This study addressed the geochemical drivers of Mn removal, including pH, alkalinity and the presence of mineral particles. We conducted laboratory experiments and field monitoring at two drinking water reservoirs in southwestern Virginia – Falling Creek Reservoir (FCR) and Carvins Cove Reservoir (CCR). In laboratory experiments in pH and alkalinity-adjusted nanopure water solutions, we observed substantial Mn removal within 14 days only under high pH conditions (pH≥10). In experiments with high pH and moderate to high alkalinity (> 80 mg/L CaCO3), near-total Mn removal occurred within 2 hours, at a rate of 0.25 mg/L-1 hr-1. Mn removal occurred alongside precipitation of microscopic (<5 μm diameter) and macroscopic (>100 μm diameter) particles. Elemental analysis of particles with energy-dispersive X-ray spectroscopy (EDS) supports their identification as Mn(IV) oxides (MnOx), which suggests Mn removal driven by oxidation. Elevated alkalinity in high pH solutions promotes Mn oxidation by maintaining high pH through buffering, which sustains conditions favorable for Mn oxidation. Our results also suggest sorption of Mn and mineral-catalyzed Mn oxidation by Mn oxides formed through oxidation by dissolved oxygen. In experiments using filtered and unfiltered water from the two reservoirs, we observed significant Mn removal in experiments with unfiltered water, suggesting that particles may remove Mn by catalyzing oxidation or nucleating Mn oxide precipitation. Mn removal occurred at 0.05 d-1 in unfiltered FCR water and 0.002 d-1 in unfiltered CCR water. We observed no Mn removal in filtered water from either reservoir. Scanning electron microscope (SEM) and EDS of visible particles from reservoir water experiments suggests that quartz and clay minerals present in the water column may nucleate or catalyze Mn oxide formation. Overall, this research shows that Mn removal under HOx operation is influenced by a variety of factors, including pH, alkalinity and suspended particles. / Master of Science / Elevated concentrations of manganese (Mn), a naturally occurring contaminant, can impair drinking water quality in several ways – by introducing poor taste and smell, staining pipes and appliances, and potentially harming the health of young children. Hypolimnetic oxygenation (HOx) is a novel water treatment method deployed in lakes and reservoirs to control water column contamination of metals and nutrients, including Mn. By pumping oxygen into lakes and reservoirs, HOx systems create conditions favorable for Mn removal from the water column. Previous work in two southwestern Virginia drinking water reservoirs documented differences between sites in how effectively HOx systems are able to remove Mn. These reservoirs have significant differences in their chemical profiles – most notably in pH and alkalinity, which suggests a role for background water chemistry in influencing removal rates in lakes and reservoirs with HOx systems. We used laboratory experiments to simulate the effects of pH and alkalinity on Mn removal rates in oxygenated lakes and reservoirs. We observed substantial Mn removal within 14 days under high pH conditions (pH 10-11) and negligible removal in solutions at or under pH 8. In experiments with pH 10-11 and alkalinity over 80 mg/L, near-total Mn removal occurred within 24 hours. During the 24 hour removal window, we observed yellow-brown discoloration of our experimental solutions within 12 hours, followed by formation of loosely aggregated brown to black particles. Microscopy and elemental analyses indicate that initial discoloration occurs due to formation of 1-2 μm wide manganese oxides with needle-like crystals. The visible aggregates are also manganese oxides. Based on mineral characterization and the time series of Mn removal observed in our experiments, we believe that initial formation of Mn oxides creates a positive feedback loop in solutions of pH 10-11 and alkalinity over 80 mg/L. Mn oxides promote further Mn oxide formation by facilitating conversion of Mn in solution into forms that easily settle from water. Observations of particulate formation and solution chemistry in filtered vs. filtered reservoir water from FCR and CCR supports a pivotal role for particles in facilitating Mn removal. Our research addresses the impacts of water chemistry Mn removal in drinking water, and improves understanding of Mn cycling in natural freshwaters.

The world energy production, transformation, storage, and usage are under a dramatic change. Actions are being taken by Governments to slow down the effects of the climate change. Wind energy is expected to be a central pillar for this change. However, a key issue facing the expansion of wind energy, especially in Sweden, is the integration of the massive amounts of new generation into the electricity grid (Energinet et al., 2021; Ingeberg, 2019; IVA, 2020). Another challenge facing the expansion of the wind energy is that it can’t be used by end-sector which rely on energy-dens carriers (IRENA, 2020b). In the pursuit of solutions to these challenges, green hydrogen produced by offshore wind energy emerges an alternative. Motivated by the recent Swedish plans to develop offshore wind power capacity in the Baltic Sea, as well as the problematic environmental statues in the Baltic Sea, this work investigate the cost of green hydrogen produced from offshore wind energy in Sweden and evaluates the environmental impacts of utilizing by-product oxygen on the marine ecosystem in the Baltic Sea.  The first step of this work considers the economic feasibility of a 2 GW offshore wind energy dedicated for hydrogen production in the Baltic Sea outside Sweden, with three alternative electrolyzer placement: onshore electrolyzer (III), centralized offshore electrolyzer (II), and decentralized offshore electrolyzer (I). The proposed assessment of this work investigated the hydrogen production cost using electricity from offshore wind energy in the Baltic Sea in Sweden. The LCoE and LCoH in relation to three configurations reflecting the electrolyzer placement were analyzed and compared. The electrolyzer operation at nominal capacities of 06%, 65%, and 70% were considered for the three configurations. The results shows that the LCoE and LCoH differed between the three configurations. The results showed that the lowest LCoE and LCoH is achieved by the configuration where the electrolyzer system decentralized at the turbine platform at a price of 1.7 €/kg. Reflecting the impact of the electrolyzer nominal capacities, which are at 60%, 65%, and 70%, on the LCoH, the result showed that the three configurations are equally competitive. However, when the nominal capacity of 65% were compared among the three configurations, it was showed that the LCoH at the onshore electrolyzer were 2.6 €/kg compared to the LCoH at the centralized electrolyzer which resulted in LCoH of 2.7 €/kg. The second step of this work considers the evaluation of the environmental impact of artificial oxygenation by reviewing existing studies. The results of the reviewed studies on the environmental impacts of artificial oxygenation indicate that the utilization of the by-product oxygen would contribute to important environmental benefits for the Baltic Sea. The use of the by-product oxygen to oxygenate would maintain the processes that removes nutrients, keep the sea water oxygenated, and the seabed habitable for marine animal. There are, however, some aspects that need to be considered and understood when planning for oxygenation, such as the complicated physical and biogeochemical interactions. Hence, this requires further studies and investigations.

No description available.

Evaluation of the sources and cycles of water quality contaminants in watersheds is critical for effective surface water resource management. In particular, iron (Fe) and manganese (Mn), commonly found in rocks and sediments, have adverse impacts on water quality. However, controlling Fe and Mn in surface water systems is often complex and requires careful consideration of the hydrologic and biogeochemical factors that influence the speciation and mobility of these metals. This dissertation investigates the sources and cycles of Fe and Mn in surface waters designated for human use. Here, I present the findings from three field- and laboratory-based studies conducted at sites in western Virginia, United States. The first study examines the impacts of reservoir-derived and watershed-derived metals on water quality along the 180 km reach of the Roanoke River downgradient from Leesville Dam. The results from this study showed strong temporal influences on river water quality immediately downgradient of the dam, resulting from seasonal reservoir dynamics. Further downgradient in the Roanoke River, water quality was strongly tied to hydrologic conditions resulting from influences generated in the watershed. The second study investigated the effects of increasing dissolved oxygen (DO) concentrations in the hypolimnion of stratified drinking water reservoir on Fe and Mn oxidation and removal. Results from a whole-ecosystem experiment showed that increasing DO concentrations through hypolimnetic oxygenation was effective for preventing the accumulation of soluble Fe in the water column. Although Mn oxidation increased under well-oxygenated conditions, soluble Mn still accumulated in the hypolimnion. Results from a laboratory experiment demonstrated that the oxidation of Mn was strongly tied to the activity of Mn oxidizing microbes. The third study examined the relative contribution of external and internal metal loadings to the exchange of metals between sediments and the water column and the source/sink behavior of a seasonally stratified reservoir under varying hydrologic conditions in the inflows and outflows and redox conditions in the reservoir hypolimnion. Results from this study showed that redox conditions strongly influenced the exchange of metals between the sediment and aqueous phase, but had little effect on the source/sink behavior of the reservoir, while external tributary loadings had little effect on internal redox cycles, but was a strong indicator for whether the reservoir behaved as a net metal source or sink. Overall, the findings from these studies exemplify the value of characterizing the hydrologic and biogeochemical drivers of Fe and Mn cycles for managing the water quality effects of these metals in surface water supplies. / Ph. D.

Bubble plume oxygenation systems are commonly used to mitigate anoxia and its deleterious effects on water quality in thermally stratified lakes and reservoirs. Following installation, increases in sediment oxygen flux (JO2) are typically observed during oxygenation and are positively correlated with the bubble plume gas flow rate. Studies show that JO2 is controlled by the thickness of the diffusive boundary layer (DBL) at the sediment-water interface (SWI), which is in turn controlled by turbulence. As a result, JO2 can be quite spatially and temporally variable. Accurately predicting oxygenation-induced JO2 is vitally important for ensuring successful oxygenation system design and operation. Yet despite the current understanding of physical and chemical controls on JO2, methods for predicting oxygenation-induced JO2 are still based on empirical correlations and factors of safety. As hypolimnetic oxygenation becomes more widely used as a lake management tool for improving and maintaining water quality, there is a need to move from the current empirically based approach to a mechanistic approach and improve the ability to predict induced JO2. This work details field campaigns to investigate and identify appropriate models of oxygen supply to the SWI and oxygen demand exerted from the sediment, with the intent to use these models to predict oxygenation-induced JO2. Oxygen microprofiles across the SWI and near-sediment velocity measurements were collected in situ during three field campaigns on two oxygenated lakes, providing simultaneous measurements of JO2 and turbulence. Field observations show that oxygenation can increase JO2 by increasing bulk hypolimnetic oxygen concentrations, which increases the concentration gradient across the SWI. Oxygenation can also enhance turbulence, which decreases the DBL thickness and increases JO2. Existing models of interfacial flux were compared to field measurements to determine which model best predicted the observed JO2. Models based on the Batchelor scale, friction velocity, and film-renewal theory all agree reasonably well with field observations in both lakes. Additionally, the oxygen microprofiles were used to fit a transient model of oxygen kinetics in lake sediment and determine the appropriate kinetic model. Oxygen microprofiles in both lakes can be described using zero-order kinetics, rather than first-order kinetics. The interfacial flux and sediment kinetic models are incorporated into a coupled bubble plume and 3-D hydrodynamic lake model, allowing for spatial and temporal variation in simulated JO2. This comprehensive model was calibrated and validated to field data from two separate field campaigns on Carvin's Cove Reservoir, Virginia. Simulated temperature profiles agreed quite well with field observations, while simulated oxygen profiles differed from observed profiles, particularly in the bottom 1 m of the water column. The model overestimates oxygen concentrations near the sediment, which results in higher simulated JO2 than was observed during the field campaigns. These discrepancies are attributed to oxygen-consuming chemical processes, such as oxidation of soluble metals, which are not accounted for in the hydrodynamic model. Despite this, the model is still able to capture the impact of bubble plume operation on JO2, as simulated JO2 is higher when the diffusers are operating. With some additional improvements to the water quality modeling aspects of the model, as well as further calibration and validation, the model should be able to reproduce observed JO2 provided oxygen concentrations near the SWI are accurately reproduced as well. The current work is an attempt to push toward a comprehensive lake oxygenation model. A comprehensive model such as this should improve the ability to predict oxygenation-induced JO2 and lead to improvements in the design and operation of hypolimnetic oxygenation systems. / Ph. D.

The Occoquan Reservoir is part of the largest indirect potable reuse systems in the United States. It in an important water supply source for the Northern Virginia area, as well as, an ecological and recreational area. Furthermore, the Occoquan Reservoir protects the water quality of the Chesapeake Bay because it acts as a trap for sediments and pollutants. Continuous water quality monitoring and evaluation is critical to preserve this important water resource. Reservoir water quality can be affected by the delivery of pollutants from point and nonpoint sources, potentially causing problems such as eutrophication, excess salinization, presence of compounds that affect human and aquatic health. Different management strategies have been implemented at the Occoquan Reservoir to nutrient loading into the reservoir and address eutrophication issues, including nitrate addition to hypolimnetic waters and installation of a hypolimnetic oxygenation system. The goal of this study is to assess how current management strategies implemented in the Occoquan Reservoir have affected the water quality from 1973 to 2019, with particular emphasis on the data since 2003. This analysis of the Occoquan Reservoir and its tributary watershed includes the evaluation of hydrometeorological data and morphometric characteristics; establishment of long-term trends for water quality constituents; and determination of the trophic state of the reservoir. Data from water samples from four different stations located at the Occoquan Reservoir and four stations located throughout the Occoquan tributary watershed were analyzed for nutrients, principal ions and metals, synthetic organic compounds (SOCs), and other water quality parameters. Long-term water quality trends were determined using Mann-Kendall test and relationship between constituents was evaluated using Principal Component Analysis (PCA). Trophic state of the reservoir was assessed using Carlson's Trophic State Index (TSI), Vollenweider Model, and Rast, Jones, and Lee's Model. Results indicate the Occoquan Reservoir is a eutrophic waterbody. However, the nitrate management strategy and the installation of the hypolimnetic system have improved reservoir water quality, reducing concentrations of nutrients and metals. / Master of Science / The Occoquan Reservoir is part of the largest indirect potable reuse systems in the United States. Indirect potable reuse refers to the planned discharge of reclaimed water into a water supply source, such as a reservoir or lake. The Occoquan Reservoir also serves as an ecological and recreational area, and serves to protects the water quality of the Chesapeake Bay because it acts as a trap for sediments and pollutants. To protect the different ecosystem services that the reservoir provides, it is critical to continuously monitoring and evaluate its water quality. Reservoir water quality can be affected by the delivery of pollutants from industrial and municipal waste discharges (point sources), as well as, from urban and agricultural runoff (nonpoint sources). Contaminants include nutrients (such as nitrogen and phosphorus), ions, metals, and synthetic organic compounds (SOCs) that can affect human and aquatic health. Different management strategies have been implemented at the Occoquan Reservoir to reduce load of pollutants into the reservoir, particularly to reduce concentrations of nutrients, as excessive nutrients can degrade water quality. Two strategies implemented are the addition of nitrogen, in the form of nitrate, and the installation of an oxygenation system at the reservoir bottom waters. The goal of this study is to assess how current management strategies implemented in the Occoquan Reservoir have affected the water quality from 1973 to 2019, with particular emphasis on the data since 2003. This analysis of the Occoquan Reservoir and its tributary watershed includes the evaluation of the hydrological, meteorological, and morphometric characteristics of the Occoquan Reservoir and Watershed; establishment of long-term trends for water quality constituents; and determination of the productivity (trophic state) of the reservoir. Data from water samples from four different stations located at the reservoir and four stations located throughout the watershed were analyzed for nutrients, principal ions and metals, SOCs, and other water parameters indicative of water quality. Statistical analyses were employed to determine long-term water quality trends (Mann-Kendall test) and relationship between constituents (Principal Component Analysis - PCA). The trophic state of the reservoir was assessed using three methods: Carlson's Trophic State Index (TSI), Vollenweider Model, and Rast, Jones, and Lee's Model. Results indicate the Occoquan Reservoir is eutrophic, or highly enriched with nutrients and productive. However, management strategies employed have improved the water quality and the reservoir continues to improve, though at a slow rate.

When properly designed, hypolimnetic aeration and oxygenation systems can replenish dissolved oxygen in water bodies while preserving stratification. A comprehensive literature review of design methods for the three primary devices was completed. Using fundamental principles, a discrete-bubble model was first developed to predict plume dynamics and gas transfer for a circular bubble-plume diffuser. This approach has subsequently been validated in a large vertical tank and applied successfully at full-scale to an airlift aerator as well as to both circular and linear bubble-plume diffusers. The unified suite of models, all based on simple discrete-bubble dynamics, represents the current state-of-the-art for designing systems to add oxygen to stratified lakes and reservoirs. An existing linear bubble plume model was improved, and data collected from a full-scale diffuser installed in Spring Hollow Reservoir, Virginia (U.S.A.) were used to validate the model. The depth of maximum plume rise was simulated well for two of the three diffuser tests. Temperature predictions deviated from measured profiles near the maximum plume rise height, but predicted dissolved oxygen profiles compared very well to observations. Oxygen transfer within the hypolimnion was independent of all parameters except initial bubble radius. The results of this work suggest that plume dynamics and oxygen transfer can successfully be predicted for linear bubble plumes using the discrete-bubble approach. To model the complex interaction between a bubble plume used for hypolimnetic oxygenation and the ambient water body, a model for a linear bubble plume was coupled to two reservoir models, CE-QUAL-W2 (W2) and Si3D. In simulations with a rectangular basin, predicted oxygen addition was directly proportional to the update frequency of the plume model. W2 calculated less oxygen input to the basin than Si3D and significantly less mixing within the hypolimnion. The coupled models were then applied to a simplified test of a full-scale linear diffuser. Both the W2 and Si3D coupled models predicted bulk hypolimnetic DO concentrations well. Warming within the hypolimnion was overestimated by both models, but more so by W2. The lower vertical resolution of the reservoir grid in W2 caused the plume rise height to be over-predicted, enhancing erosion of the thermocline. / Ph. D.

L’insuffisance cardiaque aigue est une émergence médicale qui nécessite une prise en charge multidisciplinaire. L’Extracorporeal Life Support (ECLS) peut être envisagé comme option thérapeutique pour les formes d’insuffisance cardiaque aigue réfractaire au traitement conventionnel. L’objectif de ce projet de recherche clinique est de fournir une vue d’ensemble de l’ECLS dans la prise en charge du choc cardiogénique et de l’arrêt cardiaque réfractaire. L’intoxication médicamenteuse et la myocardite sont les meilleures indications à l’implantation de l’ECLS en considération de leur potentiel de récupération myocardique très élevé. La défaillance primaire du greffon après transplantation cardiaque et l’infarctus du myocarde présentent des résultats plus mitigés avec l’ECLS en raison d’une physiopathologie plus complexe. Le choc cardiogénique postcardiotomie après une intervention de chirurgie cardiaque montre des résultats décevants en raison du profile préopératoire des patients. L’arrêt cardiaque aussi exige une prise en charge immédiate et l’ECLS peut être considéré comme une solution thérapeutique de sauvetage. Une meilleure sélection des patients s’impose afin d’améliorer les résultats de l’ECLS pour l’arrêt cardiaque réfractaire intrahospitalier. Les résultats de l’ECLS pour l’arrêt cardiaque réfractaire extrahospitalier sont dictés principalement par le temps de réanimation cardio-pulmonaire et le rythme cardiaque. Les rythmes non choquables pourraient être considérés comme une contre-indication formelle à l’utilisation de l’ECLS autorisant une concentration de nos efforts sur les rythmes choquables où les chances de survie sont plus importantes / Acute heart failure is a clinical situation requiring a prompt multidisciplinary approach. Extracorporeal Life Support (ECLS) could represent a therapeutic option for acute heart failure refractory to standard maximal treatment. The aim of this report is to offer an overview of ECLS in the management of refractory cardiogenic shock and cardiac arrest. Drug intoxication and myocarditis are the best indications of ECLS in consideration of their high potential of myocardial recovery. Primary graft dysfunction after heart transplantation and acute myocardial infarction show reduced survival rates owing to their more complex pathophysiology. Postcardiotomy cardiogenic shock after cardiac surgery operations displays poor outcomes due to the preoperative profile of the patients. ECLS could be also considered as a rescue solution for refractory cardiac arrest. A better selection of in-hospital cardiac arrest patients is mandatory to improve ECLS outcomes. In-hospital cardiac arrest patients with a reversible cause like drug intoxication and acute coronary syndrome should benefit from ECLS whereas end-stage cardiomyopathy and postcardiotomy patients with an unclear cause of cardiac arrest should be contraindicated to avoid futile support. ECLS for refractory out-ofhospital cardiac arrest should be limited in consideration of its poor, especially neurological, outcome and the results are mainly limited by the low-flow duration and cardiac rhythm. Nonshockable rhythms could be considered as a formal contraindication to ECLS for refractory out-of-hospital cardiac arrest allowing a concentration of our efforts on the shockable rhythms, where the chances of success are substantial

Many non-human animal species use colour to signal dominance, condition or reproductive status. These signals have not previously been noted in humans. This thesis investigates the effects of skin colouration and pigmentation on the apparent health of human faces. Section 2 showed that individuals with increased fruit and vegetable and carotenoid consumption have yellower skin (Study 1) due to increased carotenoid pigmentation in the skin (Study 2). In Section 3, participants enhanced the redness, yellowness and lightness of the skin portions of colour-calibrated facial photographs to optimise healthy appearance. This suggests roles for blood (red) and carotenoid/melanin (yellow) colouration in providing perceptible cues to health. The contrast between lips and facial skin colour was not found to affect the apparent health of the faces, except in the b* (yellowness) axis, where enhanced facial yellowness caused an apparent blue tint to the lips. In Section 4 participants enhanced empirically-derived oxygenated blood colour more than deoxygenated blood colour to optimise healthy appearance. In two-dimensional trials, when both blood colour axes could be manipulated simultaneously, deoxygenated blood colour was removed and replaced with oxygenated blood colour. Oxygenated blood colouration appears to drive the preference for redness in faces. In Section 5 participants increased carotenoid colour significantly more than they increased melanin colour in both single-axis and two-dimensional trials. Carotenoid colour appears to drive the preference for yellowness in faces. In a cross-cultural study (Section 6), preferences for red and yellow in faces were unaffected by face or participant ethnicity, while African participants lightened faces more than UK participants. A preference for more redness in East Asian faces was explained by this group’s lower initial redness. The thesis concludes that pigments that provide sexually-selected signals of quality in many non-human animal species – carotenoids and oxygenated blood - also provide perceptible cues to health in human faces.

La transplantation d’îlots de Langerhans microencapsulés est un traitement prometteur du diabète de type 1. La microcapsule protège l’îlot du système immunitaire, tout en permettant la diffusion de petites molécules. Comme la microcapsule empêche la revascularisation des îlots, leur oxygénation se fait par diffusion d’oxygène et ils sont exposés à l’hypoxie. Le manque d’oxygène est un facteur limitant dans la survie des îlots microencapsulés. Il est connu que les plus petits îlots sont plus résistant à l’hypoxie à cause d’une meilleure diffusion de l’oxygène. À cette fin, les agrégats de cellules dispersées d’îlots seront étudiés. Lorsque les cellules des îlots sont dispersées, elles ont la propriété de se ré-assembler dans une structure semblable à celle des îlots. La présente étude a permis de mettre au point une technique de formation des agrégats, de les caractériser et de comparer la résistance à l’hypoxie des îlots et des agrégats. Ceux-ci ont une structure semblable aux îlots et ils sont de plus petite taille. Pour cette raison, ils sont plus viables après un choc hypoxique tout en renversant efficacement l’hyperglycémie de souris diabétiques. Les agrégats sont une alternative intéressante pour la transplantation d’îlots microencapsulés puisque leur oxygénation est plus efficace. / Transplantation of microencapsulated islets of Langerhans is a promising treatment for type 1 diabetes mellitus. The microcapsule allows the diffusion of small molecules, while protecting the islet from the antibodies and immune cells. However, microcapsule prevents islet revascularization, thus oxygenation depends on diffusion and islets are exposed to hypoxia. Poor oxygenation is a major limitation in microencapsulated islet survival. It was shown that smaller islets are more resistant to hypoxia because of a better oxygen diffusion. In this study, dispersed islet cell aggregates will be used to improve the oxygenation. When islet cells are dispersed into single cells, they have the ability to re-associate into an islet-like structure. This study allowed to set up a technique to form aggregates, to characterized them and to compare the resistance to hypoxia of islets and aggregates. Aggregates have a similar structure than islets and they are smaller. For this reason, they survive better to a hypoxic treatment, while restoring efficiently normoglycemia in diabetic mices. Aggregates are an interesting solution for microencapsulated islet transplantation because they have a better oxygenation.