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Det är välkänt att klimatförändringar på grund av global uppvärmning är en av de största kriserna som hotar jorden. Det är en enorm utmaning för mänskligheten att minska koldioxidutsläppen, den främsta orsaken till global uppvärmning. Enkelt genomförbara åtgärder är inte tillräckliga och teknik för att ta bort koldioxid från atmosfären anses nödvändig för att temperaturökningen inte ska överstiga de 1,5 °C som anges i Parisavtalet. Direkt infångning av koldioxid från luft (vanligen kallad direkt luftinfångning, (Eng. Direct air capture - DAC)) är en ny teknik som kan ta bort koldioxid direkt från atmosfären. För närvarande är denna metod dyr; upp till 1000 USD per ton avlägsnad koldioxid. Denna höga kostnad beror främst på den relativt låga koldioxidkoncentrationen i luften, vilket leder till att en stor anläggning behövs för att fånga upp gasen och därmed stora investeringar. Tekniken är mycket energiintensiv, antingen elektrisk eller termisk, och för att göra en direkt infångning effektivare, måste anläggningen drivas med energi som inte har några eller mycket låga koldioxidutsläpp. Energin på Island är billig och dess produktion innebär ett mycket lågt koldioxidavtryck. Syftet med arbetet i denna avhandling är att utforska om metoden för direkt infångning av koldioxid från luft kommer att vara en mer genomförbar metod än koldioxidinfångning från punktkällor (eng. point source - PS) på Island på grund av god tillgång till billig och ren energi. Lärandekurvan för direkt luftfångning studerades tillsammans med scenarier för metodens tekniska utveckling. Tre olika fall med punktkällor på Island studerades för jämförelse. Två olika direkta luftinfångningstekniker analyserades också, en som drivs av en stor mängd elektricitet och en som drivs mestadels av termisk energi. Det resulterade i att i bästa fall, där inlärningshastigheten är hög och tekniska förbättringar är signifikanta, så skulle produktionskostnaden för direkt luftinfångning (levelized cost of energy, LCOC) vara lägre än motsvarande för infångning från en punktkälla. Energikostnaden påverkar LCOC för DAC idag men med teknisk utveckling förväntas energibehovet minska och därför kommer energikostnadens påverkan att bli lägre. Det är dock fortfarande viktigt, med tanke på bidraget till att minska globala uppvärmningen, att energin som driver DAC-anläggningen har ett lågt koldioxidavtryck, vilket kan garanteras på Island. Tvärtom, om inlärningshastigheten för DAC-tekniken är låg och inga tekniska förbättringar sker i lösningsmedel eller sorbenter, är och kommer DAC-tekniken att bli dyrare än infångning från punktkällor om båda anläggningarna finns på Island. En hög inlärningshastighet och teknikutveckling är beroende av trycket att nå målen i Parisavtalet. Det är därför mycket viktigt för DAC att efterfrågan på koldioxidinfångning ökar. Dessutom har DAC mer potential att påverka klimatförändringarna eftersom DAC kan vara en kolnegativ teknik om den kombineras med permanent lagring av koldioxid. PS-avskiljningen kan endast vara en kolneutral teknik och detta om den kombineras med permanent lagring av koldioxid. / It is well known that climate change due to global warming is one of the greatest crises facing the Earth. It is a huge challenge for mankind to reduce CO2 emissions, the major cause of global warming. Mitigation measures are not enough. Technologies to remove the CO2 from the atmosphere are considered necessary, so the temperature rise does not exceed 1.5°C as stated in the Paris Agreement. Direct air capture (DAC) is a new technology that can remove carbon dioxide directly from the atmosphere. Currently, this method is expensive, up to 1000 USD per ton CO2 removed. This high cost is mostly due to the relatively low concentration of CO2 in the ambient air, leading to a large unit to capture the gas and therefore high capital investment. The technology is very energy-intensive, either electrical or thermal, and to make direct air capture more efficient the plant needs to be powered with energy that has no or very low CO2 emissions. The energy in Iceland is low cost and its production has a very low carbon footprint. This thesis aims to find out if the direct air capture method will be more feasible than a point source CO2 capture in Iceland due to good access to low-cost and clean energy. The learning curve for direct air capture was studied along with scenarios for its technological development. Two different direct air capture technologies were analyzed, one that is powered by a large amount of electricity and one powered mostly by thermal energy. Three different point source cases in Iceland were studied for comparison. For the best-case scenario, where the learning rate is high and technological improvements are significant, the levelized cost of direct air capture is lower than levelized cost of point source capture. The cost of energy affects the levelized cost of direct air capture today but with technical development, the energy needed is expected to go down, and therefore the effect of energy cost will be lower.  However, it is still important, concerning contribution to reducing global warming, that the energy powering the direct air capture plant has a low carbon footprint, which can be assured in Iceland. On the contrary, if the learning rate of the direct air capture technology is low and no technical improvements occur in solvents or sorbents the direct air capture technology is and will be more expensive than point source capture considering both located in Iceland. The high learning rate and development in technology are dependent on the pressure to reach the goals of the Paris Agreement. It is therefore vital for direct air capture that the demand for carbon removal measures is enhanced due to pressure to reach the Paris Agreement goals. Furthermore, direct air capture has more potential to affect climate change than point source capture as direct air capture can be a carbon-negative technology if coupled with the permanent storage of CO2. The point source capture can only be a carbon-neutral technology if coupled with the permanent storage of CO2.

Urban environments have been identified as a non-point source contributor of nutrient loadings into watersheds. Interannual surges of nutrient loadings into local water systems are more damaging than mean interannual nutrient loadings. Virginia has outlined the need to reduce urban nutrient loadings. Mean interannual nutrient loadings and interannual nutrient loadings variability are expected to increase under climate change (CC). However, there are few studies that provide a predictive framework for abating nutrient loadings under CC. Thus, there is a lack of information regarding how effective water quality policy will be in the future. Using the Difficult Run watershed in Fairfax County, VA, as a site of study, we used mathematical programming to compare how the costs of abating nutrient loads differed under differing climates in the Mid-Atlantic. We first compared the costs of abating mean interannual nutrient loadings in the watershed based on historical climate conditions to those predicted for CC. We then evaluated how changes in the interannual variability of nutrient loadings for CC affect the costs of meeting watershed goals. We found that abating mean interannual nutrient loadings was substantially costlier for CC relative to meeting the same goals under historical climate conditions. Further, we found that the costs of abating interannual nutrient loadings variability increased under CC relative to meeting the same goals under historical climate. One implication of this study suggests that policy makers seeking to meet water quality goals over time must front-load supplemental BMPs today in order to offset the changes predicted for CC. / Master of Science

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Effluent from on-site sewage treatment and disposal systems (OSTDS) is generally known to impact groundwaters and surface waters with nitrogen (N) and phosphorus (P) and other contaminants. Little research has quantified this problem along the Indian River Lagoon (IRL), especially in Indian River County (IRC) where there are 26,660 active systems. This study assessed the effects of OSTDS on contamination of surface and groundwaters along three urbanized canals and the St. Sebastian River in IRC, all of which flow into the Central IRL. Multiple lines of evidence were used to define the source of the nutrient loadings including the novel approach of using the artificial sweetener, sucralose, as an indicator of human sewage impact. Results indicate that areas with high densities of OSTDS are contributing N to surface waters and elevating N:P ratios through submarine groundwater discharge and promoting eutrophication in the Central IRL. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-20T14:01:59Z No. of bitstreams: 1 VALÉRIO DE ARAÚJO GOMES - DISSERTAÇÃO PPGEQ 2007..pdf: 2306567 bytes, checksum: aa927c50f8346bfbe8e90901136c65fe (MD5) / Made available in DSpace on 2018-03-20T14:01:59Z (GMT). No. of bitstreams: 1 VALÉRIO DE ARAÚJO GOMES - DISSERTAÇÃO PPGEQ 2007..pdf: 2306567 bytes, checksum: aa927c50f8346bfbe8e90901136c65fe (MD5) Previous issue date: 2017 / A determinação de concentração de poluentes lançados na atmosfera é um elemento importante na previsão de impactos ambientais causados por emissões de efluentes industriais, sendo fundamental na avaliação de viabilidade de novas plantas, ou mesmo para plantas existentes. Em função da ampliação dos parques industriais e da aproximação dos centros urbanos, cada vez mais fica evidente a necessidade de dispor de dados de simulações da qualidade do ar, para tomar decisões em relação ao tipo de tratamento dos efluentes gasosos, posicionamento de plantas, projetos de chaminés (altura), e principalmente do tipo de controle e processo que será necessário para minimizar as concentrações lançadas no meio ambiente. O presente trabalho teve como objetivo, principalmente, desenvolver uma rotina aplicada as emissões de fluoreto gasoso proveniente de reduções eletrolíticas de alumínio. A referência adotada foi o modelo desenvolvido pela Environmental Research & Technology Inc. chamado BLP – Buoyant Line and Point Source (modelo fundamentado na distribuição gaussiana), aplicando algumas considerações específicas. A implementação foi realizada utilizando o Mathcad 11 Enterprise Edition. Posteriormente ao desenvolvimento foram feitas várias simulações com informações coletadas pelo programa de monitoramento de fontes estacionárias da Alumar e comparados com os dados coletados na estação de monitoramento contínuo de qualidade do ar localizada na vila de Coqueiro (intermediações do limite da fábrica, 2,500 Km). Complementarmente, também foi realizada uma simulação para comparar o resultado do modelo proposto com os resultados do CALPUFF (software comercial referendado pela EPA – Environmental Protection Agency) que foi utilizado durante a elaboração do estudo de impacto ambiental da complementação da sala de cubas – linha 3. O modelo proposto apresentou uma correlação de 82% com os dados históricos coletados na estação localizada na vila de Coqueiro e um erro de 4,35% quando comparado com as simulações do CALPUFF. / The determination of the pollutants concentration released into the atmosphere is an important element in the prediction of environmental impacts caused by emissions from industrial effluents, being fundamental in the feasibility evaluation of new plants, or even for existing plants. Due to the industrial parks expansion and the approximation of urban centers, it is increasingly evident that there is a need for air quality simulation data to make decisions regarding the type of treatment of gaseous effluents, plant positioning, chimneys dimensions (height), and especially of the type of control and process that will be necessary to minimize the concentrations released in the environment. The main objective of this work was to develop a routine applied to the emission of gaseous fluoride from electrolytic smelting of aluminum. The reference adopted was the model developed by Environmental Research & Technology Inc called BLP - Buoyant Line and Point Source (model based on the Gaussian distribution), applying some specific considerations. The implementation was performed using Mathcad 11 Enterprise Edition. After the development, several simulations were carried out with information collected by Alumar's stationary source monitoring program and compared to the data collected at the continuous air quality monitoring station located in the village of Coqueiro (distant 2,500 km). In addition, simulations were also carried out to compare the results of the proposed model with the results from CALPUFF (commercial software endorsed by the EPA - Environmental Protection Agency) that was used during the elaboration of the environmental impact study of the complementation of the potroom - line 3. The proposed model presented a correlation of 82% with the historical data collected at the station located in the village of Coqueiro and an error of 4.35% when compared to the simulations of the CALPUFF.

Il y a près d’une décennie, l'utilisation des supernovae de type Ia comme indicateurs de distances a permis de découvrir l'expansion accélérée de l'univers. Les expériences de seconde génération ont augmenté de manière significative la taille et la qualité des échantillons à grand décalage vers le rouge. Cependant, l'échantillon de référence des supernovae à faible décalage vers le rouge, nécessaire à la cosmologie restait très restreint. The Nearby Supernova Factory a mesuré, à l'aide d'un instrument spectro-photométrique dédié (the Supernova Integral Field Sepctrograph), près de 200 nouvelles supernovae de type Ia. Ma thèse de doctorat a été effectuée à l'Institut de Physique Nucléaire de Lyon et au Lawrence Berkeley National Laboratory dans le cadre du projet international the Nearby Supernova Factory et a pour but l'étalonnage spectro-photométrique du spectrographe à champ intégral. Afin d'atteindre la précision souhaitée, une attention particulière a été apportée à plusieurs aspects majeurs de la procédure d'étalonnage, incluant: la détermination de la réponse impulsionnelle de l'instrument en vue de l'extraction 3D de sources ponctuelles, l'estimation de la qualité photométrique d'une nuit, l'obtention de l'extinction atmosphérique par nuit sur un domaine de longueur d'onde étendu, sa modélisation en terme de composantes physiques et sa variabilité au cours d'une nuit donnée. Une chaîne d'étalonnage multi-standard a été mis en \oe{}uvre utilisant approximativement 4000 observations spectro-photométriques d'étoiles standards. J'exposerai également à la fin de ce manuscrit les résultats scientifiques préliminaires de la collaboration SNfactory. / Ten years ago, type Ia supernovae used as distances indicators led to the discovery of the accelerating expansion of the universe. Today, a second generation of surveys has significantly increased the high-redshift type Ia supernovae sample. The low-redshift sample was however still limiting the cosmological analysis using SNe. In this framework, the Nearby Supernova Factory has followed 200 nearby type Ia supernovae using the dedicated Supernovae Integral Field Spectrograph with spectro-photometric capacities. My PhD thesis has been carried out at the Institut de Physique Nucléaire de Lyon and at the Lawrence Berkeley National Laboratoryin the framework of the international cosmological project SNfactory. In order to reach the design spectrophotometric accuracy, attention has been focused on several key aspects of the calibration procedure, including: determination of a dedicated point spread function for 3D point source extraction, estimating the nightly photometric quality, derivation of the nightly sky extinction over the extended optical domain, its modeling in terms of physical components and its variability within a given night. A full multi-standards calibration pipeline has been implemented using approximately 4000 observations of spectrophotometric standard stars taken throughout the night over nearly 500 individual nights. Preliminary scientific results of the whole SNfactory collaboration will be presented at the end of this thesis.

In this thesis we look at acoustic wave propagation under water. We look in particular at waves generated by a point source and what happens with the propagation when we model the bottom as flat or as curvilinear. We assume the source to be working at a certain frequency and therefore we model this problem by solving the Helmholtz equation. Since Helmholtz equation has some unwanted numerical properties we are interested in finding new numerical methods that could accelerate the solver. In this thesis we use the Waveholtz iteration, which solves Helmholtz equation by connecting it to the time-dependent wave equation. We use finite differences and the SBP-SAT method to approximate the spatial problem numerically and for modelling the sea bottom we use curvilinear coordinates.  To compare the Waveholtz iteration we also solve Helmholtz equation with a naive solver. The naive solver consists of approximating the equation with finite differences and then solving the linear system of equation by some iterative solver, which for our tests will be GMRES. The results show that the Waveholtz iteration converges in less iterations than our naive solver. It also shows that the number of iterations stays unchanged when changing our discretization, which otherwise is a big problem for our naive solver. This allows us to increase the accuracy of our numerical solution without changing the computation time too much.  We show that the number of iterations increases according to theory for an increasing frequency, and that for open problems we even see a smaller increase. For certain resonant frequencies in Helmholtz equation we do not expect the Waveholtz iteration to converge. In the neighbourhood of these frequencies the convergence becomes slow and we need many iterations for a solution of a certain accuracy. By reformulating the Waveholtz iteration as a Krylov solution we can see that resonances in Helmholtz equation have a smaller impact of the convergence. / I detta examensarbete undersöker vi akustisk vågutbredning i vatten. Vi kollar specifikt på vågor som genereras av en punktkälla och vad som sker när vi modellerar botten som plan eller som kurvlinjär. Då vi antar att punktkällan arbetar vid en bestämd frekvens, kommer vi modellera det fysikaliska problemet genom att lösa Helmholtz ekvation. Helmholtz ekvation har dock några numeriska egenskaper som är oönskade, och därför finns ett intresse av att hitta nya numeriska metoder som löser ekvationen. I detta examensarbete undersöker vi Waveholtz iteration, som löser Helmholtz ekvation genom att koppla den till den tidsberoende vågekvationen. Vi använder finita differenser och SBP-SAT metoden för att approximera det rumsliga problemet numeriskt. För att ge en detaljerad beskrivning av botten använder vi kurvlinjära koordinater. För att jämföra Waveholtz iterationen med något löser vi även Helmholtz med hjälp av en naiv lösare. Den naiva lösaren består av att approximera problemet med finita differenser och sedan lösa det linjära systemet rakt av med en iterativ lösare (vilket för våra fall kommer vara GMRES). Resultatet visar att Waveholtz iteration konvergerar på ett lägre antal iterationer än vår naiva lösare. Det visar även att antalet iterationer inte förändras när vi ändrar diskretisering, vilket annars är ett problem för vår naiva lösare. Detta innebär att vi kan få en högre noggrannhet utan att förlänga beräkningstiden alltför mycket.  Vi visar även att antalet iterationer ökar som förväntat med en ökad frekvens, samt att för öppna problem så ökar antalet iteration mindre än enligt teorin. Vid vissa resonanta frekvenser i Helmholtz ekvation förväntar vi oss att Waveholtz iteration inte kommer konvergerar. I närheten av dessa frekvenser blir konvergensen långsam och vi behöver många iterationer för att lösa problemet. Genom att formulera Waveholtz iteration som en Krylov lösning kommer resonanser i Helmholtz ekvation ge en mindre negativ effekt på konvergensen än om den är formulerad som en fixpunkts iteration.

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