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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Kinetics of the Hydrodechlorination Reaction of Chlorinated Compounds on Palladium Catalysts

Chen, Nan 23 August 2003 (has links)
" Hydrodechlorination is the reaction of a chlorinated organic compound (R-Cl) with hydrogen to form a carbon-hydrogen bond and HCl: R-Cl + H2 = R-H + HCl. This reaction is used in refrigerant manufacturing, industrial by-product reclamation and waste management. These practical applications require in-depth understanding of hydrodechlorination reaction. In this research work, we studied four families of chlorinated compounds; CF3CF3-xClx(x=1-3), CH4-xClx (x=1-4), CF4-xClx (x=1-4) and dichloropropanes (1,1-, 1,2-, 1,3-, 2,2-), on supported palladium catalysts to create a theory capable of predicting the hydrodechlorination rate on chlorinated compounds and to explore the reaction mechanism. A possible set of elementary reaction steps of hydrodechlorination reaction was proposed from our kinetics study of all these compounds. In this set of reaction steps, the irreversible scission of the first C-Cl bond in a chlorinated compound was proposed to be the rate-determining step; gas phase H2 and HCl were suggested to be in equilibrium with surface H and Cl species; adsorbed Cl was assumed to be the most abundant surface intermediate. The overall rate of hydrodechlorination reaction could be derived from these reaction steps as r=k'[R-Cl]/(1+K'[HCl]/[H2]0.5). In this rate equation, k'is the product of the adsorption equilibrium constant of the chlorinated compound on catalyst surface times the rate constant for the scission of the first C-Cl bond scission step, and K'is the square root of the equilibrium constant for the equilibrium between H2, HCl and their corresponding surface species: 2HCl + 2* = H2 + 2Cl*. The hydrodechlorination reaction of CF3CFCl2 was performed in the presence of H37Cl to study the reversibility of C-Cl bond scission, and the removal of the first Cl atom from CF3CFCl2 was found to be an irreversible step. Hydrodechlorination experiments of CF3CFCl2 with D2 and HCl mixture revealed that D2 and HCl were in equilibrium with surface adsorbed hydrogen and chlorine during reaction. The forward rate and reverse rate of this equilibrium were at least 400 times higher than the overall hydrodechlorination rate. This result supported the assumption of equilibrium for 2HCl + 2* = H2 + 2Cl*. Additionally, the activation energy for the rate determining step was extracted from hydrodechlorination reaction kinetics results of CH4-xClx (x=1-4), CF4-xClx (x=1-4) and dichloropropanes (1,1-, 1,2-, 1,3-, 2,2-) compounds. It was found that for each of the series compounds, a linear relationship existed between C-Cl bond scission activation energy and gas phase C-Cl bond strength. This observation corroborates our assumption that the removal of the first Cl atom from a chlorinated compound is the rate-determining step in the hydrodechlorination reaction. Thus, all kinetic and isotope experimental results obtained from this study are consistent with the proposed reaction steps for the chlorinated compounds tested. This set of reaction steps can also be used to predict the hydrodechlorination reaction rate of a chlorinated compound, once its gas phase C-Cl bond energy is calculated and the turnover rate of a reference chlorinated compound with similar structure is known. Some work has been done to study hydrodechlorination reaction steps and reaction intermediates beyond the rate-limiting step. Isotope tracing experiments with D2 indicated that CH3-, CH2- groups adjacent to a C-Cl bond could undergo deuterium exchange. The study of reactions steps using ab initio methods, including calculation of rate constants, is also under way. Calculations for the CH4-xClx (x=1-4) family showed that the heat of adsorption and C-Cl bond dissociation energy on a Pd surface were linearly related to their gas phase C-Cl bond strength."
112

DESENVOLVIMENTO, VALIDAÇÃO E APLICAÇÃO DE UM MÉTODO QuEChERS PARA A DETERMINAÇÃO DE PESTICIDAS ORGANOCLORADOS

Stremel, Tatiana Roselena de Oliveira 12 April 2018 (has links)
Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-07-31T12:30:12Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tatiana Roselena de Oliveira Stremel.pdf: 2464228 bytes, checksum: 246fc4842a96b73dff9b3d790b4e16dc (MD5) / Made available in DSpace on 2018-07-31T12:30:12Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tatiana Roselena de Oliveira Stremel.pdf: 2464228 bytes, checksum: 246fc4842a96b73dff9b3d790b4e16dc (MD5) Previous issue date: 2018-04-12 / A maior parte dos pesticidas organoclorados (OCPs) possuem comercialização controlada ou proibida a décadas, no entanto são ainda encontrados em todos os locais do planeta. A determinação destes compostos em matrizes complexas como tecido de peixe é alvo constante de pesquisas, especialmente com o objetivo de minimizar consumo de reagentes e tempo. Este estudo objetivou desenvolver e validar um método QuECheRS com ultrassom e d-SPE para determinação por CG/ECD/MS de p,p’-DDE, p,p’-DDT, α-endosulfan, β-endosulfan, Aldrin e Dieldrin em tecidos de peixe, aplicar em amostras de tecidos de peixe comercializadas e em tecidos coletados em ambiente natural e realizar uma avaliação de risco das concentrações de OCPs detectadas nos tecidos. Três planejamentos fatoriais foram empregados para otimizar a etapa de preparo da amostra. O método desenvolvido foi validado para verificar seu desempenho e um possível efeito matriz, sendo posteriormente aplicado na extração de OCPs de músculo de Tilápia e Lambari comercializados em supermercados de Ponta Grossa e em músculo, ovas e vísceras de Lambari coletado da represa de Alagados, em Ponta Grossa. Ao final realizou-se uma avaliação de risco relacionando o consumo diário local, com massa corporal média da população e contaminação por OCPs nos tecidos analisados. Na validação o método apresentou recuperações entre 77,3% e 110,8%, com RSD inferior a 13% e os limites de detecção estiveram entre 0,24 μgkg-1 e 2,88μgkg-1, mostrando boa sensibilidade e precisão. Resíduos dos OCPs estudados foram detectados nos tecidos analisados em concentrações que variaram entre 3,4 μgkg-1 e 417,6 μgkg-1, verificando-se que os poluentes possuem uma tendência a bioacumular em maior proporção nas vísceras, do que em ovas e no músculo, a presença destes compostos nas ovas, demonstra que indivíduos da espécie analisada entram em contato com os OCPs desde a fase de embrião. Na avaliação de risco verificou-se que ao se consumir esses peixes, esses OCPs podem ao longo do tempo gerar efeitos adversos para a saúde dos consumidores. O método proposto mostrou-se efetivo na determinação de baixas concentrações de OCPs em tecidos de peixe, utilizando pequena massa de amostra (0,5 gramas), viabilizando a análise sem a necessidade de agrupamento (pool), ao mesmo tempo possibilitou a análise de tecidos, de peixe de pequena massa corporal total (Lambari), avaliando ainda a bioacumulação dos OCPs em diferentes tecidos. O método é aplicável para análise de OCPs aplicado à área toxicológica. / Most organochlorine pesticides (OCPs) are controlled or banned for decades, but they are still found everywhere in the world. The determination of these compounds in complex matrices such as fish tissue is a constant goal of research, especially with the aim of minimizing reagent consumption and time. The aim of this study was to develop and validate a Quechers method with ultrasound and d-SPE for determination of p, p'-DDE, p, p'-DDT, α-endosulfan, β-endosulfan, Aldrin and Dieldrin in fish tissues, apply on samples of commercially available fish tissues and on tissues collected in the natural environment and carry out a risk assessment of the concentrations of OCPs detected in the tissues. Three factorial designs were used to optimize the preparation stage of the sample. The method developed was validated through figures of merit and matrix effect, and it was later applied in the extraction of OCPs from Tilapia and Lambari muscle marketed in supermarkets in Ponta Grossa and Lambari muscle, eggs and viscera collected from the Alagados dam in Ponta Thick. At the end of the study, a risk assessment was performed relating local daily consumption, mean body mass of the population and OCP contamination in the tissues analyzed. In the validation, the method presented recoveries between 77.3% and 110.8%, with RSD lower than 13% and detection limits between 0.24 μg kg -1 and 2.88 μg kg -1, showing good sensitivity and precision. Residues of the OCPs studied were detected in the tissues analyzed at concentrations ranging from 3.4 μgkg-1 to 417.6 μgkg-1, with pollutants having a tendency to bioaccumulate more in the viscera than in roe and in muscle, the presence of these compounds in the eggs, demonstrates that individuals of the analyzed species come into contact with OCPs from the embryo stage. In the risk assessment it was found that there is a risk when consuming these fish, these OCPs may over time generate adverse effects on the health of consumers. The proposed method was effective in the determination of low concentrations of OCPs in fish tissues, using a small sample mass (0.5 grams), making the analysis possible without the necessity of pooling, at the same time making possible the analysis of tissues, of fish of small total body mass (Lambari), also evaluating the bioaccumulation of OCPs in different tissues. The method is promising for OCP analysis applied to the toxicological area.
113

Evaluation of organochlorines and heavy metals in the Pearl River Delta and Hong Kong, with emphasis on bioaccumulation in freshwater fish

Zhou, Hai Yun 01 January 1999 (has links)
No description available.
114

Caracterização geoambiental e avaliação dos parâmetros que influenciam na mobilidade do HCH no meio poroso / Geoenvironmental characterization and assessment of parameters that influence the mobility of the HCH in porous medium.

Letícia dos Santos Macedo 17 October 2014 (has links)
Este trabalho apresenta a caracterização geoambiental de solos de uma área contaminada, localizada no município de Santo André, Estado de São Paulo, Brasil. O objetivo foi determinar parâmetros experimentais para permitir o estudo de alguns aspectos do transporte do pesticida organoclorado Hexaclorociclohexano (HCH). A área de estudo contém células com cerca de 30.000 toneladas de um material contendo HCH em elevadas concentrações. As investigações de campo demonstram que há concentrações de HCH na água subterrânea. Em 2011, foram coletadas amostras deformadas e indeformadas de solo em quatro diferentes pontos superficiais da área contaminada, e posteriormente uma amostra composta da camada de solo de alteração de rocha (SAR), a fim de responder a questionamentos quanto à mobilidade do contaminante na área. A caracterização geoambiental, baseada em ensaios laboratoriais, foi realizada por meio das seguintes análises: análise granulométrica, limites de Atterberg, densidade específica, porosidade, umidade do solo, curva de retenção de água no solo, condutividade hidráulica, ensaio de adsorção, pH, condutividade elétrica, capacidade de troca catiônica (CTC), teor de matéria orgânica e teor de voláteis. O solo superficial da área é heterogêneo e a capacidade de adsorção dos solos analisados foi menor do que o esperado. Esta caracterização subsidiou o estudo de fluxo e transporte do HCH, por meio de simulação numérica, utilizando o programa Hydrus 1D. As simulações tiveram dois objetivos diferentes: no primeiro foi avaliado os resultados da simulação em comparação à situação atual no campo; no segundo foi avaliada a sensibilidade do transporte em função da alteração dos parâmetros obtidos experimentalmente Ks; Kd; s e (Van Genuchten); e dos parâmetros obtidos na literatura. Os resultados permitiram concluir que o modelo Hydrus 1D consegue representar a contaminação do HCH no solo. O parâmetro de degradação na água foi essencial para chegar em ordens de grandeza de concentrações próximas das identificadas em campo. Os parâmetros de degradação, difusividade, dispersividade e condutividade hidráulica são os que mais afetam os resultados finais de concentração do HCH na água subterrânea e, portanto, merecem atenção maior durante as futuras investigações. / This paper presents the geoenvironmental characterization of soils from a contaminated site, located in Santo André, São Paulo State, Brazil. The objective was to determine experimental parameters to allow the study of some aspects of transport of the organochlorine pesticide hexachlorocyclohexane (HCH). The study site contains trenches with about 30,000 tons of a material containing high concentrations of HCH. The site investigations show that there are HCH concentrations in groundwater. In 2011, disturbed and undisturbed soil samples were collected at four different surface points of the contaminated site, and then a sample of soil from rock alteration layer (SAR) was also composed for characterization in order to answer questions concerning the mobility of contaminant in the site. The environmental characterization based on laboratory tests, was performed by the following analyzes: grain size distribution, Atterberg limits, specific gravity, porosity, moisture content, water retention curve, hydraulic conductivity, pH, electrical conductivity, cation exchange capacity (CEC), organic matter content and volatile content. The surface soil of the area is heterogeneous and the adsorption capacity of the soils analyzed were lower than expected. This characterization allowed the study of flow and transport of HCH through numerical simulation using the Hydrus 1D software. The simulations had two different goals, the first was evaluated the simulation results compared to the current situation in the field. In a second step the sensitivity of transport due to the change of the parameters obtained experimentally Ks; Kd; s and (Van Genuchten); and parameters obtained from the literature. The results showed that the Hydrus 1D model simulates HCH contamination in soil. Water degradation parameter was essential to get orders of magnitude similar to those identified in field concentrations. The degradation, diffusivity, hydraulic conductivity and dispersivity parameters are those that most affect the final results of concentration of HCH in groundwater and therefore deserve more attention in future investigations.
115

Preparação de eletrodos de mistura de óxidos metálicos produzidos a partir de líquidos iônicos e avaliação do seu desempenho ante a eletrooxidação do Alaclor / Preparation of mixed metal oxide electrodes produced from ionic liquids and evaluation of their performance against the electrooxidation of Alachlor

Rodrigo de Mello 26 February 2018 (has links)
O presente trabalho teve como objetivo a produção de ânodos de mistura de óxidos metálicos de composição nominal Ti/Ru0,3Ti0,7O2 utilizando um líquido iônico como solvente no preparo da solução precursora. A utilização deste tipo de solvente permite a síntese de materiais com morfologia e estrutura específicas, visto sua influência nas propriedades dos materiais. Neste trabalho foram utilizados líquidos iônicos baseados no imidazol, com o intuito de avaliar os efeitos do tamanho da cadeia carbônica ligada ao anel aromático heterocíclico, utilizando para comparação um eletrodo comercial (De Nora do Brasil). Por meio da caracterização física foi possível verificar que os eletrodos produzidos no laboratório apresentaram um filme mais compacto e com a formação de grânulos, o que indica um aumento na densidade de metais depositados. Além disso, o aumento na temperatura de calcinação favoreceu a deposição do óxido metálico catalítico (RuO2) na superfície do eletrodo ao se utilizar o hidrogenossulfato de 1-butilimidazólio ([HBIm]HSO4) como solvente na solução precursora. O eletrodo comercial apresentou uma área superficial superior aos eletrodos produzidos no laboratório, sendo a maior parte dessa área referente aos sítios internos desse eletrodo. O ânodo produzido utilizando [HBIm]HSO4 calcinado a 550 °C apresentou 15% mais remoção do pesticida alaclor em meio de sulfato que o eletrodo comercial, além de um consumo energético 16% menor. No caso das eletrólises realizadas na presença de cloreto, houve uma menor remoção do pesticida, apesar da melhora na resposta eletroquímica dos eletrodos nesse meio. Esse desempenho negativo pode estar relacionado à geração de substâncias que apresentam aderência à superfície dos eletrodos durante o processo de oxidação, obstruindo parcialmente a superfície ativa. / The present work aims to the production of mixed metal oxide anodes with nominal composition Ti/Ru0,3Ti0,7O2 using an ionic liquid as solvent in the preparation of the precursor solution. The use of this type of solvent allows the synthesis of materials with specific morphology and structure, since their influence on the properties of the materials. In this work, ionic liquids based on imidazole were used in order to evaluate the effects of the carbon chain size bonded to the heterocyclic aromatic ring, using a commercial electrode (De Nora do Brasil) for comparison. By means of the physical characterization, it was possible to verify that the laboratory made electrodes presented a more compact film with formation of granules, which indicates an increase in the deposited metal density. Moreover, the increase in the calcination temperature favored the deposition of the catalytic metal oxide (RuO2) on the surface of the electrode by using 1-butylimidazolium hydrogen sulfate ([HBIm]HSO4) as the solvent in the precursor solution. The commercial electrode presented a surface area superior to the laboratory made anodes, being the greater part of that area referring to the internal sites of this electrode. The anode produced using [HBIm]HSO4 calcined at 550 °C showed 15% more alachlor removal in sulfate medium than the commercial electrode, in addition to a 16% lower energy consumption. In the case of the electrolysis carried out in the presence of chloride, there was less pesticide removal, despite the improvement in the electrochemical response of the electrodes in this medium. This negative performance may be related to the generation of substances that have adhesion to the surface of the electrodes during the oxidation process, partially obstructing the active surface.
116

Poluentes orgânicos persistentes e ingestão de plásticos em albatrozes e petréis (Procellariiformes) / Persistent organic pollutants and plastic ingestion in albatrosses and petrels (Procellariiformes)

Colabuono, Fernanda Imperatrice 04 August 2011 (has links)
Os albatrozes e petréis (Procellariiformes) são aves oceânicas e migratórias de grande interesse conservacionista. Neste trabalho foram estudadas duas classes de poluentes bastante conhecidos por afetarem negativamente as aves marinhas: os poluentes orgânicos persistentes e os plásticos. Bifenilos policlorados (PCBs) e pesticidas organoclorados foram detectados no tecido adiposo, fígado e músculo de oito espécies de Procellariiformes. Apesar da grande variabilidade intraespecífica nas concentrações, os perfis de PCBs e pesticidas organoclorados foram semelhantes entre os indíviduos, com predôminância de PCBs penta, hexa e heptaclorados e do p´p-DDE. A condição corporal se mostrou um fator importante na variação e redistribuição dos organoclorados nos tecidos das aves. As análises de isótopos estáveis de carbono e nitrogênio no fígado e músculo das aves mostraram que a dieta não foi suficiente para explicar as concentrações de organoclorados nas espécies estudadas e reforçaram a influência de fatores como idade, distribuição e especifidade da dieta na contaminação por estes compostos em aves marinhas. PCBs e pesticidas organoclorados foram detectados em pellets e fragmentos plásticos encontrados no trato digestório das aves estudadas, com perfis semelhantes aos encontrados nos tecidos dos Procellariiformes. A ocorrência de poluentes orgânicos em plásticos evidencia a capacidade destes de adsorver e transportar estes compostos e reforça o potencial dos plásticos como uma fonte adicional de contaminação para os animais que os ingerem, como as aves marinhas. / Albatrosses and petrels (Procellariiformes) are migratory oceanic birds of considerable conservational interest. The aim of the present study was to evaluate two classes of pollutants that negatively affect seabirds: persistent organic pollutants and plastics. Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were detected in the adipose tissue, liver and muscle of eight species of Procellariiformes. Although organochlorine concentrations exhibited a high degree of intra-species variability, the profiles of PCBs and OCPs were similar among the individuals, with predominance of penta, hexa and heptachlorobiphenyls and p´p-DDE. Body condition was an important factor in the variation and redistribution of organochlorine compounds in the tissues of the birds. Stable isotope analysis of carbon and nitrogen in the liver and muscle revealed that diet alone was insufficient to explain the organochlorine concentrations in the species studied, suggesting the influence of factors such as age, distribution and diet specificity regarding organochlorine contamination in seabirds. PCBs and OCPs were detected in plastic fragments and pellets found in the digestive tract of Procellariiformes, with profiles very similar to those found in the tissues of the birds. The occurrence of organic pollutants in plastics demonstrates their ability to adsorb and transport these compounds and underscores the potential of plastics as an additional source of contamination in organisms that ingest these products, such as seabirds.
117

In Utero Exposure to Organochlorine Pesticides and Early Menarche in the Avon Longitudinal Study of Parents and Children

Namulanda, Gonza, Maisonet, Mildred, Taylor, Ethel, Flanders, W. Dana, Olsen, David, Sjodin, Andreas, Qualters, Judith R., Vena, John, Northstone, Kate, Naeher, Luke 01 September 2016 (has links)
Introduction Epidemiologic data supporting the role of organochlorine pesticides in pubertal development are limited. Methods Using a nested case-control design, serum collected during pregnancy from mothers of 218 girls who reported menarche before 11.5 years of age (cases) and 230 girls who reported menarche at or after 11.5 years of age (controls) was analyzed for 9 organochlorines and metabolites. We analyzed the association between in utero organochlorine concentrations and early menarche using multivariate logistic regression controlling for mother's age at menarche, or mother's prenatal BMI. Results We did not observe an association between in utero exposure to HCB, β-HCH, ϒ-HCH, p,p′-DDT, p,p′-DDE, oxychlordane or trans-nonachlor and early menarche. Conclusions This study is the first to examine the association between in utero exposure to HCB, β-HCH, ϒ-HCH, oxychlordane or trans-nonachlor and early menarche. In utero exposure to organochlorine pesticides does not appear to have a role in the timing of menarche in this study.
118

Polluants Organochlorés et Risque de Survenue du Cancer de la Prostate. Interactions Gène-Environnement / Organochlorine Pollutants and the Risk of Prostate Cancer. Gene-Environment Interactions

Emeville, Elise 17 December 2014 (has links)
Le cancer de la prostate (CaP) est la pathologie tumorale la plus fréquente chez les hommes dans les pays occidentaux. L’âge avancé, les origines ethno-géographiques et la présence d’antécédents familiaux de CaP sont les principaux facteurs de risque clairement établis. Les expositions aux substances chimiques issues de l’activité humaine, en particuliers ceux présentant des propriétés hormonales (perturbateurs endocriniens), sont suspectées. L’objectif général cette thèse est d’étudier le rôle de certains polluants universels présentant des propriétés hormonales, tels que le DDE (principal métabolite du DDT) et les PCBs, ainsi que celui des polymorphismes de gènes codant pour des enzymes intervenant dans le métabolisme des xénobiotiques (GSTM1, GSTT1) et des œstrogènes (CYP17, CYP19, CYP1B1, COMT, UGT1A1) dans la survenue du CaP ou de sa récidive après traitement par prostatectomie radicale. Ce projet s’appuie sur les données obtenues lors de l’étude cas-témoins en population générale en Guadeloupe (KARUPROSTATE) et de la file active des cas traités par prostatectomie radicale. / Prostate cancer (PCa) is the most frequent type of cancer in Western countries. Advanced age, ethno-geographic origin and the presence of a family history of CaP are the main clearly established risk factors. The effects of exposure to synthetic chemicals with hormonal properties, also called endocrine disruptors (EDCs), on PCa are also are suspected. The main objective of this thesis is to evaluate the relationships between plasma concentration of persistent organochlorine pollutants with hormonal properties, such as DDE (the main metabolite of DDT) and PCBs as well polymorphisms of selected genes involved in xenobiotic (GSTM1, GSTT1) and estrogens (CYP17, CYP19, CYP1B1, COMT, UGT1A1) metabolism, and the occurrence of PCa or its recurrence after treatment with radical prostatectomy. This project is based on data obtained from the population-based case-control study (KARUPROSTATE) in Guadeloupe and from cases treated by radical prostatectomy.
119

Persistent Organic Pollutants in Australian Sewage Sludge: Environmental Monitoring and Land Application Risk Assessment

Clarke, Bradley, Bradley.clarke@student.rmit.edu.au January 2008 (has links)
Presented is a study of persistent organic pollutants in Australian sewage sludge, focusing on environmental monitoring and a sewage sludge land application human health risk contaminated with these compounds. The chemicals of concern were: • Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and
120

Assessment of exposure and response to atmospherically-derived contaminants in U.S. Arctic freshwater fish

Allen-Gil, Susan M. 12 April 1995 (has links)
The Arctic has long been considered to be a pristine environment, far from population centers and pollution sources. The detection of synthetic organochlorine compounds in various elements of the Arctic food web has confirmed the global dispersion of pollutants, particularly of persistent compounds such as organochlorines and heavy metals. Levels of heavy metals, although elevated, appear to be naturally so throughout much of the Arctic. Arctic pollution is both a humanitarian and ecological concern. Many arctic coastal communities depend heavily on marine mammal fat for sustenance, and are therefore potentially exposed to high levels of organochlorines and some metals. From an ecological perspective, the structure of arctic food webs, the importance of lipid mobilization for winter survival, and the adaptive physiologies of arctic organisms may result in an enhanced response to contaminant exposure. This thesis assesses the exposure and effect of organochlorine and heavy metal exposure in inland freshwater ecosystems of Arctic Alaska, and evaluates the physiological response of arctic grayling to experimental polychlorinated biphenyl (PCB) exposure. / Graduation date: 1995

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