9 research outputs found

    Tamanho de amostras para a determinação de parâmetros físicos em planossolo por tomografia computadorizada

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    A técnica da tomografia computadorizada (TC) permite medir a densidade e a umidade de amostras de solo, constituindo uma importante ferramenta na Ciência do Solo. Este trabalho tem como objetivos descrever os aspectos da adequação do tamanho de amostras de um Planossolo e os procedimentos de avaliação e estudos por análise estatística, empregando-se um minitomógrafo computadorizado de raios gama com fonte de 241Am. O valor do erro atribuído ao equipamento são 0,051 e 0,046 Mg m-3, respectivamente, para os horizontes A e B. O valor teórico da espessura da amostra do Planossolo para uso na técnica de TC com fonte de 241Am é, aproximadamente, 4,0 cm para os horizontes A e B. Já a espessura ideal de amostras é de aproximadamente 6,0 cm, sendo menor para amostras do horizonte B em relação ao A. Obteve-se boa precisão e adaptabilidade no emprego da TC para estudos de Planossolos._________________________________________________________________________________ ABSTRACT: Computerized tomography (CT) is an important tool in Soil Science for noninvasive measurement of density and water content of soil samples. This work aims to describe the aspects of sample size adequacy for Planosol (Albaqualf) and to evaluate procedures for statistical analysis, using a CT scanner with a 241Am source. Density errors attributed to the equipment are 0.051 and 0.046 Mg m-3 for horizons A and B, respectively. The theoretical value for sample thickness for the Planosol, using this equipment, is 4.0 cm for the horizons A and B. The ideal thickness of samples is approximately 6.0 cm, being smaller for samples of the horizon B in relation to A. Alternatives for the improvement of the efficiency analysis and the reliability of the results obtained by CT are also discussed, and indicate good precision and adaptability of the application of this technology in Planosol (Albaqualf) studies

    Impact Of Anthropogenic Activity On The Hg Concentrations In The Piracicaba River Basin (são Paulo State, Brazil)

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    A sampling and analysis program has been completed between 1995 and 1998 in order to determine mercury concentrations in water, sediments, soils and fish in the Piracicaba river basin, one of the most populated and industrialized regions in Brazil. In sediment, the average Hg concentrations varied between 33 ± 17 ng g-1 and 106 ± 78 ng g-1, in samples collected during the rainy and dry season, respectively. The same averages were also found for soil samples (35 ± 14 and 109 ± 61 ng g -1). In water, the total Hg concentration varied between < 1.1 and 24.0 ng L-1. In piscivore fish, up to 943 μ g Hg kg-1 was found. Our results show that all compartments undergo Hg contamination, in view of the levels found in pristine environments. Water contamination seems to be due mainly to diffuse processes of soil erosion and suspension of river bed sediment during the rainy season. Also untreated wastewaters generated by industrial activities and from domestic sewage appear to be potential non-point sources in the most industrialized and populated part of the basin. On the other hand, atmospheric transport of mercury originating from the Campinas Metropolitan Region could be another source of mercury contamination, especially in the basin headwaters. © Springer 2005.1661-4381402Ballester, M.V., Martinelli, L.A., Krusche, A.V., Victoria, R.L., Bernardes, M., Camargo, P.B., Effects of increasing organic matter loading on the dissolved O 2, free dissolved CO2 and respiration rates in the Piracicaba river basin, southeast Brazil (1999) Water Res., 33, pp. 2119-2129Balogh, S., Meyer, M., Johnson, K., Diffuse and point source mercury inputs to the Mississipi, Minnesota, and St. Croix Rivers (1998) Sci. Total Environ., 213, pp. 109-113Barbosa, A.C., Boischio, A.A., East, G.A., Ferrari, I., Gonçalves, A., Silva, P.R.M., Dacruz, T.M.E., Mercury contamination in the Brazilian Amazon - Environmental, and occupational aspects (1995) Water Air Soil Poll., 80, pp. 109-121Bloom, N.S., Fitzgerald, W.F., Determination of volatile mercury species at the picogram level by low temperature gas chromatography with cold vapor atomic fluorescence detection (1988) Anal. Chim. Acta, 208, pp. 151-161Boldrini, C.V., Pádua, H.B., Pereira, D.N., Resende, E.K., Juras, A.A., Contaminação por Hg nos rios Mogi-Guaçu e Pardo (SP) (1983) Revista DAE, 135, pp. 106-117Brabo, E.D., Santos, E.D., De Jesus, I.M., Mascarenhas, A.F.S., Faial, K.D., Mercury contamination of fish and exposures of an indigenous community in para State, Brazil (2000) Environ. Res., 84, pp. 197-203Brabo, E.S., Angélica, R.S., Silva, A.P., Faial, K.R.F., Mascarenhas, A.F.S., Santos, E.C.O., Jesus, I.M., Loureiro, E.C.B., Assessment of mercury levels in soils, waters, bottom sediments and fishes of Acre state in Brazilian Amazon (2003) Water Air Soil Poll., 147, pp. 61-77(2002) Relatório de Qualidade Do Ar Do Estado de São Paulo 2001, , CETESB, São PauloDaniel, M.H.B., Montebelo, A.A., Bernardes, M.C., Ometto, J.P.H.B., Camargo, P.B., Krusche, A.V., Ballester, M.V., Martinelli, L.A., Effects of urban sewage on dissolved oxygen, dissolved inorganic and organic carbon, and electrical conductivity of small streams along a gradient of urbanization in the Piracicaba River Basin (2002) Water Air Soil Poll., 136, pp. 189-206Domagalski, J., Occurrence and transport of total mercury and methyl mercury in the Sacramento river basin, California (1998) J. Geochem. 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    Alterações físicas introduzidas por diferentes níveis de compactação em latossolo vermelho-escuro textura média Physical alterations induced by compaction of a coarse silty dark red latosol

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    Visando avaliar o efeito de diferentes níveis de compactação nos atributos físicos: densidade do solo, porosidade total, conteúdos volumétricos de sólidos e de água e distribuição dos poros para retenção de água/ar, diferentes quantidades de massa de um Latossolo Vermelho-Escuro textura média foram introduzidas mediante uma prensa hidráulica em anéis de PVC de 0,88 dm³. Utilizando fórmulas desenvolvidas na mecânica dos solos e com os valores de densidades obtidos no feixe de raios-gama e densidade de partículas, observou-se que a aplicação de uma carga (pressão) sobre o solo reduziu linearmente tanto a porosidade total como o espaço de aeração, e aumentou na mesma magnitude os conteúdos volumétricos de sólidos e o de água.<br>This research was conducted with the objective of studying physical alterations due to different levels of compaction in a coarse silty Dark Red Latosol (Oxisol). Compaction was obtained through a hydraulic press and bulk densities were checked in a gamma ray apparatus. Using soil mechanical equations, it was observed that the application of a strength over the soil reduced the total porosity and the aeration space, while increased in the same proportion the solid and water volumetric content

    Mudanças na estrutura do solo avaliada com uso de tomografia computadorizada Soil structure changes evaluated with computed tomography

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    O objetivo deste trabalho foi avaliar, em escala milimétrica, a modificação da densidade e da porosidade de amostras deformadas de solo submetidas a ciclos de umedecimento e secamento (U-S), por meio da tomografia computadorizada de raios gama. Amostras com 98,1 cm³ foram preparadas procedendo ao peneiramento do solo em malha de 2 mm e acondicionamento de forma homogênea em tubos de PVC. As amostras de solo foram submetidas a um, dois e três ciclos de U-S. As amostras controle não foram submetidas a nenhum ciclo de U-S. Após a aplicação dos ciclos de U-S, a porosidade das amostras diminuiu e as camadas de solo se adensaram. Os dados de tomografia computadorizada permitiram análise contínua da densidade do solo e de sua porosidade, em camadas milimétricas (0,08 cm), o que não pode ser alcançado facilmente por métodos tradicionais usados em física do solo.<br>The objective of this work was to evaluate in millimetric scale changes in soil bulk density and porosity, using the gamma-ray computed tomography in soil samples with disturbed structure due to wetting and drying (W-D) cycles. Soil samples with 98.1 cm³ were sieved using a 2 mm mesh and homogenously packed in PVC cylinders. Soil samples were submitted to 1, 2, and 3 W-D cycles. Control samples were not submitted to W-D cycles. After repetitions of W-D cycles, soil sample porosity decreased and soil layers became denser. Computed tomography allowed a continuous analysis of soil bulk density and also soil porosity along millimetric (0.08 cm) layers, what cannot be provided by traditional methods used in soil physics

    Risco de contaminação das águas de superfície e subterrâneas por agrotóxicos recomendados para a cultura do arroz irrigado

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    A produção agrícola geralmente está associada ao uso de agrotóxicos. Suas características físico-químicas, condições do solo e do ambiente determinam seu destino, assim como o seu potencial de contaminação dos mananciais hídricos. Com o intuito de prever a contaminação do ambiente por agrotóxicos, critérios e modelos matemáticos são utilizados para avaliar o risco de contaminação das águas subterrâneas e superficiais. Diante do exposto, este trabalho teve por objetivo estimar a probabilidade de contaminação de águas subterrâneas e superficiais por agrotóxicos, baseado nas suas características físico-químicas, com auxílio de modelos e parâmetros matemáticos preexistentes. Para análise do risco de contaminação de águas superficiais, foi utilizado o método de Goss, o qual é dividido em dois grupos: potencial de transporte de agrotóxicos dissolvidos em água e adsorvido ao sedimento. Os critérios utilizados para avaliar o potencial de lixiviação foram os sugeridos pela Agência de Proteção Ambiental dos EUA e pelo Índice de GUS. Os resultados obtidos neste trabalho permitem concluir que o uso de modelos de predição do comportamento de agrotóxicos é útil para se obter uma estimativa do risco de contaminação ambiental, pois alguns resultados de monitoramentos confirmam a tendência do comportamento de certos agrotóxicos no ambiente.Agricultural production is generally associated with the use of pesticides, their physicochemical characteristics, soil conditions and the environment will determine their fate, as well as the potential for contamination of water bodies. In order to predict environmental contamination by pesticides, parameters and mathematical models are utilized to assess the risk of contamination of groundwater and surface water. For this reason, the objective of this study was estimate the probability of contamination of groundwater and surface waters by pesticides based on their physicochemical characteristics with the aid of preexisting mathematical models and parameters. To analyze the risk of surface water contamination, the Goss method was used, which as composed by two groups: pesticide potential transport dissolved in water and adsorbed to the sediment. The parameter used to evaluate the leaching potential were those suggested by the US Environmental Protection Agency (EPA) and the GUS Index. The results obtained allow to conclude that the use of models to predict the behavior of pesticides is useful to obtain an estimate of the risk of environmental contamination, as some monitoring results confirm the tendency of the behavior of certain products into the environment

    Enraizamento de estacas lenhosas de pereira tratadas com AIB e mantidas em ambiente de estufa tipo B.O.D. e de telado Rooting of hardwood cuttings of pear tree with IBA under B.O.D. chamber and greenhouse environment

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    Pesquisou-se o enraizamento da pereira em ambiente controlado de estufa tipo B.O.D. e em telado simples. Utilizou-se a cultivar híbrida 'Limeira', destinada exclusivamente para fins culinários e para porta-enxerto. Estacas lenhosas sem folhas, medindo 25 cm de comprimento, foram tratadas com ácido indolbutírico (AIB) nas concentrações de 0; 2.000; 4.000 e 6.000 mg.L-1 por 10 segundos. Como substrato, utilizou-se da mistura de vermiculita e areia grossa (2:1 v/v), sendo a mesma umedecida com meio contendo solução salina MS e sacarose 1%. As estacas permaneceram por 42 dias dentro de estufas tipo B.O.D. (temperatura de 25ºC, umidade relativa do ar de 90% e fotoperíodo de 8 horas) e de telado com irrigação por microaspersão, sem controle ambiental. Em ambiente controlado de estufa, as estacas não-tratadas com AIB iniciaram intensa brotação das gemas e formação de calo após sete dias do plantio. Já em ambiente de telado, essas estacas demoraram 21 dias para o início de brotação das gemas, mostrando menor desenvolvimento de calo. Nas estacas tratadas com AIB, os calos surgiram nas regiões dos cortes após o terceiro dia de incubação na estufa B.O.D. As raízes desenvolveram-se a partir dos tecidos da base e dos calos, tornando-se mais nítidas a partir de 14 e 28 dias, respectivamente, para os ambientes de estufa e de telado. Após 42 dias, o melhor percentual de enraizamento (83%) foi verificado no tratamento com AIB a 2.000 mg.L-1, em ambiente de estufa B.O.D. O emprego dessa estufa, com temperatura, luz e umidade relativa controladas, mostrou-se viável em relação ao telado, no processo de enraizamento das estacas lenhosas da pereira 'Limeira', podendo favorecer o sistema de propagação vegetativa da pereira e encurtar o período da formação de mudas.<br>The rooting of cuttings pear under controlled environment of chamber (B.O.D. type) and greenhouse was searched. Hardwood cuttings of 'Limeira' pear, without leaves, measuring 25 cm of length, were treated with 0, 2000, 4000 and 6000 mg.L-1 of indolbutyric acid (IBA), for 10 seconds. The vermiculite and sand mixture substrate (2:1 v/v) was used and humidified with half contends MS saline solution and sucrose 1%. The cutting stayed per 42 days inside both B.O.D. chamber (temperature of 25ºC, relative humidity of 90% and photoperiod of 8 hours) and greenhouse with irrigation for aspersion, without environmental control. In B.O.D chamber, the cuttings not treated with IBA began an intense sprouting of the buds and callus formation after seven days of planting. On the other hand in greenhouse atmosphere, those cuttings delayed 21 days for the beginning of the bud sprouting, showing smaller callus development. In the cuttings treated with IBA, the callus appeared in the areas of the cuts after the third day of incubation in the stove B.O.D. The roots were developed starting from the tissues of the base and of the callus, becoming clearer from the 14th and 28th day, respectively, for the stove atmosphere and of greenhouse. After 42 days, the best rooting percentage (83%) was verified in the treatment with IBA at 2000 mg.L-1, in B.O.D chamber atmosphere. The utilization of B.O.D chamber, with controlled temperature, light and relative humidity, showed to be more advantageous than the process of greenhouse in the rooting of woody cutting of the 'Limeira' pear tree, that could favor the system of vegetative propagation of the pear tree and to shorten the period of formation of young plants
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