Industry sector is of great importance for economic development in every country. However, increasing discussions about environmental impacts led to strategies to minimize its effects, optimize production and technology, in a search for a process capable of superior production and lesser impact on nature. This thesis proposes development and analysis of supports for production of ceramic plates of a semi-porous kind (BIIb class), with water absorption between 6 -10%, and porcelain plates, with water absorption smaller than 0.5%. Inside the supports, we incorporated solid residues from the primary treatment of brine to be electrolyzed for production of caustic soda, hydrogen, and chlorine, using dry technology. The study was conducted from a partnership between industries from thermoplastic resin and ceramic plates production. Nowadays, Solid Residue from Brine Treatment (SRBT) is reinjected in salt mines which, although environmentally adequate, might not be the best solution. Therefore, we believe that SRBT incorporation at ceramic plate´s support is a viable alternative for better destination of this chemical residue that allows lower consumption of nature´s non-renewable resources and brings advantages to the support. This study generated 954 test subjects to verify the influence of different temperatures and SRBT concentrations in processing and densification using different tests. We test apparent density, linear retraction, water absorption, flexure strength, extraction expansion, black-heart formation, humidity expansion, thermal dilation coefficient and water loss in high temperatures. After the subject characterization, we gather that SRBT did not alter the main features of the material before burning, as presented by apparent density and mechanical strength tests. In all tested concentrations, rejects brought specific gains to mechanical strength especially for subjects of BIIb class. We infer that SRBT application in ceramic plates support is viable if one takes cautionary measures regarding homogenization of the material. / O setor industrial é de grande importância para o desenvolvimento econômico em todos os países. No entanto, discussões crescentes sobre os impactos ambientais levaram a estratégias para minimizar seus efeitos, otimizar a produção e a tecnologia, em busca de um processo capaz de produzir com qualidade superior e menor impacto sobre a natureza. Esta tese propõe o desenvolvimento e análise de suportes para produção de placas cerâmicas semi-porosas (classe BIIb), com absorção de água entre 6-10% e placas de porcelana, com absorção de água menor que 0,5%. Dentro dos suportes, incorporamos resíduos sólidos do tratamento primário de salmoura a ser eletrolisado para produção de soda cáustica, hidrogênio e cloro, utilizando tecnologia seca. O estudo foi realizado a partir de uma parceria entre indústrias de resinas termoplásticas e produção de placas cerâmicas. Atualmente, o Resíduo Sólido de Tratamento de Salmoura (RSTS) é reinjetado em minas de sal que, embora ambientalmente adequadas, podem não ser a melhor solução. Por isso, acreditamos que a incorporação da RSTS no suporte de placas cerâmicas é uma alternativa viável para melhor destinação desse resíduo químico que permite menor consumo dos recursos não renováveis da natureza e traz vantagens ao suporte. Este estudo gerou 954 corpos de teste para verificar a influência de diferentes temperaturas e concentrações de RSTS no processamento e densificação usando diferentes testes. Testamos densidade aparente, retração linear, absorção de água, resistência à flexão, expansão de extração, formação de coração negro, expansão de umidade, coeficiente de dilatação térmica e perda de água em altas temperaturas. Após a caracterização, concluímos que o RSTS não alterou as principais características do material antes da queima, como apresentado pelos testes de densidade aparente e resistência mecânica. Em todas as concentrações testadas, os rejeitos trouxeram ganhos específicos para a resistência mecânica, especialmente para corpos da classe BIIb. Infere-se que a aplicação da RSTS em placas cerâmicas de suporte é viável, caso se tomem medidas de cautela quanto à homogeneização do material.

O processo acelerado de obtenção da carne oferece grande vantagem à indústria, podendo encurtar alguns estágios de produção através da combinação de técnicas como a estimulação elétrica de carcaças, a desossa a quente e a marinação. O presente estudo foi realizado com o objetivo de avaliar a forma de desossa e o tipo de marinação em corte do músculo traseiro de bovinos (coxão duro) da raça Nelore. Determinou-se o efeito da desossa a quente e a frio e o efeito da salmoura de marinação, uma contendo 1,6% (250mM) de cloreto de cálcio e 2,4% de cloreto de sódio e outra com 1,8% de tripolifosfato de sódio e 2,4% de cloreto de sódio. Foram realizadas análises que incluíram a composição centesimal, teor de colágeno, pH, cor objetiva, textura objetiva (força de cisalhamento), perda de peso no cozimento e avaliação de maciez, suculência e sabor em cada músculo analisado. A marinação reduziu a força de cisalhamento, assim como aumentou a maciez e a suculência avaliadas pela equipe sensorial. Por outro lado a força de cisalhamento foi reduzida com a desossa quente e a maciez e a suculência aumentadas pela desossa frio. A cor foi o atributo mais afetado negativamente pelo processo de marinação, o valor a* e b* apresentou redução indicando escurecimento do vermelho, especialmente com a salmoura contendo cloreto de cálcio. A desossa interferiu no valor de a* e b* após o descongelamento indicando uma diminuição de a* e de b* na desossa quente. A desossa a quente poderá ser aplicada com sucesso em cortes bovinos provenientes de carcaças estimuladas eletricamente a baixa voltagem, sem provocar alterações negativas nos cortes. A marinação com salmoura contendo cloreto de sódio e tripolifosfato podem melhorar sensivelmente a maioria dos atributos avaliados, mas provoca alterações marcantes na cor. / The accelerated process to obtain meat offer advantages to the meat industry, and can reduce some of the stages of production through electrical stimulation of carcass, hot boning and enhancement process. In this work muscles from top round (Bíceps femoris) from Nelore steers were deboned using conventional and hot processing and marinated. The effect of deboning process and two brine solutions containing 1,6% calcium chloride and 2,4% sodium chloride and 1,8% sodium tripolyphosphate and 2,4% sodium chloride were evaluated. Proximate percent composition, collagen, pH, colour, texture (Warner Bratzler shear force), cooking loss, tenderness, juiciness and flavor in each muscle were analysed. Enhacement process reduced shear force value, increased tenderness and juiciness from sensory panel. Otherwise the shear force was reduced with hot deboned and tenderness and juiciness reduced by conventional deboning. Colour analysis was affected by enhancement process, a* and b* value showed decreased indicating darkness red colour, specially with calcium chloride brine. Hot deboning can be succesfully used in beef meat in addition to low electrical stimulaton carcass without negative alteration in meat. Enhancement process with calcium chloride, sodium tripolyphosphate and sodium chloride can improve the major of analysed attributes, but provoke colour modifications.

The thesis deals with an energy simulation of a ground heat exchanger (GHE) in classical and brine performance, which is used as an accessory of warm air heating system recovery in a low-energy family house. On basis of simulation results, the benefits of both heat exchangers were assessed. Furthermore, the energy and economics savings of heat recovery coupled with GHE were evaluated. Comparing the investment costs, the profitability of each investment were assessed and recommendations for the operation, implementation and appropriateness were outlined.

Rapporten ämnar undersöka hur avsaltning av havsvatten används för att trygga dricksvattenförsörjningen i Värmdö respektive Östhammar kommun. Vidare behandlas även de juridiska aspekterna kring ämnet på såväl kommunal som nationell nivå. Arbetet avser även att utreda vilka risker som finns med att använda avsaltningsanläggningar för såväl konsumenterna av det avsaltade vattnet som för närliggande marina miljöer. För att besvara frågeställningarna genomfördes en fallstudie över de två kommunerna. Undersökningen baseras främst på litteraturstudier som kompletterats med intervjuer och studiebesök. Genom studien har det kunnat fastställas att avsaltning sker i de båda kommunerna, men i vilken omfattning detta sker har inte varit möjligt att besvara, vilket främst beror på att mindre avsaltningsanläggningar inte omfattas av tillståndsplikt. Således finns inget register över antalet anläggningar inom kommunerna, vilket ytterligare försvårade kartläggningen. Överlag finns inget sammanhängande regelverk för avsaltning samt att flera aktörer är inblandade i regleringen, vilket ytterligare kan försvåra kartläggning samt inkorporering av metoden för vattenförsörjning. Gällande påverkan på marina miljöer sågs brinet som den primära riskkällan, medan hälsoriskerna med att konsumera avsaltat vatten är omdiskuterat. Det fanns även få studier ämnade åt de svenska förutsättningar, därav rekommenderas ytterligare studier på området. Slutligen rekommenderas ökad samverkan mellan kommuner samt resurseffektivisering av vattenförsörjningen ifall avsaltning bedöms som olämplig inom kommunerna. / The purpose of this report is to investigate if an expansion of desalination plants in Sweden could secure and amplify fresh water resources. The use of desalinated water in Sweden is currently not that widespread and there are few studies on how such expansion could impact the Swedish environment. The report aims to further investigate various health risks of consuming desalinated water and whether algae toxins from the Baltic Sea could be a potential health threat. To answer these questions a case study was conducted on the Värmdö municipality and Östhammar municipality, two archipelago municipalities located on the East coast of Sweden in Stockholm County respectively Uppsala County. Interviews with employees in both municipalities were conducted and supplemented with more interviews of other people active in the field. One of the main reasons for the interviews with employees in both municipalities was to answer the questions of how fresh water supply could be secured in the future if desalination plants were not a suitable option. Although the report was primarily based on a literature study, it was further complemented by two field excursions where two desalination plants were studied. The result of the study was that it was not possible to execute a detailed mapping of the number of desalination plants and how widespread desalination was in the municipalities, due to the fact the smaller facilities were excluded from permit obligation. A thorough mapping was likewise seen as expensive and time consuming which, if conducted by the municipalities, would require a redistribution of financial resources. The municipalities' attitude to desalination was positive, but it was not currently used in their fresh water supply. However there is currently no cohesive regulatory framework for desalination, and there is likewise a lack of a single authority with primary responsibility for desalination, which could aggravate implementation of desalination in Sweden. Consequently expanded cooperation between nearby municipalities as well as more resource efficient methods were proposed as solutions if desalination was unsuitable. The health risks of consuming desaline water was very oxymoronic; some sources said the lack of minerals in the water could result in cardiovascular diseases and other health issues, whereas other sources argued that they were due to different lifestyles. In addition algae toxins are common in the Baltic Sea which likewise could be a health risk. Overallt more research on the health risk of consuming desaline water is recommended since there are few studies on Swedish prerequisites. The main environmental impacts were the residual product from desalination, namely brine. The conclusion was that brine in low amounts probably did not pose a threat to the marine ecosystems and thus the environment, but again further studies are recommended.

Salar de Atacama (SdA) located in Northern Chile is home to one of the planet’s largest salar systems and lithium resources. Managing groundwater resources in salars is not obvious due to the lack of scientific understanding on the connectivity between the freshwater and brine systems. Using heat as a tracer in SdA provides a cost-effective method to further investigate groundwater flow in salars. This study employs 372 temperature-depth profiles from 90 boreholes between 2013-18 to understand the distinct thermal zones and flow between them in SdA. Three thermal zones exist within the southern margin of SdA’s thermal regime, at higher elevations alluvial fans containing freshwater have a temperature range between 23-28 °C. Down-gradient 2.5 km into the salar transition zone, characterized by freshwater lagoons and newly formed carbonates, the temperature range decreases to 12-17 °C. The transition zone, adjacent to the mature halite crust which hosts a lithium bearing brine and ranges in temperature from 18-22 °C. A 2D numerical groundwater and heat flow model was created to test three hydrologic scenarios to determine how the currently observed thermal regime exists and what the role of groundwater flow is between the different thermal zones. Results demonstrate that a focused flow concept matches current thermal observations with warm inflowing water discharging into the transition zone, cooling due to evaporation, reinfiltrating and preferentially flowing near the surface and discharging again at lagoons near the halite nucleus. Initial focused flow models had the halite nucleus and transition zone hydraulically connected, but results displayed advective flow between the two zones and the halite nucleus carried too much heat from current observations. Indicating the halite nucleus and transition zone has minimal connection, otherwise advective flow would result in thermal equilibrium and a lack of distinct zones as observed. Proper interpretation of temperature-depth profiles along with 2D models place critical constraints on the connectivity between the brine and freshwater systems, providing insight into salar surface energy budgets and a more comprehensive understanding of groundwater flow in the southern margin of SdA. This work gives a new perspective on the groundwater system in SdA while also contributing a novel case study to using heat as a tracer in salar systems.

Cette thèse porte sur l'étude de la caractérisation et le traitement de saumures alcalines. La carbonatation directe de saumures résiduaires (SR), par introduction d'une partie du CO2 issu de fumées industrielles, est réalisée dans un souhait de réduction des émissions de CO2 et en vue d'une valorisation potentielle des produits obtenus. Cette recherche se concentre sur l'étude des composés carbonatés, l'objectif général est d'établir le lien entre la réactivité des carbonates et leur valorisation (ici, désulfuration de fumées acides). Les SR sont complexes, l'étude de leur composition chimique et minéralogique a été réalisée en partie par spectroscopie Raman afin de mettre en évidence les interactions OH-Cl dans les échantillons humides. Les différents hydroxydes sont consommés au cours de la carbonatation pour précipiter des carbonates de calcium (calcite, aragonite). La composition chimique détermine les réactions de carbonatation alors que les paramètres physiques influencent la vitesse des réactions ainsi que la morphologie et la pureté des carbonates. L'évolution des phases au cours de la carbonatation des SR a été suivie par spectroscopie et un premier modèle statistique de prédiction des concentrations en carbonates a été développé. La deuxième partie de ce travail porte sur la caractérisation des carbonates obtenus et des paramètres, tel que l'hydratation, pouvant influencer leur valorisation. L'importance de l'hydratation dans la réactivité des produits DECALCO a été observée de l'échelle microscopique au pilote semi-industriel. Les essais de désulfuration de fumées acides ont été menés avec des taux de conversion du SO2 atteignant 65 à 70 % / This study is a contribution to the characterization and the treatment of alkaline industrial wastes. The direct carbonation of residual brines (RB) by CO2 bubbling results in a gas emission reduction and a potentially valorization of resulting products. This research was focused on carbonate products. The main objective is to link reactivity and valorization (here, desulfurization of industrial fumes). The RB are complex, their chemical and mineralogical composition was studied in particular by Raman spectroscopy to monitor OH-Cl interaction in humid samples. The different hydroxides phases are consumed during carbonation to precipitate calcium carbonates (calcite and aragonite). The chemical composition of RB determines the main part of the reaction of carbonation whereas physical parameters influence the reaction kinetics, the by-products morphology and purity. The feasibility of on-line monitoring of the phases evolution during carbonation using spectroscopy has been validated and a first statistical model for the prediction of carbonate concentration has been developed. The second part of this works concerns the characterization of precipitated carbonates and some parameters as hydration which can influence their valorization. The importance of hydration on the carbonates reactivity was observed in microscopy and at pilot scale. Desulfurization tests of industrial fumes in semi-humid way provided a conversion rate of SO2 ranging between 65 and 70%

<p>To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80&deg / C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM) / Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker.</p>

<p>To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80&deg / C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM) / Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker.</p>

The present work describes the phytochemistry study and of biological activity of the species Scutellaria racemosa Pers (Labiatae) and Pfaffia tuberosa Spreng (Amaranthaceae). Four compounds were isolated of the S. racemosa Pers: lupeol (14), oroxilin A (10), dinatin (12) and oroxyloside (11). The antimicrobial and cytotoxic activities and the capacity of inhibition of enzymes prolyl oligopeptidase (POP), dipeptidyl peptidase IV (DPP IV) and acetylcholinesterase (AChE) of the crude extract (EB), fractions and isolated compounds of the S. racemosa Pers were evaluated. The n-hexane (FH) and ethyl acetate (FA) fractions were the most active against Staphylococcus epidermidis, Bacillus subtilis and Pseudomonas aeruginosa. The evaluation of the crude extract and fractions using the Brine Shrimp Lethality Test indicated that this plant does not present toxicity. About the tests of enzymatic inhibition, the ethyl acetate (FA) and n-butanol (FB) fractions of S. racemosa Pers and the compounds dinatin (12) and oroxyloside (11) demonstrated significant capacity of inhibition of the POP. The inhibition promoted for the dinatina (12) (100 μM) corresponded 43% and for the oroxyloside (11) (100 μM) corresponded 34% of the total enzyme tested. The crude extract (EB) and the respective fractions of the Pfaffia tuberosa Spreng were also evaluated about the antimicrobial and cytotoxic activities and of enzymatic inhibition of the POP, DPP IV and AChE. Through these assays, it was verified that the crude extract (EB) and the fractions of the Pfaffia tuberosa Spreng do not present important antimicrobial and cytotoxic activity. In relation to the tests of inibitory activity of the POP, the dichloromethane (FD) and ethyl acetate (FA) fractions present IC50 of 21.4 and 28.5 μg/mL against of POP, respectively. Dichloromethane, ethyl acetate and n-butanol fractions (FD, FA and FB) presented low activity against DPP IV (< 20%). The ethyl acetate (FA) and n-butanol (FB) fractions showed significant inhibition of the AChE in the amounts, 6.25 and 25 μg, respectively. / O presente trabalho descreve o estudo fitoquímico e a atividade biológica das espécies Scutellaria racemosa Pers (Labiatae) e Pfaffia tuberosa Spreng (Amaranthaceae). Quatro compostos foram isolados da S. racemosa Pers: lupeol (14), oroxilina A (10), dinatina (12) e oroxilosídeo (11). A atividade antimicrobiana, citotóxica e a capacidade de inibição das enzimas prolil oligopeptidase (POP), dipeptidil peptidase IV (DPP IV) e acetilcolinesterase (AChE) do extrato bruto (EB), frações e compostos isolados da S. racemosa Pers foram avaliadas. As frações n-hexano (FH) e acetato de etila (FA) foram as mais ativas contra Staphylococcus epidermidis, Bacillus subtilis e Pseudomonas aeruginosa. A avaliação do extrato bruto (EB) e frações através do teste de letalidade frente a Artemia salina indicou que esta planta não apresenta toxicidade significativa. Quanto aos testes de inibição enzimática, as frações acetato de etila (FA) e n-butanol (FB) de S. racemosa Pers e os compostos dinatina (12) e oroxilosídeo (11) demonstraram significativa capacidade de inibição da POP. A inibição promovida pela dinatina (12) (100 μM) correspondeu a 43% e pelo oroxilosídeo (11) (100 μM) correspondeu a 34% do total de enzima testada. O extrato bruto (EB) e as respectivas frações da Pfaffia tuberosa Spreng também foram avaliadas quanto a atividade antimicrobiana, citotóxica e de inibição enzimática da POP, DPP IV e AChE. Através destes ensaios, verificou-se que o extrato bruto (EB) e a frações da Pfaffia tuberosa Spreng não apresentam importante atividade antimicrobiana e citotóxica. Em relação aos testes de atividade inibitória da POP, as frações diclorometano (FD) e acetato de etila (FA) foram as que apresentaram os melhores resultados, com IC50 de 21,4 e 28,5 μg/mL, respectivamente. As frações diclorometano, acetato de etila e n-butanol (FD, FA e FB) apresentaram baixa capacidade de inibição da DPP IV (< 20%). As frações acetato de etila (FA) e n-butanol (FB) apresentaram significativa inibição da AChE, nas quantidades de 6,25 e 25 μg, respectivamente.

The ongoing changes in the extent and the properties of sea ice, associated with the warming climate, are affecting the polar ecosystem and the interactions between the atmosphere, sea ice and the underlying waters. How sea ice biogeochemistry will change in the foreseeable future is currently uncertain, but is a crucial problem to tackle.<p>To better understand how sea ice biogeochemistry could change, we investigated the factors regulating the distribution of some dissolved compounds (e.g. nutrients, dissolved organic matter (DOM)) and gaseous compounds (e.g. Ar, O2, N2, CH4) in sea ice, from ice growth to ice decay. The results were obtained from a 19-day indoor experiment in Hamburg (Germany) and a five-month-long field survey in Barrow (Alaska). They were then compared to the physical properties of the ice (temperature, salinity, and other derived parameters such as brine volume fraction) and different biological parameters (bacterial activity, bacterial abundance, chlorophyll-a and phaeopigments).<p>Our work indicates that the physical properties of sea ice exert a strong influence on the distribution of the biogeochemical compounds in the ice, through their impact on brine dynamics, gas bubble formation and ice permeability. We have described 4 stages of brine dynamics, which affect the distribution of the dissolved compounds (e.g. silicate and DOM) in sea ice. However, inert gas (Ar) shows a different dynamic in comparison to the dissolved compounds, indicating a different transport pathway. We suggest that the formation of gas bubbles in sea ice is responsible for that different transport pathway, because gas bubbles should move upward owing to their buoyancy in comparison to brine, while dissolved compounds are drained downward due to gravity. Our observations further indicate that the critical permeability threshold for the upward gas bubble transport should range between 7.5 and 10 % of brine volume fraction, which is higher than the 5 % suggested for the downward brine transport. Increasing ice permeability and prolonged gas exchange tend to draw gas concentrations toward their solubility values, except when the under-ice water is supersaturated relative to the atmosphere (e.g. CH4) or when in-situ production occurs in sea ice (e.g. O2).<p>Because ammonium and O2 obviously accumulate in the ice layers where convection is limited, we suggest that the changes of these biogeochemical compounds in sea ice depend on the competing effect between the physical transport and the biological activity; the biological impact on these biogeochemical compounds in sea ice is obvious when the biological production rate exceeds largely the physical transport rate. We further discussed on the potential of using Ar and N2 as inert tracers to correct the physical controls on O2 and to determine the net community production in sea ice.<p>In addition to the physical and biological controls, the chemical properties of some biogeochemical compounds (e.g. nitrate, ammonium, DOM) may further influence their distribution in sea ice; further investigations are however needed to confirm this.<p>Finally, based on our findings, we present an update of the processes regulating the distribution of gases in sea ice, with references to recent observations supporting each of the process. We also provide some insights on how sea ice biogeochemistry could change in the future and the research priorities for an accurate quantification of these changes.<p><p>Les changements dans l’extension et les propriétés de la glace de la mer, liés au réchauffement climatique, affectent l’écosystème polaire, ainsi que les interactions entre l’atmosphère, la glace de mer et l’eau sous-jacente. Cependant, des incertitudes subsistent quant aux changements potentiels qui affecteront la biogéochimie de la glace de mer dans un futur proche.<p>Afin de mieux comprendre les changements potentiels qui affecteront la biogéochimie de la glace de mer, nous avons étudié les facteurs qui influencent la distribution de certains composés dissouts (e.g. nutriments, matière organique dissoute (DOM)) et gazeux (e.g. Ar, O2, N2, CH4) au sein de la glace de mer, depuis la croissance de la glace, jusqu’à sa fonte. Les résultats ont été obtenus à partir d’une expérience de 19 jours dans un bassin expérimental à Hambourg (Allemagne) et une étude de terrain de 5 mois à Barrow (Alaska). Ils ont été ensuite comparés aux propriétés physiques de la glace (température, salinité et autres paramètres dérivés) et à des paramètres biologiques (activité bactérienne, abondance bactérienne, chlorophylle-a et phaeopigments).<p>Nos travaux ont montré que les propriétés physiques de la glace exercent une forte influence sur la répartition des composes biogéochimiques dans la glace de mer, à travers leur impact sur la dynamique des saumures, la formation de bulles de gaz et la perméabilité de la glace. Nous avons décrit 4 stades dans la dynamique des saumures qui influencent la distribution des composés dissouts (e.g. silice et DOM) dans la glace. Cependant, le gaz inerte étudié (Ar) montre une dynamique différente de celle des composés dissouts, indiquant un mécanisme de transport différent. Nous suggérons que la formation de bulles de gaz dans la glace de mer est le mécanisme responsable de cette différence, parce que les bulles de gaz devraient migrer vers le haut, à cause de leur différence de densité par rapport aux saumures, alors que les saumures sont drainées vers le bas à cause de la gravité. Nos observations montrent également que le seuil critique de perméabilité pour l’ascension des bulles de gaz devrait se trouver entre 7.5 et 10 % de volume relatif en saumure ;seuil qui est plus élevé que les 5 % suggérés pour le transport de saumure vers le bas. L’augmentation de la perméabilité de la glace et les échanges de gaz prolongés tendent à amener les concentrations de gaz vers leur valeur de solubilité, sauf lorsque l’eau sous-jacente présente une sursaturation parrapport à l’atmosphère (e.g. CH4), ou lorsque une production in-situ se produit au sein de la glace (e.g. O2).<p>Etant donné que l’ammonium et O2 s’accumulent clairement dans les couches de glace où la convection est limitée, nous suggérons que les variations de ces composés biogéochimiques dans la glace dépendent de la balance entre le transport physique et l’activité biologique ;l’impact de cette dernière sur les composés biogéochimiques est particulièrement visible lorsque le taux de production biologique du composé excède largement la vitesse d’élimination du composé par le transport physique. Nous avons ensuite discuté du potentiel d’utiliser Ar et N2 comme traceurs inertes pour corriger l’impact des processus physiques sur les variations de O2, afin de déterminer la production communautaire nette dans la glace de mer.<p>Les propriétés chimiques de certains composés biogéochimiques (e.g. nitrate, ammonium, DOM) pourraient également influencer leur répartition au sein de la glace de mer, en plus des processus physiques et biologiques. Cependant, il est nécessaire d’avoir plus d’études à ce sujet pour confirmer cela.<p>Enfin, sur base de nos résultats, nous présentons une mise à jour des processus qui régulent la répartition des gaz dans la glace de mer, avec des références à des observations récentes qui illustrent chacun des processus. Nous donnons également un aperçu des changements qui pourraient affecter la biogéochimie de la glace de mer à l’avenir, et des pistes de recherches pour une quantification précise de ces changements. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished