• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 852
  • 692
  • 149
  • 98
  • 19
  • 18
  • 10
  • 10
  • 9
  • 8
  • 7
  • 6
  • 4
  • 3
  • 3
  • Tagged with
  • 2214
  • 312
  • 291
  • 257
  • 255
  • 235
  • 228
  • 212
  • 144
  • 135
  • 135
  • 134
  • 132
  • 129
  • 127
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
371

Numerical Studies on the Effects of Atmospheric Radiation on the Evolution of Tropical Cyclones / 大気放射が台風の発達に及ぼす影響に関する数値的研究

Xu, Menggeng 25 March 2024 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第25124号 / 理博第5031号 / 新制||理||1717(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 竹見 哲也, 教授 榎本 剛, 教授 向川 均 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM
372

Intraseasonal Variations In Sea Level Pressure And Association With Tropical Convection

Kiranmayi, L 01 July 2008 (has links)
This thesis deals with tropical intraseasonal variation (TISV) having time scales in 20-80 day range. Variations on this time scale have been observed to have profound influence on the weather and climate of the entire globe, and hence its study forms an important area of current research. A large number of studies have been carried out on this topic since the pioneering work of Madden and Julian in 1971. However, the observational studies are biased towards using the outgoing longwave radiation (OLR) as the variable of interest, and other variables, pressure in particular, have received less attention. The present thesis explores features of intraseasonal variations in sea level pressure (SLP) with the following main objectives. 1. Compare and contrast wavenumber – frequency spectra of OLR, zonal winds and SLP. 2. Quantify temporal and spatial variations of different tropical modes observed in the above variables. 3. Investigate intraseasonal variations in sea level pressure in the tropics and its meridional connections. 4. Document the movement of cloud bands during the periods of high and low TISV activity during different seasons. 5. Explore the relations between intraseasonal variations in SLP and monsoon rainfall over India. The study considered global data for a time period of 25 years from 1979 to 2003. Spectral analysis and correlations are the main tools of analysis. A combined FFT-wavelet spectral method, which uses FFT in longitude and wavelet transform in time, was developed for this purpose. This method provided an effective way of obtaining wavenumber - frequency spectra as well as in quantifying temporal variations of different modes. The transform gives spectral intensity as a function of wavenumber, frequency and time. The analysis is applied to OLR, zonal wind and SLP to understand spectral characteristics of different modes and their temporal variations. The thesis shows that the nature of spectra for OLR, SLP and wind is different although these variables are physically connected. OLR spectrum shows many of the equatorial modes observed from the previous studies for an equivalent depth of 40 m. Spectra of zonal winds at three vertical levels (850 mb, 500 mb and 200 mb) shows peaks corresponding to MJO, Kelvin modes at an equivalent depth of 75 m and Rossby Haurwitz modes. SLP spectrum is different from others. It has peaks at wavenumber zero and at MJO and Rossby Haurwitz modes. Another important new result of the thesis is the spatial and temporal behavior of SLP on intraseasonal time scales. It is shown that the the global atmosphere exhibits quasi-periodic oscillations in SLP with variations in the tropics and high latitudes strongly correlated but in opposite phases. Importantly, the strength of TISV is correlated with sea surface temperature (SST) anomalies in the equatorial Pacific Ocean. This may have some predictive value for predicting the active and weak TISV activity.
373

As áreas tropicais úmidas e as febres hemorrágicas virais: uma abordagem geográfica na área ambiental e na de saúde / The humid tropical areas and the infectious hemorrhagic diseases: a geographical approach of the Earth environmental and the humans\' health

Moraes, Paulo Roberto 17 August 2007 (has links)
Os ambientes terrestres têm sido gradativamente alterados pelo ser humano, mas a partir da Revolução Industrial, o homem começou a atuar de maneira mais intensa sobre o meio, fazendo com que as modificações ambientais tomassem proporções alarmantes, tanto em velocidade quanto em dimensão. As mudanças, como as climáticas, hídricas e biológicas, entre outras, ocorridas durante o século XX foram as maiores já registradas. As alterações ambientais associadas ao quadro demográfico do mundo contemporâneo, às condições socioeconômicas e à revolução técnico-científico-informacional que interligou o mundo, acabaram resultando em um cenário nunca vivenciado pela humanidade e ao mesmo tempo preocupante, tanto para saúde ambiental da Terra como para a humana. Se por um lado essa situação, baseada principalmente no avanço tecnológico, resultou numa verdadeira revolução nas taxas de mortalidade e na esperança de vida, por outro lado criou um ambiente que vem facilitando a emergência e reemergência de doenças, que pode comprometer o próprio futuro. Esse estudo tem por objetivo principal dar subsídios para o acesso a um conhecimento integrado, em escala global, tanto das alterações ambientais das áreas tropicais úmidas e do quadro socioeconômico dos países localizados nessa faixa tropical, quanto do surgimento e/ou expansão de quatro doenças infecciosas de caráter hemorrágico - dengue hemorrágica, febre amarela, marburg e ebola - no período de 1981 a 2005. No campo teórico-metodológico, a Geografia, mediante as suas características científicas de transitar pelos campos das ciências naturais e humanas, devido ao seu objeto de estudo, ofereceu a sustentação científica necessária para a realização, enquanto o avanço tecnológico das comunicações e da informática, associado ao processo de globalização pelo qual o mundo passa, proporcionou uma realidade de trabalho totalmente nova, permitindo a execução operacional do estudo. Foram realizados levantamentos bibliográficos e estudos sobre aquecimento global, mundo tropical, devastação das florestas tropicais úmidas, condições socioeconômicas dos países localizados nesta porção do globo e expansão das doenças citadas nos últimos 25 anos. O conjunto dos dados foi transformado em uma tabela síntese e em material cartográfico que retrata a situação atual desses países, destacando o nível das condições sócio ambientais e o risco saúde em que se encontram. / The terrestrial environments have been gradually altered by human being but from the Industrial Revolution on, this process has been even more intensive, resulting in environmental modifications of fast, huge and alarming proportions. The changes, such as the climatic, hydric and biological ones, among others, that took place in the 20th century, were the largest registered. The environmental alterations, associated to the current demographic panorama, to the socioeconomic conditions and to the technical-scientific-informational revolution - that have linked the whole world - resulted in a scenario never before experienced by humanity and, at the same time, very preoccupying for the Earth environmental health as well as for the humans. If on one hand that situation, based mainly on the technological progress, has resulted in lower mortality rates and higher life expectancy at birth, on the other hand it has also created an environment that made the emergence and re-emergence of diseases much easier to occur, so that future may be at risk. This study intend to bring up subsidies that allow for access to global integrated knowledge, not only about the environmental changes in the countries located in humid tropical areas and their socioeconomic conditions, but also about the influence of these alterations on the appearance and/or expansion of four infectious hemorrhagic diseases - hemorrhagic dengue, yellow fever, marburg and ebola - in the period from 1981 to 2005. In the theoreticalmethodological field, Geography - in face of its scientific characteristics of acting on the fields of both natural and human sciences, due to its object of studying - offered the necessary scientific support for the study accomplishment, while the technological progress in Communications and Computer Sciences, associated to the current world process of globalization, provided a new view of working, which allowed the operational execution of this study. The study was also based on bibliographical researches in world warming, tropical world, deforestation of tropical rain forests, socioeconomic conditions of the countries where the forests are placed and in the expansion of the mentioned diseases over the past 25 years. The set of data were synthesized in a table and in cartographic material that show the socio environmental conditions and the health risk of these countries.
374

As áreas tropicais úmidas e as febres hemorrágicas virais: uma abordagem geográfica na área ambiental e na de saúde / The humid tropical areas and the infectious hemorrhagic diseases: a geographical approach of the Earth environmental and the humans\' health

Paulo Roberto Moraes 17 August 2007 (has links)
Os ambientes terrestres têm sido gradativamente alterados pelo ser humano, mas a partir da Revolução Industrial, o homem começou a atuar de maneira mais intensa sobre o meio, fazendo com que as modificações ambientais tomassem proporções alarmantes, tanto em velocidade quanto em dimensão. As mudanças, como as climáticas, hídricas e biológicas, entre outras, ocorridas durante o século XX foram as maiores já registradas. As alterações ambientais associadas ao quadro demográfico do mundo contemporâneo, às condições socioeconômicas e à revolução técnico-científico-informacional que interligou o mundo, acabaram resultando em um cenário nunca vivenciado pela humanidade e ao mesmo tempo preocupante, tanto para saúde ambiental da Terra como para a humana. Se por um lado essa situação, baseada principalmente no avanço tecnológico, resultou numa verdadeira revolução nas taxas de mortalidade e na esperança de vida, por outro lado criou um ambiente que vem facilitando a emergência e reemergência de doenças, que pode comprometer o próprio futuro. Esse estudo tem por objetivo principal dar subsídios para o acesso a um conhecimento integrado, em escala global, tanto das alterações ambientais das áreas tropicais úmidas e do quadro socioeconômico dos países localizados nessa faixa tropical, quanto do surgimento e/ou expansão de quatro doenças infecciosas de caráter hemorrágico - dengue hemorrágica, febre amarela, marburg e ebola - no período de 1981 a 2005. No campo teórico-metodológico, a Geografia, mediante as suas características científicas de transitar pelos campos das ciências naturais e humanas, devido ao seu objeto de estudo, ofereceu a sustentação científica necessária para a realização, enquanto o avanço tecnológico das comunicações e da informática, associado ao processo de globalização pelo qual o mundo passa, proporcionou uma realidade de trabalho totalmente nova, permitindo a execução operacional do estudo. Foram realizados levantamentos bibliográficos e estudos sobre aquecimento global, mundo tropical, devastação das florestas tropicais úmidas, condições socioeconômicas dos países localizados nesta porção do globo e expansão das doenças citadas nos últimos 25 anos. O conjunto dos dados foi transformado em uma tabela síntese e em material cartográfico que retrata a situação atual desses países, destacando o nível das condições sócio ambientais e o risco saúde em que se encontram. / The terrestrial environments have been gradually altered by human being but from the Industrial Revolution on, this process has been even more intensive, resulting in environmental modifications of fast, huge and alarming proportions. The changes, such as the climatic, hydric and biological ones, among others, that took place in the 20th century, were the largest registered. The environmental alterations, associated to the current demographic panorama, to the socioeconomic conditions and to the technical-scientific-informational revolution - that have linked the whole world - resulted in a scenario never before experienced by humanity and, at the same time, very preoccupying for the Earth environmental health as well as for the humans. If on one hand that situation, based mainly on the technological progress, has resulted in lower mortality rates and higher life expectancy at birth, on the other hand it has also created an environment that made the emergence and re-emergence of diseases much easier to occur, so that future may be at risk. This study intend to bring up subsidies that allow for access to global integrated knowledge, not only about the environmental changes in the countries located in humid tropical areas and their socioeconomic conditions, but also about the influence of these alterations on the appearance and/or expansion of four infectious hemorrhagic diseases - hemorrhagic dengue, yellow fever, marburg and ebola - in the period from 1981 to 2005. In the theoreticalmethodological field, Geography - in face of its scientific characteristics of acting on the fields of both natural and human sciences, due to its object of studying - offered the necessary scientific support for the study accomplishment, while the technological progress in Communications and Computer Sciences, associated to the current world process of globalization, provided a new view of working, which allowed the operational execution of this study. The study was also based on bibliographical researches in world warming, tropical world, deforestation of tropical rain forests, socioeconomic conditions of the countries where the forests are placed and in the expansion of the mentioned diseases over the past 25 years. The set of data were synthesized in a table and in cartographic material that show the socio environmental conditions and the health risk of these countries.
375

Quantification of Precipitation Asymmetries in Tropical Cyclones and Their Relationship to Storm Intensity Changes Using TRMM Data

Pei, Yongxian 12 October 2017 (has links)
The climatology of precipitation asymmetries in Tropical Cyclones (TCs) and their relationship to TC intensity changes using 16 years of data from the Tropical Rainfall Measuring Mission (TRMM) satellite. TC Inner core precipitation asymmetries were quantified using the Fourier wavenumber decomposition method upon the pixel level data of 3,542 TRMM TMI overpasses. Composites of wavenumber–1 and wavenumber 1–6 total precipitation asymmetries were constructed to show the distribution pattern under different storm motion speed, vertical wind shear and the combined effects of varying vertical wind shear and storm motion. Results indicate that motion–relative total precipitation asymmetry is located down–motion. The phase of motion–relative maximum asymmetry shifts cyclonically by adding the wavenumber–2–6 asymmetry to wavenumber–1. Shear is more dominant than motion on the distribution of precipitation asymmetry. The analysis of combined effects of motion and shear shows when shear is weak, and shear is to the left of motion, the precipitation asymmetry is explained more by storm motion. The main contributor to the general asymmetry pattern is from the moderate and heavy precipitation. The wavenumber 2–6 energy localizes the maximum heavy precipitation asymmetry. The quantified wavenumber 1–6 asymmetries is also applied to differentiate between different intensity change categories and the asymmetry evolution of a rapidly intensifying storm. The precipitation asymmetry properties of rapid intensification (RI) and non–RI storms are examined. The dataset of 2,186 global tropical storms through category 2 hurricanes is divided by future 24–h intensity change and includes storms with at least moderately favorable environmental conditions. The normalized wavenumber 1–6 asymmetries, indicates quantitatively that the lower asymmetry of precipitation is most strongly correlated with future intensity change. The precipitation field of non–RI storms are more asymmetric than RI storms. The 595 sampled overpasses are classified into 14 categories in the timeline of an RI event from 48 hours before RI until RI ends. The decrease of normalized wavenumber 1–6 asymmetries in the inner core region of all four types of precipitation several hours before RI onset was quantitatively demonstrated to be critical for TC RI.
376

A Variable Resolution Global Spectral Method With Finer Resolution Over The Tropics

Janakiraman, S 08 1900 (has links)
Variable resolution method helps to study the local scale phenomenon of interest within the context of global scale atmosphere/ocean dynamics. Global spectral methods based on spherical harmonics as basis functions are known to resolve a given function defined on the sphere, in an uniform manner. Though known for its mathematical elegance and higher order accuracy, global spectral methods are considered to be restrictive for developing mesh-refinement strategies. The only mesh refinement strategy available until now is due to the pioneering work of F. Schmidt. Schmidt transformation can study only one region with higher resolution. The study of tropical dynamics is an interesting theme due to the presence of teleconnections between various phenomena, especially Indian Monsoon and the El-Nino. The Inter-Tropical Convergence Zone (ITCZ)is a continental scale phenamenon. It is in the ITCZ, many monsoon systems and tropical cyclones do occur. To study such phenomena under variable resolution method, high resolution is required in the entire tropical belt. Hitherto such a kind of mesh refinement strategies were not available in global spectral models. In this work, a new variable resolution method is developed that can help to study the tropical sub-scale phenomena with high resolution, in global spectral models. A new conformal coordinate transformation named ’High resolution Tropical Belt Transformation(HTBT)’ is developed to generate high resolution in the entire tropical belt. Mathematical demonstrations are given to show the existence of additional conformal transformations available on the sphere, indicating additional degrees of freedom available to create variable resolution global spectral method. Variable resolution global spectral method with high resolution over tropics is created through HTBT. The restriction imposed by Schmidt’s framework that the map-ping factor of the transformation need to have a finite-decomposition in the spectral space of the transformed domain is relaxed, by introduction of a new framework. The new framework uses transformed spherical harmonics Bnm as basis for spectral computations. With the use of FFT algorithm and Gaussian quadrature, the efficiency of the traditional spectral method is retained with the variable resolution global spectral method. The newly defined basis functions Bnm are the eigenvalues of the transformed Laplacian operator . This property of Bnm provide an elegant direct solver for the transformed Helmholtz operator on the sphere. The transformed Helmholtz equations are solved accurately with the variable resolution method. Advection experiments conducted with variable resolution spectral transport scheme on the HTBT variable grid produces near-dispersion free advection on the tropical belt. Transport across homogeneous resolution regions produce very less dispersion errors. Transport of a feature over the poles result in severe grid representation errors. It is shown that an increase in resolution around the poles greatly reduces this error. Transport of a feature from a point close to poles but not over it, does not produce such representation errors. Fourth-order Runge-Kutta scheme improves the accuracy of the transport scheme. The second order Magazenkov time-scheme proves to be better accurate than the leap-frog scheme with Asselin filter. The non-divergent barotropic vorticity equation is tested with two exact solutions namely Rochas solution and Rossby-Haurwitz wave solutions. Each of the solution tests certain unique and contrasting characteristic of the system. The numerical behaviour of the solutions show non-linear interactions in them. The singularity at the poles, arising due to the unbounded nature of the latitudinal derivative of the map factor of HTBT, triggers Gibbs phenomena for certain functions. However the recent advances in spectral methods, especially spectral viscosity method and Boyd-Vandeven filtering strategy provide ways to control the Gibbs oscillation and recover higher accuracy; make the variable resolution global spectral method viable for accurate meteorological computations.
377

熱帶導數與熱帶反導數 / Tropical Derivatives and Anti-derivatives

王靜萍 Unknown Date (has links)
在這篇論文中,我們定義了熱帶導數和熱帶反導數.當我們對兩個相同的熱帶多項式求導數時,可能會得到不同的函數.為了克服此困難,我們限制在最大係數多項式下才求導數.熱帶導數的定義與古典導數相當不同.特別的是,我們有d/dxan⊙x^(⊙n)= an⊙x⊙n-1.將它線性化,我們得到d/dx[an⊙x^(⊙n)⊕an-1⊙x⊙n-1 ⊕…. a1⊙x⊕a0] = an⊙x⊙n-1 ⊕an-1⊙x⊙n-2⊕…⊕a1.我們將會解釋為什麼使用這種定義.導數對了解熱帶幾何很有幫助,它也引出了一些與古典導數相似的資訊.最後,我們討論如何定義及求熱帶多項式的熱帶反導數 / In this thesis, we define the tropical derivatives and anti-derivatives. When we differ- entiate two identical tropical polynomials, we might get two different functions. In order to overcome the diffculties, we restrict the polynomials to largest coeffcient polynomials to avoid unpredictable results when taking derivatives. The definitiion of the tropical derivatives is quite diffrent from the definition of classical derivatives. In particular, we have d/dxan⊙x^(⊙n)= an⊙x⊙n-1 . To extend it linearly, we obtain d/dx[an⊙x^(⊙n)⊕ a n-1⊙x⊙n-1 ⊕…. a1⊙x⊕a0] = an⊙x⊙n-1 ⊕a n-1⊙x⊙n-2⊕…⊕a1. We will explain why we use this kind of definition. The derivatives are helpful in understanding more about tropical geometry, and it carries out some information similar to classical derivatives. Finally, we discuss how to define and find tropical anti-derivatives for tropical polynomials. Keywords : Tropical derivatives, tropical anti-derivatives, tropical polynomials.
378

Effects of Arctic Geoengineering on Precipitation in the Tropical Monsoon Regions

Nalam, Adithya January 2017 (has links) (PDF)
Arctic geoengineering wherein sunlight absorption is reduced only in the Arctic has been suggested as a remedial measure to counteract the on-going rapid climate change in the Arctic. Several modelling studies have shown that Arctic geoengineering can minimize Arctic warming but will shift the Inter-tropical Convergence Zone (ITCZ) southward, unless offset by comparable geoengineering in the Southern Hemisphere. In this study, we investigate and quantify the implications of this ITCZ shift due to Arctic geoengineering for the global monsoon regions using the Community Atmosphere Model version 4 coupled to a slab ocean model. A doubling of CO2 from pre-industrial levels leads to a warming of ~ 6 K in the Arctic region and precipitation in the monsoon regions increases by up to ~15 %. In our Arctic geoengineering simulation which illustrates a plausible latitudinal distribution of the reduction in sunlight, an addition of sulfate aerosols (11 Mt) in the Arctic stratosphere nearly offsets the Arctic warming due to CO2 doubling but this shifts the ITCZ southward by ~1.5⁰ relative to the pre-industrial climate. The combined effect from this shift and the residual CO2-induced climate change in the tropics is a decrease/increase in annual mean precipitation in the Northern Hemisphere /Southern Hemisphere monsoon regions by up to -12/+17%. Polar geoengineering where sulfate aerosols are prescribed in both the Arctic (10 Mt) and Antarctic (8 Mt) nearly offsets the ITCZ shift due to Arctic geoengineering, but there is still a residual precipitation increase (up to 7 %) in most monsoon regions associated with the residual CO2 induced warming in the tropics. The ITCZ shift due to our Global geoengineering simulation, where aerosols (20 Mt) are prescribed uniformly around the globe, is much smaller and the precipitation changes in most monsoon regions are within ±2 % as the residual CO2-induced warming in the tropics is also much less than in Arctic and Polar geoengineering. Further, global geoengineering nearly offsets the Arctic warming. Based on our results we infer that Arctic geoengineering leads to ITCZ shift and leaves residual CO2 induced warming in the tropics resulting in substantial precipitation changes in the monsoon regions.
379

Deposição do mercúrio através da serapilheira na Mata Atlântica, Parque Estadual da Pedra Branca, RJ

Teixeira, Daniel Cabral 24 October 2017 (has links)
Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-10-24T16:58:28Z No. of bitstreams: 1 DanielCabralTeixeira.pdf: 2770074 bytes, checksum: 0d0c1bc812ba890678e907aec3eab6b6 (MD5) / Made available in DSpace on 2017-10-24T16:58:28Z (GMT). No. of bitstreams: 1 DanielCabralTeixeira.pdf: 2770074 bytes, checksum: 0d0c1bc812ba890678e907aec3eab6b6 (MD5) / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A Mata Atlântica, um hotspot mundial com grande diversidade de plantas e animais, está localizado na região mais industrializada do Brasil, uma fonte em potencial de elementos químicos para a atmosfera. Recentemente, foi descrito a entrada de Hg via serapilheira para o solo principalmente, após a captação estomática (poros foliares), agindo como via importante para o transporte deste poluente do ar para o solo durante o seu ciclo biogeoquímico. Este fluxo de mercúrio é mais evidente em florestas tropicais, que apresentam as maiores produções de serapilheira. O objetivo deste trabalho foi quantificar a concentração total do Hg na serapilheira, e estimar sua deposição no Parque Estadual da Pedra Branca, na cidade do Rio de Janeiro, durante o período de um ano. Foram analizadas, folhas de cinco espécies dominantes, para se avaliar a concentração de Hg nas folhas do dossel e testar as correlações com os parâmetros anatômicos foliares, tais como as freqüências estomáticas e tricomáticas. A média anual da concentração de Hg foi de 237+ 52 ng g-1 e o fluxo de 184 + 98 μg m-2 sobre uma produção de serapilheira de 7,6 t.ha-1. A concentração mensal de Hg variou de acordo com a temperatura de dois meses anteriores. A precipitação mensal teve uma forte correlação negativa com as concentrações de Hg somente durante os meses de altas temperaturas. Estas correlações confirmam a dependência com os eventos fisiológicos, controlados por processos bioquímicos que definem a abertura estomática, sendo mais eficiente durante altas temperaturas e solo sem deficiência hídrica. A concentração de Hg na folhagem do dossel revelou uma grande variação interespecífica de 60 ng g-1 em Metternichia príncipes; 84 ng g-1em Colubrina. glandulosa; 170 ng g-1 em Cordia trichotoma; 190 ng g-1 em Piptadenia gonoacantha; até 215 ng g-1 em Alchornea iricurana.. Uma correlação positiva ocorreu entre as concentrações de Hg e a densidade estomática, exceto pelas espécies com tricomas, demonstrando mais uma evidência da captação estomática e possível papel da adsorção superficial dos tricomas. Estes valores elevados, mesmo para áreas urbanas poluídas, mostram a complexidade dos fenômenos climáticos e fisiológicos que regem a captação de Hg em florestas tropicais. Esta captação potencial da Mata Atlântica deve ser considerada para sua conservação e preservação, uma vez que o destino do Hg, vindo da serapilheira, no solo é desconhecido. Devido ao status de poluente global do Hg, o desenvolvimento de leis internacionais para emissões atmosféricas de Hg, é crucial. / The Atlantic Forest, a hotspot in the world with a great diversity of plants and animals, is located in the most industrialized region of Brazil, a potential source of chemical elements for the atmosphere. Recently, was described the Hg litterfall input to the soil mainly, after the stomatal (leaf pores) uptake, acting as an important way to transport this pollutant from air to soil. This flux of mercury is more notable in tropical forests, which have the higher annual litter production. The aim of this work was quantify the total concentration of Hg in litterfall, and estimate how much was deposited in the Parque Estadual da Pedra Branca, na cidade do Rio de Janeiro. Leaves of the five most predominant species were analyzed to assess the Hg concentrations by canopy leaves and test the correlations with foliar anatomical parameters, such as stomatal and trichomatic frequency. The annual mean of Hg concentration was 237, 7+ 52 ng g-1 and the flux was 184, 2 + 98 μg m-2 over a 7,6 t.ha-1 of litter production. The past two months temperature was correlated to the monthly concentration deviation, showing the relation with biochemistry process ruling the plant growing. The monthly precipitation had a strong negative correlation with the Hg concentrations of the higher temperature months. These correlations confirm the dependency on physiological events, controlled by biochemistry processes that rule the stomatal opening, being optimal during high temperatures and soil with no water deficiency. The green foliage Hg concentration revealed a great interespecific variation, from 60 ng g-1 - Metternichia principes, 84 ng g-1 - Colubrina. glandulosa,170 ng g-1 - Cordia trichotoma, 190 ng g-1 - Piptadenia gonoacantha to 215 ng g-1 - Alchornea iricurana. There was a clear positive correlation between these concentrations and the stomatal density of these species, except by the species with trichomes, showing one more evidence of the stomatal uptake and the superficial trichomes adsorption roles. These results are very high even to a polluted urban area, and show the complexity of phenological and climatic phenomena that rules the Hg uptake in tropical forests. This potential uptake of Mata Atlantica must be considered for their conservation and preservation, once the Hg soil destination came from litter, is unknown. Due to the global Hg pollutant status, the development of international laws, to Hg air emissions, is crucial.
380

Construção e avaliação inicial de um trecho de pavimento asfáltico executado com misturas de solo tropical, fosfogesso e cal / Construction and initial evaluation of a stretch of asphalt pavement runs with mixtures of tropical soil, lime and gypsum

METOGO, Daniel Arthur Nnang 13 August 2010 (has links)
Made available in DSpace on 2014-07-29T15:18:21Z (GMT). No. of bitstreams: 1 Daniel Arthur Nnang 1.pdf: 7371846 bytes, checksum: 7f44feffcd51ca0d8112ebff33daa070 (MD5) Previous issue date: 2010-08-13 / Presently in Brazil, there is a real difficulty to reuse solid waste. Among them, the phosphogypsum, a byproduct of phosphatic acid production. The huge deposits of this waste become problematic both environmentally and economically. Therefore, researches are being conducted to find a reuse of this material in geotechnical engineering. In the specific case of its application in paving, beyond reuse waste, seek to reduce the exploitation of natural materials, traditionally used in construction of roads. Laboratory tests showed the possibility of use of phosphogypsum in paving when mixed with soil or chemically stabilizer. Thus, this study evaluates on field, the mechanical behavior of mixtures of phosphogypsum, tropical soil of Aparecida de Goiania-GO and lime, when used in base layers of asphalt pavement. For that, laboratory tests were performed to characterize the mixtures to be used on field and was constructed an experimental pavement with mixtures of soil (80%) + phosphogypsum (20%), soil (80%) + phosphogypsum (11%) + lime (9%), soil (91%) + lime (9%) and gravel (100%). During the experimental pavement construction, field tests specifics of paving were conducted, to check its good execution and evaluate its initial performance. To better understand the behavior of the experimental pavement, a second step of field tests was conducted, six months after the release of traffic. From this study, was been observed that both in laboratory and field, the mixture soil (80%) + phosphogypsum (11%) + lime (9%) was that which presented the best mechanical performances and can thus replace the gravel for construction of low cost pavement. However, care should be adopted to control the expansion of this mixture. / Atualmente, observa-se no Brasil uma real dificuldade de reaproveitamento dos resíduos sólidos. Dentre eles, tem-se o fosfogesso, subproduto da produção de ácido fosfático. Os gigantescos depósitos deste resíduo tornam-se problemáticos tanto do ponto de vista ambiental como econômico. Por esse motivo, estudos estão sendo realizados com o objetivo de encontrar uma reutilização desse material em geotecnia. No caso de sua aplicação em pavimentação, além de reaproveitar os resíduos, procura-se reduzir a exploração de materiais naturais tradicionalmente empregados em construção de estradas e vias urbanas. Ensaios laboratoriais mostraram a possibilidade de uso do fosfogesso em pavimentação quando associado aos solos locais e misturas estabilizadas quimicamente. Sendo assim, neste trabalho avalia-se o comportamento mecânico em campo de misturas de fosfogesso, solo tropical da região de Aparecida de Goiânia-GO e cal, quando usadas em camadas de base de pavimento asfáltico. Para tanto, foram realizados ensaios de laboratório para caracterizar as misturas a serem executadas em campo e construída uma pista experimental constituída por subtrechos com misturas solo (80%) + fosfogesso (20%), solo (80%) + fosfogesso (11%) + cal (9%), solo (91%) + cal (9%) e cascalho (100%). Durante a construção dessa pista, foram realizados ensaios de campo próprio à pavimentação, para checar a boa execução da pista e avaliar o comportamento inicial do pavimento. Para entender melhor o comportamento da pista experimental, uma segunda etapa de ensaios de campo foi realizada seis meses após a liberação do tráfego. Deste trabalho, observou-se que tanto em laboratório como em campo, a mistura solo (80%) + fosfogesso (11%) + cal (9%) foi que apresentou os melhores desempenhos mecânicos, podendo assim substituir o cascalho para construção de pavimento de baixos custos. Porém, devem ser adotados cuidados para controlar a expansão dessa mistura. Palavras

Page generated in 0.035 seconds