O fósforo (P) é um elemento altamente demandado pela agricultura mundial para produção de alimentos. Os solos de regiões tropicais apresentam baixo teor de P disponível às plantas, devido à escassez natural herdada do material de origem e predominância de processos de fixação, sendo necessário o suprimento deste nutriente via adubação. Os fertilizantes fosfatados solúveis utilizados apresentam baixo aproveitamento devido a reações que se iniciam desde a interface solo-grânulo até o trajeto difusivo do P no solo. Pesquisas têm abordado sobre o potencial do silício (Si) em competir por sítios de adsorção de P no solo, tornando este nutriente mais disponível às plantas e aumentando o aproveitamento dos adubos fosfatados. Visando desenvolver estratégias para melhorar a eficiência agronômica do fosfato monoamônio (MAP) os objetivos deste trabalho foram: a) construir um dispositivo para granular fertilizante em pequenas quantidades, b) avaliar a difusão e disponibilidade do P a partir dos fertilizantes produzidos, em dois solos de característica textural e capacidade máxima de adsorção de P contrastantes e c) avaliar a eficiência agronômica e o aproveitamento do P dos fertilizantes propostos neste estudo em conjunto com o superfosfato orgânico-complexado (SOC) e o MAP, por meio da técnica isotópica com 32P. Foram conduzidos quatro experimentos no Laboratório de Fertilidade do Solo do Centro de Energia Nuclear na Agricultura (CENA-USP), Piracicaba - SP. Os solos utilizados nos ensaios foram classificados como Latossolo Vermelho-Amarelo distrófico (LVAd) e Latossolo Vermelho distrófico (LVd). Conduzidos simultaneamente, o primeiro e segundo experimentos constituíram de estudo da difusão do P por meio da incubação dos fertilizantes em placa de petri preenchidas com cada um dos solos, montados em delineamento inteiramente casualizado, compostos por 11 tratamentos (9 fertilizantes com diferentes proporções P-Si (1-9 a 9-1) no grânulo mais o MAP e o tratamento controle) e cinco repetições. O terceiro e quarto experimentos foram instalados em casa de vegetação com a cultura do milho cultivada nos dois tipos de solo, num delineamento inteiramente casualizado, em esquema fatorial 5x4, sendo cinco fertilizantes fosfatados dentre os quais três foram selecionados no estudo de incubação (proporções P-Si no grânulo: 2-8, 6-4 e 8-2) o SOC e o MAP, aplicados em quatro doses de P (0, 30, 60, 90 mg kg-1). Foi possível construir o granulador projetado, e com uso deste produzir os fertilizantes propostos. No estudo de incubação, observou-se que a presença de Si no grânulo do fertilizante fosfatado alterou o pH do solo ao redor dos grânulo e a difusão e disponibilidade do P em ambos os solos estudados. O P difundiu-se poucos centímetros no solo, ficando restrito às primeiras secções em torno do ponto de aplicação do fertilizante. No experimento em casa de vegetação, observou-se que o fertilizante contendo a maior quantidade de Si no grânulo proporcionou maiores valores de P acumulado, P na planta proveniente do fertilizante e aproveitamento do P do fertilizante, bem como melhores índices de eficiência agronômica relativa em relação ao MAP. O SOC proporcionou os menores resultados em todos os parâmetros avaliados / Phosphorus (P) is a highly demanded element for world agriculture for food production. Tropical soils present low level of this nutrient in phyto-available form due to natural inherited shortage of source material and predominance of fixation processes, requiring the supply of this nutrient via fertilization. The soluble phosphate fertilizers used have low utilization by plants due to reactions that start from the soil-granule interface to the P diffusive path in the soil. Research has addressed on the silicon (Si) potential to compete for P adsorption sites in the soil, making this nutrient more available to plants and increasing the use of fertilizer P. In order to develop strategies to increase the agronomic efficiency of monoammonium phosphate (MAP) the objectives of this study were: a) to build a device for the production of granulated fertilizer in small quantities b) assess the diffusion and availability of P from the fertilizer produced in two contrasting textural characteristics and maximum P adsorption capacity and c) evaluate the agronomic efficiency and utilization of P from fertilizers proposed in this study compared with the organic-complexed superphosphate (OCS) and MAP by 32P isotope technique. Four experiments were conducted at the Soil Fertility Laboratory of Center for Nuclear Energy in Agriculture (CENA-USP), Piracicaba SP, Brazil. The soils used in the experiments were classified as Oxisol and Haplortox collected from the surface layers. The first and second experiments, conducted simultaneously, constituted the fertilizer incubation study in petri dishes in a completely randomized design with 11 treatments (9 fertilizer with different P- Si proportions (1-9 to 9-1) in the granule, plus the MAP and the control) and five replicates. The third and fourth experiments were conducted in a greenhouse with corn grown in the two types of soil in a completely randomized 5x4 factorial design, with five phosphate fertilizer among which three were selected in the study of incubation (proportions P-Si in the granule: 2-8, 6-4 and 8-2), OCS and MAP applied in four rates of P (0, 30, 60, 90 mg kg-1). It was possible to build the projected granulator, and use this to produce the proposed fertilizer. In the study of incubation, it was observed that the presence of Si in phosphate fertilizer granule changed the pH of the soil around the granules and the diffusion of P in both soils. The P diffused few centimeters in both soils, being restricted to the first sections around the applied granule. It was observed that, in the greenhouse experiment, in both soils, the fertilizer containing the highest amount of Si in the granule provided the highest plant accumulated P values, P in the plant derived from fertilizer and of fertilizer P utilization and best relative agronomic efficiency rate in relation to MAP and the OCS. The OCS gave the lowest results in all parameters

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The development of an accurate and precise geochronology is imperative to understanding archives containing information about Earth’s past. Unable to date all intervals of an archive, researchers use methods of interpolation to approximate age between dates. Sections of the radiocarbon calibration curve can induce larger chronological uncertainty independent of instrumental precision, meaning even a precise date may carry inflated error in its calibration to a calendar age. Methods of interpolation range from step-wise linear regression to, most recently, Bayesian statistical models. These employ prior knowledge of accumulation rate to provide a more informed interpolation between neighboring dates. This study uses a Bayesian statistical accumulation model to inform non-sequential dating of a sediment core using a high-throughput gas-accepting accelerator mass spectrometer. Chronological uncertainty was iteratively improved but approached an asymptote due to a blend of calibration uncertainty, instrument error and sampling frequency. This novel method resulted in a superior chronology when compared to a traditional sediment core chronology with fewer, but more precise, dates from the same location. The high-resolution chronology was constructed for a gravity core from the Pigmy Basin with an overall 95% confidence age range of 360 years, unmatched by the previously established chronology of 460 years. This research reveals that a larger number of low-precision dates requires less interpolation, resulting in a more robust chronology than one based on fewer high-precision measurements necessitating a higher degree of age interpolation.

The geology and mining industries rely heavily on reliable quantitative data on the elemental composition of various rocks and minerals. The analytical accuracy of the best measurement systems are, however, limited to the accuracy with which the composition of a generally accepted reference sample is known, which serves to calibrate an instrument or validate a method. Thus, there is an established market for well-characterised reference materials which trade internationally as value added commodities. International organisations prepare strict procedures for the preparation and certification of these reference materials. ISO/REMCO is the ISO Committee on Reference Materials that carries out and encourages a broad international effort for the harmonisation and promotion of reference materials, their production and their application. In view of recent developments in ISO/REMCO related to updated guides and changes in definitions, SARM 1 to 6 (the NIMROCs) are in danger of losing their status as certified reference materials (CRMs). Due to the continued popularity of the NIMROCs and the availability of bulk sample, the National Metrology Institute of South Africa (NMISA) embarked on a project to re-certify three materials from the suite of six igneous rock samples, i.e. SARM 2 (Syenite), SARM 3 (Lujavrite) and SARM 4 (Norite). The aim of the re-certification project was to re-certify the materials with a single primary reference measurement procedure in a single laboratory to comply with one of the possible routes to the establishment of metrological traceability as described in ISO Guide 34. Eight elements (Ba, Sr, Cd, Mo, Cu, Ni, Pb and Zn) of SARM 2, SARM 3 and SARM 4 were value assigned during this study to ensure that they comply with the ISO Guide 30 and ISO GUM requirements for traceability and measurement uncertainty. Traceability to the SI units of mass and amount of substance at the highest level of accuracy was established by employing the definitive technique of double isotope dilution ICP-MS, with primary assay standards traceable to the NIST SRM 3100 series and gravimetrically prepared samples. For the first time assigned values with uncertainty statements for these elements in these reference materials were calculated according to the ISO GUM and CITAC/EURACHEM guidelines for expression of the uncertainty of measurement. The uncertainties of the assigned values for all elements were within the target of 5% relative set during the development of the methodology, except for elements in concentrations below 10 mg.kg-1. The ID-ICP-MS results are supported by good comparability with results reported in the literature since 1978, as well as the original certified values published in 1978. The results from this study for all elements in these reference materials have the potential to become new certified values in accordance with the requirements of ISO Guides 34 and 35. This will improve the usefulness of these reference materials to the South African and international geology and mining communities for the purposes of analytical quality control and method validation in exploration and geochemical analysis. Confirmation of the homogeneity and stability of the remaining units of the reference materials is considered necessary to complete the re-certification project. / Thesis (PhD)--University of Pretoria, 2010. / Chemistry / unrestricted

No description available.

Le mercure est un contaminant présent dans l'ensemble des compartiments de l'environnement et l'homme y est directement exposé via l'alimentation. Actuellement, les organismes gouvernementaux évaluent la sécurité des produits alimentaires en se basant essentiellement sur la concentration totale de cet élément. Cependant, la toxicité du mercure dépend, entre autre, de l'espèce absorbée (dont le méthylmercure, sa forme la plus toxique). Par conséquent, l'analyse de spéciation, c'est à dire la détection et quantification des différentes formes chimiques de cet élément, présente un intérêt croissant. Le principal objectif de ce projet a donc été de développer et de valider, sous assurance qualité, une méthode sensible et d'une grande exactitude, basée sur l'utilisation de la dilution isotopique. Elle sera par la suite appliquée comme méthode de référence par l'agence pour l'analyse en spéciation du mercure dans les produits de la pêche afin de permettre une meilleure évaluation des risques encourus par le consommateur. La première partie de ce travail a porté sur l'étude du cycle biogéochimique du mercure et de l'état de l'art des diverses méthodes de préparation de l'échantillon, de séparation et de quantification du Hg dans les matrices biologiques, afin d'émettre des choix analytiques. Ainsi, les principaux composés mercuriels susceptibles d'être retrouvés dans les produits de la pêche (le méthylmercure et le mercure inorganique) ont été déterminés par couplage GC-ICP-MS et une quantification par dilution isotopique. La seconde partie des travaux a été consacrée à l'optimisation de la méthode de préparation des échantillons et de la technique de quantification. Ces travaux sur différents matériaux de référence certifiés ont montré que des modifications de la distribution naturelle de l'échantillon pouvaient survenir dès l'étape d'extraction, préconisant un marquage isotopique avant extraction solide-liquide par digiPREP des espèces mercurielles et dérivation par propylation par le tétrapropylborate de sodium et agitation rotative. Les résultats expérimentaux ont été traités par dilution isotopique simple et multiple. Les teneurs obtenues ont été similaires, pour l'ensemble des matrices analysées, montrant que peu ou pas de transformation inter-espèces surviennent au cours de la procédure analytique. Une quantification par double marquage isotopique et dilution isotopique simple a donc été conservée. L'évaluation des critères analytique a démontré que la méthode est validée pour la spéciation du mercure dans les produits de la pêche, selon les normes françaises AFNOR NF V03-110 de 1998 et de 2010. La dernière partie des travaux a porté sur l'application de la méthode validée à la spéciation du mercure dans des échantillons biologiques réels, ainsi qu'à la participation à plusieurs essais interlaboratoires d'aptitudes organisés par le CSL-FAPAS sur un échantillon de thon en conserve et par l'IRMM sur le matériau IMEP-109 de homard. / Mercury is a contaminant which is found in all compartments of the environment and to which human beings are directly exposed when eating food. Government agencies assess the safety of food products by using total mercury concentrations. However, its toxicity depends on the species absorbed (among which methylmercury is its most toxic form). Therefore, the analysis of speciation, i.e. detection and quantification of different chemical forms of this element, is of high interest. The main objective of this project was to develop and validate, under quality assurance, a sensitive and highly accurate method, based on the use of isotope dilution. This method will then be applied as a reference method by the agency for speciation analysis of mercury in seafood, in order to better assess risks to the consumer. The first part of this work focused on the biogeochemical cycle of mercury and the state of art of the various methods of sample preparation, separation and quantification of Hg in biological matrices in order to make analytical choices. Thus, mercury compounds (methyl mercury and inorganic mercury) were determined by gas chromatography (GC) coupled with an inductively coupled plasma mass spectrometer (ICP-MS) and quantified by isotope dilution. The second part of the work was dedicated to the optimization of the method of sample preparation and the quantification technique. The work was made on different certified reference materials and showed that changes of the natural distribution of the sample could occur during the extraction step. Therefore, isotopic tracers had been added to the sample before this step. Mercury species were extracted by a solid-liquid extraction by using a digiPREP and derivated by propylation using tétrapropylborate the sodium and a rotary agitation. Data were treated by simple and multiple isotope dilution. Achieved concentrations were similar for all analyzed matrices. Results showed that inter-species transformation hardly occurred during the analytical procedure. This was the reason why the use of two isotopic tracers for quantification by simple isotope dilution was kept. To end, the method was validated for the speciation of mercury in seafood, in respect with the French norms AFNOR NF V03-110 of 1998 and 2010. Finally, the work ended with the applicability of the validated method for mercury speciation analysis in real biological samples and our participation in several inter-laboratory proficiency tests organized by the CSL-FAPAS on a sample of tuna and by the IRMM on the material IMEP-109 (lobster).

A ciclagem do nitrogênio (N) apresenta dinâmica complexa, pelas múltiplas transformações e por sua mobilidade no sistema solo-planta-atmosfera. Assim, o estudo das taxas de conversão do ciclo interno de N é fundamental, visto que essas taxas têm efeito direto na produtividade e na qualidade ambiental de um agroecossistema. O objetivo deste trabalho foi avaliar o efeito da temperatura e umidade na taxa de mineralização bruta de N (TMB) em solos cultivados com canade- açúcar no estado de São Paulo, e por meio de modelo matemático, estimar a TMB considerando as variações de temperatura e umidade do solo in situ. Foram utilizados um LATOSSOLO VERMELHO distrófico (LVd) e um LATOSSOLO VERMELHO eutrófico (LVe), coletados nos municípios de Piracicaba e Santa Cruz das Palmeiras, respectivamente. As amostragens foram realizadas nas camadas de 0-10, 10-20 e 20-30 cm do solo, em julho de 2010. A quantificação da TMB em laboratório foi realizada por meio de incubações nas temperaturas de 15, 20, 25 e 30 °C, além de quatro umidades (30, 40, 60 e 80 % da capacidade máxima de retenção de água - CMRA). Foi utilizada a técnica da diluição do isótopo 15N, com aplicação de solução de (15NH4)2SO4 nas amostras de solo e determinação do teor de N-NH4 + e da abundância isotópica 48 e 96 h após a marcação. A simulação da mineralização bruta em condições de campo foi efetuada por meio das isotermas da TMB juntamente com dados de umidade e temperatura do solo dos dois ensaios. O período modelado ocorreu entre as fases de adubação e colheita da soqueira. O conteúdo de N-NH4 + do solo apresentou valores reduzidos nas diferentes temperaturas, independentemente da camada, umidade e tipo de solo. As TMB foram relativamente baixas (menores que 2,5 mg kg-1 dia-1 de N) para todos os tratamentos. Em geral, a taxa de consumo bruto (TCB) foi maior que a TMB, indicando alta imobilização/nitrificação. Foi verificado estímulo na TMB com o aumento da umidade e temperatura, para ambos os solos. A TMB e TCB foram maiores na temperatura de 25 °C e a 60 % da CMRA. A modelagem matemática indicou maior TMB entre os meses de novembro a março, marcada pelas chuvas intensas e temperaturas elevadas. O acúmulo de N-NH4 + amonificado durante os meses simulados alcançou 133 e 91 kg ha-1 para os solos LVe e LVd respectivamente.. A metodologia de diluição do isótopo 15N é uma potencial ferramenta para quantificar a mineralização de N / The N cycling has a complex dynamics, due to the multiple transformations and its mobility in the soil-plant-atmosphere. Thus, the study of the conversion rates of the N internal cycle is crucial because these rates have direct effect on yield and environmental quality of an agroecosystem. The aim of this study was to evaluate the effect of temperature and humidity on gross N mineralization (GNM) in sugarcane cropped soils in São Paulo state, and through mathematical model estimates the GNM considering the variations of soil temperature and humidity in situ. Was used a Typic Hapludox (TH) and a Typic Eutrustox (TE), sampled in the cities of Piracicaba and Santa Cruz das Palmeiras respectively. Samples were taken at 0-10, 10-20 and 20-30 cm soil, in July 2010. Quantification of GNM in the laboratory was performed by incubation at 15, 20, 25 and 30 °C, and four humidities (30, 40, 60 and 80 % of the water holding capacity - WHC). Was used the 15N isotope dilution technique, with application of (15NH4)2SO4 solution in the soil samples and subsequent determination of N-NH4 + and isotopic abundance after 48 and 96 h of labeling. The simulation of gross mineralization under field conditions was performed through the GNM isotherms and the data from soil moisture and temperature of the two sites. The modeled period was between the N fertilization and sugarcane harvesting phases. The N-NH4 + soil content showed reduced values at different temperatures, regardless of layer, moisture and soil type. The GNM were relatively low (less than 2.5 mg kg-1 day-1 of N) for all treatments. In general, the gross consumption (GC) was higher than the GNM, indicating high immobilization/nitrification. Stimulation was observed in GNM with increasing humidity and temperature, in both soils. The GNM and GC were higher at 25 °C and 60 % of WHC. Mathematical modeling indicated higher GNM between the months November to March, marked by heavy rains and high temperatures. The accumulation of mineralized N-NH4 + in the model achieved 133 and 91 kg ha-1 for soils and LVe LVd respectively. The 15N isotope dilution method is a potential tool to quantify the N mineralization.

gamma-Lactones are found in a wide variety of food and beverage products, in particular grapes and wine. This thesis details the work completed on some gamma-lactones in wine: their synthetic preparation, development of quantification methodologies and sensory studies. Chapter 1 outlines the history of the Australian wine industry from the arrival of the first vines on the First Fleet in 1788 with Captain Arthur Philip. This chapter provides: an overview of Australia’s position in the world of grape and wine production; an analysis of the export arm of the industry; and a look at the different wine producing regions around the country. The latter part of the chapter focuses on the different volatile compounds found in wine. Part A: Chapter 2 provides an overview on the history of barrel manufacture and the use of oak wood in cooperage, with an emphasis on oak’s well known ability to impart desirable characteristics to wine through the extraction of volatile aroma compounds. This chapter provides a summary of these odorants with a particular emphasis on the oak lactones. Previous sensory studies and synthetic work are discussed. Of great importance to this work are the recent advancements in 1,2-dioxine chemistry, highlighted in this chapter. Chapter 3 details the synthetic work completed for the preparation of all four possible oak lactone stereoisomers. A suitably substituted racemic 1,2-dioxine featured as the common intermediate and enabled preparation of the gamma-lactone moiety upon reaction with a chiral malonate diester and separation of the diastereomers by column chromatography. A key step involved the decarboxylation of the ester cleaved gamma-lactone diastereomers, which could be directed to give either the cis- or trans-products. Standard chemical transformations were then utilised to produce the desired stereoisomers of oak lactone. Chapter 4 describes the results from the sensory studies that were completed on the synthetic oak lactone samples. Odour detection thresholds were measured in both a white and a red wine. The thresholds in the former medium were calculated to be 24 ug/L, 172 ug/L, 132 ug/L and 305 ug/L, while in the latter medium the thresholds were calculated to be 57 ug/L, 380 ug/L, 175 ug/L and 285 ug/L, for (4S,5S)-cis-, (4S,5R)-trans-, (4R,5R)-cis- and (4R,5S)-trans-oak lactone, respectively. Difference testings were completed on the pairs of enantiomers and also on mixtures of the nature-identical isomers: between the cis-enantiomers a significant difference was found at the 99% confidence level, while between the trans-enantiomers and also the mixtures of cis- and trans-isomers little difference was observed. Chapter 5 contains the experimental procedures for Part A. Part B: Chapter 6 discusses the sensory properties of some gamma- and delta-lactones, with the focus on a series of five-alkyl substituted gamma-lactones: gamma-octalactone, gamma-nonalactone, gamma-decalactone and gamma-dodecalactone. Topics covered in this chapter include chirality, biosynthetic pathways and quantification results in wine from previous studies for these gamma-lactones. Chapter 7 concerns the method development for the quantification of gamma-lactones in wine using a stable isotope dilution assay (SIDA). Deuterated analogues were prepared from commercially available racemic gamma-lactones for use as internal standards. Initially a head space solid-phase microextraction (HS SPME) method was developed using d5-standards; however, analysis of bottled wine samples revealed the presence of co-eluting compounds that contained several of the selected ions. Thus an alternative method was developed using d7-standards, with a specific focus on sample clean-up, via solid-phase extraction (SPE). Using this procedure, 44 white and 120 red wines were analysed for their gamma-lactone content. The lactones were found to be significantly more common in the red wines, with gamma-nonalactone the most abundant lactone in this series. Chapter 8 deals with the extension of the SIDA method, as developed in Chapter 7, for use with a chiral gas chromatography column. Optically pure standards were prepared, from either L- or D-glutamic acid, and used to determine the order of elution of the enantiomers. A method was developed for the quantification of the individual enantiomers of gamma-octalactone, gamma-nonalactone, gamma-decalactone and gamma-dodecalactone. The enantiomeric distribution of gamma-nonalactone was investigated in 34 red wines; the (R)-stereoisomer was found to be dominant with an average of 59%, although there were wines analysed that did contain the (S)-stereoisomer in greater amounts. Chapter 9 describes the results from the sensory studies that were completed on the individual enantiomers of the gamma-lactones. Odour detection thresholds were measured in a red wine. The thresholds were calculated to be 238 ug/L, 285 ug/L, 34 ug/L and 8 ug/L for the (R)-enantiomers, while the thresholds were calculated to be 135 ug/L, 91 ug/L, 47 ug/L and 39 ug/L for the (S)-enantiomers, of gamma-octalactone, gamma-nonalactone, gamma-decalactone and gamma-dodecalactone, respectively. Chapter 10 contains the experimental procedures for Part B. Chapter 11 contains the appendices, followed by the references in Chapter 12.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 152-160). Also available in electronic format on the Internet.