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Monitoring obsahu rtuti a methylrtuti v rybím mase a zhodnocení rizik spojených s konzumací tohoto masa / Monitoring of mercury and methylmercury content in fish meat and evaluation of risks associated with the consumption of this meatKřížová, Lucie January 2021 (has links)
Mercury and its compounds are one of the most toxic global pollutants in the environment. It occurs in all segments of the environment, and it attains the food chain ang human body by people consuming fish. The theoretical part of this thesis examines the characteristics of mercury, its occurrence, the roots of its pollution, and the toxicity of various forms of mercury. Consequently, the thesis delineates analytical methodologies applied to determine the overall level of mercury and chemical forms of mercury. The practical part focuses on monitoring the level of mercury and methylmercury in 12 extracts of fish meat. The analyzer AMA 254 has been used to determine the level of mercury and methylmercury in these extracts. Based on the level that resulted from the measurements, the thesis concludes a risk that correlates with consuming this type of meat.
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Maternal Transfer of Dietary Methylmercury and Implications for Embryotoxicity in Fathead Minnows (Pimephales promelas)Bridges, Kristin N. 12 1900 (has links)
Mercury (Hg) is a ubiquitous environmental contaminant, which is capable of global atmospheric transport. As a result, even the most pristine aquatic ecosystems are affected by atmospheric Hg deposition, following which microbial transformation yield organic Hg forms, the most concerning of which is methylmercury (MeHg). Methylmercury is capable of bioaccumulation and biomagnification in food webs, resulting in potentially toxic body burdens due to regular dietary exposure in long-lived organisms at higher trophic levels. It is also a molecular mimic of some endogenous amino acids, providing a route of transfer from mother to offspring via large amino acid transporters. Exposure during neurodevelopment can lead to serious, irreversible neurological dysfunction, associated with a variety of cognitive and motor abnormalities across species. The present studies evaluate the effects of maternally-transferred dietary MeHg, at environmentally relevant concentrations on early life stage fathead minnows (Pimephales promelas). Embryos were collected from adult fatheads exposed to one of three diets with varying concentrations of MeHg for 30 days. Adult reproductive metrics were also monitored over the course of the study, with results indicating no effects on spawning frequency, clutch size, or total egg output. In embryos, Hg concentration was a function of female diet and the duration (number of days) of female exposure. Offspring spawned in tanks administered the low Hg diet displayed altered embryonic movement patterns (hyperactivity), decreased time to hatch, decreased mean larval size, and alterations to several metabolite abundances when compared with controls. Significantly altered metabolites include those associated with cellular energetics, fatty acid metabolism, and polyamine synthesis, indicating current environmental exposure scenarios are sufficient to disrupt important cellular pathways. Dysregulation of the dopaminergic system of embryos is also characterized, and may be a possible mechanism by which hyperactive behaviors are observed in these embryos. Offspring from tanks administered the high Hg diet exhibited delayed hatching, increased mortality, and physiological abnormalities. Brain tissue of exposed adults from the low diet were dissected into regions, and also evaluated for alterations in dopamine cycling. Collectively, these results indicate current exposure scenarios in North American lakes and rivers are sufficient to cause reductions in fitness and survival of early life stage fish. The potential for community structure impacts exists, as sensitive individuals and species become disproportionately affected by chronic, low-level MeHg exposure.
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Etude de la transformation des formes chimiques du mercure par des bactéries sulfato-réductrices à différentes échelles d'observation / Mercury transformations at the cell scale : a sulfate-reducing bacteria studyAlbertelli, Marine 18 December 2017 (has links)
Le mercure est un polluant ubiquiste dont les espèces organiques, telles que le méthylmercure (MMHg), s'accumulent dans la chaîne trophique et sont fortement toxiques pour les organismes vivants. Des microorganismes anaérobies sont capables de transformer le mercure inorganique en MMHg, et inversement, par des processus qui n’ont pas été complètement établis. Cette étude vise à mieux comprendre les transformations du mercure chez des bactéries sulfato-réductrices modèles : D. dechloracetivorans BerOc1, capable de méthyler et déméthyler le mercure, et D. desulfuricans G200, utilisé ici comme témoin non méthylant. Les objectifs de cette étude sont donc de déterminer où ont lieu les processus de méthylation et déméthylation du mercure à l’échelle cellulaire ainsi que d’identifier les ligands du mercure impliqués dans ces processus. Dans un premier temps, la toxicité du mercure inorganique (IHg) et du MMHg a été évaluée sur la croissance des deux souches. Les potentiels de méthylation et de déméthylation, la localisation du mercure et ses ligands ont été déterminés au niveau de la culture et à l’échelle cellulaire. Ces paramètres ont été évalués à différentes concentrations de mercure ainsi qu’au cours d’une cinétique. Ce travail de thèse a mis en avant que IHg et MMHg ont moins d’impact sur la croissance des deux souches étudiées en sulfato-réduction du fait de la forte précipitation du mercure. Une ou des étapes limitantes interviendraient dans le processus de méthylation. De plus, une différence de localisation cellulaire du mercure a été constatée au cours du temps, suggérant un export de ce dernier, et selon la souche bactérienne suggérant des mécanismes cellulaires différents. L’imagerie par TEM EDX et l’analyse élémentaire par nano-fluorescence X ont permis d’observer la co-localisation du mercure avec le soufre. L‘étude de la spéciation par HR XANES a confirmé la prédominance de ligands thiols associés aux processus de méthylation et de déméthylation. Une forme tétragonale est prédominante dans les échantillons exposés à HgCl2 en croissance suggérant que cette espèce est formée via un processus biologique. / Mercury is a wide spread pollutant that build up in living tissues. The transformation of mercury into methylmercury is primarily a natural and biological process mediated by anaerobic bacteria. Understanding the parameters influencing the formation of methylmercury is critically important due to its highly toxic, bioaccumulative and persistent nature. Herein we aim to study the mechanism by which model strains used in laboratories can transform inorganic and methylmercury. The objectives of this study are determining where mercury methylation and demethylation processes take place at the cell scale and identifying the mercury ligands involved in these processes. At first, the toxicity of inorganic mercury (IHg) and MMHg were measured on the bacterial growth. The methylation and demethylation potentials, the localization of mercury and its ligands were determined in the culture and at the cell scale. These parameters were evaluated at different concentrations of mercury as well as during kinetic. This study has highlighted that IHg and MMHg have less impact on the growth of both strains in sulfate reduction because of the high precipitation of mercury. One or more limiting steps would occur in the methylation process. In addition, a difference in cell localization of mercury has been observed over time, suggesting an export at 24h of exposure. Mercury localization also depends on the bacterial strain suggesting different cell mechanisms. TEM EDX imaging and elemental analysis by X-ray nano-fluorescence showed mercury co-localized with sulfur. The study of HR XANES speciation confirmed the predominance of thiol ligands associated with methylation and demethylation processes. A tetragonal form is predominant in samples exposed to growing HgCl2 suggesting that this species is formed via a biological process.
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Assessment of Metals in Tissues of Marine-Associated Birds in South FloridaNay, Caitlyn A 04 May 2018 (has links)
Seabirds – broadly defined as any bird species associated with the marine environment – are exposed to a wide range of environmental contaminants. Vectors of exposure to metal pollution include by external contact, inhalation, and most often ingestion of food and incidental seawater. Seabirds are often considered marine ecosystem bioindicators due to their high trophic position, relatively long lifespan, and wide geographic ranges. We examined the concentration of total mercury (THg), lead (Pb), and cadmium (Cd), in the kidney, liver, breast muscle, and feathers of seven species of juvenile and adult seabirds commonly found in South Florida: brown pelican Pelecanus occidentalis (n=16), northern gannet Morus bassanus (n=16), double-crested cormorant Phalacrocorax auritus (n=15), royal tern Thalasseus maximus (n=15), herring gull Larus argentatus (n=9), laughing gull Leucophaeus atricilla (n=15), and osprey Pandion halietus (n=15). Trace amounts of lead and cadmium were found in the subsample of birds tested, suggesting that the birds living in south Florida do not face a significant threat from those metals. Results of total mercury in 101 specimens ranged from 0 to 45.07 mg/kg (dry wt), 0.15 to 132.13 mg/kg (wet wt), 0.06 to 352.35 mg/kg (wet wt), and 0.06 to 23.43 mg/kg (wet wt) in feathers, liver, kidney, and breast muscle respectively. Individual birds found to have the highest levels of total mercury were collected from centers in Monroe County. Osprey showed the highest total mercury values overall. These findings suggest a potential link to the Everglades and runoff into the Florida Bay, thus possibly exposing birds who utilize the Florida Bay at a higher risk for mercury poisoning.
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Investigation of white blood cell phagocytosis as a potential bio-marker of mercury immunotoxicity in birdsHolloway, Jennifer C. January 2001 (has links)
No description available.
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Effects of methylmercury on reproduction and offspring development and potential benefits of supplemental selenium and vitamin E intake in ratsBeyrouty, Peter. January 2002 (has links)
No description available.
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Mercury and selenium speciation and toxicity in common loonsFarren, Alex January 2004 (has links)
No description available.
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Managing the issue of mercury exposure in NunavutSolomon, Patricia-Ann. January 2005 (has links)
No description available.
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[pt] AVALIAÇÃO DO TRANSPORTE DE MERCÚRIO (HG) ENTRE OS COMPARTIMENTOS AMBIENTAIS AR, ÁGUA E SEDIMENTO DA BAÍA DE SEPETIBA POR MEIO DE UM MODELO DE BALANÇO DE MASSA / [en] MERCURY (HG) TRANSPORT ASSESSMENTS BETWEEN THE AIR, WATER AND SEDIMENT ENVIRONMENTAL COMPARTMENTS AT SEPETIBA BAY EMPLOYING A MASS BALANCE MODELGUILHERME MARTINS LOPES FERREIRA 07 August 2023 (has links)
[pt] A contaminação causada por diversos metais, dentre eles o mercúrio
causa diversos problemas de saúde devido a sua bioacumulação, portanto
foi necessária a construção de modelos para determinar a sua concentração.
Alguns modelo multimeios foram criados para determinar através do tempo
a contaminação de metais. Nesse estudo o mercúrio foi analisado tanto na
sua forma inorgânica (HgCl2) quanto no formato orgânico (CH3HgCl). Eles
serão construídos em dois diferentes compartimentos ambientais, água e os
sedimentos, na Baía de Sepetiba, corpo aquático localizado próximo a
cidade do Rio de Janeiro. Para a construção deste foram necessárias
adaptações em outros modelos já conhecidos na literatura definido para
lagos, levando em conta que a baía se comportaria da forma semelhante
além de outras considerações como os tipos de emissões existentes. Na
construção foi necessário encontrar dados sobre emissões diretas deste
contaminante na baía, fluxos de saída da água e do ar dessa região, um
dimensionamento de cada um dos seguimentos deste local, no caso de dados
que não foram encontrados especificamente para a Baía de Sepetiba, além
de dados pluviométricos e de entrada de aerossóis, considerou-se também
valores de outros trabalhos similares para outras baías, de onde se retirou
coeficientes de volatilidade entre os seguimentos e o particionamento desses
contaminantes entre os meios. Conhecendo os fatores locais e construindo
os equacionamentos fornecidos pela modelagem foi possível se calcular
utilizando o Python 3 como ferramenta o comportamento destes
contaminantes através do tempo, e compara os valores obtidos por estes
modelos com dados fornecidos pela literatura e verificar a discrepância entre
eles, que para o caso do período de tempo selecionado, 2002 a 2018, sendo
a concentração obtida experimentalmente de mercúrio total por kg de
sedimentos foi de 53,09 microgramas e a encontrada através do modelo matemático
construído foi 74,39 microgramas, tendo com isso uma diferença de aproximadamente
40 por cento em massa dos valores experimentais para os valores modelados. / [en] The contamination caused by several metals, among them mercury causes several health problems due to its bioaccumulation, so it was necessary to build models to determine it concentration. Some multimedia models have been created to determine metal concentration over time. In this study. Mercury was analyzed in its inorganic (HgCl2) and organic (CH3HgCl) form. They will be built in two different environmental compartments, water and sediment, in Sepetiba Bay, a water body located near the city of Rio de Janeiro. For the construction of this, adaptations were necessary in other models already know in the literature defined for lakes, taking to account that the bay would behave in a similar way, in addition to other considerations such as the type of existing emissions. In its construction, it was necessary to find data of direct emissions of this contaminant in the bay, outflows of water and air from that region, a dimension of each of the segments on this location, in the case of data were not found specifically forthe Sepetiba Bay, in addition for rainfall and aerosols input data, values from other similar works from other bay were also considered, from wherevolatility coefficients were removed between the segments and the portioning of these contaminants between the media. Knowing the local factors and building the equations provide by the modeling , it was possible to calculate, using Python 3 as a tool, the behavior of these contaminants over time, and compare the values obtained by these models with data provided by the literature and verify the discrepancy between them, that for the case of the selected time period, 2002 to 2018, the concentration obtained experimentally was 75.70*10-3 mg of total mercury per kg of contaminant and the one found through the constructed mathematical model was 74.39*10-3 mg of total mercury per kg of contaminant, thus having a difference of less than 41 percent in mass from the experimental values to the mathematically modeled values.
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The impact of a benthic omnivore on the biomagnification of mercury in top-predator fishBowling, Anna Marie 25 August 2009 (has links)
No description available.
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