Made available in DSpace on 2014-10-09T12:54:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:55Z (GMT). No. of bitstreams: 0 / Os radionuclídeos artificiais e naturais podem ser comumente encontrados em diversos compartimentos da crosta terrestre. Algumas espécies de cogumelos têm uma alta capacidade em absorver radionuclídeos e elementos tóxicos vindos do solo. A dieta alimentar destaca-se como uma das principais vias de contaminação radioativa. Portanto, a medida da radioatividade no ambiente e em alimentos é extremamente importante para monitorar os níveis de radiação aos quais o homem possa estar exposto de forma direta ou indireta. A biomonitoração ambiental tem demonstrado que diversos organismos como os crustáceos, peixes e cogumelos são usados para avaliar a contaminação e a qualidade dos ecosssistemas. Existem vários radionuclídeos que podem ser acumulados por cogumelos, incluindo 40 K, 137Cs, 232Th e 238U. No entanto há poucos estudos em países do hemisfério Sul, sobre os níveis de radioatividade natural e artificial em cogumelos. Este trabalho consistiu na determinação das atividades específicas de elementos radioativos naturais e 137Cs em cogumelos comestíveis comercializados em São Paulo-Brasil. As amostras de cogumelos comestíveis foram adquiridas em diferentes pontos comerciais da cidade de São Paulo, especialmente em mercados municipais, porém algumas foram adquiridas diretamente de produtores de algumas regiões como Mogi das Cruzes, Mirandópolis, Suzano e Juquitiba. Cerca de 400 g de cada espécie de cogumelos comestíveis foram coletadas, incluindo Agaricus sp, Lentinula sp e Pleurotus sp. Todas as amostras foram preparadas e acondicionadas em recipientes de polietileno, seladas e armazenadas por aproximadamente 35 dias, para que fosse estabelecido o equilíbrio radioativo secular, antes que se iniciassem as contagens. As atividades gama do 40K, 137Cs, 232Th e 238U foram medidas por espectrometria gama. O equipamento utilizado consistiu de um detector de Germânio Hiperpuro conectado a um sistema eletrônico. As medidas foram de aproximadamente 200000 segundos. A eficiência do detector foi medida utilizando os materiais de referência: IAEA-300, IAEA-327 e IAEA-375. Os resultados obtidos para as amostras de cogumelos comestíveis variaram de 461 a 1535 Bq kg 1, 1,4 a 10,6 Bq kg 1, 6,2 a 54,2 Bq kg 1 e 14 a 66 Bq kg 1 em peso seco, para 40K,137Cs, 232Th e 238U, respectivamente. Os níveis de 137Cs estão de acordo com o fallout radioativo do hemisfério Sul, apresentando concentrações abaixo dos níveis máximos estabelecidos pela CNEN. Comparando os resultados obtidos com outros trabalhos da literatura, comprovou-se que os valores das atividades encontradas para os radionuclíddeos naturais estão dentro dos níveis normais de radioatividade para este produto. As espécies de cogumelos analisadas podem ser consumidas sem riscos de contaminação. O método de análise empregado neste estudo demonstrou-se adequado para estimar a atividade 232Th e 238U e determinar as atividades de 40K e 137Cs, em amostras biológicas. Este estudo assinala a primeira vez em que cogumelos comestíveis, no Brasil foram estudados para avaliar o conteúdo radioativo e, como tal, é uma contribuição para investigações futuras nesta área. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

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O presente trabalho considera o problema de oxidação de matéria orgânica e inorgânica em esgoto sanitário através da ozonização, buscando aprofundar o conhecimento nos aspectos dúbios levantados em pesquisas conduzidas no Departamento de Hidráulica e Saneamento da EESC (Escola de Engenharia de São Carlos) na USP (Universidade de São Paulo) e também citadas na literatura da área. O projeto que tem cunho experimental utilizou uma coluna de ozonização de seção transversal quadrada de 0,19 m de lado e 2,00 m de altura, formada por duas faces paralelas de acrílico e duas faces paralelas de vidro, onde as bolhas de ozônio ascensionais eram fornecidas por um difusor microporoso instalado na base da coluna. Gerou-se um banco de dados acerca das características hidrodinâmicas das bolhas ascensionais (velocidade ascensional, porcentagem pontual da concentração, diâmetro equivalente e área interfacial específica), além de alguns parâmetros físicos e químicos (ozônio residual dissolvido e gasoso, temperatura, pH, alcalinidade, condutividade, turbidez, cor verdadeira, sulfeto, DQO, série de sólidos e série de carbono), localizados como relevantes ao processo de oxidação de matéria orgânica e inorgânica através da ozonização, variando a vazão de ozônio de 50 a 300 L/h e o nível líquido de 0,30 a 1,80 m. Constatou-se que o valor de todas as características hidrodinâmicas estudadas aumenta com o aumento da vazão de gás ozônio injetado no difusor microporoso. Vale mencionar que a velocimetria a laser não intrusiva foi a ferramenta utilizada na determinação da velocidade bi-dimensional ascensional das bolhas, além de auxiliar na determinação do diâmetro equivalente. Já a porcentagem pontual da concentração das bolhas foi determinada através da contagem de radiação de uma sonda de Césio-137. As análises dos parâmetros físicos e químicos mostraram de forma geral e repetitiva que a redução de pH e alcalinidade não foram influenciadas pela dosagem de ozônio aplicada; que a porcentagem de redução da DQO teve um comportamento oscilatório, ora influenciado ora não influenciado pela dosagem de ozônio aplicada; que a condutividade teve redução nula; e que a turbidez e a cor verdadeira tiveram influência da dosagem de ozônio na eficiência de redução. A observação dos experimentos permitiu inferir que tanto as características físicas como as características de qualidade do efluente influem no tipo de comportamento observado para a DQO em função do tempo de contato. Os comportamentos previstos pela solução de equações básicas geradas para explicar o efeito inibidor de compostos intermediários permitiram obter evoluções monotonicamente crescentes ou monotonicamente decrescentes no tempo, além dos comportamentos oscilatórios da eficiência de redução da DQO observados neste trabalho. Os resultados experimentais das velocidades ascensionais, perfis da concentração das bolhas, diâmetros equivalente e áreas interfaciais específicas, em conjunto com os parâmetros físico-químicos (ozônio residual dissolvido e gasoso, temperatura, pH, alcalinidade, condutividade, turbidez, cor verdadeira, sulfeto, DQO, série de sólidos e série de carbono), formam um banco de dados a ser utilizado nas simulações da coluna de ozonização que virão a decorrer do presente trabalho. As equações governantes aqui apresentadas são merecedoras de estudos posteriores para o entendimento da dinâmica existente nas colunas de ozonização e a busca da otimização de seu uso. / This present work is a study about the oxidation problem of organic and inorganic matter in sanitary effluent by means of the ozonation, trying to improve the knowledge of dubious aspects considered in prior researches conducted in Department of Hydraulic and Sanitation of the EESC (Escola de Engenharia de São Carlos) at USP (Universidade de São Paulo) and also found in specific studies. The project, which has experimental objective, used a column of ozonation of square transversal section of 0.19 m of side and 2.00 m of height with two parallel faces of acrylic and two parallel faces of glass, where bubbles of ozone in ascension were provided by a microporous diffuser installed in the base of the column. A file of data about hydrodynamic characteristics of the bubbles in ascension (velocity in ascension, punctual percentage of the concentration, equivalent diameter and specific interface area) was stored, besides some physical and chemical parameters (waste ozone dissolved and gaseous, temperature, pH, alkalinity, conductivity, turbidity, real color, sulphet, COD, set of solids and set of carbon), important to the process of inorganic and organic matter oxidation by means of ozonation, changing the flow of the ozone from 50 to 300 L/h and the liquid level from 0.30 to 1.80 m. It was noticed that the value of all hydrodynamic characteristics analysed increases when the flow of the ozone injected in the microporous diffuser also increases. It is important to mention that no-indisposition laser velocimetry was used as an instrument to determine the bi-dimension velocity of the bubbles in ascension and to help determine the equivalent diameter, whereas the punctual percentage of the concentration of the bubbles was determined by means of counting Cesium-137 radiation. Analysis of chemical and physical parameters showed in a general and repetitive way that the reduction of the pH and alkalinity was not influenced by the dose of ozone used; the percentage of COD reduction had oscillated behaviour, being or not influenced by the dose of the ozone used. It also showed that conductivity had zero reduction and turbidity and real color here influenced by the dose of the ozone in terms of efficient reduction. The observation of the experiments permitted to infer that both physical and quality characteristics of the effluent influence the type of the behaviour of COD versus contact time. The behaviour expected by the solution of basic equations done to explain the inhibiting effect of intermediate compounds permitted to obtain increasing and decreasing evolutions in time, as well oscillated behaviour of the efficiency of COD reduction observed in this work. The experimental results of the velocities in ascension, the profile of the bubble concentration, equivalent diameter and specific interface area with chemical and physical parameters (waste ozone dissolved and gaseous, temperature, pH, alkalinity, conductivity, turbidity, real color, sulphet, COD, set of solids and set of carbon) organize a file of data to be used in simulations of the ozonation column which will elapse from this present work. Specific equations here presented are worthy of further studies for the understanding of the dynamic present in the ozonation columns and the search of the optimization of its application.

Le 134Cs et le 137Cs, isotopes radioactifs du césium relâchés entre autres à la suite des accidents de Tchernobyl et Fukushima, sont des sources de préoccupations majeures pour la sécurité sanitaire et la protection des écosystèmes. La contamination des plantes est liée en partie à leur capacité à absorber le césium présent dans la solution du sol via des transporteurs. Le césium emprunte en effet, au moins en partie, le système de transport potassique sans disposer de transporteurs qui lui sont spécifiques. Il existe une grande diversité de transporteurs potassiques et la part du flux total qu’ils prennent en charge dépend du niveau de potassium fourni à la plante. Nous avons fait varier ce niveau et étudié son impact sur l’absorption et la distribution du césium dans la plante. Outre les phénomènes de compétition existant entre les deux éléments, le type de transporteurs dominant à un niveau de potassium donné a également une influence sur le transport du césium. Nous avons ainsi pu mettre en évidence des familles de transporteurs potassiques ayant de plus fortes chances d’être impliquées dans le transport de césium. Ainsi, les résultats produits pendant cette thèse mettent en évidence le rôle in planta du transporteur KUP9, jusque-là peu étudié, dans les flux de césium chez Arabidopsis thaliana. Nous n’observons pas de modifications de l’absorption du potassium chez les mutants invalidés sur ce transporteur : il serait donc possible de le manipuler pour moduler l’absorption de césium sans que la nutrition potassique ne soit altérée. / 134Cs and 137Cs, two radioactive isotopes unintentionally released after the Chernobyl and the Fukushima accidents, are of major concern for ecosystems protection and human health. Plants contamination is due to their ability to absorb cesium from the soil solution via transporters. Indeed, cesium which is supposed to have no role in plants can pass through potassium transporters. Proteins involved in potassium transport are diverse and the part of fluxes covered by each of them depends on the level of potassium supplied to the plant. We tested the effects of this level on uptake and distribution of cesium into the plant. Beside competition between the two elements, transporters which are dominant for a given potassium supply condition modify the cesium transport. Making the link between these modifications and knowledge on identity and properties of potassium transporters, we highlighted candidates with high potential for cesium transport. Hence, results produced during my thesis demonstrate in planta the role of KUP9 transporter, which has received little attention so far, in cesium fluxes in Arabidopsis thaliana. Changing in potassium uptake has not been observed in mutant lines disrupted in this KUP9 transporter suggesting interestingly that it could be possible to modulate cesium uptake without alteration of potassium nutrition.

No description available.

The first comprehensive analysis of surface waters in the Labrador Sea for 236U was completed via Accelerator Mass Spectrometry. Through the analysis of 236U the method for AMS measurement was fine-tuned to allow for more precise results. Surface samples for the anthropogenic isotopes 137Cs and 129I were also collected along with two depth profiles of 129I. Samples were also collected in the Beaufort Sea and analyzed for the aforementioned isotopes. It was found that anthropogenic 129I from reprocessing plants is easily discernible at different concentrations among water bodies in both the Labrador and Beaufort Sea. 137Cs in surface waters is close to global fallout levels with no discernable influence from reprocessing plant inputs, but follows a similar trend to that of 129I with depth in the Beaufort Sea. 236U among surface waters in the Labrador Sea did not follow the same trends as 129I but had concentrations indicative of a mix of global fallout as well as reprocessing plant influenced waters. 236U samples from the Beaufort Sea were contaminated by an unknown source of 236U and were inconclusive but were reproducible and allowed for continued development of the AMS analysis methodology.

Potassium is essential macroelement and large amount of potassium is taken up by plants, because it's the major osmotic of plant cell. Due to various potassium availability in different kinds of soil, plants have evolved transport system that can maintain sufficient K+ uptake between several orders of magnitude of potassium concentration. In Arabidopsis thaliana mechanism of K+ acquisition is well understood and it's known that AtHAK5 is mainly involved in K+ uptake in its very low concentrations. AtHAK5 belongs to KT/HAK/KUP family that consist 13 members in A. thaliana. There's known function for some members for example in auxin transport in root tip (TRH1) or in K+ efflux in stomatal closure (KUP6). In this thesis possible involvement of yet unstudied transporters KUP5, KUP7, KUP9 and KUP10 in K+ acquisition and homeostasis in A. thaliana was investigated. In vitro cultivation showed that kup9 mutant has very short lateral roots in K+ deficiency. On the other hand kup5 mutant showed significantly higher dry weight in K+ deficiency than Col-0. Kup9 phenotype was successfully replicated in subsequent cultivations and anatomy of lateral root apical meristems was investigated. Root tips of kup9 were differently organized in K+ deficiency and they showed signs of early termination of meristems. To...

The effects of Cs deposition on the field emission (FE) properties of single-walled carbon nanotube (SWNT) bundles were studied. In addition, a comparative study was made on the effects of O2, Ar and H2 gases on the field emission properties of SWNT bundles and multiwall carbon nanotubes (MWNTs). We observed that Cs deposition decreases the turn-on field for FE by a factor of 2.1 - 2.9 and increases the FE current by 6 orders of magnitude. After Cs deposition, the FE current versus voltage (I-V) curves showed non-Fowler-Nordheim behavior at large currents consistent with tunneling from adsorbate states. At lower currents, the ratio of the slope of the FE I-V curves before and after Cs deposition was approximately 2.1. Exposure to N2 does not decrease the FE current, while exposure to O2 decreases the FE current. Our results show that cesiated SWNT bundles have great potential as economical and reliable vacuum electron sources. We find that H2 and Ar gases do not significantly affect the FE properties of SWNTs or MWNTs. O2 temporarily reduces the FE current and increases the turn-on voltage of SWNTs. Full recovery of these properties occurred after operation in UHV. The higher operating voltages in an O2 environment caused a permanent decrease of FE current and increase in turn-on field of MWNTs. The ratios of the slopes before and after O2 exposure were approximately 1.04 and 0.82 for SWNTs and MWNTs, respectively. SWNTs compared to MWNTs would appear to make more economical and reliable vacuum electron sources.

Technological advancement and the quest for power have gradually contaminated our environment, as industrialization, agriculture, and nuclear activities progressed. In the year 1986, a terrible nuclear incident occurred in Ukraine, in which the nuclear reactor exploded. The explosion resulted in the release of radionuclides with a massive concentration of 137Cs and 131I. Among these,137Cs was the most persistent one having a half-life of 30.2 years. The137Cs spread to Sweden due to advection, dispersion,and diffusion by wind, fallout over by precipitation via adsorption, and absorption in northern parts of Sweden experiencing a heterogeneous distribution. This fallout affected both the terrestrial and aquatic environments. This research aims to investigate where the 137Cs went and how its concentration changed with time in Swedish mushrooms, lakes, and in the Gulf of Bothnia. Also, to search for the environment that holds137Cs for a longer period and why it is so. More than 30 years have passed since the incident, and it isexpected that 137Cs would have decayed to values of its half-life. Swedish food authority recommends that up to 10,000 Bq/kg of 137Cs in mushrooms is safe for human consumption. The advocated limitsfor fish and seawater are 1500 Bq/kg and 40 Bq/kg, respectively.The method embraced to answer the research questions is based on data from the Swedish Radiation Safety Authority, the Radiant Earth project between Uppsala University and SLU, and also the data published in the literature. Decay models were generated for 137Cs.These models help in explaining the processes of accumulation and extraction of 137Cs. A closer look is also given to processes that have animpact on factors such as weathering, erosion, wind, washout, and bioturbation, and the rate of intake in environments. The aquatic environment, because Gävleborg was most affected during the incident, the highest value in the fish measured in the year 1988 was 23,508 Bq/kg. However, after 31 years (2016), the value was 4.5 Bq/kg. The values for Jämtland, Västerbotten, and Västernorrland were also almost equivalent to those for Gävleborg, estimated in the year 2016 to be around 4.5 Bq/kg. Observations of water data in Gävleborg show a wide range between 2-996 Bq/kg. In the Gulf of Bothnia, the highest 137Cs value recorded for sediment data in the year 2003 was 310 Bq/kg, and the lowest value of 181 Bq/kg was observed in the year 2015. In terrestrial environments, the maximum value recorded for Craterellus tubaeformis mushrooms was 522,000 Bq/kg in the year 1987. On the other hand, the lowest value recorded for Chanterelle mushrooms was 101.5 Bq/kg in the year 2017. Observations from a sample collected in Uppsala in the year 2017 indicates a value of 15 Bq/kg. Several mushroom species (Chanterelle, Craterellus tubaeformis) had distinct concentrations within the same geographical area and time, i.e., the Västernorrland in the year 2017.Due to weathering and erosion, when 137Cs reaches a water body (sea, ocean, estuary, river, lake or wetland), it dissolves in the water increasing its concentration. As a result, it increases the overall concentration of 137Cs in the fish. The results show that most of the 137Cs is locked in the sediments, with time buried under new sediment. However, due to resuspension and bioturbation, the contaminants may end up in the aquatic environment again. Models for lakes show irregular behaviour since their sizes are not as large as seas and small intakes depict high concentrations. Based on the mushroom results, 137Cs concentrations have been greatly reduced compared with Chernobyl levels. Different mushroom species exhibit different levels of 137Cs in the same area. Most radionuclides are found in the top layer of organic soil, making this layer crucial for taking up 137Cscontamination. Over time, these radionuclides, including 137Cs, are buried beneath the soil layers and cease to contribute to the system.

Mesoporous silica gel containing embedded phosphotungstic acid (PTA) was synthesized by sol-gel co-condensation of tetraethoxysilane with PTA in acidic media. The obtained material had high BET surface area and pore volume. A characteristic band of the Keggin structure of PTA was present in its FT-IR spectrum while its XRD patterns were absent. This proved the embedding of PTA on a sub-molecular level. The material demonstrated high adsorption capacity of Cs. Unexpectedly, porosity of the adsorbent increased after substitution of most protons by cesium cations. Cation exchange also favored agglomeration of the material particles. Kinetic studies showed that the adsorption data correlates strongly with the pseudo-second order model. The adsorbent had two types of adsorption sites: heteropolyacid anions and silanol groups. However, adsorption on silanol groups was very sensitive to the temperature. At the increased temperature, the nature of adsorption fit the Langmuir model extremely well. The obtained results can be used in the development of an effective adsorbent for clean-up of water contaminated by radioactive cesium-137.