IG - Instituto de Geociências

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2172

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Agora exibindo 1 - 4 de 4

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Efeitos das variações sazonais do clima tropical úmido sobre as águas e sedimentos de manguezais do estuário do rio Marapanim, costa nordeste do Estado do Pará
(Instituto Nacional de Pesquisas da Amazônia, 2008) SILVA, José Francisco Berrêdo Reis da; COSTA, Marcondes Lima da; VILHENA, Maria do Perpétuo Socorro Progene
To evaluate the short period climatic variations impact over Amazonic mangrove ecosystem, studies were carried out on the northeast coast of Para State. Sediments, surficial and interstitial waters were collected and examinated throughout salinity, pH and Eh (mV) measurements; mineralogical determination using X-ray diffraction and electronic microscopy. Chemical analysis of dissolved sulfides, sulfate and chloride, among others were made in samples collected seasonally, under spring and neap tides conditions. The seasonal chloride variations in the interstitial waters shows 20 g/l during the dry season and less of 10 g/l in the season; the concentration in surficial are higher at neap tides (rainy season) and spring tide (dry season). The dissolved sulfides were found only at 10 cm, indicating sediment exposure to the atmospheric oxygen advectives fluxes. The dissolved iron rates increases between 0-10 cm and the pH tends to neutrality. The saturation of interstitial waters at dry season is indicated by evaporitic minerals: gypsum and halite. The pluviometric variations are responsible by gradual changes in the nutrient and physical chemical properties of surficial and interstitial waters, into the saline equilibrium control at coastal waters, in the salinization and desalinization of sediments and the distribution of mangrove vegetation at the estuary. The prolonged exposure of sediments during the dry season and the morphological characteristics contribute to the total or partial oxidation of surficial sediments, modifying the mineralogy of sediments and the physical chemical characteristics of interstitial waters.
Acesso aberto (Open Access)
Guaruman: a natural amazonian fiber with potential for polymer composite reinforcement
(Associação Brasileira de Metalurgia e Materiais, 2019-08) GOMES, Laercio Gouvêa; SILVA, Alisson Clay Rios da; CÂNDIDO, Verônica Scarpini; REIS, Raphael Henrique Morais; SERGIO, Neves Monteiro; PINHEIRO, Miriane Alexandrino
The Amazonian region of South America is known for its diversified number of plants from which food, medicine, wood and fibers have, since long time, been produced by local natives. A typical example is the guarumã (“guaruman”as suggested English spelling) scientifically identified as Ischinosiphon koem, an abundant plant found in the low lands alongside rivers of the state of Para in Brazil. Fibers extracted from the stem of the guaruman are used in ropes and baskets owing to their strength. In the present work, the possibility of applying guaruman fibers as reinforcement of polymer matrix composites is, for the first time, investigated. Amounts up to 30 vol% of continuous and aligned fibers were incorporates into epoxy matrix composites. Density measurements disclosed the guaruman to be one of the lightest natural fibers. Tensile tests indicate that the guaruman fiber addition was able to improve the composite elastic modulus. However, no significant change was found in the ultimate strength, total strain and resilience. On the other hand, a cost-effective analysis revealed a substantial reduction of ~29% in the epoxy composite price due to the incorporation of fibers. Preliminary ballistic evaluation disclosed a potential for application of guaruman epoxy composites in multilayered armor.
Acesso aberto (Open Access)
Impactos do avanço da soja no balanço de radiação no leste da Amazônia
(Instituto Nacional de Pesquisas da Amazônia, 2013-06) SOUZA, Paulo Jorge de Oliveira Ponte de; ROCHA, Edson José Paulino da; RIBEIRO, Aristides
The deforestation of the Amazon, especially for pasture use, has been explored by several researchers who have pointed out as a consequence, serious environmental problems. The continuous expansion of agriculture on areas of cattle ranching in the Amazon, as well as on native areas, must be seen with caution since few studies have been conducted in order to investigate which probable environmental impacts can be generated due to the presence of soybean monoculture in the region. This study evaluates the local impacts of the replacement of forest by soybean (Glycine max (L.) Merrill) on radiation balance components in an area that represents the agricultural border advancement in Amazonia. A micrometeorological experiment was installed in an area of soybean cultivation in Paragominas-PA and data from forest ecosystems were collected in Caxiuanã forests located in Melgaço-PA both during 2006 and 2007. During the soybean growing season the mean impact found in net radiation represented a reduction of 17.9% of the value commonly observed in the forest. During the off-season the impact on net radiation was 15.5%. Principal mechanisms that control these impacts were associated with the high soybean albedo and high loss of long wave radiation. Although the greatest impact occurs during the crop growing season, the time of occurrence of this negative effect is restricted to only 1/3 of the year, which leads to a higher impact of the off-season on energy balance in cumulative terms.
Acesso aberto (Open Access)
O papel da grande mineração e sua interação com a dinâmica urbana em uma região de fronteira na Amazônia
(Universidade Federal de Minas Gerais, 2016) MELO, Ana Carolina Campos de; CARDOSO, Ana Cláudia Duarte
This article deals with particularities of the urbanization process associated to the mining dynamics, which articulate directly the extraction territories to the global accumulation circuits. On the Amazon frontier, the forms of capital operationalization, altered the urban structuring, the urban-rural relationship and caused an enormous impact on the nature and on the most vulnerable sections of the population. The analysis is based on the Lefebvrian derivation of extended urbanization and on the notion of levels of social reality; has the objective of exploring the relational connections of the urban with the global and local levels and allow the construction of parallels between the iron ore extraction at the Serra dos Carajás and the gold exploration, at the Vale do Husco, northern region Chile. We observe an urban dynamic governed by the global sphere, and parallel processes, embryos of a new urban matrix, in the local sphere, centered on the reproduction of life and the construction of citizenship.

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