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Contribution of soil organic carbon to the ion exchange capacity of tropical soils

SOARES, Marcio Roberto; ALLEONI, Luis Reynaldo Ferracciu
Fonte: HAWORTH PRESS INC Publicador: HAWORTH PRESS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.9%
Highly weathered soils represent about 3 billion ha of the tropical region. Oxisols represent about 60% of the Brazilian territory (more than 5 million km 2), in areas of great agricultural importance. Soil organic carbon (SOC) can be responsible for more than 80% of the cation exchange capacity (CEC) of highly weathered soils, such as Oxisols and Ultisols. The objective of this study was to estimate the contribution of the SOC to the CEC of Brazilian soils from different orders. Surface samples (0.0 to 0.2 m) of 30 uncultivated soils (13 Oxisols, 6 Ultisols, 5 Alfisols, 3 Entisols, I Histosol, 1 Inceptisol. and I Molisol), under native forests and from reforestation sites from Sao Paulo State, Brazil, were collected in order to obtain a large variation of (electro)chemical, physical, and mineralogical soil attributes. Total content of SOC was quantified by titulometric and colorimetric methods. Effective cation exchange capacity (ECEC) was obtained by two methods: the indirect method-summation-estimated the ECECi from the sum of basic cations (Ca+ Mg+ K+ Na) and exchangeable Al; and the direct ECECd obtained by the compulsive exchange method, using unbuffered BaCl2 solution. The contribution of SOC to the soil CEC was estimated by the Bennema statistical method. The amount of SOC var ied from 6.6 g kg(-1) to 213.4 g kg(-1). while clay contents varied from 40 g kg(-1) to 716 g kg(-1). Soil organic carbon contents were strongly associated to the clay contents...

Unconfined shear strength of compacted unsaturated plastic soils

Marinho, Fernando Antonio Medeiros; Oliveira, Orlando Martini de
Fonte: ICE PUBL; LONDON Publicador: ICE PUBL; LONDON
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.89%
A central goal in unsaturated soil mechanics research is to create a smooth transition between traditional soil mechanics approaches and an approach that is applicable to unsaturated soils. Undrained shear strength and the liquidity index of reconstituted or remoulded saturated soils are consistently correlated, which has been demonstrated by many studies. In the liquidity index range from 1 (at w(l)) to 0 (at w(p)), the shear strength ranges from approximately 2 kPa to 200 kPa. Similarly, for compacted soil, the shear strength at the plastic limit ranges from 150 kPa to 250 kPa. When compacted at their optimum water content, most soils have a suction that ranges from 20 kPa to 500 kPa; however, in the field, compacted materials are subjected to drying and wetting, which affect their initial suction and as a consequence their shear strength. Unconfined shear tests were performed on five compacted tropical soils and kaolin. Specimens were tested in the as-compacted condition, and also after undergoing drying or wetting. The test results and data from prior literature were examined, taking into account the roles of void ratio, suction, and relative water content. An interpretation of the phenomena that are involved in the development of the undrained shear strength of unsaturated soils in the contexts of soil water retention and Atterberg limits is presented...

Análise da potencialidade de alguns solos não lateríticos para utilização em barreiras impermeáveis; Analysis of the potential use of non lateritic soils in hydraulic barriers

Piedade Junior, Célio Roberto Campos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/03/2003 PT
Relevância na Pesquisa
35.93%
Apresenta-se uma avaliação do potencial de alguns solos não lateríticos, compactados, para uso como barreira impermeável, com bases em suas condutividades hidráulicas e contrações axiais. Dez tipos diferentes de solos foram analisados, sendo seis classificados como Não Laterítico Argiloso (NG') e quatro como Não Laterítico Siltoso (NS') de acordo com o sistema de classificação MCT. Nas análises foi verificada a influência de parâmetros de compactação e de algumas propriedades dos solos na condutividade hidráulica e na contração axial dos solos compactados. Verificou-se que, para a maioria dos solos houve a diminuição da condutividade hidráulica com o aumento da energia de compactação. Com relação à umidade de moldagem, os menores valores de condutividade hidráulica estiveram associados a umidades iguais ou acima da ótima. Alguns solos não tiveram a condutividade hidráulica influenciados pelo teor de umidade, talvez como reflexo de suas características de compactação, pois mostraram massa específica constante com a umidade, para uma dada energia de compactação. Constatou-se que a condutividade hidráulica diminui com o aumento do índice de plasticidade, da umidade volumétrica e com os resultados do ensaio de absorção de azul de metileno. Para a contração axial nota-se que ela foi pouco influenciado pelo aumento do teor de umidade e pela energia de compactação...

Análise da influência do teor de umidade na absorção d'água e sucção dos solos em estudo de erodibilidade; Analysis of the influence of moisture content on water absorption and suction in soil studies erodibility

Menezes, Marla Bruna Melo de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/04/2010 PT
Relevância na Pesquisa
35.83%
O estudo da erodibilidade ganha importância quando se tratam de solos localizados em regiões tropicais, caracterizadas por altas pluviosidades e evaporações que dificilmente permitem ao maciço atingir um estado de saturação em campo. A erodibilidade e as propriedades hidráulicas determinam as condições de infiltração e de escoamento superficial e podem acelerar as feições erosivas através das perdas de partículas. Neste trabalho, observou-se que o grau de saturação in situ estabelece um potencial de sucção matricial (Sm) capaz de orientar o fluxo, absorção e armazenamento da água nos poros do solo. Deste modo, foi possível correlacionar as propriedades de absorção de água com as sucções mátricas de três solos (arenoso, argiloso e areno-argiloso), com comportamento erosivo e não-erosivo, ensaiados a diferentes teores de umidade inicial. Após o controle da sucção e umidade, através da panela de pressão de Richards, os solos foram submetidos ao ensaio de erodibilidade proposto por Nogami & Villibor (1979). Os índices de absorção (Iabs), de perda de massa por imersão (P) e de erodibilidade (E) determinados neste ensaio, quando correlacionados com as curvas características dos solos, mostraram a influência da sucção matricial no início do processo erosivo. Verificou-se uma tendência de aumento da perda de massa por imersão...

Valores de referência de metais pesados em solos de Mato Grosso e Rondônia; Reference Values for heavy metals in soils from Mato Grosso and Rondônia states, Brazil

Santos, Sabrina Novaes dos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/06/2011 PT
Relevância na Pesquisa
35.82%
Os órgãos de monitoramento ambiental necessitam de indicadores de referência para a avaliação continuada dos impactos ambientais. Indicadores são obtidos por meio da comparação dos teores totais de elementos tóxicos de um solo com valores determinados em condições naturais (não poluídos) ou com valores de referência. No Brasil, com a crescente demanda social pela melhoria e manutenção da qualidade ambiental, alguns estudos foram realizados com o objetivo de estabelecer valores orientadores para metais pesados em solos. Estes são valores préestabelecidos quanto à presença de substâncias químicas que possibilitam a verificação de possível contaminação. A legislação brasileira estabelece três valores orientadores: Valores de Referência de Qualidade (VRQs), de Prevenção (VP) e de Investigação (VI). O VRQ indica o limite de qualidade para um solo considerado limpo a ser utilizado em ações de prevenção da poluição do solo e no controle de áreas contaminadas. Foram coletadas amostras de solo dos estados de Mato Grosso e Rondônia, nas profundidades de 0-5, 5-10, 10-20 e 20-30 cm, em áreas de vegetação nativa (sem ou mínima intervenção antrópica). Objetivou-se com essa dissertação: (i) determinar os valores de referência de metais pesados em solos de Mato Grosso e Rondônia; (ii) avaliar métodos de extração de teores pseudototais de metais pesados (EPA 3051 e Água Régia); (iii) correlacionar estes valores com atributos físicos e químicos dos solos; (iv) correlacionar os resultados desse estudo com valores já estabelecidos para solos de outros estados brasileiros. Partiu-se das hipóteses: i) não ocorrerão diferenças entre os teores naturais de metais pesados nos solos de Mato Grosso e Rondônia pelos dois métodos de extração de teores pseudototais de metais; ii) os VRQ de metais pesados para os solos de Mato Grosso e Rondônia são diferentes dos VRQ obtidos para solos de outros estados brasileiros; e iii) haverá correlação significativa entre os teores naturais de metais pesados e os atributos físicos e químicos dos solos. Houve diferença entre os métodos da água régia e EPA 3051 para recuperação dos metais Co...

Factors affecting Hg (II) adsorption in soils from the Rio Negro basin (Amazon)

Miretzky, Patricia; Bisinoti, Márcia Cristina; Jardim, Wilson F.; Rocha, Júlio César
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: 438-443
ENG
Relevância na Pesquisa
35.85%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Mercury (II) adsorption studies in top soils (top 10 cm) from the Rio Negro basin show this process depends strongly on some selected parameters of the aqueous phase in contact with the soils. Maximum adsorption occurred in the pH range 3.0-5.0 (>90%). Dissolved organic matter shows an inhibitory effect on the availability of Hg (II) to be adsorbed by the soils, whereas a higher chloride content of the solution resulted in a lower adsorption of Hg (II) at pH 5.0. Soils with higher organic matter content were less affected by changes in the salinity. An increase in the initial Hg (II) concentration increased the amount of Hg (II) adsorbed by the soil and decreased the time needed to reach equilibrium. A Freundlich isotherm provided a good model for Hg (II) adsorption in the two types of soil studied. The kinetics of Hg (II) adsorption on Amazonian soils showed to be very fast and followed pseudo-second order kinetics. An environmental implication of these results is discussed under the real scenario present in the Negro River basin, where acidic waters are in contact with a soil naturally rich in mercury.

Pedotransfer functions to estimate water retention parameters of soils in northeastern Brazil

Barros,Alexandre Hugo Cezar; Lier,Quirijn de Jong van; Maia,Aline de Holanda Nunes; Scarpare,Fábio Vale
Fonte: Sociedade Brasileira de Ciência do Solo Publicador: Sociedade Brasileira de Ciência do Solo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2013 EN
Relevância na Pesquisa
35.84%
Pedotransfer functions (PTF) were developed to estimate the parameters (α, n, θr and θs) of the van Genuchten model (1980) to describe soil water retention curves. The data came from various sources, mainly from studies conducted by universities in Northeast Brazil, by the Brazilian Agricultural Research Corporation (Embrapa) and by a corporation for the development of the São Francisco and Parnaíba river basins (Codevasf), totaling 786 retention curves, which were divided into two data sets: 85 % for the development of PTFs, and 15 % for testing and validation, considered independent data. Aside from the development of general PTFs for all soils together, specific PTFs were developed for the soil classes Ultisols, Oxisols, Entisols, and Alfisols by multiple regression techniques, using a stepwise procedure (forward and backward) to select the best predictors. Two types of PTFs were developed: the first included all predictors (soil density, proportions of sand, silt, clay, and organic matter), and the second only the proportions of sand, silt and clay. The evaluation of adequacy of the PTFs was based on the correlation coefficient (R) and Willmott index (d). To evaluate the PTF for the moisture content at specific pressure heads...

Factors affecting Hg (II) adsorption in soils from the Rio Negro basin (Amazon)

Miretzky,Patricia; Bisinoti,Márcia Cristina; Jardim,Wilson F.; Rocha,Júlio César
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
35.85%
Mercury (II) adsorption studies in top soils (top 10 cm) from the Rio Negro basin show this process depends strongly on some selected parameters of the aqueous phase in contact with the soils. Maximum adsorption occurred in the pH range 3.0-5.0 (>90%). Dissolved organic matter shows an inhibitory effect on the availability of Hg (II) to be adsorbed by the soils, whereas a higher chloride content of the solution resulted in a lower adsorption of Hg (II) at pH 5.0. Soils with higher organic matter content were less affected by changes in the salinity. An increase in the initial Hg (II) concentration increased the amount of Hg (II) adsorbed by the soil and decreased the time needed to reach equilibrium. A Freundlich isotherm provided a good model for Hg (II) adsorption in the two types of soil studied. The kinetics of Hg (II) adsorption on Amazonian soils showed to be very fast and followed pseudo-second order kinetics. An environmental implication of these results is discussed under the real scenario present in the Negro River basin, where acidic waters are in contact with a soil naturally rich in mercury.

CORRELATIONS BETWEEN HOT CALCIUM CHLORIDE-EXTRACTED BORON AND CHEMICAL AND PHYSICAL ATTRIBUTES OF SOME BRAZILIAN SOILS

Alleoni,Luís Reynaldo Ferracciú; Camargo,Otávio Antonio de; Valadares,José Maria Aires Silva
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/1999 EN
Relevância na Pesquisa
35.83%
Relationship between soluble boron extracted with a hot CaCl2 0.01 mol L-1 solution and pH; organic carbon; exchangeable cations; cation exchange capacity (CEC); base saturation; total, free and amorphous iron and aluminum oxide contents; clay content; and specific surface area were performed for surface and subsurface samples of five soils. The soils were a Rhodic Hapludox, an Arenic Paleudalf and three Typic Hapludox, all representative soils of the State of São Paulo, Brazil. To quantify the relations between soluble boron and the different soil characteristics, simple linear correlations and multiple regressions, using a stepwise regression program, were performed. Hot-CaCl2 extractable boron (HCB) was significantly correlated with clay content (r = 0.69*), specific surface area (r = 0.68*), CEC (r = 0.63*) and total aluminum oxides (r = 0.70*) in all five soils. In addition, there was a correlation between HCB and organic carbon (r = 0.75*) in the four Oxisols. The correlation coefficient between the product (carbon x clay) and soluble boron contents was also highly significant (r = 0.78**). Multiple regression analysis showed that total aluminum oxide, as well as exchangeable calcium and aluminum, were correlated with HCB, explaining 85% of the variation. The product (carbon x clay) took into account the effect of textural gradient and showed high positive correlation with hot-CaCl2 0.01 mol L-1extractable boron.

Adjustment of the expedite method for clay content determination in Rondônia soils.

SCHLINDWEIN, J. A.; MIOTTI, A. A.; FIORELI-PEREIRA, E. C.; PEQUENO, P. L. DE L.; BORTOLON, L.; MARCOLAN, A. L.
Fonte: Ciência Rural, Santa Maria, v. 41, n. 12, p. 2096-2100, dez. 2011. Publicador: Ciência Rural, Santa Maria, v. 41, n. 12, p. 2096-2100, dez. 2011.
Tipo: Artigo em periódico indexado (ALICE)
EN
Relevância na Pesquisa
35.85%
Soil clay content is an important soil attribute and has been used to classification of phosphorus status in the soil in order to determinate the needing of phosphorus amounts to be applied to crops production. The aim of this research was to adjust the method for soil clay content determination, adopted by the laboratories of Southern Brazil (ROLAS-RS/SC), for soil clay content evaluation in Rondônia soils. The study was conducted using 50 soil samples from Rondônia State with wide range clay content. It was tested shaking periods (1.5, 2.0 and 2.5h) associated with periods for soil particles decantation (1.5 and 2.0h) to correlate with the standard method for soil texture testing, known as the pipette method. Clay content determined through this method was significantly correlated with pipette method. The better treatment was the combination of 2.0h of shaking and 1.5h of decantation, resulted in total period of 3.5h, which reduced the period to determine the soil clay content without loss of accuracy.; 2011

Avaliação das Flutuacões Sazonais de Umidade e Sucção em um Perfil de Solo Tropical.; Predict of Suction and Humidity of Tropical Soils Using Mechanistic Model.

SILVA JÚNIOR, Arlam Carneiro
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Geotecnia e Construção Civil; Engenharias Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Geotecnia e Construção Civil; Engenharias
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
35.85%
The evaluation of soil-atmosphere interaction is crucial in several examples of geotechnical works as compaction operations, construction and operation of dams and slope stability. Generally, in these examples, the soils are in unsaturated state. The main objective of this study is to assess and refine the mechanistic approach to predict the changing conditions of suction and moisture of a soil profile unsaturated. Three methods for predicting soil-water characteristic curve were evaluated, and a new method was proposed. The prediction methods, examined in this study, are based on particle size and other index properties. Were considered the soil of the experimental field of Furnas in Aparecida de Goiania (Goiás - Brazil), the soil of the experimental field of the University of Brasilia and soils of temperate climate. Good results were obtained from the prediction methods used. Were monitored for six months, the water content, suction, groundwater and atmospheric conditions of the experimental field of Furnas. The water content was obtained by removal of soil samples and suction was obtained by two measuring methods: filter paper and tensiometer. A device for installation and under the filter paper in the field was developed. The method of the paper filter had good results of total suction and the use of a tensiometer allowed measurements of a limited range of matric suction. Water content and suction predictions were made for the experimental field of Furnas from numerical analysis. It considered soil-water characteristic curves experimental and provided in numerical analysis. It have found most difficult to predict suction and moisture for the shallowest depth analyzed.; A avaliação da interação solo-atmosfera tem um papel fundamental em diversos exemplos de obras geotécnicas como operações de compactação...

Persistence and mobility of triasulfuron, metsulfuronmethyl, and chlorsulfuron in alkaline soils / Ajit K. Sarmah.

Sarmah, Ajit K.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 701186 bytes; application/pdf
Publicado em //1998 EN
Relevância na Pesquisa
45.82%
This study examined the fate of three common sulfonylurea herbicides in highly alkaline soils through a series of laboratory and field experiments to determine if existing leaching models could be used to describe their field behaviour under Australian climatic conditions. A liquid chromatographic method was developed to simultaneously determine levels of triasulfuron, metsulfuronmethyl, and chlorsulfuron in soil and water. The investigation of base hydrolysis for the herbicides in aqueous buffer and soil solutions determined that it was unlikely to be a major loss pathway for sulfonylureas in alkaline soils. The herbicides were found to have low sorption, very little retardation and high mobility, moving at a marginally slower rate than water. Degradation did not follow first-order kinetics, but rather a two-stage process appeared to be involved. Both VARLEACH and LEACHM models predicted the measured concentration of the herbicides reasonably well in profile under low rainfall conditions but were less adequate under high rainfall. Forecasts with the LEACHP model predicted levels of the herbicides for a dominant soil type of the cereal belt of southern Australia with median rainfall after a year.; Thesis (Ph.D.)--University of Adelaide...

Sorption and release of pesticides in soils : the role of chemical nature of soil organic matter / Riaz Ahmad.

Ahmad, Riaz
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 110524 bytes; application/pdf
Publicado em //1999 EN
Relevância na Pesquisa
45.74%
The aims of this study were: 1. to examine the sorption behaviour of selected nonionic and ionic pesticides in a range of soils; 2. to characterise the nature of soil organic matter in a diverse group of soils and relate the structural and molecular variations of organic matter to sorption of nonionic pesticides; and 3. to study the release behaviour of carbaryl and ethion from two historically contaminated soils and to elucidate the mechanisms of their aging/sequestration. (abstract); Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 1999; Bibliography: leaves 198-227.; xx, 260 leaves, [3] leaves of plates : ill. (chiefly col.) ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

Response of microbial activity and biomass to changes in soil salinity and water content.

Yan, Nan
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
36.04%
Salinization is a serious land degradation problem because osmotic stress and toxic ions cause poor plant growth and low soil microbial activity. The effect of salinity on soil microbes has been studied previously, but usually at constant salinity. However, in the field salinity may vary over time. Another factor influencing the effect of salinity on soil microbes is the soil water content. The osmotic potential, which is a measure of the salt concentration in the soil solution, increases as soils dry. The aim of the experiments described in this thesis was to assess how soil microbial activity and microbial biomass respond to changes in soil salinity and soil water content. One non-saline and four saline soils from Monarto, South Australia (35° 05´ S and 139° 06´ E) were used in the experiments. Soils were air-dried after collection. In some experiments, salinity was induced by adding certain amount of NaCl (dissolved in RO water), or decreased by leaching. Preliminary experiments were carried out to quantify the salts or water needed to reach the desired salinity. Pea (Pisum sativum L.) straw (C/N=26) was used as available substrate in most experiments except for experiments in Chapter four, where glucose was used. Soil CO₂ release (respiration as measure of microbial activity) was measured daily throughout each experimental period...

Chemistry of indigenous Zn and Cu in the soil-water system : alkaline sodic and acidic soils / by Amir Fotovat.

Fotovat, A.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 708617 bytes; application/pdf
Publicado em //1997 EN
Relevância na Pesquisa
35.85%
In this study the soil aqueous phase chemistry of Zn and Cu in alkaline sodic soils are investigated. The chemistry of trace metal ions at indigenous concentrations in alkaline sodic soils are reported. Metal ions at low concentrations are measured by the graphite furnace atomic absorption spectrometry (GFAAS) technique.; Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1998; Copies of author's previously published articles inserted.; Bibliography: leaves 195-230.; xx, 320 leaves : ill. (some col.) ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

A influência da variação da umidade pós-compactação no comportamento mecânico de solos de rodovias do interior paulista; The influence of post-compaction moisture content variation on the mechanical behavior of soils from São Paulo state pavements

Takeda, Marcelo de Castro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/05/2006 PT
Relevância na Pesquisa
35.94%
Na construção de rodovias, as condições de umidade e densidade observadas na compactação são, geralmente, próximas daquelas correspondentes ao pico da curva de compactação obtida no ensaio Proctor. É sabido que variações ambientais no decorrer da vida do pavimento podem alterar, de maneira significativa, a umidade do subleito e dos seus componentes e assim, as suas propriedades resilientes. O objetivo principal desta pesquisa é avaliar a influência da variação da umidade pós-compactação no módulo de resiliência de solos de rodovias do interior paulista a partir de resultados de ensaios de laboratório. Foram coletados e caracterizados setenta e três solos, e, dentre estes, selecionados trinta para a etapa de estudo da variação da umidade pós-compactação, após a realização de ensaios MCT, difração de raios-x, microscopia eletrônica de varredura e azul de metileno para determinação da gênese. Os solos selecionados apresentam características distintas quanto à gênese, sendo metade laterítico e metade não-laterítico. Os corpos-de-prova foram compactados na umidade ótima e submetidos a processos de secagem e umedecimento e, posteriormente, realizados ensaios triaxiais cíclicos. Os resultados permitiram a modelagem do 'M IND.R' em função do estado de tensão para diferentes umidades e a avaliação da competência de alguns modelos matemáticos nesta representação. Estudou-se a influência da gênese e da granulometria sobre o valor do 'M IND.R' e avaliou-se a conseqüência da variação da umidade sobre este para solos lateríticos e não-lateríticos. Determinou-se uma expressão para estimar a variação do 'M IND.R' com a variação da umidade a partir do parâmetro k1...

Condutividade hidráulica de solos compactados em ensaios com permeâmetro de parede flexível; Hydraulic conductivity of compacted soils in flexible wall permeameter tests

Alonso, Thiago de Paula
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/09/2005 PT
Relevância na Pesquisa
35.85%
Cincos solos compactados do estado de São Paulo foram estudados para uso como barreira impermeável de aterros sanitários. Foram realizados ensaios em permeâmetro de parede flexível com utilização do sistema de controle hidráulico de volume constante (sistema fechado), ensaios em permeâmetro de parede rígida e ensaios de contração. Verificou-se que menores valores de condutividade hidráulica estão associados a teores de umidade de moldagem igual ou acima do teor de umidade ótimo fornecida no ensaio de Proctor normal. Teores de umidade acima do ótimo e graus de compactação superiores a 100% não causaram significativas reduções na condutividade hidráulica, que tende a se estabilizar a partir destes parâmetros. Foram sugeridas condições de compactação para quatro dos cinco solos analisados, de forma que a condutividade hidráulica não excedesse 1.'10 POT.-7' cm/s, valor sugerido para barreiras impermeáveis. A contração axial e volumétrica não foi influenciada pelo teor de umidade de moldagem e grau de compactação, para corpos-de-prova compactados nas condições de compactação sugeridas. Os resultados de condutividade hidráulica em ensaios com permeâmetros de parede rígida se mostraram, aproximadamente...

Microbiological degradation index of soils in a semiarid climate

Bastida, F.; Moreno, J. L.; Hernández Fernández Muñoz, María Teresa; García Izquierdo, Carlos
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 259768 bytes; application/pdf
ENG
Relevância na Pesquisa
35.85%
11 pages, 8 tables.; Soil degradation and desertification affect many areas of the planet. One such area is the Mediterranean region of SE Spain, where the climatological and lithological conditions, together with the relief of the landscape and anthropological activity, including agricultural abandonment, are responsible for increasing desertification. It is therefore considered to be of extreme importance to be able to measure soil degradation quantitatively. The aim of this study was to make a microbiological and biochemical characterisation of different soil catenas in SE Spain, including in a wide range of plant cover densities in an attempt to assess the suitability of the parameters measured to reflect the state of soil degradation and the possibility of using the parameters to elaborate a microbiological degradation index (MDI) valid for use in semiarid climates. For this, several indices related with the organic matter content (total organic carbon, TOC, water-soluble carbon, WSC, and water-soluble carbohydrates, WSCh), with the size of microbial populations (microbial biomass carbon, MBC) and related activity (respiration and enzymatic activities) were determined in the soils of three different catenas in different seasons of the year. The values of these parameters were seen to be closely related with the degree of vegetal cover...

Fate, transport, and bioavailability of arsenic in manured and contaminated soils of Delaware

Gardner, Sheila
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
45.77%
Sims, J. Thomas; Over the past several years, trace element contamination, specifically arsenic (As), in soils and water has become an alarming environmental issue. All metal/metalloids are potentially hazardous at some concentration (Langdon et al., 2003), and As is known to be carcinogenic, phytotoxic, and biotoxic at extremely low concentrations. The most toxic forms of As are arsine gas, followed by inorganic trivalent compounds, organic trivalent compounds, inorganic pentavalent compounds, and finally elemental As (Cullen and Reimer, 1989). Inorganic As has been listed by the United States Environmental Protection Agency (USEPA) as a Class A human carcinogen and has been linked to bladder, kidney, liver, lung, and skin cancers, as well as impaired nerve function (Research Triangle Institute, 1998). In 2001 the USEPA reduced the allowable levels of As for oral intake in drinking water from 50 µg L-1 to 10 µg L-1, and states have been required to comply with this regulations since 2006. Delaware has complied with this standard since 2001. In 2004, the Delaware Department of Natural Resources and Environmental Control (DNREC) established an Interim Arsenic Soil Cleanup Standard for Residential Properties at 23 mg kg-1 for surface soils from zero to two feet below ground surface...

Copper accumulation, distribution and fractionation in vineyard soils of Victoria, Australia

Pietrzak, Ursula; McPhail, Derry
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.89%
The use of copper-based fungicides by Victorian vinegrowers has increased the total copper concentration in some vineyard soils to 250 mg/kg compared to background levels of approximately 10 mg/kg. The Australian and New Zealand guidelines for the assessment of contaminated sites recommend that total copper concentrations in soil exceeding 60 mg/kg require environmental investigation, and this level is exceeded in 8 of the 14 vineyards investigated. The focus of this paper is to measure the accumulation, distribution and fractionation of copper in contaminated and uncontaminated soils as a step towards understanding copper existence in soils and its potential for availability to flora and fauna. Physical and chemical properties and total copper concentrations were measured in soil samples from four selected wine-producing regions of Victoria, including vineyard soils and adjacent background soils. Copper fractionation in soils with high total copper concentrations was measured using a selective extraction procedure. Copper in surface soils (0-1 cm) and throughout soil profiles (maximum depth of 50 cm) was separated in the following fractions: water soluble (WS), exchangeable (E), sorbed (S), easily reducible Mn (ERMn), bound to carbonates (CA)...