排序方式： 共有16条查询结果，搜索用时 15 毫秒
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Jacqueline E. M. Allan J. M. D. Coey Mauro Resende J. D. Fabris 《Physics and Chemistry of Minerals》1988,15(5):470-475
Four occurrences of highly magnetic soil in Brazil have been analysed with a view to identifying the magnetic minerals and quantifying the soil magnetization. Techniques used include X-ray diffraction, X-ray fluorescence and Mössbauer spectroscopy. This approach leads us to identify several ways that these soils, which have spontaneous magnetization in the range 1s<35 j/t/kg,="" can="" come="">One soil, which forms on dolerite (19.6 wt% Fe2O3), is found to contain fully-oxidized titanomaghemite inherited from the parent rock. This oxide has a canted ferrimagnetic spin structure with s=36 J/T/kg of sample. The three others, formed on very iron-rich rock (50–90 wt% Fe2O3), contain magnetite or maghemite as the magnetic species and in two cases the soil is more magnetic than the parent rock (largely composed of pure hematite). 相似文献
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Stella M. Resende 《Journal of Atmospheric Chemistry》2007,56(1):21-32
The atmospheric reaction between HS and NO2 was theoretically investigated at 298 K and 1 atm of pressure. Our results show that the first reaction step will lead to the formation of HSNO2 or HSONO, spontaneously and exothermically. HSONO easily decomposes into HSO + NO. On the other hand, HSNO2 can hardly dissociate in the reactants, and its isomerization to other adducts is much hindered. Production of HNO + SO and SNO + OH was found to be unfavorable. Thus, the main products would be HSO + NO and HSNO2, and new investigations focusing on the atmospheric fate of HSNO2 are suggested. A general discussion of the fate of HS under atmospheric conditions is presented. Recent investigations indicate that NO2, O2 and N2O should be the most important oxidants of HS, while the O3 influence will not be significant. 相似文献
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Corbiniano Silva Luiz Claudio Gomes Pimentel Luiz Landau Paulo Fernando Lavalle Heilbron Filho Fabiana Guimarães Resende Gobbo Pryscila de Jesus de Sousa 《Environmental Earth Sciences》2017,76(3):133
Accidents in nuclear power plants are problems of great complexity, mainly due to their consequences, such as the population evacuation from the enterprise influence area. The decision-making and emergency plans must be well articulated and require good local geographic space knowledge and the interactions of their environments. This study is a contribution to the emergency plans for the Almirante Álvaro Alberto Nuclear Power Plant, currently the only nuclear complex in Brazil, located in Angra dos Reis, Rio de Janeiro. The study confirmed the region’s main geoenvironmental aspects as winds and rainfall, landslides and population density were evaluated as important elements in the local emergency process. Their integrated analysis supported scenario identification and critical regional points and highlighted population evacuation escape routes. These important results characterized the support to local emergency management actions and guidelines. Furthermore, the geographic information systems was configured as an integrated spatial and temporal analysis platform to associate meteorological, geological/geomorphological and socio-economic data, playing a key role to support the evacuation planning in the event of nuclear power plant accidents. 相似文献
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Geological and anthropogenic influences on sediment metal composition in the upper Paracatu River Basin, Brazil 总被引：1，自引：1，他引：0
Daniel Santos Mulholland Geraldo Resende Boaventura Daniel Ferreira Araújo 《Environmental Earth Sciences》2012,67(5):1307-1317
This work reports a geochemical study of sediments from the upper Paracatu River Basin. The objective is to define the influences of Au, Zn, and Pb mineral deposits and mining activities on the sediment metal sources, distribution, and accretion. The samples were analyzed using ICP/OES, AAS, and XRD techniques and were treated with principal components analysis and the geo-accumulation index. The main geochemical processes that control the sediment composition are pyrite oxidation, muscovite weathering, carbonate dissolution, and the erosion of oxisols enriched with Zn and Pb. The upper Rico Stream has high Al, Fe, Cu, Cr, Co, and Mn concentrations due erosion of oxisols and pyrite oxidation and muscovite alteration present in the parental rock. The artisanal alluvial gold mining increased the primary rock-minerals?? weathering and Hg sediment concentration. The lower Escuro River and Santa Catarina Stream are enriched with Zn and Pb due the erosion of metal-rich soils formed over galena, sphalerite, calamine, and willemite mineral deposits located upstream. Elements such as Ca, Mg, and Ba have low concentrations throughout the sampled area due the high solubility of these metals-bearing minerals. The dispersion of metals is limited by the basin geomorphology and their affinity to silt-clayey minerals and Fe and Mn oxides and hydroxides in circumneutral pH waters. 相似文献
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R. Resende L. N. Lamas J. V. Lemos R. Calçada 《Rock Mechanics and Rock Engineering》2010,43(6):741-761
The goal of this paper is to simulate the interaction of stress waves and rock fractures in a particle micromechanical model. Stress waves travelling in fractured rock masses are slowed down and attenuated by natural heterogeneities, voids, microcracks and, above all, by faults and fractures. Considerable laboratory and theoretical investigation have uncovered the major aspects of this phenomenon, but models that cover the core mechanisms of the wave propagation in rock masses are necessary to investigate aspects of wave–fracture interaction, which are not completely clear, and in the future simulate full-scale real problems. The micromechanical model is based on the particle discrete element model that reproduces rock through a densely packed non-structured assembly of 2D disks with point contacts. The model of a hard rock core is developed and an irregular rock joint is generated at mid-height. A new contact constitutive model is applied to the particles in the joint walls. Numerical static joint compression tests are performed and a typical hyperbolic stress–displacement curve is obtained. Conditions for good quality wave transmission through non-jointed unorganized particulate media are determined, hybrid static–dynamic boundary conditions are established and plane waves are emitted into the compressed joint. The transmitted and reflected waves are extracted and analysed. Joint dynamic stiffness calculated according to the hypotheses of the Displacement Discontinuity Theory shows to increase with the static joint compression until the joint is completely closed. Still in its early stages of application, this rock micromechanical model enables the joint behaviour under static and dynamic loading to be analysed in detail. Its advantages are the reproduction of the real mechanics of contact creation, evolution and destruction and the possibility of visualizing in detail the joint geometry changes, which is hard to accomplish in the laboratory. 相似文献
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Sin Chan Chou Andr&#; de Arruda Lyra Jorge Lu&#;s Gomes Daniel Andr&#;s Rodriguez Minella Alves Martins Nicole Costa Resende Priscila da Silva Tavares Claudine Pereira Dereczynski Isabel Lopes Pilotto Alessandro Marques Martins Lu&#;s Felipe Alves de Carvalho Jos&#; Luiz Lima Onofre Idal&#;cio Major Manuel Penhor Ad&#;rito Santana 《Climate Dynamics》2020,54(9):4021-4042
Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work. 相似文献
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C.M. Denardini H.C. Aveiro P.D.S.C. Almeida L.C.A. Resende L.M. Guizelli J. Moro J.H.A. Sobral M.A. Abdu 《Journal of Atmospheric and Solar》2011,73(11-12):1555-1559
We analyze the daytime efficiency of the interplanetary electric field (IEF) penetration to the equatorial ionosphere based on a correlation analysis carried out between different levels of decomposition applied to IEF intensity measured at the ACE spacecraft and ionospheric electric field intensity inferred from ground based magnetometers located in the equatorial region in Brazil. We compare the time variations of those two electric field intensities by means of a scale-by-scale decomposed time series through wavelet multi-resolution analysis. Efficiency is here defined as the fraction of the variation of the IEF intensity that has penetrated into the equatorial region, and it increases with increasing fraction. Two cases of prompt penetration electric fields (PPEF) are analyzed: one occurring on March 31, 2001, and other on April 17, 2002. Our results show that the penetration effect with time scale ranging around 1 h is maximized in relation to other scales. 相似文献
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A.M Tye N.M.J Crout S Preston W Davison G.I Paton L Resende 《Geochimica et cosmochimica acta》2003,67(3):375-385
Cadmium and zinc were added at 3 and 300 mg kg−1, respectively, to 23 soils and incubated at 16°C and 80% field capacity for 818 d. Following addition of metal, changes in the radio-labile concentrations of both elements were examined on seven separate sampling occasions over 818 d. At each sample time, soil pore water was extracted using Rhizon soil solution samplers, and concentrations of Cd, Zn, dissolved organic carbon, and major cations and anions were determined. The chemical speciation program WHAM 6 was used to determine free metal ion activity, (M2+). Similar measurements were made on a set of historically contaminated soils from old mining areas, sewage sludge disposal facilities, and industrial sources. The two data sets were combined to give a range of values for p(Cd2+) and p(Zn2+) that covered 5 and 4 log10 units, respectively. A pH-dependent Freundlich model was used to predict Zn2+ and Cd2+ ion activity in soil pore water. Total and radio-labile metal ion concentration in the solid phase was assumed to be adsorbed on the “whole soil,” humus, or free iron oxides to provide alternative model formats. The most successful models assumed that solubility was controlled by adsorption on soil humus. Inclusion of ionic strength as a model variable provided small improvements in model fit. Considering competition with Ca2+ and between Zn2+ and Cd2+ produced no apparent improvement in model fit. Surprisingly, there was little difference between the use of total and labile adsorbed metal as a model determinant. However, this may have been due to a strong correlation between metal lability and pH in the data set used. Values of residual standard deviation for the parameterized models using labile metal adsorbed on humus were 0.26 and 0.28 for prediction of p(Cd2+) and p(Zn2+), respectively. Solubility control by pure Zn and Cd minerals was not indicated from saturation indices. However there may have been fixation of metals to non-radio-labile forms in CaCO3 and Ca-phosphate compounds in the soils in the higher pH range. Independent validation of the Cd model was carried out using an unpublished data set that included measurements of isotopically exchangeable Cd. There was good agreement with the parameterized model. 相似文献