Дисертації з теми "Isotopes du mercure"
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Hannachi, Fazia. "Étude des isotopes de mercure de la région de transition A ~ 186." Paris 11, 1987. http://www.theses.fr/1987PA112475.
High-spin states in ¹⁸⁵⁻¹⁸⁷⁻¹⁸⁸Hg have been investigated via the ¹⁶¹-¹⁶⁴Dy (²⁸Si, xn) reactions by in-beam γ-ray spectroscopic techniques using the “Chateau de Cristal” 4π-multidetector array. Level schemes have been established. Spins and parities of the states have been deduced from transitions multipolarities obtained from measurements of the angular distribution and linear polarization of the γ-rays. The shape coexistence of both prolate and oblate band structures built on states originating from νil3/2 subshell, has been observed for the first time in ¹⁸⁵⁻¹⁸⁷Hg as well as the rotational bands built on the 1/2⁻[521] and 7/2⁻[514] states in ¹⁸⁵Hg. In ¹⁸⁸Hg negative-parity bands are well developed. The various band structures are interpreted within the framework of the cranked shell model. The oblate structures are well reproduced by considering νil3/2 excitations while it is more difficult to conclude about the nature of the particle involved in the prolate ones
Enrico, Maxime. "Atmospheric mercury deposition and mercury stable isotope compositions in peat bogs." Thesis, Toulouse, INPT, 2015. http://www.theses.fr/2015INPT0103/document.
During the past few decades, peatlands were successfully used to investigate historical mercury (Hg) deposition. The chronology of Hg accumulation rates (HgARs) to peatlands is well constrained, with recent increases in HgAR associated with anthropogenic Hg emissions and deposition. The use of Hg stable isotopes in peatland ecosystems provides new opportunities to better characterize and understand historical Hg deposition. In an extensive study conducted at the Pinet peat bog (French Pyrenees) we identify gaseous elemental Hg (GEM) dry deposition, via foliar uptake, as the dominant Hg transfer pathway from the atmosphere to peat vegetation. Based on the Hg isotope analysis of multiple northern hemispheric peat records, we find that GEM dry deposition dominates Hg deposition globally. We suggest that peatlands can be used as archives of both past Hg wet deposition, Hg dry deposition and GEM concentration. We present the first quantitative reconstruction of historical atmospheric GEM concentrations using peat archives from the Pyrenees. The Human impact on Hg cycling caused a gradual increase in GEM concentrations from 0.2 (10,000 – 4000 BP) to 3.5 ng m-3 (20th Century) and was accompanied by a change in atmospheric Hg isotope signatures. This first comprehensive study on Hg isotope deposition to peatlands is promising and should be extended to pre-anthropogenic times to investigate natural variations in atmospheric Hg dynamics during the Holocene
Feng, Caiyan. "Spéciation et composition isotopique du mercure pour étudier les voies de contamination bio-environnementale du mercure." Thesis, Pau, 2015. http://www.theses.fr/2015PAUU3018/document.
Mercury (Hg) is a global pollutant and its ecotoxicological effects are strongly dependent on its chemical form mainly as methylmercury (MeHg). Due to the high bioaccumulation and biomagnification of MeHg in food webs, human exposure occurs through the consumption of fish, but also rice nearby Hg mining area (China). Hg isotopes composition is a potentials powerful tool and has been recently used to trace Hg contamination and biogeochemical processes in environment and living organisms. In this work, Hg speciation and isotopic composition of bio-environmental samples has been investigated in order to elucidate Hg contamination pathways between contaminated sites and target living organisms such as soil-rice plant system in a Hg mining region and aquatic biota in a river impacted by a chlor-alkali plant. An ecotoxicological study has also demonstrated how Hg isotopic composition in different fish organs allows to better understand Hg metabolic pathways and induced toxicological response
Hannachi, Fazia. "Etude des isotopes de mercure de la région de transition ...186." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376058223.
Nigron, Etienne. "Isotopes radioactifs produits par voies non conventionnelles." Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4032.
Nuclear medicine uses radionuclides for diagnosis and therapy. Nowadays, the nuclear medicine tends to adapt more efficiently to each patient. To achieve this goal, a wide range of radionuclides must be available for the physician's requirements. A theranostic approach (therapy and diagnosis) can be implemented from drug's design in order to guide medicine towards a personalised medicine. ln this sense, studies on the production of innovative radionuclides using unconventional pathways (deuteron beams, non-standard target materials: enriched targets or fission products) were conducted during this thesis. Reaction pathways¹⁹⁷ Au(d,2n) ¹⁹⁷ᵐHg and ⁷⁰Zn(d,x)⁶⁷ Cu were identified as relevant and their cross section were measured. The production parameters limiting the production of contaminants were proposed and yields were calculated for the highlighted reactions. For the measurements of these cross sections, a new experimental device has been designed to directly measure the particle flow. An intensive study on the optimal operational conditions was performed by defining an uncertainty of measurements of 2%. This device allows obtaining cross-section values with diminished uncertainties in comparison with the commonly used method of monitor reactions which have uncertainties of the order of 10%. The possibility of recovering light fission products from spent nuclear fuel was also explored. These fission products can be considered as a target to produce radionuclides of medical interest. Some nuclei, which can be created from these fission products, have been identified and their production pathways, based on their cross sections, have been studied in detail. The yield curves were calculated for the reaction paths were recognised as potentially interesting/feasible for this mean
Sun, Ruoyu. "Les variations isotopiques du mercure dans le charbon et les produits de combustion du charbon : une évaluation de la traçabilité des émissions du mercure des centrales au charbon." Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2055/.
Mercury (Hg) is a toxic, persistent and globally distributed pollutant. Since the industrial revolution, human activities have augmented the global Hg cycle at the Earth's surface by a factor of three. Hg emissions from coal-fired power plants represent at present the largest single anthropogenic source. However, quantitative tracing of the fate of coal Hg emissions from different countries or regions is a challenging issue. The objective of this PhD dissertation was to use Hg stable isotope signatures to address this problem. Firstly, we developed a combustion-trapping protocol to extract, purify and pre-concentrate Hg from solid samples with low Hg levels such as coal and coal combustion products. Purified coal Hg was then measured for its isotope compositions by high-precision (~0. 1‰, 2s) multi-collector inductively coupled plasma mass spectrometry. In summary we find that coals from different global coal basins are often isotopically distinguishable at the p=0. 05 or 0. 10 level, and that combustion and capture processes in coal-fired power plants do not substantially change feed coal Hg isotope signatures. We consider these combined results to be sufficiently promising to recommend detailed atmospheric Hg isotope tracer studies of coal plant Hg emissions. However, we anticipate that the different gaseous and particulate forms of Hg in coal flue gas emissions may carry more contrasting Hg isotope signatures than we estimated for bulk emissions. Therefore, caution should be taken in near-field and far-field coal Hg emission tracing, and additional studies on the Hg isotope signatures of coal plant Hg emissions are necessary
Barre, Julien. "Evaluation de la contamination atmosphérique des écosystèmes en utilisant la composition isotopique du plomb et du mercure dans les lichens." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3049/document.
The isotopic signature of lead (Pb) and mercury (Hg) was measured in epiphytic lichens from Pyrénées-Atlantiques. An integrated and spatialized sampling was developed using geographical information system (GIS) to take into account the diversity of the territory (land-use, forest, agriculture, industries and urban areas). At meso-scale (county, Pyrenees-Atlantiques) the isotopic composition allows to differenciate areas impacted by anthropegenic activities and discriminate the origin of the contamination that it of industrial or urban type. At local scale, the isotopic signature of Hg and Pb in lichens and mosses sampled in Iraty forest (Franco-Spanish border) allowed to evaluate the kind of atmospheric deposits in these atmospheric bio-monitors and the potential of this new tool for the monitoring of atmospheric depositsin remote ecosystems. Finally, on the mercurifere area of Almadén (Castella la Mancha, Spain) the isotopic fingerprint of Hg in lichens and sediments appears to be a relevant tool to study the transfer of Hg from mining activities to hydrosystems and atmosphere
Monperrus, Mathilde. "Utilisation de traceurs isotopiques stables pour la spéciation du mercure et des buthylétains : Application à l'étude de la biométhylation du mercure dans les environnements aquatiques." Pau, 2004. http://www.theses.fr/2004PAUU3031.
The first part of this work involves the development of new analytical methods for the speciation analysis of mercury and butyltin compounds in environmental matrices. The optimization of these new methods for speciation analysis is based on the isotope dilution technique and has been developed specially for the simultaneous determination of mercury and butyltin compounds taking into account the simultaneous sample preparation and the simultaneous detection. The analytical development has been carried out for the different environmental matrix found in the aquatic ecosystems: water samples, biological tissues and sediments. In the second part of this work, the developed analytical techniques have been used to investigate biogeochemical cycles of mercury and butyltin into aquatic environments. Experimental methods, using isotopically enriched species as tracers, have been developed and have allowed the evaluation of mercury transformation mechanisms (methylation/demethylation) in the different compartments of the aquatics systems (in the sediments and the water column). Environmental factors and biological parameters have been also investigated in order to determine the possible link between the mercury transformation processes and the biological activities (bacterio- and phyto-plankton activities)
Bouchet, Sylvain. "Etude de la spéciation biogéochimique du mercure aux interfaces des écosystèmes tidaux côtiers." Pau, 2009. http://www.theses.fr/2009PAUU3008.
The mercury biogeochemistry in coastal ecosystems and especially the transformations and mobility of the mercury species (inorganic mercury, methylated forms, and elemental mercury) have been evaluated with laboratory and field experiments. The mercury speciation and reactivity in superficial sediments have been studied under transient redox conditions using a laboratory microcosm and stable isotopic tracers. These transient conditions influence the transformations and partitioning of the mercury species. These transformations have been related to early diagenetic processes, specific bacterial activities and the evolution of the organic matter. The behavior of added mercury species reveals also the temporal ecosystem response to a chronic contamination. The mercury speciation and reactivity have been investigated at the different interfaces (sediment – water – atmosphere) of the intertidal zone of the Arcachon Bay (SW France). The exchange fluxes as well as transformation potentials have been evaluated in situ using flux chambers and mercury isotopic tracers. The flux intensities and transformation mechanisms exhibit seasonal variations according to the sediment biogeochemical conditions. The intertidal sediment interfaces appear as highly dynamic zones for mercury exchange to the water column and the atmosphere
Le, Coz Yves. "Mise en évidence de bandes dipolaires dans les isotopes de mercure à l'aide du multidétecteur EUROGAM." Lyon 1, 1995. http://www.theses.fr/1995LYO10030.
Laffont, Laure. "Fractionnement des isotopes stables de mercure dans un écosystème tropical en Amazonie bolivienne et dans les cheveux de populations humaines exposées." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/854/.
Samples of sediments, rocks, fish and human hair from the Bolivian Amazon basin, where gold-mining is active for decades, have been analysed by MC-ICPMS to study the stable isotopes fractionations of Hg. Evidence of mass-dependent (MDF) and mass-independent (MIF) fractionation have been observed in hair and fish samples. MIF is induced by photochemical reactions of Hg(II) and monomethylmercury (MMHg) in surface waters and MDF is observed only during the MMHg bioaccumulation process in organisms. Isotopic balance of Hg is improved thanks to sediments and rocks data showing a weak input of mercury by chemical weathering but significant atmospheric depositions of Hg(0) on soils. These first results obtained in hair and at a regional scale confirm that the stable isotopes of Hg constitute a powerful tool to trace biogeochemical processes and to evaluate mercury sources in living organisms
Grafeuille, Sylvie. "Contribution à l'étude de la structure des isotopes de mercure au moyen de la réaction (p,d)." Paris 11, 1985. http://www.theses.fr/1985PA112236.
The mercury isotopes were studied by means of the two pick-up reactions (p,d) and (p,t). Enriched targets of ²⁰⁴Hg, ²⁰²Hg, ²⁰¹Hg, ²⁰⁰Hg, ¹⁹⁹Hg, ¹⁹⁸Hg and ¹⁹⁶Hg were bombarded by a 25 Mev proton beam from the Orsay MP tandem accelerator. Emitted particles were analyzed by a split-pole magnetic spectrometer. We present all the results (nearly 150 states) of the analysis of the (p,d) reactions. Our (p,d) and (p,t) study show new discontinuities around ²⁰⁰Hg in systematics of mercury isotopes. Part of the results are compared to the U(5) limits of Interacting Bosons (and Fermions) Models. The light nuclei can be considered reasonably described but this could be somewhat fortuitous
Renedo, Elizalde Marina. "Sources and fate of methylmercury in the Southern Ocean : use of model seabirds and mercury stable isotopes." Thesis, La Rochelle, 2017. http://www.theses.fr/2017LAROS031/document.
Despite their distance from industrial pressure, marine southern and Antarctic environments are contaminated by worldwide distributed pollutants, such as mercury (Hg), through atmospheric transport and oceanic currents. So far, Hg contamination pathways in the Southern Ocean remains poorly understood, particularly in the Indian sector, and new studies are required to elucidate its fate and impact in these regions. Seabirds, as top predators of marine food webs, are exposed to elevated concentrations of biomagnified methylmercury (MeHg) via dietary intake and moreover, they forage in the different marine compartments both in spatial and depth terms. Therefore, they are considered as effective bioindicators of Hg environmental contamination and the good knowledge of their ecological characteristics permits their application for tracing Hg in such remote environments otherwise of difficult access. The main objective of this doctoral work is the characterization of the exposure pathways of the MeHg accumulated in model seabirds and the identification of the processes involved in the Hg biogeochemical cycle in the Southern Ocean (from Antarctic to subtropical waters). The proposed methodological approach consisted on the combination of Hg isotopic composition and Hg speciation in tissues of a precise selection of seabirds of the Southern Ocean. In a first step, the evaluation of tissue-specific Hg isotopic signatures was accomplished notably in blood and feathers, as they can be non-lethally sampled. In chicks, both tissues can be effectively and indifferently used for biomonitoring of local contamination using Hg isotopes, whereas in adults each tissue provides access to different temporal exposure : blood at recent scale (i.e. exposure during the breeding period) and feathers at annual scale, thus providing complementary isotopic information at the different stages of seabird annual cycle. A second part was focused on the exploration of MeHg sources in four penguin species within a same subantarctic location, the Crozet Islands. Hg isotopes effectively discriminated the four populations and species-specific foraging habitats and latitudinal movements were found the main factors determining their exposure to distinct environmental MeHg sources. In a third part, Hg isotopes were investigated in two ubiquitous seabird models (skua chicks and penguins) over a large a latitudinal scale from Antarctica to the subtropics. Latitudinal variations of Hg isotopic values (δ202Hg, Δ199Hg) appeared to be influenced by different extent of photochemical processes and other biogeochemical pathways such as Hg reduction, and methylation/demethylation processes, as well as trophic or metabolic processes
Abi, Ghanem Carine. ""Spéciation" des trois éléments trace mercure, plomb et cadmium dans les sédiments marins des zones côtières libanaises." Paris, AgroParisTech, 2008. http://pastel.paristech.org/5015/01/Thèse_Carine_Abi_Ghanem.pdf.
Day, Russell Davis. "Potentiel des banques d’échantillons environnementales pour les études biogéochimiques du Hg (spéciation et signatures isotopiques) dans les écosystèmes marins." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3026/document.
The specimens archived in Environmental Specimen Banks (ESBs) are among the longest time-series, most geographically robust, and highest integrity samples available for performing environmental research. Mercury (Hg) is a highly toxic and ubiquitous heavy metal that remains one of the world’s most prominent environmental contaminants, and ESBs have played a prominent role in Hg research. We review and discuss some of the ways in which ESBs have traditionally been used to study Hg in aquatic ecosystems, and show an example of how seabird eggs from the Seabird Tissue Archival and Monitoring Project (STAMP) are used for monitoring environmental Hg concentrations in subarctic and Arctic marine ecosystem. We also highlight some of the most robust sample sets archived in ESBs worldwide, which provide a valuable resource for conducting research in the emerging field of Hg stable isotope chemistry. Signatures of Hg isotope fractionation are used for source apportionment and for tracing biogeochemical cycling of Hg. We present results from two additional studies in Alaska that show how banked seabird eggs can be used for each of these purposes. As the research surrounding Hg stable isotopes continues to mature, ESBs can provide a robust and economical sample archive to expand and diversify the inventory of Hg isotope measurements, and be used to develop and test hypotheses. Samples archived in ESBs are available for request by external collaborators in order to perform high impact research, and should be fully utilized to address emerging environmental concerns
Abi, ghanem Carine. ""speciation" des trois elements trace mercure, plomb et cadmium dans les sediments marins des zones cotieres libanaises." Phd thesis, AgroParisTech, 2008. http://pastel.archives-ouvertes.fr/pastel-00005015.
Aubail, Aurore. "Étude des variations spatiales et temporelles du mercure en Arctique : utilisation des dents et des poils des prédateurs supérieurs comme tissus de biomonitoring." Phd thesis, Université de La Rochelle, 2010. http://tel.archives-ouvertes.fr/tel-00583122.
Masbou, Jérémy. "Étude des processus métaboliques, écologiques et biogéochimiques contrôlant le fractionnement isotopique du Hg chez les mammifères marins de l'Arctique." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/3093/.
Since the discovery of atmospheric Hg depletion events (AMDE) in the Arctic, the Polar Regions have become key in understanding the Hg global cycle. The impact of Hg on human health depends on both Hg concentration and chemical form. In particular, monomethylmercury (MMHg) is a potent neurotoxin. High MMHg concentrations are observed in Arctic top predators due to bioaccumulation and biomagnification processes in the food webs. Hence, the characterization of the transformations leading to the formation (methylation) and the degradation (demethylation) of MMHg is of great concern to assess its fate and impact in aquatic ecosystems. In this context, we present an environmental study on three Arctic bio-indicators: the ringed seal (Pusa hispida), the beluga whale (Delphinaperus leucas) and the polar bear (Ursus maritimus). Hg isotope analysis of the bio-indicator liver tissues show both mass dependent isotope fractionation (MDF, delta202Hg) and mass independent fractionation (MIF, delta199Hg). While the changes in d202Hg are widely linked to in vivo metabolic processes, the time trend (1988-2002, Pusa hispida) and the latitudinal gradient (60°N-71°N, Delphinaperus leucas) observed for ?199Hg signatures suggests the influence of sea ice cover on the Arctic biogeochemical Hg cycle. In a second part of this dissertation, we propose a novel and promising molecular approach with the first measurements of the isotopic compositions of Hg and carbon on the MMHg molecule in biological samples. These results are very promising for tracing MMHg origin in aquatic environments
Perrot, Vincent. "Spéciation isotopique et moléculaire du mercure dans les environnements aquatiques influencée par des processus biotiques et abiotiques." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3001/document.
Mercury (Hg) is a toxic and ubiquitous heavy metal. Only present at trace levels in the water column of aquatic systems, it can reach high amounts in food web end-members because of its ability to bioaccumulate and biomagnify in organisms as methylmercury (MeHg). Hence, the characterization of the transformations leading to the formation (methylation) and the degradation (demethylation) of MeHg is of great concern to evaluate its fate in aquatic environments. The use of the Hg stable isotopes, during laboratory experiments or in environmental samples, allowed to identify and characterize several biotic and biotic pathways involved in Hg transformations and speciation in aquatic systems. The study of Hg mass-dependent and/or mass-independent fractionation was also a competitive tool to assess its bioaccumulation process in several members of the Lake Baikal endemic food chain (Russia). Measured Hg isotopic signatures in such samples provided insight about Hg species fate and sources within the ecosystem of this lake, which has been nominated as a world heritage site by UNESCO in 1996 and constitutes the world’s largest freshwater lake in terms of volume
Carravieri, Alice. "Seabirds as bioindicators of Southern Ocean ecosystems : concentrations of inorganic and organic contaminants, ecological explanation and critical evaluation." Thesis, La Rochelle, 2014. http://www.theses.fr/2014LAROS026/document.
Antarctic and subantarctic marine environments are reached by inorganic and organic contaminants through ocean circulation and atmospheric transport. Yet, environmental contamination is poorly known in the Southern Ocean, in particular in the Indian sector. Among environmental contaminants, mercury (Hg) and persistent organic pollutants (POPs) are primarily of concern, because they are toxic, highly mobile, and they bioaccumulate in the tissues of living organisms and biomagnify up the food web. Seabirds, as upper predators, are exposed to large quantities of contaminants via food intake and have widely served as biomonitors of marine contamination, notably through the non-destructive sampling of their feathers and blood. My doctoral work has focussed on the abundant and diverse seabird species (more than 40) breeding in the French Southern and Antarctic Lands, southern Indian Ocean, in order to describe and explain contaminant concentrations over a large latitudinal gradient, from Antarctica to the subtropics, and to identify the best bioindicator species for contaminant biomonitoring. In a first methodological step, seabirds with synchronous moult of body feathers (adult penguins and chicks of all species) were recognised as good candidates as bioindicators, because, unlike most adult birds, they present low within-individual variation in feather contaminant concentrations. In a second explanatory step, the influence of intrinsic (individual traits) and extrinsic factors (feeding ecology inferred from the stable isotope method) driving variation in contaminant concentrations was evaluated in feathers of the large avian community of the Kerguelen Islands (27 species) and in blood of wandering albatrosses from the Crozet Islands (180 birds of known individual traits). Feeding ecology was the main factor driving variation in contaminant concentrations of blood and feathers, both at the community, population and individual levels, whereas age, sex, phylogeny and breeding status played a minor role. Age-class was however an important intrinsic factor to consider, with chicks usually having lower concentrations than adults. In a third step, spatio-temporal patterns of contamination were studied through selected bioindicator species and by taking into account their feeding habits. Results from different species (oceanic seabirds) and populations (skua chicks) showed that, contrary to predictions, Hg exposure gradually increases from Antarctic to subantarctic and subtropical waters, whereas, in accordance with the global distillation theory, POPs exposure has the opposite pattern. Comparisons between penguin feathers from museum collections and contemporary samples showed that bird exposure to Hg is overall not different today when compared to 50-70 years ago, but subantarctic species are possibly experiencing an increasing trend. Future research efforts should be focussed on the use of feathers as biomonitoring tools, in particular for POPs determination. The best recommended bioindicator species include the emperor penguin and snow petrel (Antarctic), king penguin, blue petrel and black-browed albatross (subantarctic), and northern rockhopper penguin and Indian yellow-nosed albatross (subtropical). Future biomonitoring studies on these species will give invaluable insights into the poorly-known temporal trends of environmental contamination in the Southern Ocean
Bridou, Romain. "Activités microbiennes anaérobies et écodynamique des contaminants métalliques et organométalliques : cas de l’étain et du mercure." Pau, 2010. http://www.theses.fr/2010PAUU3018.
Tributyltin (TBT) and mercury (Hg) as well as their organic derivatives are ubiquitous and persistent metallic micro-pollutants present at trace level in aquatic ecosystems. The microbiological alkylation and dealkylation processes of the more toxic organic forms of tin and mercury (methylmercury, tributyltin or methyltin) under oxic and anoxic conditions are poorly understood. The first part of this study reports on TBT biotransformations in simplified bacterial communities under continuous culture. The potential for TBT biodegradation and inorganic tin methylation, e. G. Sn(IV), of strains isolated from this reactor as well as various aerobic and anaerobic microorganisms were simultaneously characterized by means of stable isotopic tracers, allowing to define some alkylation and dealkylation pathways. The second section of this document is dedicated to the investigation of the capacities of sulphate-reducing prokaryotes (SRP) for mercury methylation and demethylation. The use of Hg stable isotopic tracers allowed the systematic study of this phenomenon in environmental organisms under different physiological conditions (fermentation, nitrate respiration, sulphate respiration and substrate starvation). In conclusion, the study of isotopic fractionation of Hg during its methylation by a SRM (Desulfobulbus propionicus, DSM6523) highlighted the need to better understand the functioning of the co-occurring mechanisms implied in the regulation of net methylmercury production in aquatic ecosystems
Dessier, Aurélie. "Analyse du compartiment mésozooplanctonique et écologie alimentaire printanière de la sardine, Sardina pilchardus (Walbaum, 1782), et de l’anchois, Engraulis encrasicolus (Linné, 1758) adultes dans le Golfe de Gascogne." Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS036/document.
Dietary studies of marine species constitute an important key to improve the understanding of its biology and of its role in the ecosystem. Thus, prey-predator relationships structure and determine population dynamics and the trophic network at the ecosystem scale. Among the major study sites, the marine ecosystem is submitted to natural and anthropogenic constraints. In the North-Eastern part of the Atlantic Ocean, the Bay of Biscay is a large open area surrounded South by Spain and East by France. This bay is an historic place of intense fishery activities for which the main small pelagic species targeted are the pilchard, Sardina pilchardus and the anchovy, Engraulis encrasicolus. The aim of this work is to analyze the trophic ecology of these two small pelagic fish in spring in the Bay of Biscay. To do this, a first section is devoted to their prey composed by the mesozooplanktonic compartment, through a two-fold approach: the characterization of their spatio-temporal dynamics during the decade 2003-2013 and the measurement of their energetic content in spring. For this season, it appears that all prey types are not worth energetically and that the Bay of Biscay represents a mosaic of dietary habitat. Moreover, the spring mesozooplankton community presents a strong spatial structuration, a temporal evolution marked by a major change in abundance and a control by the microphytoplankton biomass. The second section of this work is relative to a methodological approach of the trophic ecology of S. pilchardus and E. encrasicolus. Three different trophic tracers have been used: isotopic ratios of carbon and nitrogen, parasitological fauna and mercury contamination levels. To improve the use of the first of these trophic tracers, an experimental approach has been conducted with S. pilchardus to determine a trophic discrimination factor. Finally, it appears that the use of these three trophic tracers has always been permitted to highlight a temporal variability of the relative trophic ecology of these fish. However, no spatial dynamics could be identified through these three trophic tracers
Houssard, Patrick. "Variations des concentrations en mercure dans les réseaux trophiques marins de l'Océan Pacifique Sud : état des lieux, caractérisation des sources et relations avec la dynamique trophique et physique du milieu." Thesis, Nouvelle Calédonie, 2017. http://www.theses.fr/2017NCAL0001/document.
Mercury is a naturally distributed heavy metal which is characterized, under its organic form (monomethylmercury; MMHg), by its bioaccumulation in living organisms and its biomagnifications along food chains. Since the awareness of MMHg neurotoxicity, lots of research works have focused on understanding where and how MMHg is formed and transmited to marine food webs. Those questions are keys in order to anticipate how MMHg, in commercially fish species, will respond in a context of increasing mercury emissions and climate change.This work is part of this approach by studying total mercury spatial variations from muscle tissue of three tuna species: bigeye, albacore and yellowfin tuna, captured within the south Pacific Ocean. Every tuna species demonstrated a consistent and similar spatial trend, with higher total mercury concentrations in the southwest and lower concentrations in the western equatorial Pacific. This spatial trend seems to be in accordance with varying tuna diet linked to the thermal features of the water column. By combining archival tagging data and nitrogen stable isotope analysis, we showed that the deepening of bigeye tuna vertical habitat around New Caledonia might allow them to forage on deeper and MMHg enriched preys. Additionnaly, dissolved MMHg profiles in the southwest Pacific suggest higher methylation processes in the epipelagic zone leading, possibly, to higher MMHg bioavailability for marine food chains.This study highlighted the key role of tuna trophic ecology and particularly foraging depth in their MMHg exposure. Those features have to be considered in future studies evaluating food webs contamination at a spatial or temporal scale
Marteel, Alexandrine. "Evolution naturelle des éléments présents à l'état de traces (métaux lourds, métalloides, terres rares (REE) et isotopes du plomb) dans la carotte de glace EPICA/Dome C (Antarctique de l'Est) de 263,000 à 671,000 ans avant nos jours." Phd thesis, Université Joseph Fourier (Grenoble), 2007. http://tel.archives-ouvertes.fr/tel-00223892.
L'analyse d'éléments crustaux, métaux, métalloïdes, terres rares, mercure ont été réalisées grâce à un spectromètre de masse à secteur magnétique couplé à un plasma induit. La caractérisation des isotopes du plomb et l'analyses de methylmercure et mercure inorganique ont quant à elles étaient rendues possible par l'utilisation d'un spectromètre de masse à ionisation thermique et d'un spectromètre de masse à temps de vol couplé à un plasma induit. Ces analyses ont toutes été effectuées en salle blanche.
L'étude des éléments crustaux (V, Cr, Mn, Fe, Co, Rb, Ba et U) a permis de quantifier les variations naturelles des flux de ces éléments dans les glaces de l'Antarctique de l'Est de 263 000 à 671 000 ans avant nos jours. On a remarqué de fortes variations naturelles de concentration et de flux au cours de ces 6 cycles climatiques, avec des flux de retombées plus faibles pendant les périodes chaudes (interglaciaires) et des flux plus fort pendant les périodes froides (maxima glaciaires). De plus, ces apports augmentent brutalement en Antarctique de l'Est quand δD ≤ - 430‰.
Pour la première fois, les terres rares ont pu être analysées dans une carotte de glace profonde. Les variations temporelles et la provenance des terres rares, d'origine crustale, dans l'Antarctique de l'Est ont été étudiées de 263 000 à 671 000 ans avant nos jours. Ainsi, l'origine géographique des éléments crustaux pendant les périodes glaciaires et interglaciaires a été précisée grâce à la comparaison de données de terres rares obtenues dans la carotte EPICA/Dome C et celles provenant de régions potentielles d'origine des aérosols de l'hémisphère austral. L'Australie et la province de Córdoba apparaissent comme étant les sources dominantes à part égales sur le plateau de l'Antarctique de l'Est au cours des maxima glaciaires peu prononcés (MIS 12.2, 12.4 et 14.2). Différemment, les maxima glaciaires plus prononcés (MIS 8.2, MIS 10.2, 10.4 et16.2) montrent des ratios différents : ces éléments crustaux proviennent à 80-90% de la région de Cordoba et à 20-10% de l'Australie. Pendant les périodes interglaciaires, l'Amerique du Sud (Argentine du Sud, Argentine Centrale, et peut-être la Patagonie), les montagnes Transantarctiques (glacier Koettkitz) et l'Australie apparaissent comme étant les sources dominantes au Dome C.
Les concentrations des métaux et des métalloïdes ont été mesurées de 263 à 671 ka BP afin d'examiner la variabilité à long-terme de ces éléments, d'évaluer les contributions de sources naturelles et les modes de transport. De fortes variations naturelles de concentration et de flux au cours de ces 6 cycles climatiques ont été observées, avec des flux de retombées plus faibles pendant les périodes chaudes (interglaciaires) et des flux plus fort pendant les périodes froides (maxima glaciaires). Cependant, certains métaux varient plus que d'autres. En particulier, l'approche isotopique du plomb apporte une contribution importante dans l'interprétation des variations de compositions de poussières d'origine crustale en Antarctique.
Finalement, pour la première fois, le mercure total, le methylmercure et le mercure inorganique ont été mesurés dans une carotte de glace profonde. Cette analyse montre des concentrations qui varient considérablement au cours des derniers 671 000 ans, avec de faibles valeurs pendant les interglaciaires et de fortes valeurs pendant les périodes les plus froides. L'analyse de ces éléments a permis de déterminer les variations en paleoproductivité océanique et de mieux comprendre les procédés de dépôts de mercure au cours des derniers 671 000 ans.
Huguet, Lucie. "Caractérisation biogéochimique et potentiel de méthylation du mercure de biofilms en milieu tropical (retenue de Petit Saut et estuaire du Sinnamary, Guyane Française)." Thesis, Nancy 1, 2009. http://www.theses.fr/2009NAN10080/document.
The Petit Saut dam was built on the Sinnamary River in French Guiana in 1994 and its flooding has resulted to the final immersion of 350 km² of uncleared tropical rainforest. All immersed surfaces (rocks, immersed tree branches and trunks, roots…) in the reservoir lake and in the downstream are recovered by abundant biofilms. The aim of the present work was to characterize biofilms in terms of elemental composition, organic matter content and microbial communities and to define their role in mercury methylation. A multidisciplinary approach, applied to the biofilms and the nepheloid layer of the reservoir sediment, consisted in (i) assessing carbon, nitrogen, iron, sulfur, manganese, mercury and methylmercury concentrations, (ii) characterizing the nature of organic matter using its carbon and nitrogen isotopic composition (?13C and ?15N), its C/N ratio and its fatty acids composition (focusing on bacterial biomarkers). In the reservoir, suspended particles matter is an important source of accumulating material in biofilms. Reservoir biofilms contain higher refractory organic matter than the biofilms of the estuary and than the reservoir nepheloid layer. Iron, sulfur and manganese, mercury and methylmercury concentration are stratified with depth. Even if the relative contribution of bacterial fatty acids biomarkers was low, Chlorobiaceae was identified above the oxycline, whereas iron reducing bacteria were predominant in the hypolimnion as regards sulphate reducing bacteria. In the estuary, iron weights for the major part of the biofilm and higher IRB amount is present than SRB. The more labile organic matter allows the development of various microbial metabolic groups such as methanotrophs at the Passerelle station. Presence of Firmicutes-Archaea consortia (FISH analysis) in enrichment of Passerelle biofilms and of the reservoir nepheloid layer suggests that methane could also be oxidized under anaerobic synthrophy. This study shows a new application of stable isotope incubation to determine mercury methylation potential in tropical biofilms. Methylation potential is the lowest in the biofilm from the oxycline whereas higher methylation rates are obtained for microorganisms of the water column (planktonic), nepheloid layer, biofilms sampled at -20 m and at the Passerelle station. Adding nutrient enhances mercury methylation, especially in the estuary but it doesn’t only promote growth of methylating microorganisms but also that of demethylating or not involved in Hg transformation microorganisms Differences in methylation potential could be explained by either the bacterial communities diversity and/or by biofilm composition modifying Hg bioavailability
Pethybridge, Heidi. "Ecology and physiology of deepwater chondrichthyans off southeast Australia : mercury, stable isotope and lipid analysis." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14050/document.
Analyse de spéciation a montré que le mercure est présent à plus de 91 % sous forme de MeHg, et même avec des taux supérieurs à 95 % chez les espèces des environnements les plus profonds. Les concentrations maximales en THg ont été trouvés dans les tissus musculaires (59 à 82 % de charge corporelle). Les reins et le foie possèdent aussi des taux élevés, respectivement de 0,3 à 4,2 et 0,5 à 1,5 mg kg-1 (ph), tandis que la peau enregistre les concentrations les plus faibles (> 0,3 mg kg-1, ph). Cette étude de l’organotropisme permet de conclure que les reins et le foie sont associés au métabolisme du métal, à l'élimination et au stockage à court terme, alors que le muscle est le sites le plus important du stockage du mercure à long terme. Les isotopes stables de carbone et d’azote ont été utilisés pour évaluer l'influence de la position trophique (d15N) et de la source de carbone (d13C) sur l'accumulation du THg chez les chondrichthiens. Le d15N varie entre 12,4 à 16,6 ‰ démontrant la large gamme de positions trophiques occupées par ces espèces. La variation interspécifique du d13C est quant à elle minimale (–18,7 à –17,1 ‰). Les concentrations en mercure notées chez la plupart des requins augmentent en fonction de la taille, de la position trophique (d15N) et du stade de maturité de l’animal. Dans la communauté des chondrichthiens des profondeurs on observe des taux modérés de bioamplification du mercure, ceci est révélé par la faible pente de la relation, log (THg mg kg-1 ww) = 0,2 (d15N) – 2,4 (R2 = 0,35 ; P <0,05). Le THg et les acides gras de 61 espèces appartenant aux niveaux trophiques intermédiaires ont été analysés dans le but d’étudier les régimes alimentaires des proies et la bioaccumulation de ce métal à travers la chaîne alimentaire démersale. L'utilisation intégrée de ces techniques biochimiques a fourni des données fondamentales sur la reproduction, l'accumulation en mercure et l'écologie trophique des chondrichthiens des profondeurs. La compréhension de ces fonctions est impérative non seulement pour la mise en place d’une gestion durable des pêcheries, mais aussi pour la protection des habitats des chondrichthiens et leurs écosystèmes associés
For most deepwater chondrichthyans, fisheries and conservation management is problematic, largely due to the lack of scientific data resulting from inherent logistical challenges working within deep-sea environments. Furthermore, many conventional analytical techniques (stomach content analysis and morphometrics) require large sample sizes and are often quantitatively inadequate. Thus, new and more robust methods requiring fewer specimens are needed. Biochemical ‘tracer’ techniques are increasingly being used to resolve complex ecological and biological questions at individual species and population levels. This research explored the integrated use of multiple biochemical techniques (lipid and fatty acid profiling, stable nitrogen and carbon isotope and mercury analysis) to understand aspects of the reproduction, feeding ecology, metal accumulation and physiology of deepwater chondrichthyans. Most were from the Order Squaliformes. Other species include those from the Families: Chimaeridae, Rhinochimaeridae, Scyliorhinidae and Hexanchidae. All specimens were caught as fisheries bycatch from the continental slope waters off southeast Australia. The examination of lipid composition and partitioning revealed that deepwater chondrichthyans have large, lipid rich (38–70 % wet weight, ww) livers high in neutral lipids and monounsaturated fatty acids. Liver is a multifunctional tissue, playing a vital role in lipid distribution and biosynthesis, buoyancy regulation and storage. In contrast, muscle is a structural organ, low in lipid (<2 %) and consisting primarily of polar lipids. Lipid composition of kidney and pancreas show that they, too, have complex roles in lipid metabolism and storage. Lipid analysis of reproductive tissues revealed high maternal investment in deepwater chondrichthyans as indicated by high lipid content in mature pre-ovulated ovarian follicles (18–34 %). Variable levels of triacylglycerols (8–48 %), diacylglyceryl ethers (0.2–28 %) and wax esters (0.5–20 %) were observed in all specimens, demonstrating the use of multiple lipid classes to fuel embryonic development. The maternal provisions differed between oviparous and viviparous species and between elasmobranchs and holocephalans. Greater lipid investment was displayed by sharks living in deeper environments, suggesting lower fecundity and increased vulnerability to fishing. Diet was examined by complementary lipid biomarker and traditional stomach content techniques. A total of 41 prey taxa were identified using stomach content analysis and consisted mainly of bathyal-demersal fish and cephalopods. Using multidimensional scaling analysis, the extent of variability in composition within each species was determined by grouping the signature fatty acid profiles of shark tissues with profiles for demersal fish, squid and crustaceans. Both techniques showed that deepwater chondrichthyans are opportunistic predators, and that there is some degree of specialisation and overlap between them. Total (THg) and inorganic (monomethyl, MeHg) mercury concentrations and tissue distribution were examined to determine the extent of biomagnification and evaluate levels for human consumption. Mean THg levels for most species were above the regulatory threshold (>0.1 mg kg-1 ww) and levels as high as 6.6 mg kg-1 ww were recorded. Speciation analysis demonstrated that 91% mercury was bound as MeHg with higher percentages (>95%) observed in species occupying deeper environments. Higher levels of THg were stored in muscle which accounted for between 59–82% of the total body burden of mercury. High levels were also found in kidney (0.3–4.2 mg kg-1 ww) and liver (0.5–1.5) with lower levels observed in skin (>0.3). Both the kidney and liver are likely to be associated in metal metabolism, short term storage and elimination procedures, while the muscle is the major site for long term storage. Stable isotopes were used as natural dietary tracers, to further evaluate dietary relationships and to assess the influence of trophic position (d15N) and carbon sources (d13C) on THg accumu
lation. Isotopic nitrogen (d15N) values ranged from 12.4 to 16.6 ‰ demonstrating a broad range of trophic positions. Minor variation in carbon (d13C) enrichment was observed between species (–18.7 to –17.1‰). In most shark species, mercury concentrations increased with size, trophic position (d15N), and maturity stage, but not between location or collection period. As a community, deepwater sharks demonstrated moderate rates of THg biomagnification, as indicated by the regression slope (log (THg) = 0.2 d15N – 2.4, R2 = 0·35, P < 0·05). THg and fatty acid analyses of 61 mid-trophic species were measured for their usage in studies of diet in high-order predators and mercury bioaccumulation in the extended demersal food chain. The integrated use of these biochemical techniques has provided fundamental data on the reproduction, metal accumulation and trophic ecology of deepwater chondrichthyans. Understanding these parameters is imperative not only for the implementation of sustainable management but for habitat protection of deepwater chondrichthyans and their associated ecosystems
Duval, Bastien. "Ecodynamics of trace metals and metalloids in Pyrenean lakes in relation to climate change and anthropogenic pressure." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3046.
The management and conservation of Pyrenean high mountain lakes within the current context of climate change and increasing anthropogenic pressure require detailed knowledge of their biogeochemical functioning. In this doctoral thesis, five sampling campaigns were carried out (2017-2019) in more than 20 alpine lakes. The analysis of water samples allowed us to study the occurrence, the depth profiles, the geographical distribution and the seasonal trends of a large array of physico-chemical and biogeochemical parameters. Specifically, the cycle of carbon dioxide (CO2) and the fate of Potentially Harmful Trace Elements (PHTEs) were investigated. The mercury (Hg) was specially studied through the development of an analytical procedure for the measurement of trace concentrations in natural waters and through biogeochemical investigations on the distribution and the fate of Hg species in the water column, as well as in sediment archives.The new and robust procedure developed in this work to measure the total alkalinity (TA) and the dissolved inorganic carbon (DIC) allowed us to determine the other two parameters of the CO2 system, the pH and the fugacity of CO2 (fCO2). The bedrock characteristics of the watershed appear to be the most important parameters influencing the acid status of the studied lakes. Moreover, obtained fCO2 values indicate that lakes are sources of CO2 for the atmosphere.The measurement of various physico-chemical parameters allowed us to discriminate and classify the studied lakes according to their water geochemistry, highlighting the importance of the trophic status of the lakes, the geological background and the atmospheric inputs. The occurrence, sources and behaviour of the PHTEs were investigated with evidence of a contrast between geological and atmospheric inputs. Intensive monitoring revealed some PHTEs to be highly sensitive to environmental changes such as temperature and redox conditions.Monitoring natural concentrations of total Hg in aquatic systems remains a difficult challenge and there is a need for the development of low cost and easy handling analytical methods. The method for analysis of trace Hg concentrations developed and optimized in this work was successfully operational and exhibits a suitable limit of detection and an excellent reproducibility. Hg speciation results in the water column demonstrated the pristine state and the dynamic of the Pyrenean lakes. The homogeneity in the non-gaseous total Hg concentrations in the studied lakes confirmed the absence of local sources and the potential use of these ecosystems as sentinels of regional to global Hg contamination. While inorganic mercury (iHg) did not show seasonal variations, monomethylmercury(MMHg) was significantly higher in autumn 2018 and dissolved gaseous mercury (DGM) varied strongly within and among lakes. In-situ experiments confirmed the conditions that promote Hg methylation (stratified anoxic waters), demethylation and photoreduction (intense UV light).The historical Hg record in sediment archives highlighted temporal trends in Hg accumulation rates (HgARs) with a progressive increase since the 16th Century and the industrialization, mirroring the Hg production in Almadén mines (Southern Spain). Besides, Hg stable isotopes allow the identification of distinct anthropogenic sources as well as past climate variability.Overall, environmental changes in lake ecosystems, induced by either climatic conditions (temperature, light intensity) or anthropogenic pressure (atmospheric inputs, eutrophication, atmospheric CO2) are likely to produce significant impacts among CO2, specific PHTEs and Hg biogeochemical cycles in mountainous ecosystems
Li, Chuxian. "Variabilité Holocène des poussières atmosphériques et du mercure dans l’hémisphère Sud." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30277.
The Southern westerly winds (SWW) play an important role in regulating Southern Ocean carbon budget by enhancing the absorbance of atmospheric CO2 or resurfacing deep ocean carbon. Changes in SWW intensity are thought to determine whether Southern Ocean acts as a net CO2 sink or source, thereby affecting atmospheric CO2 concentration and then global climate. SWW also affect Southern Hemisphere (SH) dust trajectory and mercury biogeochemical cycling, which in turn can be used to trace SWW dynamics. Less is known about the past SWW variabilities and historical mercury cycle. The aim of this PhD study is to improve our understanding of the SWW trend and mercury deposition in the Holocene at remote SH sites by using geochemical and isotopic proxies in peat archives. We investigated Amsterdam Island (AMS) peat record coupled with three other peatlands in the SH mid latitudes as long-term archives of atmospheric dust and/or mercury deposition. At the northern edge of SWW and free from anthropogenic disturbance, AMS is a key site to study SWW dynamics. We find that during the Holocene, dust and mercury deposition at AMS oscillated on millennial time scales. Mercury isotope signatures, which are sensitive to rainfall inputs, indicate that high dust, high mercury events correspond to low rainfall. We suggest that these events were caused by a poleward shift of the SWW at AMS. The peat mercury records also inform on recent, human perturbation of the natural mercury cycle in the SH. We find however that the 4-fold anthropogenic mercury enrichment we observe in the SH since 1450AD, is smaller than the 16-fold enrichment in the northern hemisphere. These scientific contributions should help improve global climate models and international environmental policy under the Minamata convention on mercury
Woolf, Vincent Martell. "Mercury elemental and isotopic abundances in mercury-manganese stars /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
Petts, Andrew. "Shape coexistence and collectivity in neutron-deficient mercury isotopes." Thesis, University of Liverpool, 2010. http://livrepository.liverpool.ac.uk/3073/.
Larsson, Tom. "Instrumental and methodological developments for isotope dilution analysis of gaseous mercury species." Doctoral thesis, Umeå : Department of Chemistry, Umeå Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1448.
Bérail, Sylvain. "Nouvelles stratégies d’introduction d’échantillon en MC-ICP-MS pour la bio-géochimie isotopique du mercure en ultra-trace." Thesis, Pau, 2018. http://www.theses.fr/2018PAUU3019/document.
In addition to the quantitative and speciation analysis, the analysis of mercury stable isotopes by MC-ICP-MS are now a tool of choice to track sources and pathways of this element in the environment. This PhD thesis presents the development of hyphenation between pre-concentration techniques and MC-ICP-MS to measure isotopic composition of mercury at ng.L-1 levels (Ultra-trace). The on-line pre-concentration strategy will create short transient signals which represent a real challenge for MC-ICP-MS. In order to solve it, a data treatment strategy for this particular signals and a correction method for the isotopic drift were developed.The hyphenation between a cold vapor generation, a dual gold amalgamation (CVG-DGA) and a MC-ICP-MS was developed to determine total mercury isotopic composition. This new technique gives external precisions ranging from 0.20 to 0.30‰ (2SD) for Hg concentration in solution of 5 ng.L-1. This PhD thesis also reports a new method to perform mercury compound specific isotopic analysis (CSIA) using a gas chromatography fitted with a PTV injector (GC-PTV) coupled to the MC-ICP-MS. This allows the isotopic analysis of several species with external precisions ranging from 0.30 to 0.40‰ (2SD) for mercury concentration down to 150 ng.L-1 in biological samples.The analytical developments proposed in this PhD thesis allows to automatically and directly measure mercury isotopic compositions at ultra-trace levels (down to 5 ng.L-1) while keeping precision compatible with main environmental questions. This will allow to analyze environmental compartment containing very low amount of mercury (natural waters, planktons,…) and then open new perspectives for a better understanding of the bio-geochimical cycle of mercury
Kadlecova, Milada. "Contamination mercurique des sédiments et cours d'eau du nord de la France et de la République Tchèque." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10148/document.
Mercury (Hg) is naturally occurring toxic element; however global mercury emissions are dominated by anthropogenic sources. The global cycle of mercury has seen an increase in mercury deposition, especially in aquatic ecosystems, since the beginning of the industrial revolution. First part of the thesis summarizes the source of mercury, its properties and toxicity from the general point of view, but also the current state of knowledge on the biogeochemical cycle of mercury and in particular behaviour of mercury inside the sediments of the aquatic environment and factors influencing its transformation into methylated form. The sediment in aquatic systems may acts as the ultimate sink, where mercury in its various complexes is deposited. The mercury in sediments can then be converted to its more toxic organic form, methylmercury (MeHg), by the transformation processes controlled by various physical, chemical and biological factors. More over remobilization of mercury species from sediments is possible due to diffusion and resuspension and so sediments may act as potential source of mercury for aquatic biota. Bioaccumulation and biomagnifications can then continue up the food chain where humans, among other animals, consume the organic mercury. It is clear that determination of total mercury is not sufficient to understand its fate in the environment; determination of MeHg provides very useful additional information. The sensitive and precise analytical method for MeHg determination is necessary. The methodological part of the thesis deal with the methods for determination of mercury species in sediments. The method for methylmercury determination in sediments using automated Headspace sampler equipped with Trap and coupled with Gas Chromatography and Atomic Fluorescence Detector was developed and is define. The special attention is also given to the necessity of clean sampling procedures and the proper storage and pre-treatment of the samples and the field study of Hg distribution in sediments. The mercury contamination of sediments from the South Moravia and Northern France are compared. The mercury species and other elements (Fe, Mn, S) were analysed in sediments and/or pore water and/or surface water collected from the sampling sites in the Deûle and Lys River (France) and Jihlava and Morava River (Czech Republic). In order to better assess the mercury contamination of aquatic ecosystem, the pore water concentration could be evaluated to understand the availability of mercury from sediment. The use of diffusive gradient in thin film (DGT) technique is applied to measure pore water mercury concentration in river sediments. Different resins gels for mercury determination are used: Spheron-Thiol, Duolite GT-73 and TiO2. River Deûle act as a sink for enormous anthropogenic Hg from the industrial activities and is considered as a potential significant source of methylmercury to the surrounding environment. The last part of thesis deals with the application of well-established isotope experiments to study methylation/demethylation processes in sediments of Deûle River. For this purpose, species-specific isotopically enriched tracers in the form of inorganic mercury IHg (199Hg) and MeHg (201MeHg) have been added to the sediment slurries. Mercury labelled species were used as the tracers to follow their chemical fate and calculate the extent of the transformation reaction yield occurring during the 24 hours experiment. This experiment methodology is refined by applying advanced matrix algebra to resolve the contributions of several different enriched stable isotope species specific tracers to the isotope pattern found, making the calculation of methylation/demethylation rates possible
Bernards, Christian [Verfasser]. "Investigation and supersymmetric description of even-even mercury isotopes / Christian Bernards." München : Verlag Dr. Hut, 2011. http://d-nb.info/1018982418/34.
Lambertsson, Lars. "Mercury species transformations in marine and biological systems studied by isotope dilution mass spectrometry and stable isotope tracers." Doctoral thesis, Umeå : Univ, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-467.
Bearhop, Stuart. "Stable isotopes in feathers and blood as a tool to investigate diet and mercury dynamics of seabirds." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323395.
Pastershank, Georgine M. "Unifying ecosystem concepts and mercury biomagnification in an estuarine environment using stable isotopes (delta-¹³C and delta ¹§5N)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ66182.pdf.
Brewster, Jasmine Dawn. "Characterizing the diet and habitat niches of coastal fish populations in the Beaufort Sea Tarium Niryutait Marine Protected Area." Marine Ecological Progress Series, 2016. http://hdl.handle.net/1993/31961.
February 2017
Moreton, Jennifer Anne. "The application of inductively coupled plasma source mass spectrometry to clinical biochemistry and environmental science." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242920.
Al-Reasi, Hassan Ali. "Tracking mercury biomagnification in fish from the Gulf of Oman using stable isotopes (carbon-13carbon-12 and nitrogen-15nitrogen-14)." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/26836.
Pastershank, Georgine M. "Unifying ecosystem concepts and mercury biomagnification in an estuarine environment using stable isotopes (delta-carbon-13 and delta nitrogen-15)." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9387.
Day, Goodacre Thomas. "Developments of the ISOLDE RILIS for radioactive ion beam production and the results of their application in the study of exotic mercury isotopes." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/developments-of-the-isolde-rilis-for-radioactive-ion-beam-production-and-the-results-of-their-application-in-the-study-of-exotic-mercury-isotopes(02c79aff-86c7-4eaf-8701-f70c0ccdcdd4).html.
Jiang, Ping. "Mercury Sulfide Dissolution in Environmental Conditions: Thermodynamic and Kinetic Approaches." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3027.
Matulik, Adam G. "A Trophic-Level Interaction for Elasmobranch Species in Florida Bay, South Florida, Using Stable Isotope Ratios in Rgard to Mercury-Species." NSUWorks, 2011. http://nsuworks.nova.edu/occ_stuetd/187.
Grégoire, Daniel. "Photosynthetic and Fermentative Bacteria Reveal New Pathways for Biological Mercury Reduction." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38722.
Barillari, Domenico K. "Precision mass measurements of some isotopes of tungsten and mercury for an adjustment to the mass table in the region A=184 to A=204." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0017/NQ45134.pdf.
SOUZA, GILBERTO BAPTISTA DE. "MERCURY AND SELENIUM IN MARINE ORGANISMS FROM THE CENTRAL-NORTH COAST OF THE STATE OF RIO DE JANEIRO, EMPLOYING THE STABLE ISOTOPES 13C AND 14N AS BIOMARKERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=36960@1.
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Neste estudo foram determinadas as concentrações de Se e Hg, no tecido hepático, muscular e renal, de 70 golfinhos de cinco espécies diferentes (Tursiops truncatus, Stenella frontalis, Steno bredanensis, Sotalia guianensis e Pontoporia blainvillei) e uma espécie de ave marinha (Sula leucogaster), encontrados mortos, durante os anos de 2001 e 2013, na Costa Centro-Norte fluminense. A fim de identificar o processo de bioacumulação e biomagnificação, foram determinadas as concentrações de Se e Hg no fígado e no músculo de cinco espécies de peixe (Trichiurus lepturus, Micropogonias furnieri, Mugil liza, Sardinella brasiliensis, Scomber japonicus) e um cefalópode (Loligo plei). Para auxiliar no estudo dos níveis de Se e Hg, também foram avaliados os valores dos isótopos estáveis Delta 13C e Delta 15N no músculo de todas as espécies envolvidas. As concentrações mais elevadas de mercúrio e selênio foram observadas no fígado dos golfinhos, que apresentaram valores entre 11,2 e 684 mg kg elevado a potência negativa 1 para o Hg e entre 10,2 e 111 mg kg elevado a potência negativa 1 para Se. No músculo foram observadas concentrações mais baixas de Se e Hg nos golfinhos, apresentando concentrações de Hg que variaram entre 1,8 a 9,8 mg kg elevado a potência negativa 1, e de Se que variaram entre 1,9 a 2,3 mg kg elevado a potência negativa 1. A concentração de Hg no rim variou de 1,5 a 22 mg kg elevado a potência negativa 1 e de Se entre 7,6 a 12 mg kg elevado a potência negativa 1 nos golfinhos. Entre as presas, as concentrações mais elevadas de Hg e Se foram observadas no fígado, o mercúrio variou entre 0,3 e 1,6 mg kg elevado a potência negativa 1 e o selênio entre 6,6 e 40,4 mg elevado a potência negativa 1. As concentrações de Hg muscular ficaram entre 0,45 e 0,046 mg kg elevado a potência negativa 1 e de Se muscular entre 2,3 e 1,4 mg kg elevado a potência negativa 1 nas presas. Os golfinhos apresentaram maior enriquecimento de nitrogênio com valores médios entre 14,0 e 17,5 por mil. Para os isótopos estáveis de carbono, os valores médios variaram entre menos 16,8 e menos 15,5 por mil nos cetáceos. A razão isotópica entre as presas varou entre 8,3 e 13,5 por mil para o Delta 15N e entre menos 18,3 a menos 11,9 para o Delta 13C. Foi observado poder de biomagnificação positivo para o mercúrio nas espécies S. guianenis (log [Hg] = menos 0,031 mais 0,195 asterisco Delta 15 N; r igual a 0,719; p menor 0,001) e S. frontalis (log [Hg] igual a menos 0,15 mais 0,21 asterisco Delta 15 N; r igual 0,68; p menor que 0,0001), sendo possível concluir que a biomagnificação do Hg é efetiva na região estudada.
This study determined the concentrations of Se and Hg in the liver, muscle and kidney tissue, of 70 dolphins from five different species (Tursiops truncatus, Stenella frontalis, Steno bredanensis, Sotalia guianensis and Pontoporia blainvillei) and a species of seabird (Sula leucogaster), found dead during 2001 and 2013 on the North-Central Coast of the State of Rio de Janeiro. In order to identify the bioaccumulation and biomagnification processes, the concentrations of Se and Hg in the liver and muscle of five species of fish (Trichiurus lepturus, Micropogonias furnieri, Mugil liza, Sardinella brasiliensis, Scomber japonicus) and a cephalopods (Loligo plei) were determined. To assist in the study of Se and Hg, Delta 13 C and Delta 15 N stable isotopes in the muscle of all investigated were also evaluated species involved. The highest concentrations of mercury and selenium were observed in dolphin liver, which presented values between 11.2 and 684 mg kg elevated to negative power 1 for Hg and between 10.2 and 111.3 mg kg elevated to negative power 1 for Se. In muscle lower concentrations of Se and Hg were observed for these species, showing Hg concentrations ranging from 1.8 to 9.8 mg Kg elevated to negative power 1, while Se ranged from 1.9 to 2.3 mg kg elevated to negative power 1. Hg concentrations in the kidney varied from 1.5 to 22.0 mg kg elevated to negative power 1 and Se between 7.6 to 12.2 mg kg elevated to negative power 1 in dolphins. Among the prey, higher concentrations of Hg and Se were observed in liver, mercury varied from 0.28 to 1.6 mg kg elevated to negative power 1 and selenium between 6.6 and 40.4 mg kg elevated to negative power 1. Hg muscle concentrations were between 0.45 and 0.046 mg kg elevated to negative power 1 and muscle Se between 2.3 and 1.4 mg kg elevated to negative power 1 in the prey. Dolphins show higher nitrogen enrichment with mean values between 14.0 and 17.5 per thousand. For the stable carbon isotopes, the mean values ranged between less 16.8 and less 15.5 per thousand in cetaceans. The isotopic ratio of the prey ranged between 8.3 and 13.5 per thousand for Delta 15N and between less 18.3 and less 11.9 for Delta 13C. Positive biomagnification power was observed for mercury to species S. guianenis (log [Hg] equal less 0.031 more 0.195 asterisk Delta 15N; r equal 0.719; p less than 0.001) and S. frontalis (log [Hg] equal less 0.15 more 0.21 asterisk Delta 15N; r 10 equal 0.68; p less than 0.0001), and indicating that the biomagnification of Hg is effective in the region studied.
Pietilä, H. (Heidi). "Development of analytical methods for ultra-trace determination of total mercury and methyl mercury in natural water and peat soil samples for environmental monitoring." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526206202.
Tiivistelmä Elohopeaa pääsee ilmakehään sekä luonnollisista lähteistä (mm. tulivuorenpurkaukset ja kiviaineksen rapautuminen), että ihmisen toiminnan kautta. Elohopean viipymäaika ilmakehässä on hyvin pitkä, minkä vuoksi se voi kulkeutua kauas päästölähteestä ennen päätymistään maaperään ja vesistöihin. Ympäristössä olevasta epäorgaanisesta elohopeasta voi muodostua erittäin myrkyllistä metyylielohopeaa, joka rikastuu helposti ravintoketjussa. Metyylielohopean muodostuminen on merkittävä osa elohopean biogeokemiallista kiertoa, minkä vuoksi metyylielohopean määrittäminen näytteen kokonaiselohopeapitoisuuden ohella antaa tärkeää tietoa elohopean käyttäytymisestä ympäristössä. Tutkimuksessa kehitettiin analyysimenetelmät, joilla määritettiin ultrapieniä kokonaiselohopea- ja metyylielohopeapitoisuuksia humuspitoisista luonnonvesistä ja turvemaanäytteistä. Tutkimuksessa käytetyt näytteet oli kerätty turvemaametsien valuma-alueilta Sotkamosta. Luonnonvesinäytteiden kokonaiselohopeapitoisuuksien määrityksessä käytettiin kylmähöyrymenetelmää (CV) yhdistettynä induktiiviplasma-massaspektrometriaan (ICP-MS). Vesi- ja turvenäytteiden metyylielohopeapitoisuuksien määrityksessä elohopeaspesiekset erotettiin kaasukromatografisesti (GC) ja määritettiin isotooppilaimennus-ICP-MS:lla. Ennen GC-ICP-MS -määritystä näytteet esikäsiteltiin typpiavusteisella tislausmenetelmällä ja esikonsentroitiin ’purge and trap’ -tekniikalla. CV-ICP-MS ja ’purge and trap’ GC-ICP-MS -menetelmät optimoitiin huolellisesti sekä laiteparametrien, että reagenssimäärien suhteen. Menetelmillä saatavien tulosten oikeellisuus varmistettiin vertailumateriaalien ja/tai vertailumenetelmien avulla. Kehitettyjä analyysimenetelmiä hyödynnettiin tutkimuksessa, jossa seurattiin metsähakkuiden mahdollisia vaikutuksia elohopean huuhtoutumiseen ja metyloitumiseen ojitetuilla turvemailla
Lavoie, Raphael A. "Relating trophic structure to mercury distribution in a Gulf of St Lawrence food web: From zooplankton to colonial seabirds using stable nitrogen and carbon isotope analysis." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28093.
Richter, Larissa. "Especiação química e composição isotópica de elementos traço no ambiente : arsênio no pantanal e mercúrio na floresta amazônica." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3036.
Arsenic (As) and Mercury (Hg) are toxic elements which presence in the environment may be attributed to natural or anthropic sources. In both cases, the toxicity and the dynamics in the environment are strongly dependent of the elements form/chemical specie. At the Pantanal, previous studies found high As concentrations in alkaline-saline lakes and low concentrations in fresh water lakes. Aiming to investigate the difference between these lakes, As origin and chemical speciation (CS), samples of water, sediments and soils were collected in distinct lakes and in different periods. As content was quantified by ICP-MS and its CS was analyzed by LC-ICP-MS. Results shown that As(V) was the main specie in this environment, which origin was attributed to three main factors: 1) the flood system combined with the high evaporation rates; 2) the high pH of the lakes and 3) the presence of high concentrations of Fe, Al and organic matter. On the other hand, in the Amazon rainforest, high rates of Hg emissions are observed due to forest burning. Nonetheless, no work in the literature has investigated what changes forest burning causes in Hg’s CS nor in its isotopic composition (IC). To fill this gap, prescribed burning experiments were performed in two different localities of the Brazilian Amazon rainforest, where samples of litter, soils and ashes were collected. IC was investigated by MC-ICP-MS and CS by GC-ICP-MS. IC results showed that during forest burning Hg isotopes did not fractionate sharply. Thus, Hg emissions to the atmosphere have an isotopic signature that correspond to a mixture of litter and soils’ isotopic signatures. For CS, it had been shown that forest leaves capture atmospheric methylmercury (MMHg), transferring it to the litter and consequently, to the soils, which cumulate this contaminant along the time. After burning, MMHg from litter can be lost completely whilst soils MMHg can be partially lost
O arsênio (As) e o mercúrio (Hg) são elementos tóxicos cuja presença no ambiente pode ter origem natural e/ou antrópica. Em ambos casos tanto a toxicidade quanto a dinâmica no ambiente são fortemente dependentes da forma/espécie química na qual se encontra o elemento. No Pantanal, estudos anteriores encontraram altas concentrações de As em lagoas alcalino-salinas e baixas concentrações em águas doces. Visando investigar as diferenças entre as lagoas, a origem e a especiação do As, coletaram-se amostras de águas, sedimentos e solos em lagoas distintas e em diferentes períodos. Os teores de As foram determinadas por ICP-MS e a especiação química (EQ) foi analisada por LC-ICP-MS. Observou-se que a espécie predominante foi o As(V), atribuindo-se a sua origem à três fatores: 1) o regime de cheias somado as altas taxas de evaporação; 2) O pH elevado das lagoas e 3) A presença de altos teores de Fe, Al e matéria orgânica. Na floresta Amazônica, por sua vez, observam-se elevadas emissões de Hg devidas às queimadas. Todavia, nenhum estudo investigou as mudanças que essas provocam na EQ ou na composição isotópica (CI) do Hg. Para sanar essa lacuna, efetuaram-se experimentos de queima programada em duas localidades na Amazônia Legal, nas quais amostras de liteira, solos e cinzas foram coletadas. Analisou-se a CI por MC-ICP-MS e a EQ por GC-ICP-MS. Os resultados da CI indicaram que durante as queimadas o Hg não se fraciona isotopicamente de maneira acentuada. Assim, estimou-se que as emissões de Hg possuem uma assinatura isotópica que corresponde a uma mistura das assinaturas da liteira e dos solos. Para a EQ, observou-se que as folhas captam o metilmercúrio (MMHg) atmosférico e o depositam nos solos, que o acumulam com o tempo. Após a queimada, o MMHg da liteira pode ser majoritariamente perdido enquanto aquele encontrado nos solos pode ser apenas parcialmente perdido