The sea surface microlayer is the upper thin interfacial boundary between ocean water and atmospheric air. The microlayer is known to be influenced by surface-active substances (SAS), largely organic matters adsorbed on the ocean surface. SAS samplers have been developed to investigate the chemical composition and effects of SAS but these samplers lack fast sampling and ease of use. To overcome these deficiencies, a new and novel microlayer sampler equipped with a set of rotating glass disks for fast sampling was built and modified. In this project, two closely connected scientific issues associated with the sampler were addressed. Firstly, the thickness of the solution layer adsorbed onto the glass disk was investigated in laboratory experiments using a range of optical techniques. Secondly, the sampler itself was evaluated in different oceanic environments and operated with a range of additional scientific sensors. / Graduate

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Les travaux présentés dans cette thèse portent premièrement sur la caractérisation de nouveaux photosensibilisateurs par des méthodes spectroscopiques. Ainsi les cinétiques de la réaction d'oxydation entre deux photosensibilisateurs à l'état triplet, imidazole-2-carboxaldehyde et 6-carboxypterine, et trois halogénures ont été déterminées par photolyse laser. La réactivité de l'état singulet de la 6- carboxypterine avec les halogénures et quatre acides organiques a été étudiée par fluorimétrie. Ces photosensibilisateurs sont relevants pour la photochimie à la surface de l'océan, mais également à la surface des particules atmosphériques. Les réactions mises en évidence mènent à la formation d'espèces radicalaires très réactives, influençant ainsi la composition de la phase condensée et gazeuse de l'environnement marin. La suite de cette étude s'est focalisée sur l'analyse des produits formés à partir de processus photo-induites à interface air-eau en présence d'une microcouche de surface d'un organique, utilisant deux organiques différents, l'octanol et l'acide nonanoique. En présence d'un photosensibilisateur et de lumière UVA, les changements en phase gaz ont été suivi par SRI-ToF-MS en ligne et en phase condensée par UPLC-(ESI)-HRMS. Ainsi on a démontré que la photochimie à la surface mène à la formation de produits fonctionnalisés et insaturés initiée par une abstraction d'hydrogène sur l'organique surfactant. Ces produits, observés en phase condensée et gazeuse, ont le potentiel de contribuer à la formation d'aérosols. Etonnamment, des produits ont également été observés dans les deux phases sans l'ajout d'un photosensibilisateur et montrant une activité photochimique de l'acide nonanoique seul à l'interface air-eau. Les mécanismes potentiels et les conséquences environnementales sont discutés / The works presented in this thesis concern firstly the characterization of two new photosensitizers by spectroscopic methods. This way the kinetics of the oxidation reaction between the triplet state of the photosensitizers, imidazole-2-carboxaldehyde and 6-carboxypterin, and three halides have been determined by laser flash photolysis. Also, the reactivity of the singlet state of 6-carboxypterin with halides and four organic acids has been studied by static fluorimetry. These photosensitizers are relevant for the photochemistry at the surface of the ocean, but also at the surface of atmospheric particles. The reactions evidenced by these studies lead to the formation of very reactive radical species influencing the composition of the condensed and gas phase of the marine environment. This study then focalized on the analysis of the products formed at the organic coated air-water interface through photo-induced processes. Two different organics were used as surfactants, octanol and nonanoic acid. In the presence of a photosensitizer and UVA light, the changes in the gas phase were monitored online by SRI-ToF-MS and in the condensed bulk phase by UPLC-(ESI)-HRMS offline analysis. These analysis showed that photochemical reactions at the interface lead to the formation of functionalized and unsaturated compounds initiated by a hydrogen abstraction on the organic surfactant. These products, observed in the condensed and gas phase have the potential to contribute to the formation of aerosols. Surprisingly, some of these products were also observed in the two phases without the presence of a photosensitizer, bringing into evidence a photochemistry of nonanoic acid at the air-water interface. Potential formation mechanisms of the products and environmental consequences are discussed

Direct numerical simulations, where both the large and small scales in the flow are fully resolved, provide an excellent instrument to validate multiphase flow processes and also further our understanding of it. Three multiphase systems are studied using a finite difference/front-tracking method developed for direct numerical simulations of time-dependent system¬¬s. The purpose of these studies is to demonstrate the benefit in developing accurate sub-grid models that can be coupled with the direct numerical simulations to reduce the computational time. The primary reason to use the models is that the systems under consideration are sufficiently large that resolving the smallest scales is impractical. The processes that are examined are: (1) droplet motion and impact (2) nucleate boiling and (3) convective mass transfer. For droplet impact on solid walls and thin liquid films, the splash characteristics are studied. The collision of a fluid drop with a wall is examined and a multiscale approach is developed to compute the flow in the film between the drop and the wall. By using a semi-analytical model for the flow in the film we capture the evolution of films thinner than the grid spacing reasonably well. In the nucleate boiling simulations, the growth of a single vapor from a nucleation site and its associated dynamics are studied. The challenge here is the accurate representation of the nucleation site and the small-scale motion near the wall. To capture the evaporation of the microlayer left behind as the base of the bubble expands we use a semi-analytical model that is solved concurrently with the rest of the simulations. The heat transfer from the heated wall, the evolution of the bubble size and the departure diameter are evaluated and compared with the existing numerical results. The mass transfer near the interface, without fully resolving the layer by refining the grid is accommodated by using a boundary layer approximation to capture it. The behavior of the concentration profile is taken to be self-similar. A collection of potential profiles is tested and the accuracy of each of these models is compared with the full simulations.

<div>For over 20 years, biaxially oriented polypropylene (BOPP) has been used in capacitors as the dielectric material. BOPP has very high breakdown strength, low electric loss, and is relatively inexpensive however, it suffers from low dielectric constant and low usage temperature. The ever growing technology market requires more robust capacitors which can be used in high temperature and pulsed power applications, and the aim of this research is to meet or exceed dielectric properties of BOPP by combining specific polymer materials in layered structures, biaxially orienting the films, and heat setting the films to further improve thermal stability. Post-processing is done on custom built machines which track real-time true stress, true strain and birefringence values, allowing for a more complete picture of mechano-optical properties generated during the stretching process. These data, along with offline characterization techniques such as X-ray scattering and DSC, were coupled with dielectric property testing to help form relationships between polymer processing, morphology, and dielectric properties.</div><div><br></div><div>In Chapter 3, microlayer PET and PVDF (50:50 ratio) films with 32 total layers and thickness around 125 micron were provided by PolymerPlus. Films were first stretched uniaxially at varying temperatures in order to optimize processing conditions. Characterization confirmed PVDF crystal form transformation from alpha to beta form when films were stretched at 95^oC, and presence of - PVDF when stretched in molten state at 185^oC, sandwiched between solid PET layers. Dielectric properties were tested for films stretched at 150^oC, which exhibited low dielectric constant when PVDF spherulites or smaller, broken up fibrils were present, but improved dielectric constant when PVDF morphology consisted of long, highly ordered fibrils. Uniaxial drawing helped lower dielectric loss, and it further signicantly decreased at very high strains. In this case, morphology of uniaxially drawn PET did not have a strong correlation with dielectric constant, but higher PET crystallinity and orientation likely helps to lower dielectric losses.</div><div><br></div><div>Polymer microlayer fims consisting of 32 layers, 50:50 ratio PET to PVDF films were also studied extensively using thermal heat setting technique. Samples with good thickness uniformity after stretching were selected for these experiments, and offline characterization techniques were applied to study morphology. Films were annealed at temperatures around PVDF melting peak, which caused transformation of PVDF polymorphs from primarily alpha to combined gamma and/or gamma' forms. When oriented at 150^oC to 1.5X1, and ' -PVDF were detected in small amounts (via DSC) after annealing at 172^oC, and only ' after higher temperature annealing. Stretching at 150^oC to higher strains produced high amounts of '-PVDF only when annealed at 155^oC for films stretched to 3.5X1, and annealed at 150^oC for films stretched to 2.5X1. Offline characterization led to development of a structural model for PVDF layers alone, by de-laminating film layers. Then, morphology was correlated with dielectric properties by testing lms at room temperature, and at constant frequency, in temperature ramping experiments. Temperature ramping dielectric experiments showed that high percent crystallinity of PET may also help improve loss behavior at high temperatures. Furthermore, samples containing gamma and/or gamma'-PVDF had increasing dielectric constant with increasing temperature, however dielectric loss also greatly increased with increasing temperature. A significant conclusion was that the annealed sample without gamma or gamma'-PVDF present had only a slightly lower dielectric constant at high temperature testing, but also had much lower loss, making it a potential candidate for high temperature capacitor applications.</div><div><br></div><div>Other materials for potential dielectric film applications were studied as well. Two fluoropolymer films consisting of monolayers of ETFE and THV were uniaxially oriented and their morphology was characterized offline to elucidate structure-process-property relationships. Film samples produced were not large enough to be tested for dielectric properties, however morphology development during uniaxial orientation was evaluated. Both films showed nearly affine stretching behavior, and mechano-optical properties were studied during stretching at several temperatures. Combinations of X-ray scattering experiments and AFM led to proposed morphological structure models for each material at varying levels of deformation.</div><div><br></div><div>Finally, in collaboration with A. Schulman, Inc., PET and EVOH compounded blend and three layer PET-EVOH-PET films were oriented uniaxially and the morphology of the two was compared to each other. Potential applications include high barrier food packaging applications, due to the very high oxygen barrier but poor water vapor barrier of EVOH, which can be complimented by PET's high water vapor barrier. Uniaxial orientation of these two film systems showed that mechano-optical behavior was significantly different for blend versus layered films. Crystalline orientation factors were calculated from 1D WAXS data, which showed PET orientation was largely unaffected by increasing EVOH content in blend films, but blending decreased orientation of EVOH. PET's orientation in layered films was also largely unaffected by amount of EVOH in inner layer. EVOH's orientation factor was higher in all layered film compositions compared to neat EVOH film after stretching, suggesting that the coextrusion process is beneficial to increasing orientation of EVOH.</div><div><br></div>

Particulate matter (PM) suspended in air varies in size from nanometers to micrometers and contains a wide range of chemical components, including organic compounds, black carbon (soot), inorganic minerals and metals. Atmospheric aerosols are generated from either primary sources like volcanic eruptions, re-suspended soil dust, sea spray, vegetative detritus, fossil fuel and biomass combustion emissions; or secondary atmospheric reactions via gas-to-particle conversion of atmospheric gases. Particle size, abundance, and chemical composition determine how a particle interacts with light and other atmospheric constituents (e.g. gases, water vapor) in addition to its impact on human health. While atmospheric scientists have been working on characterizing atmospheric aerosols for many years, major gaps persist in understanding the properties of many globally-important sources. This dissertation provides new understanding of the chemical composition of biomass burning and sea spray aerosols. PM emissions from biomass burning vary by fuel, and depend on fuel type and composition, moisture content, and combustion conditions. Although biomass smoke is critically important in global climate and local-regional health impacts, the physical and chemical composition of biomass burning aerosol is still not fully understood in the case of peat, agricultural residues and cooking fires. The Fire Laboratory at Missoula Experiments (FLAME) were designed to fulfill these gaps to improve our understanding in both historically undersampled and well-studied fuels while adding new instrumentation and experimental methods to provide previously unavailable information on chemical properties of biomass burning emissions. Globally-important biomass fuels were combusted in a controlled environment, and PM was chemically characterized to compute fuel based emission factors (EF) as the amount of chemical species released per unit mass of fuel burned. We showed that chemical composition of PM varies for different fuel types and certain fuels types (e.g., peat and ocote) emit considerably high concentrations of polycyclic aromatic compounds that are associated with negative health effects. We also showed that PM from biomass smoke contains fluoride for the first time, at approximately 0.1% by weight. With respect to the annual global emissions of PM due to biomass burning, this makes biomass burning an important source of fluoride to the atmosphere. Further, peatland fire emissions are one of the most understudied atmospheric aerosol sources but are a major source of greenhouse gases globally and cause severe air quality problems in Asia. This thesis provides the first field-based emissions characterization study, for samples collected at peat burning sites in Central Kalimantan, Indonesia. Using these EFs and estimates of the mass of fuel burned, it was estimated that 3.2 - 11 Tg of PM2.5 were emitted to atmosphere during 2015 El Niño peat fire episode which is ~10 % of estimated total annual PM flux for biomass burning. Overall, these studies computed more representative EFs for previously undersampled sources like peat, and previously unidentified chemical species like fluoride that can be used to update regional and global emission inventories. The concentration and composition of organic compounds in sea spray aerosol (SSA) alters its optical properties, hygroscopicity, cloud condensation, and ice nucleation properties and thus affects Earth’s radiative budget. In the past, SSA has been difficult to characterize, because of low concentrations relative to background pollutants. Nascent SSA was generated during a mesocosm, using a wave-flume at the University of California, San Diego and was characterized for saccharides and inorganic ions in order to assess their relative enrichment in fine (PM2.5) and coarse (PM10-2.5) SSA and sea surface microlayer (SSML) relative to seawater. For the first time, we showed that saccharides comprise a significant fraction of organic matter in fine and coarse SSA contributing 11 % and 27 %, respectively. Relative to sodium, saccharides were enriched 14-1314 times in fine SSA, 3-138 times in coarse SSA, but only up to 1.0-16.2 times in SSML. The saccharide and ion concentration in SSML and persistent whitecap foam was quantitatively assessed by another mesocosm study performed under controlled conditions. We demonstrated that relative to sodium, saccharides were enriched 1.7-6.4 times in SSML and 2.1-12 times in foam. Higher enrichment of saccharides in foam over the SSML indicates that surface active organic compounds become increasingly enriched on aged bubble film surfaces. Similarly, we showed that fine SSA contains saccharides characteristic of energy-related polysaccharides, while coarse SSA contains saccharides that are characteristic of structure-related polysaccharides. The ultrafiltration studies showed that structure-related polysaccharides effectively coagulate to form large particulate organic matter and size is likely the reason for their exclusion from small SSA. The enrichment of organic species in SSML, foam and SSA led to an enrichment of inorganic ions probably through chelation with organic molecules. Mean enrichment factors for major ions demonstrated the highest enrichment in fine SSA for potassium (1.3), magnesium (1.4), and calcium (1.7). Consequently, due to these organic and inorganic enrichments, SSA develops a significantly different chemical profile compared to seawater. These improved chemical profiles of SSA should be used to develop laboratory proxies to further study the transfer of organic matter across the ocean-air interface and the physical properties of SSA. . Overall, the results presented in this dissertation provide new chemical profiles for previously understudied emission sources like peatland fire emissions, and previously unquantified chemical species like F- in biomass burning emissions and enrichment of saccharides and ions in SSA. These data could be used in updating regional and global emission inventories, atmospheric modeling and human exposure studies.