DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Item Adsorption of gaseous elemental mercury on soils : influence of chemical and/or mineralogical characteristics.(2019) Montoya, Juan Andres; Lena, Jorge Carvalho de; Windmoeller, Claudia CarvalhinhoGaseous 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.Item Análise da erodibilidade de saprolitos de gnaisse.(2004) Morais, Fernando de; Bacellar, Luis de Almeida Prado; Sobreira, Frederico GarciaAs voçorocas são freqüentes em áreas com rochas do embasamento cristalino. A evolução destas feições é sempre fortemente condicionada pelos processos de erosão hídrica subsuperficial, embora os processos superficiais também sejam importantes. Este trabalho objetivou investigar os processos erosivos subsuperficiais atuantes nas voçorocas e compreender que fatores mineralógicos e texturais poderiam influenciar a erodibilidade dos saprolitos. Para tanto, foram realizados ensaios de caracterização e de avaliação da erodibilidade em amostras representativas, sendo o principal destes o ensaio de furo de agulha. Os resultados indicam que a erosão por carreamento não ocorre e que os saprolitos apresentam susceptibilidade variável à erosão por piping, mesmo quando derivados de uma mesma unidade litológica, mas superior à do horizonte B latossólico. Dados preliminares indicam que os saprolitos mais susceptíveis à erosão por piping são os de textura siltosa (determinados em ensaios granulométricos sem defloculante e agitação) e pobres em minerais agregadores, como os argilominerais.