Electrofluid dynamic (EFD) energy conversion in gas flows with suspended nanoparticles

This work presents simulations of the Electrofluid Dynamic energy conversion process in slender channel devices having very small particles (in both micro and nano scales) as charge carriers. Solutions are discussed for a system composed by coupled differential equations, which includes the equation for the total current along the channel, the equations for total energy and momentum of the mixture (gas and solid particles), the continuity equation and the equations for energy and momentum of a single particle. Results for suspended particles of higher diameters have been previously published in the Literature, but the simulations here presented exhibit an appreciable increase in the values for output currents.

Radioactivity distribution in some Permian sediments from the Irati and Corumbatal formations of the Parana basin, southeastern Brazil

in the city of Limeira, southeastern Brazil, an important exposure of Permian sediments of the Parana basin was revealed by an open pit mine that exploits limestone for production of soil correction compounds and raw materials for the ceramic industry. The radioactivity of these sediments was investigated in some detail and the results provided a general view of the vertical distributions of uranium, thorium and potassium concentrations and of the element ratios U/K, U/Th and Th/K. In general, the concentrations of the main natural radioactive elements are low, with uranium being enriched in some limestone and shale levels. In addition the results showed that the U-238 series is in radioactive disequilibrium in many of the analyzed samples. Although the origin of the observed disequilibrium has not been investigated, the results suggest that it is due to weathering processes and water interaction with the rock matrix. (C) 2003 Elsevier Ltd. All rights reserved.

Preference ratios for mercury and other chemical elements in the Madeira River, Brazil

Samples of water, suspended solids, and bottom sediments from the Madeira River, Rondonia state, Brazil, were physically and chemically analyzed to investigate the actual Hg mobilization in the aquatic environment and compare it with that of other heavy metals and elements in the area. Two dimensionless Hg preference ratios were defined, expressing (1) the ratio of Hg and other elements in the liquid phase divided by the ratio of Hg and other elements in bottom sediments (P(l.phase)) and (2) the ratio of Hg and other elements in the particulate matter divided by the ratio of Hg and other elements in bottom sediments (P(s.solids)). These preference ratios are useful for comparing Hg transport in three different phases (liquid, particulate matter, and bottom sediments). They also were applicable to any analyzed elementin the area studied, because they generated an almost constant value when the maximum calculated was divided by the minimum (P(l.phase) = 2931; P(s.solids) = 84) and because of their sensitivity to the dominance of sorption processes by Fe oxides and hydroxides. Mercury could be transported preferentially to other analyzed elements in the particulate phase only if its concentration reached values at least 10(4)-fold higher than those expected or quantified in the area. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Pb-210 and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapa, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tracing source and evolution of suspended particles in the Rio Negro Basin (Brazil) using chemical species of iron

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Speciation of butyltin derivatives in surface sediments of three southern Brazilian harbors

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Environmental evaluation of metals in sediments and dragonflies due to sugar cane cultivation in neotropical streams

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mercury in soils and sediments from gold mining liabilities in Southern Amazonia

The 1980-1990 Amazonian gold rush left an enormous liability that increasingly has been substituted by developing fish aquaculture. This work aimed at the identification of the mercury levels in the environment, associated with fish farms located in the North of Mato Grosso State, Southern Amazon. Sediment and soil samples were analyzed for total organic carbon and total mercury. Results indicate that the chemical characteristics of the sediment largely depend on the management procedures of the fish pond (liming, fish food used and fish population). The soils presented relatively low concentrations when compared with other data from the literature.

TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

Este artigo apresenta os resultados de datação por TL e OSL de solos, e fragmentos de tijolos de um túmulo, que foi ocupado por duas freiras mumificadas encontradas no Mosteiro da Luz, localizado no Estado de São Paulo, Brasil. As idades encontradas por TL e OSL foram comparadas às obtidas a partir de C-14 dos colágenos contidos em amostras de osso das múmias. A maioria das idades obtidas são do século XVIII. A espectroscopia de radiação-gama foi utilizada para avaliar concentrações de radioisótopos naturais nas amostras e para calcular as taxas de dose anual que resultaram em 3,0 a 5,3 Gy/kano. As concentrações radioativas são próximas daquelas obtidas através de Análise por Ativação de Nêutrons. Os conteúdos de elementos U, Th e Ce são superiores aos encontrados na maioria dos sedimentos.

Flotation of blocolloids suspended in liquid phases of different compositions and pH values

The flotation capacity was determined for cells of yeasts strains belonging to the genera Hansenula, Candida and Saccharomyces. A heterogeneous group of yeasts, comprising strains from the three genera, was identified as showing high flotation capacities (degrees of flotation above 50%), which were practically not affected by variations in medium pH in both the synthetic medium and 2% molasses. Thus, the flotation capacity of the cells in this yeast group seemed strongly dependent on the liquid phase properties and/or growth medium composition, more than on the simple variation in pH of the cell suspensions. A second group of strains, belonging to the Saccharomyces genus, including also brewing yeast strains, was identified as having lower flotation capacities (degrees of flotation below 50% at pH 1.5), which showed no alterations or variations significantly affected by the medium pH. Foam volumes obtained with Saccharomyces strains were greater in synthetic media than in molasses owing to the higher air flow rates required for flotation in molasses. The flotation efficiency decreased in molasses in all cases as well as the foam volume, except in the case of Hansenula cells, which showed an increased foam volume. This was probably due to variations in product excretion by the different yeasts and/or differences in cell wall composition.

Distribution profile and availability of Cr, Ni, Cu, Cd and Pb in different sediments from anhumas surface water collection reservoir, Araraquara-São Paulo State, Brazil

In this work the influence of the anhtropogenic activities in the uptake of metals at a reservoir for public water supply in Araraquara City, São Paulo State, Brazil was studied. For this, the distribution of Cr, Ni, Cu, Cd and Pb in sediments collected from Anhumas reservoir, at seven sampling points and at three depths for each point was investigated. The pseudo-total and available metals contained in the different sediment samples were assessed using an ICP-AES technique. Among the five metals studied, cadmium possesses the largest relative potential availability, with percentages of 20 to 98% for the three different sediment types. In addition, the following decreasing availability order was characterized: Cd > Cu > Pb > Ni > Cr.

Determination of butyltin compounds in surface sediments from the São Paulo State coast (Brazil) by gas chromatography-pulsed flame photometric detection

Occurrence and the effects of butyltin compounds (BTs) have been studied for some years, mainly in countries of the Northern Hemisphere. Due to widespread use of tributyltin compounds (TBTs) and considering their deleterious effects, it is necessary to conduct studies on its occurrence, especially in the marine environment because of its excessive use in coatings of ship hulls to prevent fouling. Moreover, it was important to extend the evaluation to areas where there is no current information about their occurrence. The present work reports the occurrence of BTs in marine sediments of São Paulo state, Brazil. Commercial and leisure harbor sampling sites were selected because these areas are potentially exposed to BTs from antifouling paints used on ship hulls. Analytical conditions for organotin analysis in marine sediments were optimized for GC with pulsed flame photometric detection. Detection limits ranged from 8.4 to 66.3 ng g(-1) using a 610-nm filter, and the linearity range was 20-500 ng g(-1). Concentration levels of BTs were highest in Santos harbor (360 ng g(-1) TBT in average) and Guaruja marina (670 ng g(-1) TBT in average), which seems to be related to intensive boat traffic. Lower levels of BTs were observed in Cananeia, where only fishing boats are present (50 ng g(-1) TBT in average). (C) 2002 Elsevier B.V. B.V. All rights reserved.

A method for evaluating Ra-228 in environmental matrices and its use at Pocos de Caldas plateau, Brazil

This work describes a methodology developed for performing the extraction, detection and quantification of Ra-228 in waters, suspended solids and sediments. The technique proved to be useful for analyzing samples from the hydrological environment of Morro do Ferro, Pocos de Caldas plateau, Brazil. The 228Ra activity in underground waters of 5 boreholes drilled in the area varied from 0.02 up to 14.5 Bq/l, whereas for the surficial waters the variation was from 0.04 to 0.51 Bq/l; for the suspended solids, the values ranged from 1.5 up to 419 Bq/g, whereas it was possible to find a value of 2.04 Bq/g for the sediments. These results show the applicability of the method for characterizing different matrices of environmental interest. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

From Plinthic Acrisols to Plinthosols and Gleysols: iron and groundwater dynamics in the tertiary sediments of the upper Amazon basin

Topography has been reported to be the major factor ruling the spatial distribution of Acrisols, Plinthosols and Gleysols on the seasonally flooded, low elevation plateaux of the upper Amazon basin occupied by Tertiary (Ica & Solimoes) sediments. In this study, detailed morphological and mineralogical investigations conducted in a representative 25-ha site were combined with hydro-geochemical data to relate the vertical and lateral soil differentiations observed to the hydro-geological history of that part of the basin. As a result of the uplift of the Andes, several cuts in the extensive Tertiary marshlands have formed, at first, slightly incised plateaux of low elevation. There, weathering under hot and humid climates would have generated a reddish, freely drained and bioturbated topsoil layer and the vertical differentiation in subsoil sediments of a plinthite over an iron-depleted mottled clay. The second episode of soil differentiation is linked to the replacement of the forest by a savannah under the drier climates of the late Pleistocene, which favours surface runoff and the infill of the incisions by fine particles. This infill, combined with the return to the present humid climate, has then enabled the local groundwater to rise on the plateaux and to generate episaturation at the topsoil/subsoil transition close to the depressions. Nowadays, ferrous iron is released from the partly iron-depleted topsoil weathering front at high water levels during the rainy seasons. It moves from footslope to low-lying positions and from top to bottom in the soil profile according to the groundwater dynamics. The present general trend is thus to the lateral export of iron at high water levels due to subsurface and overland flows, its vertical transfer during the recession of the groundwater and accumulation in a nodular plinthite. In the latter, ferrous iron is adsorbed onto its softest iron masses where it feeds the neoformation of ferrihydrite that rapidly dehydrates into haematite.

Physical, chemical and microbiological characterization of the intertidal sediments of Pereque Beach, Guaruja (SP), Brazil

Physical and chemical characteristics of intertidal sediments and their relationships with bacteria and cyanobacteria, were analyzed at four stations at Pereque Beach. Granulometric analysis showed that Pereque beach has sediment that is classified as sand. The lowest value of the sediment C/N rates (6.08), mainly due to a higher concentration of organic nitrogen, was found at the northern part of Pereque Beach, where organic matter of marine source was more prominent. In this area, density (9.6 x 106 cells cm(-3)), biomass (1992.04 ngC cm(-3)) and activity of bacteria were higher than at the southern end. In contrast, cyanobacteria density varied from 2.0 to 4.0 x 10(5) cells cm(-3), with biomass and total chlorophyll a of the sediment being higher at the southern part, where there are water input from Pereque River and higher organic matter of continental origin. The variability in the microbial population is discussed in the light of the sediment granulometry, organic matter quality, fresh water inflow and pollution. (c) 2007 Elsevier Ltd. All rights reserved.