Tesi: "Chemical tracers"

1

Fahrenfeld, Nicole L. "Fecal coliform source identification using chemical tracers". Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219853511/.

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2

White, Iain Robert. "Novel applications of chemical tracers in the atmosphere and trace pollutant monitoring". Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509768.

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3

Robinson, Bruce A. "Non-reactive and chemically reactive tracers : theory and applications". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/17188.

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4

Lazzara, Matthew J. "Effects of plasma proteins on the sieving of macromolecular tracers in the kidney". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/38443.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003.
Includes bibliographical references (leaves 191-202).
The ultrafiltration of plasma in the mammalian glomerulus is the first step in the processing of blood by the kidney. Proper functioning of this process is critical to the kidney's ability to effectively eliminate waste and retain desirable substances. The glomerular barrier has long been regarded as both a size and charge selective screen for plasma solutes. The origin of this selectivity is found in the unique three-layered structure of the glomerular capillary wall (GCW), consisting of a fenestrated endothelium, the interdigitating foot processes of the glomerular epithelium, and the shared glomerular basement membrane (GBM). The selectivity properties of the GCW have commonly been probed by measuring the sieving coefficients of a variety of tracers, both proteins and exogenous polymers, across the intact glomerular barrier and across isolated components of the GCW. It was found previously that the sieving coefficients of the tracers Ficoll and Ficoll sulfate across isolated GBM were greatly elevated when BSA was present at physiological levels (Bolton et al. 1998). It was suggested that most of this increase was the result of steric interactions between BSA and the tracers which increased tracer partitioning from the bulk into the GBM. Such an effect, if present, would have important implications for the interpretation of macromolecular sieving studies, both in vivo and in vitro. The goals of this thesis research were to model the effect of an abundant protein on the partitioning of a dissimilar tracer molecule, to incorporate that effect into models for glomerular sieving, and to test the partitioning model by measuring the effect of protein concentration on the partitioning of protein and Ficoll in agarose gels. The theoretical effects of solute size on partition coefficients in straight pores or randomly oriented fiber matrices have been investigated previously for very dilute solutions, where solute-solute interactions are negligible, and also for more concentrated solutions consisting of spherical solutes of uniform size. For concentrated solutions it has been found that steric and other repulsive interactions among solutes increase the partition coefficient above the dilute limit. To extend the results for porous or fibrous media to include concentrated mixtures of solutes with different sizes or shapes, we used an excluded volume approach. In this formulation, which describes steric interactions only, partition coefficients were computed by summing all volumes excluded to a solute molecule by virtue of its finite size, the finite size of other solutes, and the presence of fixed obstacles (pore walls or fibers). For a mixture of two spherical solutes, the addition of any second solute at finite concentration increased the partition coefficient of the first solute. That increase was sensitive to the size of the second solute; for a given volume fraction of the second solute, the smaller its radius, the larger the effect. When the total volume fraction of solutes was fixed, an increase in the amount of a second, smaller solute increased the partition coefficient of the first solute, whereas an increase in the amount of a second, larger solute had the opposite effect. Results were obtained also for oblate or prolate spheroidal solutes and for fibrous media with multiple fiber radii. For constant total fiber volume fraction, an increase in the amount of a second, smaller fiber decreased the partition coefficient of a spherical solute, whereas an increase in the amount of a second, larger fiber had the opposite effect. Overall, the theory suggests that the introduction of heterogeneity, whether as mixtures of solute sizes or mixtures of fiber sizes, may cause partition coefficients to differ markedly from those of uniform systems. Using the excluded volume partitioning model, the theory for the sieving of macromolecular tracers was extended to account for the presence of a second, abundant solute. Using that theory, we returned to the experimental data of Bolton et al. (1998) and attempted to model the effect of protein concentration on Ficoll sieving. The osmotic reduction in filtrate velocity caused by an abundant, mostly retained solute will also tend to elevate the tracer sieving coefficient. The osmotic effect alone explained only about one third of the observed increase in the sieving coefficients of Ficoll and Ficoll sulfate, whereas the effect of BSA on tracer partitioning was sufficient to account for the remainder. At physiological concentrations, predictions for tracer sieving in the presence of BSA were found to be insensitive to the assumed shape of the protein (sphere or prolate spheroid). The effect of plasma proteins on tracer partitioning is expected to influence sieving not only in isolated GBM, but also in intact glomerular capillaries in vivo. To test the predicted effects of solute concentration on the equilibrium partitioning of single macromolecules and macromolecule mixtures, measurements of the equilibrium partition coefficients of BSA and four narrow fractions of Ficoll were made in agarose. Solutions of each test macromolecule were equilibrated with a known volume of gel, final liquid concentrations measured, and partition coefficients calculated by applying a material balance. The partition coefficient of each molecule was measured under dilute conditions and under conditions where BSA was present at concentrated levels. All measurements were made for two different gel solid volume fractions (4 and 6%). As expected, the partition coefficients decreased with increasing gel solid volume fraction and with increasing molecular size. Increasing BSA concentration caused an increase in the partitioning of BSA itself and that of all four sizes of Ficoll. This effect was most significant for the largest molecules. A subset of the measurements repeated at a higher ionic strength demonstrated that electrostatic interactions were unimportant. The experimental results were compared with predictions generated from the excluded volume partitioning theory. Agarose was represented as a randomly oriented array of cylindrical fibers, BSA was modeled as a prolate spheroid, and Ficoll was treated as a sphere. Comparisons of the theoretical predictions with the experimental data produced generally good agreement, indicating that steric interactions among solute molecules and between solute molecules and gel fibers could explain the partitioning behavior.
by Matthew Jordan Lazzara.
Ph.D.

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5

Antoniewicz, Maciek Robert. "Comprehensive analysis of metabolic pathways through the combined use of multiple isotopic tracers". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37457.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006.
Includes bibliographical references (p. 287-294).
Metabolic Flux Analysis (MFA) has emerged as a tool of great significance for metabolic engineering and the analysis of human metabolic diseases. An important limitation of MFA, as carried out via stable isotope labeling and GC/MS measurements, is the large number of isotopomer equations that need to be solved. This restriction reduces the ability of MFA to fully utilize the power of multiple isotopic tracers in elucidating the physiology of complex biological networks. Here, we present a novel framework for modeling isotopic distributions that significantly reduces the number of system variables without any loss of information. The elementary metabolite units (EMU) framework is based on a highly efficient decomposition algorithm identifies the minimum amount of information needed to simulate isotopic labeling within a reaction network using knowledge of atomic transitions occurring in the network reactions. The developed computational and experimental methodologies were applied to two biological systems of major industrial and medical significance. First, we describe the analysis of metabolic fluxes in E. coli in a fed-batch fermentation for overproduction of 1,3-propanediol (PDO).
(cont.) A dynamic 13C-labeling experiment was performed and nonstationary intracellular fluxes (with confidence intervals) were determined by fitting labeling patterns of 191 cellular amino acids and 8 external fluxes to a detailed network model of E. coli. We established for the first time detailed time profiles of in vivo fluxes. Flux results confirmed the genotype of the organism and provided further insight into the physiology of PDO overproduction in E. coli. Second, we describe the analysis of metabolic fluxes in the pathway of gluconeogenesis in cultured primary hepatocytes, i.e. isolated liver cells. We applied multiple 13C and 2H-labeled tracers and measured isotopomer distributions of glucose fragments. From this overdetermined data set we estimated net and exchange fluxes in the gluconeogenesis pathway. We identified limitations in current methods to estimate gluconeogenesis in vivo, and developed a novel [U-13C,2Hs]glycerol method that allows accurate analysis of gluconeogenesis fluxes independent of the assumption of isotopic steady-state and zonation of tracers. The developed methodologies have wide implications for in vivo studies of glucose metabolism in Type II diabetes, and other metabolic diseases.
by Maciek Robert Antoniewicz.
Ph.D.

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6

Jeansson, Emil. "Chemical tracers in the Nordic Seas : studies on water masses and anthropogenic carbon /". Göteborg : Göteborg University, Department of Chemistry, 2005. http://www.loc.gov/catdir/toc/fy0801/2006421403.html.

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7

Jardine, Angela Beth. "Aqueous Phase Tracers of Chemical Weathering in a Semi-arid Mountain Critical Zone". Thesis, The University of Arizona, 2011. http://hdl.handle.net/10150/144594.

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Chemical weathering reactions are important for the physical, chemical, and biological development of the critical zone. We present findings from aqueous phase chemical analyses of surface and soil pore waters during a 15 month study in a small semi-arid mountain catchment of the Santa Catalina Mountain Critical Zone Observatory. Stream water geochemical solutes are sourced to two distinct locations - fractured bedrock baseflow stores and soil quickflow stores. Solid phase observations of albite, anorthite, and K-feldspar transformation to Ca-montmorillonite and kaolinite are supported by stream water saturation states calculated via a PHREEQC geochemical model. While differences in mineral assemblages, soil depths, and horizonation suggest greater weathering in schist versus granite lithologies and in hillslope divergent versus convergent zones, soil pore water solute ratio analysis does not readily distinguish these differences. However, preliminary investigation of aqueous rare earth elements suggests detectable lithologic and landscape positional differences warranting focus for future research efforts.

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8

Kilgallon, Rachel. "Investigating the role of chemical and geochemical tracers for CO2 transport and storage". Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/21702.

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Changes in the atmospheric concentration of greenhouse gases and aerosols alter the energy balance of the climate system. CO2 is the most significant anthropogenic greenhouse gas. The primary source of the increased atmospheric concentration of CO2 since the preindustrial period is from fossil fuel exploitation. As the global need for energy is currently met by combustion of fossil fuels it is imperative that a method of reducing the levels of CO2 being emitted is used. Carbon capture and storage (CCS) is the combination of CO2 capture from large point sources, with the transport of CO2 to a suitable geological storage site where it can safely be contained. Geological CCS technology has the potential to a make a significant contribution to a low carbon technology future. As with any technology, it is imperative to identify techniques that could be used to form part of the monitoring programme. In this thesis, the role of chemical and geochemical tracers are investigated during the transport and storage of CO2. For the first part of this research, a review of the natural gas and CO2 pipeline network in North America and United Kingdom has been compiled from published literature and historical experience. Using this information, research was carried out to determine why odourising has been suggested for CO2 pipeline transport and what benefit it would add. Based on experience from natural gas, it is concluded that high pressure pipelines of CO2 through sparsely populated areas could have odourant added, but will gain little safety benefit. However, adding odourant to CO2 gas phase pipes could aid detection of leaks as well improve public assurance and should be considered in more detail. For the second part of this research, a specially constructed flow cell was designed and built to investigate how noble gases could be used as effective early warning tracers for CO2 migration in storage sites. From this equipment, experimental breakthrough curves for noble gases and SF6 travelling through a sample of Fell sandstone in relation to CO2 over a pressure gradient range of 10,000 – 50,000 Pa were generated. Although noble gases are described as conservative tracers, comparing the breakthrough curves over a range of pressure gradients show that they do not behave as simply as previously assumed. These results were then modelled using a one dimensional advective dispersion transport equation to fit curves to the experimental outputs using two different modelling approaches. A statistical approach can derive the input parameters for an analytical approach, which is needed to understand the dispersivity behaviour of the tracers. A set of values for the dispersivity of noble gases, SF6 and CO2 through porous media is presented in this research. Using a baseline value approach, initial arrival times for krypton and xenon from this research suggest that they could be used as a means of detecting CO2 migration. While helium, neon and argon appear to be unsuitable as early warning tracers for initial detection of CO2, this suggests that they can be used as part of mixture to fingerprint individual CO2 storage sites that may be in close proximity to one another. Results from the experimental and modelling analysis, identify a system where preferential paths exist depending on the change in pressure gradient. The different transport channels progress from a Darcy linear flow regime to a non-linear laminar flow. These results propose an explanation for the patterns observed from tracers in large-scale reservoirs but the output values obtained are limited by scale-dependence and would not be suitable for direct upscaling.

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9

DiPaola, Tracey Stickley. "Biological and Chemical Renovation of Wastewater with a Soil Infiltrator Low-Pressure Distribution System". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36809.

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An alternative on-site wastewater treatment and disposal system (OSWTDS) consisting of a soil infiltrator with low pressure distribution was evaluated in a soil that was unsuitable for a conventional OSWTDS under current Commonwealth of Virginia Sewage Handling and Disposal Regulations, due to a shallow seasonally perched water table and low hydraulic conductivity. The absorption field consisted of two subsystems numbered as 1 and 2 with effluent design loading rates of 5.1 and 10.2 Lpd/m2, respectively (actual loading rates of 2.4 and 4.9 Lpd/m2, respectively). Soil matric potentials compared seasonally for each subsystem and indicated that both provided similar hydraulic performance. Background water quality was generally improved by subsurface movement through the absorption fields. A bacterial tracer was found in shallow (45.7 cm) and deep (213.4 cm) sampling wells within 24 h in the two subsystems (but in low numbers) over both summer and winter sampling periods. A viral tracer was detected within 48 h in both shallow and deep wells, but only in subsystem 2 in the winter. In evaluating denitrification potential, the addition of glucose to soil core samples did increase quantitatively, although not significantly, nitrous oxide production in each subsystem, at each depth, during each season. Overall, the performance of both subsystems was very similar. The soil infiltrator functioned very well, as designed for the site and soil limitations. It appears to be a potential alternative OSWTDS for use in problem soils.
Master of Science

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10

Van, Heerden Michael Rudi. "Improving the selectivity of the radio-labelling of ion exchange resin tracers for positron emission particle tracking". Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/24310.

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Positron emission particle tracking (PEPT) is a technique which non-invasively tracks tracer particles labelled with a positron emitting radionuclide in a system of flow. The tracers are tracked through the detection in a PET scanner, of the two nearly collinear 511 keV gamma rays resulting from the annihilations of the positrons. For this technique to be effective, the tracer must be representative of the media in the system under study, and labelled with a sufficient activity of radionuclides. Organic ion exchange resins are suitable tracer materials for PEPT experiments, and are usually labelled with ⁶⁸Ga at the laboratories of PEPT Cape Town. The labelling performance relies on the chemical and physical properties of organic strongly acidic cation exchange resins and the nuclear chemistry of ⁶⁸Ga. The objective of this study is to obtain consistent tracer labelling throughout, or even beyond, the lifespan of the SnO₂ ⁶⁸Ge/⁶⁸Ga generator which degrades over time. The objective 1s achieved by integrating a purification technique into a "standard" radiolabelling method used at iThemba LABS. A small 0.5 ml Amberchrom CG-71 column is loaded with the ⁶⁸Ga generator eluent in 7 M HCl, then rinsed of most the contaminants before eluting the product with distilled water and used in the radiolabelling method. Using a 1-year-old 30 mCi SnO₂ ⁶⁸Ge/⁶⁸Ga generator eluent that has been purified by this method improved the radiolabelling performance by an average of at least 10% when compared to the performance of the un-purified product. Purifying the generator eluent will enable PEPT experiments of longer duration, and in highly shielded systems where tracers with high activity are required, such as granular and fluid flow in engineering applications.

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11

Manning, Cara Charlotte Marie. "Insight into chemical, biological, and physical processes in coastal waters from dissolved oxygen and inert gas tracers". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108917.

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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 185-213).
In this thesis, I use coastal measurements of dissolved O₂ and inert gases to provide insight into the chemical, biological, and physical processes that impact the oceanic cycles of carbon and dissolved gases. Dissolved O₂ concentration and triple isotopic composition trace net and gross biological productivity. The saturation states of inert gases trace physical processes, such as air-water gas exchange, temperature change, and mixing, that affect all gases. First, I developed a field-deployable system that measures Ne, Ar, Kr, and Xe gas ratios in water. It has precision and accuracy of 1 % or better, enables near-continuous measurements, and has much lower cost compared to existing laboratory-based methods. The system will increase the scientific community's access to use dissolved noble gases as environmental tracers. Second, I measured O₂ and five noble gases during a cruise in Monterey Bay, California. I developed a vertical model and found that accurately parameterizing bubble-mediated gas exchange was necessary to accurately simulate the He and Ne measurements. I present the first comparison of multiple gas tracer, incubation, and sediment trap-based productivity estimates in the coastal ocean. Net community production estimated from ¹⁵NO₃⁻ uptake and 02 /Ar gave equivalent results at steady state. Underway O₂/Ar measurements revealed submesoscale variability that was not apparent from daily incubations. Third, I quantified productivity by O₂ mass balance and air-water gas exchange by dual tracer (³He/SF₆ ) release during ice melt in the Bras d'Or Lakes, a Canadian estuary. The gas transfer velocity at >90 % ice cover was 6 % of the rate for nearly ice-free conditions. Rates of volumetric gross primary production were similar when the estuary was completely ice-covered and ice-free, and the ecosystem was on average net autotrophic during ice melt and net heterotrophic following ice melt. I present a method for incorporating the isotopic composition of H₂O into the O₂ isotope-based productivity calculations, which increases the estimated gross primary production in this study by 46-97 %. In summary, I describe a new noble gas analysis system and apply O₂ and inert gas observations in new ways to study chemical, biological, and physical processes in coastal waters.
by Cara Charlotte Marie Manning.
Ph. D.

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12

Mendez, Fernandez Paula. "Ecological segregation inferred using chemical tracers and contamination assessment of five toothed whales in the Northwest Iberian Peninsula". Phd thesis, Université de La Rochelle, 2012. http://tel.archives-ouvertes.fr/tel-00973748.

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The first objective of this PhD was to determine the degree of ecological segregation between five sympatric species of toothed whales (i.e. common dolphin Delphinus delphis, harbour porpoise Phocoena phocoena, bottlenose dolphin Tursiops truncatus, striped dolphin Stenella coeruleoalba and long finned pilot whale Globicephala melas) inhabiting a restricted and highly productive area, the North West Iberian Peninsula (NWIP). To this end, chemical parameters analyses were used as an "alternative method" of assessing diet and habitat of these animals over different periods of integration, complementing the information given by traditional methods of investigation such as stomach contents, faeces analyses and field observations. The second objective was to evaluate the contamination status of these species in order to estimate the toxicological risk these populations face and to complete the existing database. In this context, trace elements, carbon and nitrogen stable isotopes, as well as persistent organic pollutants (POPs) were selected as chemical parameters for our investigations.Firstly, the chemical parameters were used as ecological tracers of populations (or parts of populations) by drawing an image of the diet and habitat of the species at different time scales. We estimated that the food web has five trophic levels, with toothed whales occupying the top positions, with no significant difference in trophic positions among them, ranging from 4.3 to 5.3. While the analysis of a single chemical parameter did not completely segregate between the five species, the information gained by combining the analyses of several long-term ecological tracers (i.e. nitrogen and carbon stable isotopes in teeth and renal cadmium concentrations) revealed ecological niche segregation in two dimensions of this niche (the trophic and the spatial dimensions). However, year-to-year or seasonal variations could not be investigated, except for in common dolphin, and thus temporary overlap cannot be excluded. Additionally, we showed that polychlorinated biphenyls (PCBs) profiles could be a relevant tracer of the foraging ecology of taxonomically close species, allowing a fine separation of the species as result of their different patterns. This was particularly clear for the harbour porpoise and striped dolphin.Secondly, the contamination status of the species in this area was evaluated, with concentrations interpreted in the light of biological and ecological factors. But the bioaccumulation of trace elements appeared to be less predictable than that of POPs. Bottlenose dolphins and harbour porpoises were found to have higher PCBs concentrations than the rest of the analysed NWIP toothed whales, as well as those of adjacent NE Atlantic waters.The main results of this PhD highlight the relevance of exploiting these chemical parameters as ecological tracers, as well as their usefulness in the comprehensive study of structure and function of ecosystems through the role of top predators. Combined with the information on anthropogenic activities, this work can also contribute to the development and implementation of management plans and mitigation measures for these five species of toothed whales in the NWIP.

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13

Masserini, Robert T. Jr. "Ammonium, Nitrate, and Nitrite in the Oligotrophic Ocean: Detection Methods and Usefulness as Tracers". Scholar Commons, 2005. https://scholarcommons.usf.edu/etd/762.

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The overall focus of this research was to achieve the first detailed understanding of temporal and geographical distributions of inorganic-nitrogen-nutrients within an oligotrophic euphotic zone. In addition to low supply of nutrients, the uptake of nutrients by phytoplankton within the euphotic zone draws the nutrient concentrations down, resulting in very low concentrations of these nutrients and results in these regions being classified as oligotrophic. The site selected for the research was the West Florida Shelf (WFS). There were two main challenges. One was that the detection limits of the standard chemistries used to determine inorganic nitrogen nutrients are not low enough to permit the evaluation of the concentration of these nutrients within an oligotrophic euphotic zone. The other challenge was the adaptation and design of highly sensitive, robust, and simple instrumentation to resolve and evaluate horizontal nutrient distributions within the euphotic zone for both ship-based and Autonomous Underwater Vehicle (AUV) based platforms in near real time. With these obstacles in mind three major goals were set. First was the development of a simple and robust chemistry that could detect nitrite and nitrate with a suitably low detection limit (approximately 10 nanomolar) and could also be coupled with a highly sensitive chemistry previously developed for ammonium with the same characteristics, and incorporate these chemistries into a single laboratory analyzer designed to monitor the surface distribution of these nutrients in the water sampled with a ships flow-through system.

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14

Morris, Catherine. "Visualisation and quantification of soil wetting patterns in undisturbed soils using physical, chemical and morphological observations of tracers". Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415728.

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15

Theodory, Ronnie George. "The distribution of stable isotopes and heavy metals in Dreissena polymorpha (zebra mussel), chemical tracers for environmental contamination in Lake St. Clair". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0009/MQ52747.pdf.

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16

Haricombe, Erin. "Transport and fate of chemical and microbial tracers at University of Western Cape (UWC) campus site, Cape Flats aquifer of South Africa". University of the Western Cape, 2016. http://hdl.handle.net/11394/5233.

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>Magister Scientiae - MSc
Extreme weather events in combination with geographical changes in groundwater utilization, groundwater availability, aquifer recharge, and ultimately changes in the quality of water resources, are expected in the future. As a consequence of changing weather patterns and urbanization the demand for groundwater is likely to increase in certain areas. We know that most waterborne pathogenic health epidemics are associated with contamination of farm water and wastewater. There is however limited understanding of the nature and extent of chemical, physical and biological processes that control the fate and transport of the microorganisms in primary and secondary aquifers. In this thesis, transport results are reported, where E. coli and PDR1 were selected as the biological tracers transported through a primary aquifer at the University of the Western Cape. In conjunction with the microbes salt and Rhodamine (chemical tracers) were injected to compare their fate and transport mechanism in the primary aquifer medium. A series of controlled Darcy experiments under laboratory and field conditions were conducted. Each provided a different data and information. The results from laboratory studies were used to improve design of the field studies. In both cases, the data collected provided information on fate and transport of microbes in groundwater. The field design phase of the experiment was an up-scaling of the laboratory phase of this project. The amount of chemical tracers injected into the aquifer was increased in proportion to the size of the research site. Tracer tests using chemical and microbial tracers were conducted simultaneously. Results of laboratory tests demonstrate a 5 times slower transport of microbes, compared to tests with salts during the laboratory phase. The salts at field scale show a breakthrough occurring after 2 days whereas the microbes –did not break through during the 28 days of the observation period. A new borehole was drilled closer to the pumping borehole to eliminate distance or travel time, but this had no effect on field results for the microbes.
National Research Foundation

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17

Craddock, Paul R. "Geochemical tracers of processes affecting the formation of seafloor hydrothermal fluids and deposits in the Manus back-arc basin". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/55328.

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Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2009.
Includes bibliographical references.
Systematic differences in trace element compositions (rare earth element (REE), heavy metal, metalloid concentrations) of seafloor vent fluids and related deposits from hydrothermal systems in the Manus back-arc basin (Eastern Manus Basin, EMB and Manus Spreading Center, MSC) are used to investigate processes that affect their formation. Processes responsible for observed differences in fluids and deposits from distinct geologic settings include (a) fluid-rock interaction (with temperature, pressure and crustal composition as variables), (b) magmatic acid volatile input and, (c) local seawater entrainment and mixing with hydrothermal fluids, coupled with sulfide precipitation and metal remobilization. REE distributions in vent fluids in the Manus Basin exhibit a wide range of chondrite-normalized patterns that contrast with the relatively uniform distributions observed in mid-ocean ridge vent fluids. This heterogeneity is attributed to marked differences in fluid pH and fluoride and sulfate concentrations that significantly affect REE solubility. The data indicate that REEs can be used as indicators of the styles of magmatic acid volatile input in back-arc hydrothermal systems. Anhydrite in deposits record the same range of REE patterns, suggesting that REE distributions preserved in anhydrite can be used as indicators of past magmatic acid volatile input. Vent fluid heavy metal and metalloid concentrations also exhibit considerable differences. High metal concentrations in EMB versus MSC vent fluids reflect low pH, largely from input of magmatic acid volatiles (indicated by fluoride concentrations greater than seawater). In EMB, metal concentrations are locally affected by dissolution of previously deposited sulfide owing to low pH conditions affected by magmatic acid volatile input or seawater entrainment and mixing with hydrothermal fluid that leads to sulfide precipitation and secondary acidity generation.
(cont.) Massive sulfide deposits in the Manus Basin exhibit a wide range of mineral compositions and heavy metal enrichments. The formation of Zn-rich (sphalerite/wurtzite) deposits in the MSC and of Cu-Fe and Cu-As-rich (chalcopyrite, tennantite) deposits in the EMB reflects differences in the conditions of sulfide precipitation (temperature, pH) and in metal concentrations. The data suggest that heavy metal and metalloid distributions in massive sulfide deposits can be used as indicators of the conditions of vent deposit formation.
by Paul R. Craddock.
Ph.D.

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18

Shelton, Jenna Lynn. "Fate(s) of Injected CO₂ in a Coal-Bearing Formation, Louisiana, Gulf Coast Basin: Chemical and Isotopic Tracers of Microbial-Brine-Rock-CO₂ Interactions". Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297060.

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Coal beds are one of the most promising reservoirs for geologic carbon dioxide (CO₂) sequestration, as CO₂ can strongly adsorb onto organic matter and displace methane; however, little is known about the long-term fate of CO₂ sequestered in coal beds. The "2800' sand" of the Olla oil field is a coal-bearing, oil and gas-producing reservoir of the Paleocene–Eocene Wilcox Group in north-central Louisiana. In the 1980s, this field, specifically the 2800' sand, was flooded with CO₂ in an enhanced oil recovery (EOR) project, with 9.0×10⁷m³ of CO₂ remaining in the 2800' sand after injection ceased. This study utilized isotopic and geochemical tracers from co-produced natural gas, oil and brine from reservoirs located stratigraphically above, below and within the 2800' sand to determine the fate of the remaining EOR-CO₂, examining the possibilities of CO₂ migration, dissolution, mineral trapping, gas-phase trapping, and sorption to coal beds, while also testing a previous hypothesis that EOR-CO₂ may have been converted by microbes (CO₂-reducing methanogens) into methane, creating a microbial "hotspot". Reservoirs stratigraphically-comparable to the 2800' sand, but located in adjacent oil fields across a 90-km transect were sampled to investigate regional trends in gas composition, brine chemistry and microbial activity. The source field for the EOR-CO₂, the Black Lake Field, was also sampled to establish the δ¹³C-CO₂ value of the injected gas (0.9‰ +/- 0.9‰). Four samples collected from the Olla 2800' sand produced CO₂-rich gas with δ¹³C-CO₂ values (average 9.9‰) much lower than average (pre-injection) conditions (+15.9‰, average of sands located stratigraphically below the 2800' sand in the Olla Field) and at much higher CO₂ concentrations (24.9 mole %) than average (7.6 mole %, average of sands located stratigraphically below the 2800' sand in the Olla Field), suggesting the presence of EOR-CO₂ and gas-phase trapping as a major storage mechanism. Using δ¹³C values of CO₂ and dissolved organic carbon (DIC), CO₂ dissolution was also shown to be a major storage mechanism for 3 of the 4 samples from the Olla 2800' sand. Minor storage mechanisms were shown to be migration, which only affected 2 samples (from 1 well), and some EOR-CO₂ conversion to microbial methane for 3 of the 4 Olla 2800' sand samples. Since methanogenesis was not shown to be a major storage mechanism for the EOR-CO₂ in the Olla Field (CO₂ injection did not stimulate methanogenesis), samples were examined from adjacent oil fields to determine the cause of the Olla microbial "hot-spot". Microbial methane was found in all oil fields sampled, but indicators of methanogenesis (e.g. alkalinity, high δ¹³C-DIC values) were the greatest in the Olla Field, and the environmental conditions (salinity, pH, temperature) were most ideal for microbial CO₂ reduction in the Olla field, compared to adjacent fields.

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19

Piot, Christine. "Polluants atmosphériques organiques particulaires en Rhône-Alpes : caractérisation chimique et sources d'émissions". Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00661284.

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La réglementation plus sévère sur les niveaux de matières particulaires (PM) en atmosphère ambiante fixée par l'Union européenne à l'horizon 2015 impose de pouvoir quantifier les contributions des différentes sources d'émission. Les sources d'émissions primaires de particules peuvent être anthropiques (chauffage au bois, au fioul, émissions véhiculaires ou industrielles, combustion de déchets verts, activités de cuisine,...) ou naturelles (végétaux, poussières crustales). Des processus secondaires de formation des particules (conversion gaz-particules) peuvent également contribuer aux taux de PM mesurés. L'identification et la quantification des sources peuvent être conduites notamment à travers l'étude de la composante organique des aérosols réalisée à partir d'analyses chimiques de prélèvements sur filtres en atmosphère ambiante ou à l'émission. Dans ce travail, des méthodologies de caractérisation des sources d'émission par l'analyse de la fraction organique des PM et la quantification de leur influence sur les concentrations ambiantes en particules fines ont été développées et/ou adaptées de méthodologies existantes sur de nombreux sites d'observation. Une attention particulière a été portée sur différents sites de la région Rhône-Alpes où de nombreux épisodes de dépassements des valeurs limites en PM sont régulièrement enregistrés. Les méthodologies ont été développés dans un premier temps sur un site urbain de référence (sites des Frênes à Grenoble) et s'appuient à la fois sur des approches qualitatives d'études des sources (étude d'empreinte de grandes familles chimiques, utilisation de ratios de composés traceurs) et quantitatives (ACP, mesures isotopiques du carbone, Molecular-Marker Chemical Mass Balance). Elles permettent une bonne estimation des sources de matière organique (OM) et des PM en hiver. Leurs applications à d'autres sites de topologies différentes (ruraux, fond de vallées, proximités de sources, marin) en France et en Suisse et à d'autres saisons a permis de montrer la complémentarité des différentes approches introduites et la nécessité de leur adaptation aux spécificités des sites pour permettre une bonne estimation des PM. L'estimation des contributions des sources à l'OM reste cependant encore à améliorer. De plus, dans le cadre de leur application à des sites de vallées alpines suisses, l'approche quantitative de type CMB basée sur l'étude de traceurs organiques a pu être confrontée à une méthode basée sur l'étude de la composante inorganique des aérosols. Les méthodologies développées et mises en œuvre au cours de ce travail constituent des outils de référence dans le cadre d'études des sources d'aérosol à portée scientifique ou réglementaire à l'échelle nationale ou internationale.

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20

Brichart, Thomas. "Traceurs fluorescents à base de lanthanides en milieu complexe". Phd thesis, Université Claude Bernard - Lyon I, 2014. http://tel.archives-ouvertes.fr/tel-01066086.

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Les traceurs sont des espèces permettant de déterminer la position ou la distribution d'un produit et ceux-ci sont aujourd'hui présents dans de très nombreux domaines. Bien que chacune des applications possède un cahier des charges bien spécifique, il est possible de les retrouver dans des domaines aussi divers que la médecine (agents de contraste), l'anticontrefaçon ou encore l'exploration géologique. Nous avons ainsi développé des traceurs d'eau d'injection pétrolière composés de complexes de lanthanides. Ces traceurs, dérivés du DOTA, ont pu être détectés à des concentrations inférieures au ppb, grâce à un appareillage simple et compact. Cette détection fut rendue possible par l'utilisation de la fluorescence en temps résolu, qui permet de contourner le bruit de fond créé par la fluorescence intrinsèque des résidus pétroliers présents dans les eaux de production. Nous avons également montré comment il était possible, grâce à une synthèse en microémulsion, d'encapsuler différents luminophores au sein d'une nanoparticule composée d'un coeur d'or et d'une coquille de silice. Ainsi, ces nanoparticules ont pu être utilisées comme traceurs intelligents afin de recueillir des informations sur les propriétés physicochimiques au sein des puits comme la température, le pH, la proportion entre différents solvants, etc. Enfin nous avons pu montrer comment une utilisation judicieuse des lanthanides et des propriétés complexantes des inhibiteurs de dépôts minéraux pouvait permettre leur dosage grâce à une méthode à la fois simple et rapide. Ce dosage permettra alors d'ajuster leur concentration dans les différents puits de production de pétrole

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21

Stanley, Rachel H. R. "A determination of air-sea gas exchange and upper ocean biological production from five noble gasses and tritiugenic helium-3". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42282.

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Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007.
Includes bibliographical references (p. 215-225).
The five noble gases (helium, neon, argon, krypton, and xenon) are biologically and chemically inert, making them ideal oceanographic tracers. Additionally, the noble gases have a wide range of solubilities and molecular diffusivities, and thus respond differently to physical forcing. Tritium, an isotope of hydrogen, is useful in tandem with its daughter helium-3 as a tracer for water mass ages. In this thesis, a fourteen month time-series of the five noble gases, helium-3 and tritium was measured at the Bermuda Atlantic Time-series Study (BATS) site. The time-series of five noble gases was used to develop a parameterization of air-sea gas exchange for oligotrophic waters and wind speeds between 0 and 13 m s-1 that explicitly includes bubble processes and that constrains diffusive gas exchange to ± 6% and complete and partial air injection processes to ± 15%. Additionally, the parameterization is based on weeks to seasonal time scales, matching the time scales of many relevant biogeochemical cycles. The time-series of helium isotopes, tritium, argon, and oxygen was used to constrain upper ocean biological production. Specifically, the helium flux gauge technique was used to estimate new production, apparent oxygen utilization rates were used to quantify export production, and euphotic zone seasonal cycles of oxygen and argon were used to determine net community production. The concurrent use of these three methods allows examination of the relationship between the types of production and begins to address a number of apparent inconsistencies in the elemental budgets of carbon, oxygen, and nitrogen.
by Rachel H.R. Stanley.
Ph.D.

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22

Maier, Clamarion. "Variabilidade intra-evento da origem das fontes de sedimentos em uma bacia hidrográfica rural". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/77941.

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Este trabalho refere-se à variabilidade da origem dos sedimentos transportados durante eventos de chuva-vazão em uma pequena bacia hidrográfica rural (1,19 Km2). Esta bacia está localizada no sul do Brasil e a área é caracterizada pela presença de agricultores familiares que principalmente cultivam fumo em áreas consideradas inaptas para atividades agrícolas, de acordo com o sistema de aptidão agrícola do solo. Isto ocasiona severas perdas de solo por erosão hídrica. Neste estudo foram utilizadas técnicas hidrossedimentométricas com análises estatísticas multivariadas para determinação da procedência dos sedimentos durante a subida e a descida da onda de cheia em eventos de precipitação variada. A metodologia utilizada é denominada “método Fingerprinting” e possibilita avaliar quais são as áreas contribuintes para a produção de sedimentos intra-eventos de chuva-vazão. Foram definidas três áreas com potencial para produção de sedimentos, sendo as fontes, o canal de drenagem, as estradas e as lavouras da bacia. Foram coletadas um total de quarenta amostras distribuídas nas áreas fontes de sedimentos. Sete eventos foram monitorados entre os anos de 2009 e 2011 e 24 amostras foram coletadas ao longo destes eventos. Como traçadores foram utilizados elementos químicos, de proveniência natural ou antrópica: sódio (Na), potássio (K), magnésio (Mg), cromo (Cr), manganês (Mn), ferro (Fe), cobre (Cu), zinco (Zn), cádmio (Cd), mercúrio (Hg), chumbo (Pb) e fósforo (P). Foi demonstrado que os elementos determinados como o melhor conjunto de traçadores (P, Fe, Mn, Mg e K) possuem capacidade em determinar a origem dos sedimentos. Pode-se afirmar que há variabilidade de fontes de sedimentos durante os eventos de chuva-vazão. O estudo revelou que o canal de drenagem contribui com boa parcela dos sedimentos (0 a 72%), principalmente no início do hidrograma. Mesmo utilizando práticas agrícolas de conservação dos solos e dos recursos hídricos as lavouras são as principais fontes fornecedoras de sedimentos, crescendo sua contribuição ao longo do evento (27 a 100%). Os sedimentos oriundos das estradas não possuíram contribuição relevante (0 a 23%) durante os eventos monitorados. Existem evidências da variabilidade das fontes de sedimentos durante a subida e a descida da onda de cheia ocorrida em eventos de chuva.
This work refers to the variability of the source of sediment transported during rainfall-runoff events in a small rural catchment (1.19 km2). This basin is located in the south of Brazil and the area is characterized by the presence of family farmers who mainly cultivate tobacco in areas considered unsuitable for agricultural activities, according to the system of agricultural capability of the soil. This causes severe soil loss by water erosion. In this study we used techniques hydrosedimentometrics with multivariate statistical analyzes to determine the provenance of sediments during the rise and fall of the flood wave in precipitation events varied. The methodology is called "fingerprinting method" and allows assessing which areas are contributors to sediment yield intra-rainfall-runoff events. We defined three areas with potential for sediment production, and sources, channel drainage, roads and crops in the basin. We collected a total of forty samples distributed in source areas of sediment. Seven events were monitored between 2009 and 2011 and 24 samples were collected during these events. Tracers were used as chemicals, natural or manmade origin of sodium (Na), potassium (K), magnesium (Mg), chromium (Cr), manganese (Mn), iron (Fe), copper (Cu), zinc ( Zn), cadmium (Cd), mercury (Hg), lead (Pb) and phosphorus (P). It has been demonstrated that certain elements like the best set of tracers (P, Fe, Mn, Mg and K) have the ability to determine the origin of sediments. It can be said that there is variability of sediment sources during rainfall-runoff events. The study revealed that the drainage channel contributes good portion of the sediments (0-72%), especially early in the hydrograph. Even using agricultural practices to conserve soil and water resources crops are the main sources of sediment supply, growing their contribution throughout the event (27 to 100%). Sediment from roads did not possess relevant contribution (0-23%) during the monitored events. There is evidence of the variability of sediment sources during ascent and descent of the flood wave occurred in rain events.

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23

Tevissen, Etienne. "Méthodologie d'étude et modélisation du transport de solutes en milieux poreux naturels : application à la migration du chrome dans la nappe alluviale du Drac (Isère)". Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL089N.

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On présente une méthodologie d'étude du transport de solutés interactifs en milieu poreux naturel, basée sur l'expérimentation et la modélisation. La modélisation s'effectue grâce à un code de calcul couplant hydrodynamique et géochimie, des améliorations y sont apportées avec la prise en compte de corrections d'activité et surtout, avec la simulation d'effets cinétiques chimiques ou diffusionnels. La méthodologie proposée a été appliquée au cas de migration du chrome dans la nappe alluviale du Drac (Isère). L'étude du site expérimental associée à la connaissance générale de la chimie du chrome, a permis de définir et de cadrer les expériences à mener au laboratoire pour caractériser les interactions du chrome avec les alluvions. Ces expériences ont montré que c'est un phénomène d'adsorption qui impose la répartition du chrome hexavalent entre phases mobile et immobile. Ce phénomène a ensuite été décrit à l'équilibre thermodynamique par deux modèles, le premier utilise un phénomène élémentaire de type échange anionique entre chromate et bicarbonate, le second est résumé à une loi de Langmuir. Les courbes expérimentales ont été simulées en considérant ces deux modèles avec des limitations cinétiques. Les expériences de traçage sur le site ont montre que le chrome hexavalent y a un comportement equivalent a un traceur d'eau. Ce résultat souligne que certains paramètres capacitifs des interactions ne peuvent être déterminés au laboratoire et doivent faire l'objet de mesures in-situ

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24

Hubert, Axelle. "Chemical and mineralogical signatures of oxygenic photosynthesis in Archean and Paleoproterozoic sediments". Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2053/document.

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L’émergence des bactéries photosynthétiques oxygéniques (BPO), ou cyanobactéries, est probablement l’évènement le plus important de l’histoire de la Terre, depuis l’apparition de la vie elle-même. Par la libération d’O2 dans l’environnement, les BPO ont conduit à l’oxygénation de notre planète, jusqu’alors anoxique, et au développement de la vie complexe. Cependant, cette évolution n’est toujours pas datée. Dans cette étude, j’ai cherché à identifier des signatures chimiques spécifiques aux BPO, in situ à l’échelle du μm, dans des tapis microbien fossiles datant de 3,45 à 1,88 Ga, recouvrant ainsi une période allant de la Terre anoxique à la Terre oxygénée après le « Great Oxidation Event » (GOE). Nous avons utilisé la microscopie optique, la spectroscopie Raman, le MEB/EDX, l’EPMA, la μ-XRF à rayonnement synchrotron (SR-XRF), et des analyses isotopiques. Une nouvelle méthode de quantification élémentaire pour SR-XRF, ainsi qu’une nouvelle méthodologie de préparation d’échantillons ont été developpés. Les résultats obtenus par EPMA et μ-XRF montrent que, dans certains contextes de déposition, un enrichissement en lanthanides (par exemple La, Sm, Gd) de cellules fossiles, et un enrichissement en Cu de pyrites diagénétiques formées en association avec des BPO, pourraient représenter des signatures chimiques spécifiques aux BPO. Suite à ces résultats, je propose que les BPO ont évolué entre 3,33 et 2,98 Ga. Je propose que les techniques élémentaires telles que l’EPMA et la μ-XRF sont les techniques les plus appropriées pour trouver des signatures chimiques spécifiques aux BPO et contraindre leur émergence dans le temps
The evolution of oxygenic photosynthetic bacteria (OPB) is probably the most important biological event of Earth’s history since the emergence of life itself. The release of their by-product O2 in the environment, which was globally anoxic, fundamentally changed the face of the Earth and led to the development of complex life. However, the specific timing of this evolutionary step remains unclear. This study is based on the search for in situ chemical signatures of OPB at the microbial (μm) scale, within fossilized microbial photosynthetic mats in Archean and Paleoproterozoic sediments dated between 3.45 Ga and 1.88 Ga, i.e. spanning the anoxic Earth to the aftermath of the GOE. We used optical microscopy, Raman spectroscopy, SEM/EDS, EPMA, synchrotron radiation μ-XRF, and isotope analytical techniques. The μXRF results were improved by the use of a new sample preparation method and a new quantification method, both developed during this study.Results obtained by EPMA and μXRF show that, under certain depositional contexts, enrichment in lanthanides (such as Sm, La and Gd) in individual OPB cells, as well as a Cu enrichment in diagenetic pyrites formed in association with OPB, may represent chemical signatures of OPB. I propose that OPB evolved sometime between 3.33 Ga and 2.98 Ga. Also, I argue that elemental techniques such as EPMA and μ-XRF are the most suitable techniques to find chemical signatures of OPB and constrain the timing of their emergence

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25

Grimaldo, Morón José Teófilo. "Contribution à la synthèse de macrocycles tétraphosphorés : ligands polydentates présentant un intérêt biomédical". Grenoble 1, 1987. http://www.theses.fr/1987GRE10161.

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Synthese de ligands macrocycles tetraphores, complexants potentiels de cations paramagnetiques (gd**(3+), fe**(3+)) et de nucleide radioactifs. Etude de la reactivite de ces ligands et des essais de complexation

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26

Ogier, Lionel. "Synthèse de nouveaux analogues iodés du D-glucose". Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10264.

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Chez l'homme, de nombreuses pathologies sont liees a des dysfonctionnements du transport cellulaire du d-glucose. Les techniques d'imagerie etant un outil precieux pour detecter ces anomalies de transport, la synthese d'analogues du d-glucose radiomarques a l'iode (emetteur gamma) et utilisables en imagerie spect, a ete entreprise selon deux approches : la premiere repose sur l'utilisation du motif beta-iodoethoxyle qui a ete introduit sur diverses positions (1, 4, 5 et 6) du glucose. La seconde consiste a conserver tous les hydroxyles du glucose en introduisant le motif iode a partir des carbones du squelette. Ceci a ete effectue avec un motif iodomethyle sur les positions 3 et 6 ainsi que para-iodophenyle sur cette derniere. Tous les derives prepares ont fait l'objet d'une evaluation biologique, au moins preliminaire, sans toutefois presenter les proprietes d'un traceur du d-glucose, a l'exception du 6-deoxy-6-iodo-d-glucose (6-dig). Ce dernier, dont l'evaluation biologique sera poursuivie, a pu etre prepare a une echelle multi-grammes.

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27

Liu, Yang Ping. "Modelling estuarine chemical dynamics of trace metals". Thesis, University of Plymouth, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360359.

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28

Dehghani, Kiadehi Atena. "Development of a new technique for determining the RTD of a dispersed solid phase and its application in a deep fluidized bed". Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2491.

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L'objectif de cette thèse est le développement d’une nouvelle technique expérimentale de détermination de la distribution des temps de séjour (DTS) des particules solides dans les enceintes de manutention et de transformation de solides particulaires ainsi que le développement d’un modèle. Dans un premier temps, une nouvelle méthode optique a été développée pour mesurer la DTS des particules. Les expériences sont réalisées avec le carbure de silicium (SiC) et le pigment phosphorescent (Lumilux® Green SN-F50 WS) a été utilisé en tant que traceur. Une étude expérimentale préliminaire a été réalisée dans un lit fluidisé bouillonnant simple afin de valider la méthodologie proposée de mesure de la DTS. Dans un deuxième temps, la technique développée de la mesure de concentration a été appliquée à la détermination de la DTS dans un lit fluidisé profond. Les courbes de la DTS des particules sont déterminées expérimentalement dans différentes conditions opératoires. Dans un troisième temps, un modèle basé sur une combinaison de réacteurs idéaux est proposé pour prédire la DTS des particules du lit fluidisé étudié. Les valeurs de sortie prédites sont ensuite comparées aux données expérimentales pour l’ajustement du modèle
The aim of the present thesis is to develop a novel experimental technique for determining the residence time distribution (RTD) of solid particles in solid unit operations as well as model development. Initially, a novel optical method was developed to measure the particle RTD. Experiments are carried out with Silicon Carbide (SiC) and the pigment phosphorescent (Lumilux® Green SN-F50 WS) as tracer particle. A preliminary experimental study was conducted in a simple bubbling fluidized bed in order to validate the proposed RTD measurement methodology. In the second step, the developed technique of the concentration measurement was applied to measure the RTD of a deep fluidized bed. The particle RTD curves are determined experimentally in different operating conditions. Finally, a model consisting of the combination of the ideal reactors is proposed to predict the particle residence time distribution in the studied fluidized bed. The predicted output values are then compared with the experimental data to establish a good model fitting data

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29

OLIVEIRA, CAROLINE L. de. "Estudo de esteróis como marcadores químicos em águas destinadas ao abastecimento público na Região do Rio Paraíba do Sul, SP. Desenvolvimento e validação de metodologia analítica". reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10113.

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Made available in DSpace on 2014-10-09T12:34:54Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:07:14Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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30

Liu, Cong. "New technique for radiolabelling tracer with 64CU for positron emission particles tracking (PEPT) experiments". Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/13709.

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Positron emission particle tracking (PEPT) is a non-invasive technique for studying the flow of particulate systems within industrial equipment. The technique tracks a tracer particle labelled with a positron emitting radionuclide moving within the field-of-view of a positron emission tomography (PET) scanner. Two important components of the technique are a PET camera and PEPT tracers, which are particle tracers labelled with a positron emitting radionuclide. Currently, the majority of PEPT tracers are made with 68Ga or 18F. However, the relatively short half-life of these two radionuclides limits the application of PEPT to a maximum of 3 hours of experimental time. 64Cu is a potential candidate for PEPT tracer fabrication due to its relatively long half-life (12.7 h) which could extend the experimental running time of PEPT experiments to two uninterrupted days. The objective of the research described in this thesis was to develop a technique for radiolabelling tracers with 64Cu, and to test their efficacy in PEPT experiment. The work was conducted at Radionuclide Production Department, iThemba LABS near Cape Town, where high purity 64Cu was obtained by a two stages separation method using ion exchange chromatography.

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31

Paraskiva, Alla. "Développement de membranes pour les capteurs chimiques potentiométriques spécifiques aux ions Thallium et Sodium". Thesis, Littoral, 2017. http://www.theses.fr/2017DUNK0466/document.

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Le but de ce travail de thèse a consisté à étudier les propriétés physico-chimiques des verres chalcogénures des systèmes pour pouvoir les utiliser comme les membranes des capteurs chimiques pour le dosage des ions TI⁺ et NA⁺ . D'abord, on a effectué les mesures des propriétés macroscopiques telles que les densités et les températures caractéristiques (Tg, Tc, Tf) et leur analyse selon les compositions des verres. Après, les propriétés de transport ont été étudiés à l'aide de la spectroscopie d'impédance complexe ou par les mesures de la résistivité. Il a été ainsi montré l'effet de cation mixte pour les trois systèmes vitreux avec les ions TI/Ag et le régime de la percolation dans le système NaCl-Ga₂S₃-GeS₂ . Puis, on a réalisé les mesures de diffusion par traceur ¹⁰⁸mAg et ²⁰⁴TI pour le système (TI₂S)ₓ(Ag₂S)₅₀₋ₓ(GeS)₂₅(GeS₂)₂₅. Les résultats ont permis d'expliquer l'effet de cation mixte. Afin de mieux comprendre les phénomènes de transport des systèmes étudiés, diverses études structurales ont été déployées par spectroscopie Raman, diffusion de neutrons et diffraction de rayons X haute énergie. Enfin, la dernière partie de ce travail est entièrement consacrée à la caractérisation de nouveaux capteurs chimiques pour la détection des ions TI⁺ et NA⁺ en solution. Dans le premier cas, les électrodes sélectives aux ions TI⁺ avec les différentes compositions de membrane ont été testées afin de définir la sensibilité, la limite de détection, les coefficients de sélectivité en présence d'ions interférents, la reproductabilité, l'influence de pH. En plus, il était effectué l'échange des traceurs ²⁰⁴TI entre la solution et les verres à base des matrices GeS₂ et Ge₂S₃ pour comprendre et expliquer les différences significatives dans la sensibilité et la limite de détection présentés par les capteurs dont les membranes ont la composition de verre similaire. Dans le deuxième cas, les études montrent l'existence de la sensibilité aux ions NA⁺ donc le développement des capteurs pour le dosage des ions de sodium est possible
The aim of this thesis was to study the physicochemical properties of the chalcogenide glasses for possibility to use them as the chemical sensor membranes for the quantitative analysis of TI⁺ and NA⁺ ions. Firstly, the measurements of the macroscopic properties such as the densities and the characteristic temperatures (Tg, Tc, Tf) and their analysis according to the glass compositions were carried out. After that, the transport properties were studied through complex impedance conductivity measurements and from dc conductivity measurements. These experiments have shown the mixed cation effect in three chalcogenide glassy systems with TI/Ag ions and the percolation regime in the NaCl-Ga₂S₃-GeS₂ system. Then the silver ¹⁰⁸mAg and thallium ²⁰⁴TI tracer diffusion measurements were carried out for (TI₂S)ₓ(Ag₂S)₅₀₋ₓ(GeS)₂₅(GeS₂)₂₅ system. The result permit to explain the mixed cation effect. In order to better understand the transport phenomena of the studied systems, the various structural studies have been deployed using Raman spectroscopy, neutron diffraction and high energy X-ray diffraction. Finally, the last part of this work is entirely devoted to the characterization of new chemical sensors for detection of TI⁺ and NA⁺ ions in solution. In the first case, the sensors with different membrane compositions were tested for defining the sensitivity, the detection limit, the selectivity coefficients in the presence of interfering ions, the reproductibility, the pH influence. In addition, the ionic exchange with radioactive isotopes ²⁰⁴TI between the solution and the GeS₂ or Ge₂S₃ based glasses was performed for understanding and explaining the significant differences in the sensitivity and the detection limit presented by the sensors whose membranes have the similar glass compositions. In the second case, the studies shows the existence of sensitivity for NA⁺ ions so the development of sensors for the determination of sodium ions is possible

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32

Ghosn, Micheline. "Chemical contamination in different marine organisms along the Lebanese coast : Environmental implications and health risks". Thesis, Littoral, 2019. http://www.theses.fr/2019DUNK0552.

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La consommation mondiale des produits de la mer est en perpétuelle croissance et les produits de la pêche sont devenus parmi les produits les plus marchandés à travers le monde. Cependant, la qualité de ces derniers soulève une problématique au niveau de la santé humaine avec l’augmentation des pressions anthropiques menaçant les écosystèmes côtiers et les organismes marins. Par la suite, malgré les qualités nutritionnelles des produits de la pêche, leur consommation peut être une voie d’exposition de l’homme à différents types de contaminants chimiques dont les éléments traces métalliques (ETMs). Dans ce contexte, l’évaluation du niveau de contamination dans ces produits et les risques qu’ils peuvent engendrer s’avère être une nécessité surtout en l’absence de normes locales et de programmes de surveillance. Les objectifs de cette étude sont de deux ordres : i) l’évaluation la qualité environnementale du littoral Libanais à travers les organismes marins et, ii) l’estimation du niveau des risques sanitaires liés à la consommation d’une sélection des produits de la pêche. Le premier objectif, était d’évaluer les niveaux de contaminants métalliques (20 éléments traces) chez six espèces marines de différents niveaux du réseau trophique (algues, moules, crevettes et poissons) représentatif des eaux côtières libanaises. Les résultats ont révélé que les espèces accumulent les métaux différemment soulignant ainsi l’importance d’une approche multi-espèce pour mieux refléter le niveau de contamination du milieu. Des variations inter-sites ont été également trouvées surtout durant la période pluvieuse de l’année indiquant l’effet des apports des rivières vers la zone côtière. Les niveaux des ETMs obtenus dans les muscles et les tissus comestibles dans le cadre de notre étude étaient du même ordre de grandeur que ceux mesurés dans d’autres régions du bassin Levantin. Cependant, les foies ont montré des concentrations supérieures comparées à d’autres études, suggérant ainsi que la côte libanaise est soumise à des pressions environnementales importantes. Le deuxième objectif, concerne l’évaluation des risques sanitaires liés à la consommation de différents produits de la pêche échantillonnés le long du littoral Libanais. Pour cela, cinq espèces consommées localement (1 bivalve, 1 crustacé et 3 espèces de poisson) et échantillonnés le long du littoral Libanais au niveau de trois sites soumis à différents niveaux de pressions anthropiques ont été sélectionnés. Tous les échantillons ont été analysés pour leur contenu en éléments traces. Des métaux comme le mercure (Hg) se retrouvent sous plusieurs formes chimiques, sa forme la plus toxique étant le méthylmercure (MeHg). La voie principale de l’exposition humaine au MeHg est la consommation de produits de la pêche. Pour cela, une méthode de spéciation du Hg dans les produits de la pêche a été optimisée et validée par profil d’exactitude. Les résultats ont montré que les niveaux des ETMs et du MeHg dans les espèces concernées, étaient largement inférieurs aux limites maximales admissibles fixées par la Commission Européenne et que leur consommation ne présente pas de risques pour la santé humaine
Global food fish consumption has been in continuous increase and fishery products have become some of the most traded items in the world. However, the quality of these products is becoming an issue of concern to human health with the increase of anthropogenic activities threatening marine coastal ecosystems. Therefore, despite the well-known health benefits of fishery products, their consumption may be a route of human exposure to different kinds of chemical contaminants including trace elements. In this context, evaluating the contamination levels in these products and the risks they may engender to human health proves to be a necessity in the absence of local guidelines and monitoring programs. Thus, the thesis has 2 main objectives: i) the evaluation of environmental quality through marine organisms and, ii) the assessment of health risks related to the consumption of a selection of fishery products.The first objective was to study the levels of metallic contaminants (20 trace elements) in six marine species from different trophic levels of a food web (algae, mussel, shrimp and fish), representative of Lebanese coastal waters. The results showed that species accumulated metals differently underlining the importance of a multi-specific approach to reflect the contamination level of a certain site. Inter-site variations have been found mainly during the rainy period of the year while they were less prominent during the dry season, highlighting the effect of land-based sources and riverine effluents on the marine coastal area. Levels of trace elements in the muscles and edible tissues in species from our study, were similar to the ones reported in the Eastern Mediterranean (Levantine Basin) whereas livers showed higher levels compared to other studies suggesting that the Lebanese coast is exposed to strong environmental pressure. The second objective was to evaluate the health risks related to the consumption of different fishery products sampled along the Lebanese coast. In this prospect, five commonly consumed local species belonging to different compartments of the food chain, (1 bivalve, 1 crustacean and 3 fish species) sampled from three sites with different levels of anthropogenic pressures were selected. The samples were all analyzed for their content of trace elements. Metals such as mercury (Hg) are found in several chemical forms, the most toxic form being methylmercury (MeHg). The main route of human exposure to MeHg is the consumption of fishery products. That’s why, a method for the speciation of mercury in fishery products by HPLC-ICP-MS was optimized and validated based on an accuracy profile. The results showed that the levels of trace elements and MeHg in the selected species were all below the allowed maximum levels set by the European commission and so their consumption is not likely to cause any adverse effects to human health

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33

Chimpalee, Narong. "Studies in inorganic trace analysis". Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336038.

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34

Simon, Michelle A. "Analysis of a gas-phase partitioning tracer test conducted in fractured media". Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280654.

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This work successfully applied the gas-phase partitioning tracer method to determine the NAPL, water and air saturations in the vadose zone at the field scale. This project was one of the first, and still one of the few, field-scale gas-phase partitioning tracer tests. This work differs from other work in that it was conducted in a high water content, fractured clay. There were three primary components of this work. First, gas-phase tracers were identified and their NAPL-air and Henry's Law constants measured. There were four types of tracers used in this study: noble gases or nonpartitioning tracers; alkanes, which were expected to be nonpartitioning tracers; perfluorides, NAPL partitioning tracers; and halons, NAPL and water partitioning tracers. A laboratory method for measuring NAPL-air partition coefficients was developed and TCE-air partition coefficients were measured for the perfluoride and halon tracers. The second component of this study involved conducting a field-scale gas-phase partitioning tracer test, the results which were used to estimate NAPL, water and air saturations. The NAPL saturation, calculated to be an extremely low value, resulted in an estimate of NAPL mass present that is similar to the amount that has subsequently been extracted from the test site via SVE remediation. The alkane tracers, which had been used previously in laboratory column studies as nonpartitioning tracers, were more retarded than the perfluoride tracers at this site. It was the alkane tracers, and not the halon tracers, that were used to determine the water content. The water content was estimated to be approximately 90%, which is unexpectedly high for a vadose zone. Additionally, the tracer response time, vacuum data, and other geological data indicated that the tracer test was performed in fractured clay. The third component of this work comprised an analysis of the tracer test data to determine transport parameters. The analysis employed matching eight simple mathematical models to the experimental data. All of the models tested: two porous, three double-porosity, and three fracture-based (single fracture, multifracture, fracture-matrix) models could reasonably match the experimental data and no one model resulted in consistently superior predictions than the others.

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35

Cengiz, Betul. "Fiber Loop Ring Down Spectroscopy For Trace Chemical Detection". Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615626/index.pdf.

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Fiber loop ring down (FLRD) spectroscopy is a sensitive spectroscopic technique that is based on absorption and it is convenient for trace chemical detection. Different FLRD systems are being improved in order to increase their sensitivity. In FLRD spectroscopy, detection of a sample is done by measuring of a leaking light at each trip within an optical cavity. Intensity of leaking light has an exponential decay where it is reduced by absorption of sample and scattering of light. In this project, two FLRD set-ups at 1535 nm and 808 nm were designed. In both set-ups, optical fiber and optical fiber couplers are used to form a cavity. At 1535 nm, a FLRD set-up is constructed by utilizing a pulsed laser and used for characterization of thin films, various pure liquids and fluorescein solutions. Two different sensor regions are designed with free space collimators and ferrules for the measurement of thin films and liquids, respectively. The future endeavor of the set-up is improvement for reliability and reproducibility of the system. For visible and NIR regions, a fiber coupled laser with four colors as 642 nm, 785 nm, 808 nm and 852 nm laser is used to design of a FLRD set-up. 808 nm laser is selected to build a prototype of the FLRD system. The construction of a closed loop FLRD set-up is completed and the system is characterized. Ultimate aim in our project is to be able to do trace detection at visible and NIR regions where the chemical sensitivity is higher.

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36

Krysztofiak, Gisèle. "Transport et chimie d'espèces soufrées et bromées dans la haute troposphère et basse stratosphère diagnostiqués par des mesures sous ballon et en avion et par modélisation". Phd thesis, Université d'Orléans, 2013. http://tel.archives-ouvertes.fr/tel-01004398.

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Le phénomène de destruction de l'ozone est un sujet vaste mettant en scène de nombreux processus. Il a pour origine l'émission de composés dits gaz sources (SGs) dans la troposphère. Récemment, les espèces à très courte durée de vie (VSLS) ont été identifiées comme SGs possibles. Cependant, elles ne possèdent pas un temps de vie suffisamment long pour atteindre directement la stratosphère. Les VSLS se dégradent au cours de leur transport, conduisant à des composés intermédiaires, les gaz produits (PGs). Les SGs et les PGs des VSLS vont entrer dans la stratosphère au niveau des régions équatoriales où règne un transport vertical rapide, la convection. Les SGs à temps de vie plus long peuvent accéder à la stratosphère par tous les types de transport possibles. Une fois dans la stratosphère, les SGs et PGs vont être convertis en espèces réactives capables de détruire l'ozone. Cette thèse présente l'étude des différentes étapes se produisant avant la destruction de l'ozone : l'émission et le transport des SGs dans l'atmosphère, leur chimie de dégradation au cours de leur transport et enfin leur contribution à la destruction de l'ozone. Les traceurs chimiques tels que CO sont tout d'abord utilisés pour mettre en évidence le transport des SGs et PGs de la troposphère à la stratosphère. Puis, deux études décrivant 2 types d'espèces différentes, entrant dans le processus de destruction de l'ozone, sont présentées : pour OCS (sulfure de carbonyle) et les VSLS bromés (CHBr3 et CH2Br2). OCS est l'un des principaux précurseurs d'aérosols sulfatés présents dans la stratosphère catalysant la destruction de l'ozone par chimie hétérogène. Cependant, sa contribution à cette couche comporte de nombreuses incertitudes. Ses sources d'émissions, sa répartition avec la latitude et sa contribution à la couche d'aérosols sulfatés sont présentées. La contribution des VSLS bromées au brome de la stratosphère est une question en cours de résolution. Leur chimie au cours de leur transport dans l'atmosphère est décrite de manière détaillée.

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37

Im, Po. "Trace metals in North Atlantic precipitation". Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290230.

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38

Graham, Paul. "Trace chemical analysis and molecular dynamics utilising ultraintense femtosecond lasers". Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326471.

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39

Shtewi, Farag Zaied. "Stopped-flow ultra-trace analysis of boiler waters". Thesis, University of Salford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261988.

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40

Reid, Helen J. "Chemical studies of the degree of decomposition and dissolution in microwave digests". Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/15385.

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Most methods for the determination of trace elements in organic matter require the sample to be brought into solution, which may be achieved by heating with strong oxidising agents such as concentrated mineral acids, to decompose the organic matrix sufficiently to render the sample soluble, whilst not necessarily achieving complete decomposition. The use of microwave heating for this purpose, using sealed vessels under pressure, was investigated for a variety of food samples. One drawback of this otherwise rapid method is the time taken to cool the vessels before opening. The use of liquid nitrogen to cool the vessel walls - before, during and after the heating cycle - was investigated, and its effect on the progress of the digestion was assessed. Another problem is the control of internal pressure, which can rise very rapidly when digesting samples of high organic content, and ways of controlling excess pressure when digesting larger samples were devised. These included the use of an open pre-digestion under reflux using a microwavetransparent coolant liquid, and the use of vessels capable of withstanding higher pressures. The latter proved more convenient as they enabled complete dissolution to be achieved in a single stage without pre-digestion, although cooling of these vessels was much slower than for the low pressure vessels, so overall sample preparation time was similar. Various methods were developed for the complete dissolution of the samples using nitric acid and hydrogen peroxide. The degree of decomposition achieved for the different methods and sample types was monitored by measurement of residual carbon in the digests. A few samples were virtually completely decomposed with nitric acid alone, while the use of hydrogen peroxide, following a nitric acid digestion, was found to reduce residual carbon substantially in the others. The undecomposed material was analysed by various methods including ultraviolet/visible spectrometry, infrared spectrometry and thin layer chromatography. Decomposition products were found to include carboxylic acids, oxalates, phosphates, nitrates and nitro-aromatics. Complete decomposition of milk powder, which proved most resistant to oxidation, was achieved by further treatment with perchloric acid. This was found necessary for anodic stripping voltammetric analysis, which required the destruction of interfering organic species for accurate determination of trace elements, unlike other techniques such as inductively coupled plasma-mass spectrometry, where complete decomposition was not required.

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41

Decin, L., A. M. S. Richards, T. J. Millar, A. Baudry, Beck E. De, W. Homan, N. Smith, de Sande M. Van e C. Walsh. "ALMA-resolved salt emission traces the chemical footprint and inner wind morphology of VY Canis Majoris". EDP SCIENCES S A, 2016. http://hdl.handle.net/10150/621992.

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Context. At the end of their lives, most stars lose a significant amount of mass through a stellar wind. The specific physical and chemical circumstances that lead to the onset of the stellar wind for cool luminous stars are not yet understood. Complex geometrical morphologies in the circumstellar envelopes prove that various dynamical and chemical processes are interlocked and that their relative contributions are not easy to disentangle. Aims. We aim to study the inner-wind structure (R < 250 R-star) of the well-known red supergiant VY CMa, the archetype for the class of luminous red supergiant stars experiencing high mass loss. Specifically, the objective is to unravel the density structure in the inner envelope and to examine the chemical interaction between gas and dust species. Methods. We analyse high spatial resolution (similar to 0 ''.024 x 0 ''.13) ALMA science verification (SV) data in band 7, in which four thermal emission lines of gaseous sodium chloride (NaCl) are present at high signal-to-noise ratio. Results. For the first time, the NaCl emission in the inner wind region of VY CMa is spatially resolved. The ALMA observations reveal the contribution of up to four different spatial regions. The NaCl emission pattern is different compared to the dust continuum and TiO2 emission already analysed from the ALMA SV data. The emission can be reconciled with an axisymmetric geometry, where the lower density polar/rotation axis has a position angle of similar to 50 degrees measured from north to east. However, this picture cannot capture the full morphological diversity, and discrete mass ejection events need to be invoked to explain localized higher-density regions. The velocity traced by the gaseous NaCl line profiles is significantly lower than the average wind terminal velocity, and much slower than some of the fastest mass ejections, signalling a wide range of characteristic speeds for the mass loss. Gaseous NaCl is detected far beyond the main dust condensation region. Realising the refractory nature of this metal halide, this hints at a chemical process that prevents all NaCl from condensing onto dust grains. We show that in the case of the ratio of the surface binding temperature to the grain temperature being similar to 50, only some 10% of NaCl remains in gaseous form while, for lower values of this ratio, thermal desorption efficiently evaporates NaCl. Photodesorption by stellar photons does not seem to be a viable explanation for the detection of gaseous NaCl at 220 R-star from the central star, so instead, we propose shock-induced sputtering driven by localized mass ejection events as an alternative. Conclusions. The analysis of the NaCl lines demonstrates the capabilities of ALMA to decode the geometric morphologies and chemical pathways prevailing in the winds of evolved stars. These early ALMA results prove that the envelopes surrounding evolved stars are far from homogeneous, and that a variety of dynamical and chemical processes dictate the wind structure.

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42

David, Brian T. ""Chemical fingerprinting" of volcanic tephra found in Kansas using trace elements". Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1413.

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43

Money, Cathryn. "Trace metal chemical speciation and acute toxicity to Pacific oyster larvae". Thesis, University of Plymouth, 2008. http://hdl.handle.net/10026.1/2252.

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Controlled laboratory studies showed that the toxicity induced by biologically relevant trace metal species of Cu, Cd, Pb and Zn on embryo-larval development occurred at concentrations in excess of those found in the natural environinent, except for Cu in metal perturbed areas. Average free ion concentrations inducing 50% abnormal development( EC50feew) ere determineda s 0.23 nM CU2+8, 8.0 rim Cd2+,1 28 nM Zn2+a nd 3 62 nM Pb 2+ . However, the response to some binary metal combinations indicated enhanced (synergy) toxicity at concentrations relevant for estuarine waters (e. g. EC5of'. for Cu2+i n the presence of C(ý: +, Zn2+a nd Pb2 +w as 0.004,0.02 and 0.04 nM, respectively). A comparison of voltammetric instrumentation (voltammetric in situ profiling (VIP) system versus Hanging Mercury Drop Electrode with potentiostat) highlighted the advantage of high resolution measurements (ca. 20-60 min intervals) for environmental studies and the minimisation of artefacts associated with discrete sampling methodologies. Field-based studies were carried out in two contrasting estuaries in SW England, one heavily impacted with metal contaminants (Fal Estuary) and another subject to greater variety of anthropogenic influences (Tamar Estuary). High resolution in situ trace metal speciationm easurementsc, arried out over tidal cycles, identified important information on the temporal and spatial distributions of biologically relevant dynamic (<4 nm) metal species of Cd, Pb and Cu. Variation in embryo-larval responses to discrete samples from these estuaries, effectively paralleled the metal speciation measurements showing enhanced toxicity when the marine water influence was at its lowest. In both systems, the results indicated that the combined effect of the metals studied was likely to have provided a significant contribution to the bioassay response. However, the difficulty in de-coupling the speciation measurements with biological responses was evident and supports the need for more comprehensive campaigns to study the impact of contaminants on ecosystem functioning. Bioassay and metal speciation analysis techniques were complementary, exhibiting high sensitivity and rapid responses, and would be considered effective screening tools for waters subject to intermittent inputs of metal contaminants and areas with recognised pressures. The integrated approach has extended our knowledge of trace metal speciation in estuarine environments and their effects on the developing embryos of the Pacific oyster. This approach has the potential for wider application.

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44

Kerbrat, Michael. "Physico-chemical interactions of acidic trace gases with ice in snow /". [S.l.] : [s.n.], 2009. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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45

Leggett, Graham. "Chemical strategies for removal of trace impurities from gases and solvents". Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.731713.

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46

Caldicott, Kenneth James. "Application of trace analysis and chemometrics to environmental problems". Thesis, University of South Wales, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480930.

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47

Edwards, David M. "Metal speciation at the trace level by derivative spectroscopy". Thesis, Manchester Metropolitan University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328240.

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48

Hultén, Amanda. "Determination of trace elements in thrombocytes by ICP-MS". Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-397392.

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49

Hantoosh, Mohammed, e Mohammed Hantoosh. "Advanced Oxidation Processes of Trace Organics in Water by Solar Photolysis". Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/620873.

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Wastewater reuse is considered globally as a very important element of sustainable water management. Conventional wastewater treatment methods are not effective for the degradation of toxic trace organic compounds, so advanced treatment processes are sometimes needed when the wastewater effluent is likely to be reused or discharged to a river. The existence of toxic trace organic contaminants in the effluent wastewaters has increased awareness of environmental effects and potential concerns for human health. In this work, the advanced oxidation process (AOP) under solar irradiation was successfully used to decompose p-cresol, which is considered to be a toxic trace organic contaminant, from wastewater effluents. The objective of this thesis was to investigate the effect of the EfOM on the overall degradation of the trace organic matter and bulk organic matter through the formation of reactive oxygen species (ROS) and photoexcited dissolved organic matter intermediates (DOM*) under sunlight irradiation. Solar photolysis experiments were conducted to determine the degradation of p-cresol at different conditions, including varying the secondary effluent WW concentration, the initial concentration of the target compound and light intensity. Results from these experiments were reported and discussed to get the optimal treatment processes.

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50

Brown, Jennifer Louise Dickson. "Optical properties of chromophoric dissolved organic matter as a tracer of terrestrial carbon to the coastal ocean". View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-2/r1/brownj/jenniferbrown.pdf.

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Tesi sul tema "Chemical tracers"

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