg 1. The thermo-desorption analysis showed predominance of Hg2þ, possibly linked to organic sulfur, suggested by a good positive correlation between Hg2þ, HgT, organic mater (OM) and total S. The CH3Hgþ concentration in stream sediment samples ranged from <0.07 to 1.87 mg kg 1 and in the samples of sedimentation boxes the concentrations were 1.33 and 8.0 mg kg 1 during dry season. The sample with the highest percentage of HgT as Hg2þ (98%) presented also the highest percentage of CH3Hgþ (0.7%). These are high values, showing that care should be taken to avoid the transport of this material to the hydrological system. Further studies on the transfer through the food chain would be very important.
Manganese oxide biominerals from freshwater environments in Quadrilatero Ferrifero, Minas Gerais, Brazil.
(2015) Keim, Carolina Neumann; Nalini Júnior, Hermínio Arias; Lena, Jorge Carvalho de
Biogeochemical Mn cycling in aquatic environments is driven mostly by microbes, and includes reductive dissolution in anaerobic sediments as well as oxidation in aerobic regions. Oxidation is followed by precipitation, which occurs mainly on the extracellular structures of microorganisms. In this work, we studied the minerals precipitated on extracellular structures of native microorganisms from freshwater environments in Quadrilatero Ferrifero (Iron Quadrangle), Minas Gerais, Brazil, known to contain high levels of manganese. Light microscopy of biofilms and floating material showed diverse biomineralized structures. The most conspicuous were identified as the holdfasts of algae from the genus Ulothrix. Diatom frustules associated to manganese oxide precipitates were relatively common. In addition, both filaments and holdfasts produced by bacteria of the genus Leptothrix were found, as well as structures similar to those described as Siderocapsa and Metallogenium. Some previously unknown structures were also observed. Transmission electron microscopy of most of these structures showed the ‘crumpled tissue-paper’ morphology common in biomineralised manganese oxides. Energy-dispersive X-ray analysis (EDXA) showed that manganese and oxygen were the main components, along with minor amounts of Al, P, S, K, Ca and/or Ba. Our results bring new perspectives to the study of biomineralized manganese oxide structures from the environment. Moreover, they add information about the background of present-day microbial structures needed to better interpret fossilized microbial biominerals.
Evaluation of matrix effect on the determination of rare earth elements and As, Bi, Cd, Pb, Se and In in honey and pollen of native Brazilian bees (Tetragonisca angustula – Jataí) by Q-ICP-MS.
(2017) Oliveira, Fernanda Ataide de; Abreu, Adriana Trópia de; Nascimento, Nathália de Oliveira; Froes, Roberta Eliane Santos; Itabaiana, Yasmine Antonini; Nalini Júnior, Hermínio Arias; Lena, Jorge Carvalho de
Bees are considered the main pollinators in natural and agricultural environments. Chemical elements from honey and pollen have been used for monitoring the environment, the health of bees and the quality of their products. Nevertheless, there are not many studies on honey and pollen of native Brazilian bees. The goal of this work was to determine important chemical elements (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Lu and Yb) along with As, Bi, Cd, Pb, Se and In, in honey and pollen of native Brazilian bees, assessing analytical interferences from the matrix. A proposed analytical method was developed for these elements by quadrupole ICP-MS. Matrix effect was verified in honey matrix in the quantification of As, Bi and Dy; and in pollen matrix for Bi, Cd, Ce, Gd, La, Pb and Sc. The quality of the method was considered satisfactory taking into consideration the recovery rate of each element in the spiked solutions: honey matrix (91.6–103.9%) and pollen matrix (94.1–115.6%). The quantification limits of the method ranged between 0.00041 and 10.3 μg L−1 for honey and 0.00041–0.095 μg L−1 for pollen. The results demonstrate that the method is accurate, precise and suitable.
Hidrogeoquímica do arsênio e de outros constituintes inorgânicos presentes nas águas subterrâneas da cidade de Ouro Preto-MG.
(2010) Gonçalves, José Augusto Costa; Lena, Jorge Carvalho de; Nalini Júnior, Hermínio Arias; Paiva, José Fernando de
Águas com concentrações de As (arsênio) acima dos limites estabelecidos pelos órgãos de controle ambiental são consideradas perigosas para a saúde humana. O As é um elemento tóxico e carcinogênico. A fácies hidroquímica das águas subterrâneas estudadas é o resultado da interação entre diferentes fases presentes na solução, especificamente das relações iônicas que se estabelecem entre a fase sólida e a água. A baixa mineralização da água é resultado das condições climáticas, constituição das rochas, relevo e processos intempéricos dominantes. Os tipos e as quantidades dos componentes solubilizados nas águas estão diretamente ligados ao tempo de residência das mesmas nos aqüíferos. Dentre os principais cátions a predominância é Na+ > Ca2+ > K+ > Mg2+. Para os ânions, a grande predominância do HCO3 - >> Cl- > SO4 2- > NO3 - estabelece para as águas um caráter bicarbonatado que é decorrente do sistema CO2 — H2O, determinado principalmente pela circula- ção das águas próximas da área de recarga e da superfície do terreno. A evolução das concentrações de As, ao longo do ano, reside nas reações hidrogeoquímicas controladas pelo potencial redox Eh — pH. O pH das amostras analisadas apresentaram valores entre 5,93 e 7,92, com um valor médio de 6,72. Para o Eh foram encontrados valores entre 335 e 532 mV e um valor médio de 427. No diagrama Eh — pH, em condições de equilíbrio químico, verificou-se que as espécies de As presentes são controladas pelas condições de Eh — pH. As espécies As5+ de oxiânions (H2AsO4 - e HAsO4 2-) são predominantes. O diagrama mostra que as águas analisadas são de ambientes próximos do contato com a atmosfera, e que são de origem pluvial, de circulação mais próxima da superfície topográfica e que se acumulam de forma geralmente descontínua ao longo dos fissuramentos das rochas. Os principais fatores de liberação, mobilização e evolução do As para as águas subterrâneas são específicos e peculiares à área de estudo, tais como os condicionantes hidrológicos, geoquímicos, hidrogeológicos e topográficos. Após o período da seca, os processos oxidantes atuantes na superfície e subsuperfície das rochas deixam sobre as coberturas detríticas intemperizadas e nas rochas mineralizadas de corpos de minérios sulfetados, alvéolos ou camadas superficiais de minerais secundários de As, representados principalmente pela escorodita. Esses minerais são encontrados sobre minerais autigênicos em afloramentos e nas paredes das minas abandonadas, representados principalmente, pela arsenopirita, pirita, pirrotita e que são observadas em toda área de estudo. Com o início das chuvas, os fluxos de água superficial e subterrânea, potencializados pelo forte gradiente hidráulico do relevo, solubilizam e lixiviam os compostos presentes sobre e entre os minerais das rochas e as partículas do solo.
Assinatura geológica e influência do uso e da ocupação do solo na geoquímica de águas e sedimentos da bacia do ribeirão Caraça, Catas Altas, MG.
(2013) Mendes, Milene Aparecida Monteiro; Leite, Mariangela Garcia Praça; Lena, Jorge Carvalho de
O presente trabalho foi realizado na bacia hidrográfica do ribeirão Caraça, no município de Catas Altas, Minas Gerais. O objetivo principal foi obter parâmetros químicos e físico‑químicos para caracterizar a geoquímica das águas e sedimentos desta bacia e determinar a real influência das atividades antropogênicas presentes na área. As nascentes do ribeirão Caraça se encontram em uma área de preservação ambiental (Parque Natural do Caraça), isenta de contaminação antrópica; porém, ao longo da bacia, existem diversos problemas de ordem ambiental, que podem ter origem na presença de áreas urbanas, atividades de mineração e agrícolas. Para este trabalho, foi realizado um estudo do uso e da ocupação do solo e monitorados 24 pontos, onde foram realizadas análises sazonais de água (pH, Eh, condutividade elétrica e oxigênio dissolvido) e medidos os teores de SO42 -, Cl- e HCO3 - (alcalinidade), além de metais (Al, Fe, Mn, Mg, Ca, K, Ti, P, As, Ba, Co, Cr, Cu, Ni, Sr, V, Zn e Zr, Na, K, Ca e Mg). Esses mesmos elementos foram determinados nas amostras de sedimentos. Os resultados permitiram dividir a bacia em três áreas distintas, com diferente ocupação e geoquímica. Apesar das atividades antropogênicas mostrarem grande influência sobre a geoquímica das águas, a composição dos sedimentos é influenciada fundamentalmente pela geologia local.
Efeito da atividade mineira na dispersão de minério de ferro ao longo do alto e médio rio Piracicaba.
(2005) Guedes, Claudia Dumans; Gonçalves, Cilete; Castro, Paulo de Tarso Amorim; Matsumura, Marcelo da Silva; Lena, Jorge Carvalho de; Paiva, José Fernando de
A região em torno do alto e médio rio Piracicaba concentra um grande número de empresas de mineração. O teor de óxidos de ferro nos sedimentos do leito do rio foi analisado com o objetivo de estabelecer uma correlação entre o acúmulo de sedimento sobre o leito do rio e as atividades mineiras da região. Vinte e uma amostras foram analisadas por difração de Raios-X, separação magnética, PPC (perda de massa por calcinação) e tiveram sua composição granulométrica determinada. Aquelas amostras de trechos próximos à cabeceira do rio, recebendo a contribuição de afluentes que drenam áreas de mineração, apresentaram os maiores teores de minerais de ferro. Nestes pontos as concentrações de hematita foram cerca de quatro vezes superiores aos valores médios encontrados na extensão do rio estudada. Dois outros pontos que apresentaram concentrações elevadas de óxidos, recebem através da rede de drenagem a contribuição de afluentes ricos em produtos da erosão de itabiritos de uma região de relevo acidentado.

DEGEO - Departamento de Geologia

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