Dissertations / Theses on the topic 'Chemical Significance'

The conversion of light hydrocarbons with solid catalysts is an important class of reactions in the chemical and energy industries. Our knowledge on the exceedingly complex reaction kinetics of these catalytic reactions, especially the inter-influence between the reactions on catalyst and those in the gas phase, lags behind the requirement of technology development to improve efficiency and reduce emissions.The purpose of this study was to investigate the significance of surface-generated radicals in influencing the kinetics and mechanisms of gas-solid catalytic reactions. The results indicate that desorption is an important fate of the surface-generated radicals. The presence/absence of significant mass transfer resistance for radicals, which is different from that for the mass transfer of molecular species, determines the successful desorption/diffusion of radicals into the bulk gas phase.When a non-porous nickel mesh was used to catalyse the reactions between ethane and oxygen, it was found that the desorption/diffusion of radicals into the bulk gas phase could be facilitated by decreasing the mass transfer of radicals across the gas film around the nickel wires through increasing the gas flow rate traversing the mesh. The desorption of radicals increases the rate of chain reactions in the gas phase, resulting in the positive catalytic effects of nickel mesh. The nickel mesh can also have negative catalytic effects by quenching the gas-phase radicals by providing a surface to catalyse radical termination reactions.Many Ni-catalysed hydrocarbon oxidation reactions involve the reduction and oxidation (redox) of nickel catalyst itself. Results of this study show that the migration/diffusion of radicals on the surface, from the surface into the NiO bulk and from the surface into the gas phase can all have significant effects on the reduction kinetics. These in turn depend on the size of NiO crystallite, the presence/absence of rigid pore structure and the type of radicals formed on the catalyst surface.The use of fluidised nanoparticles as catalysts can lead to drastic reduction of reactor size for improved efficiency and reduced capital/operating costs. The catalytic oxidation of ethane with oxygen inside a fluidised bed of unsupported NiO nanoparticles in this study shows very different behaviour from the same reaction catalysed with silica-supported NiO catalysts. These differences can be explained by considering the difference in the resistance for the desorption of radicals into the bulk gas phase between the two catalytic systems.Overall, this study highlights the importance of considering the fates of surface-generated radicals in elucidating the kinetics and mechanism of gas-solid catalytic reactions. The original findings of this study are valuable for the development of innovative heterogeneous catalytic processes, especially the partial oxidation of light hydrocarbons, with high efficiency, low emission and low capital/operating costs.

Master of Science
Department of Geology
Matthew E. Brueseke
The Jarbidge Rhyolite of Elko County, Nevada, is approximately 26 mapped bodies of porphyritic rhyolite. Several of the bodies are truncated by the Idaho or Utah border, and extend into the states for an unknown distance. This study focuses on five bodies, the Mahoganies, two near Wild Horse Reservoir, the outcrop enclosing the Jarbidge Mountains, and one outcrop south of Wells. The study’s focus is providing field, petrography, geochemistry, oxygen isotope, and geochronology information about the five previously mentioned bodies. Physical volcanology encountered during this study indicates the sampled Jarbidge Rhyolite are effusive lava flows and domes that coalesced over the life of the volcanic system. First order approximations indicate that erupted products cover ~1,289 km2 and erupted material totals ~509 km3. Petrography indicates primary anhydrous mineral assemblages, assimilation of granitoid, possible assimilation of metamorphic rock and magma mixing of mafic and silicic bodies. Collectively, the Jarbidge Rhyolite lava flows sampled are compositionally restricted from rhyolite to high silica rhyolite and all samples demonstrate A-type magma characteristics. Compositions from different bodies overlap on Harker diagrams, and trace element ratios distinguish few flows from the other samples. Rare earth element patterns mimic one another, and incompatible trace element ratios overlap between bodies, likely indicating the presence of one large magma body. Oxygen isotope values for selected samples range 6.61-8.95%oVSMOW are coincident with normal igneous values. New 40Ar/39Ar geochronology indicates Jarbidge Rhyolite volcanism initiated ca. 16.7 Ma near Wild Horse Reservoir and was active at Bear Creek Summit ca.15.8 Ma. Local Steens Basalt, geochemistry, and Au-Ag mineralization indicate Jarbidge Rhyolite is similar to Middle Miocene silicic volcanics (e.g. Santa Rosa-Calico volcanic field) further west in the Oregon-Idaho-Nevada tristate region.

Large volumes of antisera were generated against Apis melli/era venom with which to develop a novel, platform technology for the inexpensive production of anti venoms. The ovine sera contained high levels of specific antibodies which neutralised the myotoxic, phospholipase A2 and in vivo activities of the venom. Methods of processing the antisera to provide Fab or F(ab')2 were investigated. F(ab')2 was thought to be clinically advantageous and, by determining the conditions necessary for the preferential breakdown of Fc and serum components other than F(ab')2' it was possible to avoid salt precipitation. Diafiltration was then used to remove most of the unwanted small fragments and anion-exchange chromatography to remove any remaining acidic impurities such as pepsin and large aggregates. The F(ab')2 was -97% pure and the yield - 199 per L of serum. This is the first specific therapy for mass envenoming by European or Africanised bees. Spiders of the genus Latrodectus (black widows) are distributed widely and about 2,500 bites are reported annually in the USA. The neurotoxic effects of the venom were studied on the isolated phrenic nerve diaphragm preparation. Low venom concentrations (ImgIL) were stimulatory while high concentrations (IOmg/L) caused nerve blockade which was potentiated by increased calcium levels. Although effective, the Merck antivenom, which is unprocessed horse serum, causes unacceptable risks. The second purpose of this project was to prepare an improved Latrodectus spider antivenom using the new platform technology. Different immunisation schedules were studied to optimise the humoral immune response. Sheep immunised with 2mg La. hesperus venom produced the highest levels of specific antibodies as assessed by ELISA, using the isolated nerve diaphragm preparation or in vivo in mice. The new process provided a pure F(ab')2 antivenom retaining 78% of the original antisera ED so neutralising power and was - twice as effective as the Merck antivenom.

Bibliography: pages 121-132.
Bacterial oxidation is currently finding significant application for the oxidative pretreatment of refractory gold-bearing sulphides. Plants processing sulphide concentrates have commonly been operated at solids concentrations of between 18 and 20 per cent (m/v) (Le 180 and 200 kg.m-3). At higher concentrations, a decline in the bio-oxidation rate has been observed. Other metallurgical processes, such as chemical leaching and cyanidation, are performed at higher solids concentrations of between 40 and 50 per cent (400 and 500 kg.m-3), providing an incentive to increase the solids concentration at which bio-oxidation plants are operated. A review of literature indicated the following factors to be potential causes of reduced bio-oxidation rates at high solids concentrations: oxygen and carbon dioxide mass transfer; a low bacteria-to-solids ratio; mechanical damage of the bacte.ria; and the build-up of inhibitory oxidation products. Interaction of these factors in the completely-mixed reactors that are commonly used for biooxidation, has confounded the interpretation of the effects of individual factors. Analysis of literature data revealed a link between the sulphide grade of a particular material and the highest solids concentration at which the bacterial oxidation rate was maximal. The oxygen demand is directly proportional to the sulphide concentration in the reactor. Correlations were used to predict the oxygen transfer potential in the experimental reactors and it was found that as long as the oxygen transfer potential exceeded the oxygen demand, the biooxidation rate was proportional to the solids concentration for a specific material. Wh~n the oxygen demand equalled or exceeded the oxygen transfer potential, then the bacterial oxidation rate was limited by oxygen availability. The sulphide grade is characteristic of a particular ore or concentrate and from the data analysis oxygen availabiiity appeared to be the underlying reason why low grade materials could be oxidised at the maximum specific bio-oxidation rate at far higher solids concentrations than high-grade f!laterials. Abstract ii The experiments performed in this study were designed to further investigate the apparent relationship, identified by analysis of literature data, between sulphide grade and the solids concentration at which the bacterial oxidation rate was maximal. The effect of both solids concentration and sulphide grade on the biooxidation rate was investigated and related to the oxygen availability in the reactor.

In 1957 Vroom presented an article that dealt with the kinetics of the sulphate cook. He showed that the lignin dissolution exhibited a temperature/time dependency that could be explained by the Arrhenius equation and that the reaction was of first order with respect to lignin. However, even before Vroom introduced the H-factor all wood components were assumed to react according to a first order reaction. In recent years progresses in this area have been made. Lignin for example is nowadays considered to dissolve during three parallel first order reactions, all with differences in activation energies.

When the kinetics are evaluated, several cooking series at different temperatures and concentrations of active cooking chemicals are needed. The data points obtained are then fitted into some equation. If the concentration of the active cooking chemicals is constant, the activation energies and the chemical dependency for the dissolution of wood components can easily be found. In order to simplify the evaluations of the kinetics, very high liquor-to-wood ratios are sometimes used, often as high as 50:1 or even 75:1. In this manner, the chemical concentrations are almost constant during the cook. The problem is that in the normal industrial cook where the liquor-to-wood ratio is about 4:1, the chemical concentration is not constant. This is due mostly to the alkali consumption that takes place in the cook for example when neutralising the acidic groups in the hemicelluloses.

A disadvantage with high liquor-to-wood ratios is the high dilution of the dissolved organic matter. A high concentration of dissolved lignin boosts the dissolution of the remaining lignin in the wood residue and xylan can redeposit on the fibres when its concentration in the cooking liquor is high.

The aim of this project was to describe how different liquor-to-wood ratios influence the kinetics during sulphate cooking of spruce.

Surface enhanced Raman scattering (SERS) has achieved much attention since its conception in 1974. The analytical technique overcomes many difficulties associated with conventional Raman whilst also increasing sensitivity. However, the increased interest and work in the field has also identified flaws, many of which are centred on the irreproducibility of the SERS enhancement effect. The majority of the work described in this thesis focusses on the ‘optimisation’ of solid-state and solution based SERS systems. Optimisation plays a crucial role in maximising both enhancement effects and reproducibility. Here criteria are outlined for the synthesis of high performance solid-state SERS substrates and the synthesis of a range of substrates is assessed, each with associated pros and cons. The most successful substrate was synthesised by exploiting redox potentials which allow for the direct deposition of silver onto copper foil. The deposition times and temperatures were optimised sequentially to generate a high performance substrate capable of detecting Rhodamine 6G at trace levels. Reproducibility comparisons of the silver on copper (SoC) substrate were carried out against commercial substrates: Klarite and QSERS, multiple univariate and multivariate methods were used to assess the substrates performance. The results confirmed that the SoC substrate performed better than both the commercial substrates. The work also highlights the importance of using multiple data analysis methods in order to assess the performance of a solid-state SERS substrate. Deposition of the silver surface was also successful on British 2p coins allowing the for the detection and discrimination of illegal and legal drugs when coupled with multivariate data analysis methods such as PCA and PLS. Solution based SERS analyses were also carried out successfully using different optimisation strategies. The initial investigation involved careful control of the individual components of a SERS system (nanoparticles, aggregating agents and analyte) in order to establish a low limit of detection for the increasingly abused ‘legal high’ MDAI. The use of a reduced factorial design was then successfully employed to explore a greater number of SERS variables and define a low limit of detection for the class B drug mephedrone. The robust experimental design also allowed an insight into the importance of each of the individual components within a solution based SERS system. The final piece of work carried out was the SERS discrimination of antibiotics: ampicillin, ticarcillin and carbenicillin. Optimisation of the solution based experiment allowed the in-situ hydrolysis of the β-lactam moiety present in ampicillin rendering it pharmacologically inactive to be followed under acidic conditions at concentrations of 10 ppm.

Information on the biosynthetic origin and functional advantage of marine mollusc natural products is not only essential to our understanding of chemical ecology, but to the development and responsible production of therapeutic agents. As demonstrating in situ activity is methodologically hindered, functions inferred by in vitro activity have been assumed for many secondary metabolites. The anatomical and ontogenetic distribution of natural products can not only provide information on the biosynthesis and storage of metabolites, but identify selective pressures likely to affect survivorship at a specific life stage. Thus, dissection and chemical analysis of distinct tissues, in combination with histochemistry may offer a valuable approach. Marine gastropods of the Muricidae are renowned for the ancient dye Tyrian purple, which evolves from choline esters of bromoindoxyl sulphate in the hypobranchial gland through a series of enzymatic and photo-oxidative reactions. Prochromogen hydrolysis by arylsulphatase liberates neuromuscular active choline esters and cytotoxic bromoindole precursors, which also occur in muricid egg masses. Although visual accounts of dye pigments in the muricid gonoduct suggest precursors may be incorporated into egg masses from a maternal source, their biosynthetic origin and the evolutionary significance of the hypobranchial gland is unknown. Thus, the Muricidae, and in particular Dicathais orbita upon which most previous research has been focused, is an ideal model for this novel approach to natural product research. To confirm observations of dye pigments in muricid gonoducts and gain an understanding of their anatomical distribution, a liquid chromatography-mass spectrometry (LC-MS) method was developed to simultaneously quantify pigments, precursors and the prochromogen, tyrindoxyl sulfate. The prochromogen was not only detected in albumen and capsule gland extracts, but bioactive intermediates and the dye 6,6’-dibromoindigo were also present in the latter. These findings provided preliminary evidence for the maternal provision of prochromogens in egg masses of D. orbita and identified regions within which to conduct histochemical investigations. Tyrindoxyl sulphate was also detected in male prostate gland extracts, along with the dibromoindigo isomer, 6,6’-dibromoindirubin and its oxidative precursor, 6-bromoisatin. This not only implies physiological differences exist between male and female gonoducts, but that these secondary metabolites are not solely intended for egg masses and may hold significance throughout the life cycle. Histomorphological inspection of the pallial gonoduct-hypobranchial gland complex was conducted over the annual cycle to determine a mechanism for precursor transfer between these structures. Although an anatomical connection was not detected, the secretions of two hypobranchial cell types thought to be involved in Tyrian purple synthesis were of remarkable biochemical similarity to those of various capsule and albumen gland lobes. Together these findings implied the potential for natural product synthesis within the pallial gonoduct of D. orbita. To establish the role of these glandular lobes in the incorporation of intracapsular fluid and capsule laminae, identical histochemical techniques were applied to transverse capsule wall sections. Biochemical correlations not only provided a simple method of deciphering the complex process of encapsulation in neogastropods, but effectively identified the destination of gonoduct secretions in egg capsules of D. orbita. Comparisons of capsule and gonoduct biochemistry revealed that the intracapsular fluid and inner capsule wall are secreted by the posterior capsule gland lobe, the middle lamina by the lateral lobes and the outer layers by the dorsal lobe, albumen and pedal glands. Investigation into the location of regulatory enzymes and precursors was conducted to establish the biosynthetic origin of Tyrian purple prochromogens and mechanisms governing bioactive precursor synthesis. Novel histochemical techniques for the localization of bromoperoxidase, the enzyme thought to facilitate prochromogen bromination, and tyrindoxyl sulphate were developed and applied to gonoduct, hypobranchial gland, and encapsulated larvae sections. Standard staining reactions for the indole precursor, tryptophan, and arylsulphatase were also applied. The histochemical approach adopted revealed that tyrindoxyl sulphate is de novo biosynthesized through the post-translational bromination of dietary derived tryptophan. Two biosynthetic sites were identified, one related to hypobranchial secondary metabolism and the second of significance to the presence of bioactive precursors in muricid egg masses. Tryptophan is stored within secretory cells of the lateral hypobranchial epithelium and once exocytosed, is united with bromoperoxidase from supportive cells to form tyrindoxyl sulphate. Prochromogen synthesis also occurs in the subepithelial vascular sinus for storage and secretion by medial hypobranchial secretory cells. Bioactive precursor synthesis on the epithelial surface is regulated by the liberation of arylsulphatase from adjacent supportive cells. These findings not only provide evidence for de novo biosynthesis of Tyrian purple precursors, but are first account of natural product biosynthesis within the gastropod hypobranchial gland. Together these findings imply a naturally selected function for the synthesis of bioactive indoles in hypobranchial gland secretions of the Muricidae and Gastropoda. Tyrindoxyl sulphate is also transported within the vascular sinus to lateral and dorsal capsule gland lobes where bromoperoxidase and arylsulphatase also occur. Arylsulphatase was also detected within the albumen gland, which along with the posterior capsule gland lobe, acts as a storage site for dietary tryptophan. Thus, tyrindoxyl sulphate and the constituents for prochromogen and precursor biosynthesis are introduced to intracapsular fluid and capsule laminae by the capsule gland. Histochemistry in combination with LC-MS revealed an identical biosynthetic profile within larval vitellus, which is elaborated during oogenesis and may also receive secretions from the albumen gland. Due to the absence of a hypobranchial gland in veligers, it appears that pelagic larvae rely on vitelline natural products until settlement and metamorphous. These findings together with the in situ antimicrobial activity of bromoindoles suggest Tyrian purple precursors are incorporated into muricid egg masses as a maternal investment in larval defence against pathogens. The results of this investigation clearly highlight the benefits of adopting a histochemical approach to natural product research. This novel alternative to radioisotopes and in situ demonstration of bioactivity, can not only aid in the elucidation of secondary metabolic pathways and chemically mediated interactions, but identify mechanisms of metabolite regulation and differentiate between biosynthetic and storage tissues. Apart from providing insight into the ecological significance of muricid secondary metabolites, the biosynthetic information provided is valuable to our understanding of chemical phylogeny and biosynthetic enzyme sequencing for the environmentally sound development of natural products as biomedical agents.

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O presente trabalho apresenta a elaboração, a aplicação e a análise de uma proposta pedagógica chamada Situação de Estudo como forma de construção do conhecimento químico na Educação de Jovens e Adultos do Instituto Estadual Padre Francisco Garcia da cidade de São Borja-RS. Esta proposta teve a intencionalidade de trazer a realidade dos estudantes para sala de aula, onde estes sujeitos possam pensar em situações reais de suas vivências, e no ambiente escolar construir o pensamento científico. O trabalho constitui-se de três principais momentos, os quais são, levantamento de temáticas relevantes fundamentalmente por meio de questionário com base em ideias freirianas. O segundo momento constitui na construção da proposta com os temas relevantes identificados a partir do estudo realizado no primeiro momento, ideias baseadas em princípios vygotskyanos, que nos revela a importância do meio cultural onde os sujeitos estão inseridos para o desenvolvimento da aprendizagem. O terceiro momento foi o desenvolvimento da proposta em sala de aula e análise qualitativa, com o objetivo de sinalizar possibilidades de produção de material para a Educação de Jovens e Adultos; bem como aprendizagens possibilitadas pela sua implementação em sala de aula. A construção do conhecimento químico através de uma perspectiva temática da Situação de Estudo, mostrou-se uma importante ferramenta de mediação e significação cultural e conceitual.
This paper presents the design, implementation and analysis of a pedagogical proposal called Study Situation as a Way of Construction of Chemical Knowledge in the Youth and Adult Education of Instituto Estadual Padre Francisco Garcia from São Borja - RS. This proposal had the intention to bring the reality of the students to the classroom, where these guys can think of real situations of their experiences, and in the school environment build scientific thinking. The work consists of three main moments, which are relevant thematic survey primarily through a questionnaire based on Freirian ideas. The second moment is the construction of the proposal with the relevant issues identified from the study at first, ideas based on Vygotskian principles, which reveals the importance of the cultural environment in which the subjects are included for the development of learning. The third time was the development of the proposal in class and qualitative analysis room, in order to highlight material production possibilities for Youth and Adult Education; and learning made possible by its implementation in the classroom. The construction of chemical knowledge through a Thematic Perspective Study situation proved to be an important tool mediation, and cultural and conceptual meaning.

Mass spectrometry, both stand alone and in conjunction with various separation science approaches, has been used for the qualitative and quantitative study of a number of systems of industrial interest. These systems include lubricant additives, organic acids, aliphatic amines and poly (ethylene) glycol oligomers. Organic acids and aliphatic amines are industrially important compounds. The acids in this study helped evaluate the capabilities and robustness of capillary electrophoresis (CE) with and without mass spectrometric detection. Transient capillary isotachophoresis (tCIP) was also examined as a pre-concentration technique. This allowed larger sample volumes to be injected on to the capillary and improved detection limits by a factor of 100. Production samples of organic acids were also successfully analysed by CE and CE-MS. Aliphatic amines, considered harmful, require trace level analysis due to regulatory legislation. CE and CE-MS methodologies were developed for them. The amines under analysis, not possessing UV active chromophores, were unamenable to conventional UV detection. Consequently an indirect-UV detection method was developed. Environmental samples from an amine plant were analysed by the methods developed. The quantitation of low mass poly (ethylene) glycol oligomers was examined by MALDI-TOF and APCI MS. The results were compared with those obtained by carbon-13 NMR. Attempts were made to obtain pure PEG200 and PEG300 oligomers by semi-preparative HPLC with fraction collection although subsequent characterisation gave mixed results. APCI-MS gave consistently lower average molecular weights than MALDI-TOF MS.

Conservators treat and repair a huge array of damaged and degrading materials on a regular basis. As such, there are many techniques and protocols in place to deal with these problems successfully, be that via preventative or interventive methods. However, there is need for new and innovative techniques that offer long term stabilisation to materials and objects that are prevalent within museum collections. As an alternative to some of these conservation techniques, hydration with supercritical carbon dioxide was investigated here. Both modern and historic, hardwood and softwood samples were successfully hydrated using this technique. The addition of a co-solvent (methanol) to the supercritical fluid solvent stream was used as a method to increase the solubility of water in carbon dioxide, and therefore improve levels of hydration. To evaluate the extent of any damage being caused during the supercritical fluid treatment, microstructural and macrostructural analytical techniques were carried out. The supercritical hydration technique allowed historic wood to be hydrated and stabilised. Strength properties were seen to be maintained or improved after the supercritical treatment, providing conservators with a viable method of hydration. A feasibility study looking at the cleaning and characterisation of historic leather samples was investigated using spectroscopic methods. The sensitivity of Diffuse Reflectance Infrared Fourier Transform spectroscopy on historic leather was explored. Additionally, changes in elemental composition on the surface of the leather were monitored using Scanning Electron Microscopy Energy Dispersive spectroscopy. Cleaning historic leather via a supercritical carbon dioxide solvent stream showed the greatest potential for future work. However, the characterisation of unattributed historic leather is a vast and complex task that would require the expertise of a leather conservator, if the investigation were to be continued.

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Este trabalho relata uma metodologia ativa para o Ensino de Ligações Químicas: Composição de paródias musicais como uma proposta de potencializar a aprendizagem significativa. Trata-se de uma pesquisa de natureza qualitativa, do tipo pesquisa-ação, e utilizou, para o levantamento de dados e para a tomada de decisões no decorrer do processo de pesquisa, questionários, observações da atividade orientada, depoimento dos educandos durante e após a elaboração das paródias musicais, fotos, vídeos e análise das letras das paródias. A pesquisa foi realizada no Colégio Pedro II, Campus Niterói, Rio de Janeiro e aplicada no 1º. ano do Ensino Médio Regular do ano letivo de 2016. Os resultados obtidos indicam que a construção de paródias musicais favoreceu o processo de ensino-aprendizagem, sendo esse recurso didáticos visto pelos alunos como alternativa para facilitar a aprendizagem. Consideramos que este trabalho pode ser replicado, abrindo possibilidades de novas criações e pesquisas sobre o emprego de estratégias de metodologias ativas no ensino de Ciências da Natureza. Com o intuito de incentivar esta aplicação, elaboramos, como produto dessa dissertação, uma videoaula onde é mostrada a aplicação da metodologia e com orientações sobre a forma de utilização.
This paper reports an active methodology for the Teaching of Chemical Bonds: Composition of musical parodies as a proposal to potentiate meaningful learning. For this purpose we used a qualitative methodology and, for data collection and decision making during the research process, questionnaires, observations of the activity oriented, testimony of the students during and after the elaboration of the musical parodies, photos, videos and analysis of the letters of the parodies. The research was carried out at Pedro II School, Niterói, Campus, Rio de Janeiro and applied in the 1st. Year of Regular High School during the academic year of 2106. The results indicate that the construction of musical parodies favors facilitate the teaching-learning process. We consider that this work can be replicated and open possibilities of new creations and research on the use of active methodologies for teaching of Natural Sciences. In order to stimulate this application, we elaborate, as a product of this dissertation, a videoconference showing the application of the methodology and guidelines on how to use it.

abstract: Consumption of seafood poses a substantial threat to global biodiversity. Chemical contamination found in both wild-caught and farmed seafood also presents significant health risks to consumers. Flame retardants, used in textiles, upholstery, plastics, and other products to reduce risk of fire-related injury, are of particular concern as they are commonly found in the marine environment and permeate the tissues of fish that are sold for consumption via multiple pathways. The widespread issue of fishery collapse could be alleviated by demonstrating to stakeholders that many unsustainable fish stocks are also unhealthy and mutually disadvantageous for both human consumers and the environment. To thoroughly investigate the confounding factors and contradictory signals enmeshed in the relationship between ecologically sustainable fisheries and flame retardant contamination, I examined the biological characteristics of regional fish stocks which drive both contamination and perceived sustainability. I found that the biological and spatial aspects of commonly consumed aquatic and marine species best predict contamination when compared with various indices of sustainability. My results confirm that knowledge of flame retardant toxicity will become increasingly more important to consumers because a high percentage of global populations rely on coastal seafood for subsistence, and although dispersal of chemical contamination is still a poorly understood phenomenon, fish harvested closer to land are likely to contain higher concentrations of potentially harmful chemicals. Because some of the same biological traits which facilitate the uptake of chemicals also contribute to how a species responds to fishing pressures, concern for private health increases public consideration for the conservation of species at risk.
Dissertation/Thesis
Masters Thesis Biology 2015

碩士
國立成功大學
地球科學系碩博士班
97
The chemical components involved in the mantle source of the North Luzon lavas have been an issue of debate. In existing mixing models, the depleted end-member was assigned to MORB source, while EMI, subducting sediments, and metasomatic fluids and melts were considered as enriched components. These models were all developed from chemical and isotope compositions of lavas from entire North Luzon arc without a detailed investigation on chemical variations of lavas in individual islands. In this study, the chemical compositions and Sr, Nd, and Hf isotope ratios of Lutao volcanic rocks are used to address the process and source controls on lavas chemistry. Twenty-eight volcanic rock samples were collected from Lutao. Based on their SiO2 and total alkali contents, these samples were classified into basalt (B), basaltic andesite (BA), andesite (A) and dacite. Basalts and andesites were subdivided into isotopically enriched groups (BE and AE, respectively) and depleted groups (BD and AD, respectively). The andesite (group A) samples have similar Sr, Nd, and Hf isotope ratios with inverse correlations between MgO and incompatible element contents, reflecting fractional crystallization after partial melting from a common source. Based on trace element variations, the group A samples are modeled to be residual melts after intensive fractional crystallization. The two group AE samples have enriched 87Sr/86Sr, 143Nd/144Nd, and 176Hf/177Hf ratios, but their abundance ratios of incompatible elements resemble those of the group A samples. A plausible explanation is that the mantle sources of the groups A and AE lavas were metasomatized by same materials; however, the metasomatic process occurred earlier in the source of AE lavas, leading to enriched 87Sr/86Sr, 143Nd/144Nd, and 176Hf/177Hf ratios. The group AD samples plot closer to MORB in the 87Sr/86Sr-143Nd/144Nd- 176Hf/177Hf space. Their Nb/La and Ti/HREE ratios are lower than MORB values implying subjection to metasomatism, an inference consistent with their Sr, Nd, and Hf isotope data. 87Sr/86Sr, 143Nd/144Nd, and 176Hf/177Hf ratios of the group BE samples are similar to those of the group AE samples. However, model calculations show that their incompatible element abundances can not be explained by derivation from a common source by different degrees of partial melting. An incompatible element enriched source is required for the group AE lavas. The groups BD and AD samples have similar 143Nd/144Nd and 176Hf/177Hf ratios, but group BD has higher Sm/Nd and Lu/Hf ratios. These results imply that the source of the group BD samples was metasomatized later than that of the group AD samples. Overall, the composition and isotope data require that the mantle sources of Lutao lavas were subjected to various metasomatic agents at different time. Based on the mixing models of Kuo (2007), the 87Sr/86Sr, 143Nd/144Nd, and 176Hf/177Hf ratios of the Lutao samples are best explained by mixing sub-equal amounts of siliceous melts derived from subducted sediments and oceanic crust.