The boundary layer of the atmosphere is a layer of air with thickness about 1 km above the ground. Open-cast mining is one of activities that polutes the air in this layer. It generates particulate matter (PM) mostly in size of aerodynamic diameter 1 - 10 µm - coarse patricles. The companies that does the mining pays for their emissions due to the law. However, these emissions are not experimentraly measured, they are calculated from given equation consisting of factors like the size of mining area, etc. Some papers have shown significantly higher concentrations of Coarse particles (or PM10) in surroundings of the mine. Other papers have found out that the origin of these high concentrations didn't come from the mining activities but is caused due to the activities at the place of measuring or nearby. There aren't many papers that measure the PM concentrations in the air in the mining area. This thesis shows the results of airship measurements in the air layers of the open-cast mine and above them. The experimentral site was brown coal mine Bílina in the North of The Czech Republic in important mining area. The measurements took place in December 2017. For measuring the number and mass concentrations was used APS - Aerodynamic Particle Sizes Spektrometr by TSI which sorts out the data into...

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Zifei Liu / The Unmix and Positive Matrix Factorization (PMF) models for source apportionment were applied to evaluate prescribed burning impacts on air quality, identify model advantages, and establish a relationship between visibility and PM₂.₅ sources. Speciated PM₂.₅ data were from the Flint Hills (FH) rural and the Kansas City (KC) urban sites. At the FH site, the Unmix model identified five sources: nitrate/agricultural, sulfate/industrial, crustal/soil, smoke, and secondary organic aerosol (SOA); while the PMF model identified the copper source in addition. The smoke source from PMF result includes both primary and secondary aerosols from prescribed burning when the smoke source in Unmix result only includes primary burning aerosols. The secondary smoke aerosols at the FH site were combined with secondary aerosols from other origins and formed the SOA source in Unmix result. Comparative analysis of the modeling results estimated the SOA to be 2.3 to 2.7 times of the primary aerosols in burning season. At the KC site, both receptor models derived seven-source solutions: nitrate/agricultural, sulfate/industrial, crustal/soil, smoke, traffic/SOA, heavy-duty diesel vehicle (HDDV), and calcium. The smoke source at the KC site carries an exceedingly organic carbon to elemental carbon (OC/EC) ratio, which is more than five times higher than in FH smoke source. The PMF results at KC site tend to classify more SOA from nitrate/agricultural and sulfate/industrial sources into traffic/SOA source. In the burning season, the smoke source from both sites showed a relatively high correlation when KC is under west and southwest wind, suggesting that part of the smoke originated PM₂.₅ at the urban site could be from the upwind burning activities. The Tobit modeling recognized the nitrate/agricultural as the leading visibility degradation impact factor at both sites. The latter chapter conducted a review of life cycle assessment (LCA) on carbon footprint (CF) of beef production. The objectives were to evaluate CF range in raising systems from different countries, identify the leading CF contributor and dominant source of uncertainty, and summarize LCA inventory defined in cattle production systems. Most existing beef LCA studies followed a “cradle to farm gate” approach. The CF in 3-phase systems ranged from 16 to 29.5 kg CO2e kg⁻¹ carcass weight. The 2-phase raising system reported a slightly lower CF than the 3-phase system (18.9 to 26.9 kg CO2e kg⁻¹ carcass weight), but no significant differences were observed. The grass-fed system in the US has the highest CF, but the CF of grass-fed systems in the European Union (EU) is 40% less than them in the US. This is because more than half of cattle farms in EU produce both beef and milk, and the CF burden was partaken by the dairy production. Cow-calf phase contributed the most CF in 3-phase raising system, while enteric fermentation was the major contributor. Feed production contributed the most in the feedlot phase if forages were applied rather than concentrates. The leading uncertainty sources reported was land use change and disparate dressing percentage. To improve the LCA accuracy, more research is needed in collecting reliable LCA inventory data such as raising period and feed intake efficiency.

[pt] O presente trabalho realiza a integração entre a solução computacional por elementos finitos para as equações que descrevem s condições elétricas reinantes no espaço interletrodos de um Precipitador Eletrostático (PE) fio-placas e dados experimentais obtidos em um canal de precipitação com a mesma forma geométrica. A integração acima é necessária à qualquer tentativa de projeto teórico de um PE, uma vez que tais equações exigem para o seu fechamento a introdução de um parâmetro denominado mobilidade de portador de carga, para o qual não se tem possibilidade de previsão teórica de valor, devido ao grande número de variáveis físicas que podem influenciá-lo. Além disso, as soluções teóricas em geral são obtidas dentro de uma modelagem que supõe a existência de um canal de placas paralelas provido de alguns eletrodos emissores consecutivamente dispostos na linha central do canal de precipitação. Essa redução da situação real à uma situação simplificada impede a observação crucial de que o fenômeno de precipitação eletrostática em um PE é um fenômeno que sofre uma variação física contínua ao longo da região de precipitação, à medida que material particulado vai sendo retirado da carga em escoamento. Qualquer solução teórica acaba sendo de pouca utilidade ao projeto de um canal de precipitação completo. No presente trabalho estamos propondo a utilização de um equipamento laboratorial que permite a medição de correntes elétricas entregues por portadores de carga em áreas discretas das placas planas aterradas em um escoamento de ar com cargas de particulados sólidos, dentro de um canal de precipitação com um número razoável de eletrodos emissores. A partir das correntes de placa medida é determinada um valor para mobilidade elétrica associada a cada região longitudinal da secção de precipitação. Essa mobilidade elétrica é então adimensionalizada em termos de alguns parâmetros, sendo que no presente representa a profundidade de penetração no campo de precipitação. Por fim utiliza-se a mobilidade elétrica adimensional como predição para as condições elétricas à serem esperadas em diferentes valores de tensão aplicada, sendo sugerido seu uso como ferramenta auxiliar no projeto de precipitadores eletrostáticos. Foi observado que o campo elétrico originado em cada um dos eletrodos apresenta uma ação alternada de aceleração ou desaceleração sobre o material particulado em suspensão, respectivamente nas regiões imediatamente após, ou antes, de cada eletrodo emissor, relativamente à direção do escoamento. Esse fenômeno físico, não mencionado em qualquer uma das referencias do presente trabalho, foi denominado aqui efeito de alternância e tem uma importância fundamental com relação ao uso da mobilidade adimensional no projeto de PÉS e também quanto às possibilidades de otimização de PÉS já em operação. / [en] This work integrates a numerical solution, obtained by finite elements and characteristic methods applied to the governing equations of the electrical conditions in the inter-electrodes region of a wire-plate Eletrostatic Precipitador (EP), with data acquired in a precipitation channel with the same geometric form. The integration above mentioned is demanded by any attempt of an analytical project of an EP due to the introduction of a paramenter, denominated mobility of the charge carriers, in the closure of the governing equations. Further, the analytical solutions are in general obtained under the modeling of a precipitation region provided with a small number of corona wires, just enough to give simetry considerations. It must be kept in mind that in an EP each channel is provided with dozens of corona wires. The simplification above interdicts the crucial observation that the precipitation phenomena in an EP suffers physical changes along the axial length of the channel, due to the continuos wuthdrawing of particulate material from the total load. Solutions apropiated to a single region are so not very useful to the project of an entire channel. In this work we present an experimental apparatus which allows the measurement of eletric currents in discrete areas of the colleting plates. The apparatus is provided with a number of corona wires that can simulate a channel of an EP. Using the values of the currents measured at each of thediscrete plates it is obtained a value for the electrical mobility associated to discrete regions longitudinally with the flow. A dimensionless mobility is then obtained in terms of some parameters. In the present work these parameters were restricted to the applied potential. It is then suggested how an EP projectist could use the method as a tool for helping in the design process. It was observed that the eletric field originated in each of the corona wires acts alternatedely accelerating or desaccelerating the charged particulate load, pespectively in the regions immediately after or before each corona wire, with respect to the main direction of the flow. This physical phenomena, not mentioned in any of the references of the present work, was denomitade here as alternation effect, and has fundamental importance in the use of the dimensionless mobility as a project tool and also in the possibilities of upgrading Eps already in use.

Dans le cadre du développement des réacteurs nucléaires à neutrons rapides refroidis au sodium, des études sont menées sur les conséquences d’un feu de sodium, et sur l'impact toxicologique de rejets éventuels d’aérosols vers l’atmosphère. La carbonatation des aérosols issus d’un feu de sodium entraîne une diminution de leur toxicité, à partir de leur rejet sous forme d'hydroxyde de sodium (NaOH). L’objectif est de développer et de valider expérimentalement un modèle cinétique de carbonatation des aérosols de NaOH. L’adaptation d’un modèle cinétique basé sur l'absorption réactive du CO2 atmosphérique et par la théorie du double film permet de décrire la carbonatation des aérosols de NaOH, initialement sous forme de gouttelettes de soude. Ce modèle définit les caractéristiques initiales des aérosols de soude en équilibre avec l'atmosphère. Il a été appliqué en considérant l'absorption du CO2 à la surface externe des particules. L’ensemble des variables du modèle ont été décrites et leurs équations explicitées. La validation du modèle cinétique a motivé la mise en place d’un dispositif expérimental dédié au suivi du comportement chimique d’aérosols issus d’un feu de sodium, dans des conditions contrôlées d’atmosphère réactive et de prélèvement d’aérosols. L’exploitation des nouvelles données expérimentales montre la compétition entre l’influence de la température, de la pression partielle en eau et en CO2. La confrontation des résultats expérimentaux avec le modèle développé a permis de le valider pour des humidités relatives supérieures à 30%. Enfin, le modèle cinétique a été explicité sous la forme d’une expression analytique pour une utilisation associée aux calculs de dispersion atmosphérique. / As part of the development of 4th generation Sodium cooled Fast Reactors, studies are conducted on the consequences of a sodium fire, including the toxicological impact of possible releases of aerosols into the atmosphere. The carbonation of aerosols from a sodium fire results in a decreased toxicity, from their release point in sodium hydroxide (NaOH). The objective is to develop and experimentally validate a kinetics model of NaOH aerosols carbonation. The kinetic model based on the reactive absorption of atmospheric CO2 and using the double film theory enables to describe the carbonation of NaOH aerosols, initially formed as soda droplets. This model defines the initial aerosol characteristics of soda in equilibrium with the atmosphere. It is applied by considering the absorption of CO2 at the particle’s external surface. All the model variables are described and their equations explained. The validation of this kinetic model has motivated the development of an experimental device dedicated to the monitoring of physicochemical behavior of aerosols from a sodium fire with a better control of conditions of reactive atmosphere and of aerosols sampling. The new experimental data show the competition between the influence of temperature, partial pressure of water and of CO2. The comparison between the experimental results validates the kinetic model based on reactive absorption for relative humidity over 30%. Finally, the kinetic model was adapted into the form of an analytic expression for its use in association with the atmospheric dispersion calculation.

L’objectif de ce travail était de contribuer à une meilleure compréhension du devenir atmosphérique des Composés Organiques Volatils d’origine Biogénique (COVB), émis par la végétation. La dégradation d’une série de COVB (myrcène, ocimène, a-farnesène, linalool, 6-méthyl-5-heptène-2-ol et 3-méthyl-1-pentène-3-ol), par les oxydants atmosphériques (OH, O3 et NO2), a été étudiée en utilisant différentes installations expérimentales (chambres de simulation atmosphérique et réacteur à écoulement à aérosol). Les paramètres cinétiques et mécanistiques qui ont été obtenus pour l’ensemble des réactions étudiées ont permis d’estimer les durées de vie atmosphérique des COVB (de quelques minutes à quelques heures). Des produits d’oxydation ont été identifiés et quantifiés, mais le bilan total en carbone en fin de réaction reste incomplet indiquant que d’autres produits sont formés mais non-identifiés. Les rendements de formation des aérosols organiques secondaires (AOS) ont été également mesurés pour les réactions avec OH et O3. L’analyse chimique des AOS (issus de la réaction avec O3) a mis en évidence la présence d’acides dicarboxyliques et de composés oligomères, démontrant l’implication des intermédiaires de Criegee dans la formation des AOS. Le réacteur à écoulement à aérosols, développé dans le cadre de ce travail, a permis de préciser les seuils de nucléation des AOS formés à partir de l’ozonolyse de certains monoterpènes. Enfin, la réactivité des COVB (principalement les diènes conjugués) avec NO2, a été trouvée assez lente et ne représente qu’un puits mineur de ces composés dans l’atmosphère. Toutefois, la mise en évidence de la formation de HONO comme produit de réaction pourrait rendre l’implication atmosphérique de ce processus non négligeable. Les résultats obtenus ont permis de discuter de l’impact de la dégradation de ces COVB dans l’atmosphère. / The aim of this work was to contribute to a better understanding of the atmospheric fate of Biogenic Volatil Organic Compounds, emitted by vegetation. The degradation of a series of BVOC (myrcene, ocimene, a-farnesene, linalool, 6-methyl-5-heptene-2-ol and 3-methyl-1-pentene-3-ol) through reactions with atmospheric oxidants (OH, O3 and NO2) has been investigated using different experimental facilities (atmospheric simulation chambers and aerosol flow tube). First, atmospheric lifetimes of these BVOCs were determined and found varying from few minutes to hours. In addition, gas phase oxidation products were identified and quantified. However carbon budget is still incomplete, indicating that others products are formed but remain unidentified. Secondary organic aerosol yield were also measured in the reactions of the studied BVOCs with OH and O3. Chemical analysis of SOA (from O3 reaction) showed the presence of dicarboxylic acids and oligomer compounds, indicating the possible involvement of the Criegee intermediate in the SOA formation. The new aerosol flow tube, developed in this work, allowed to precise nucleation threshold of SOA formed from the ozonolysis of series of monoterpenes. The reactivity of BVOC (conjugated dienes mainly) with NO2, is found to be slow process, hence, representing only a minor sink for these compounds in the atmosphere. However, the identification of HONO as a reaction product may indicate that this process could be of importance as OH radical source in the atmosphere under certain conditions. The results obtained allowed to discuss the impact of the degradation of these BVOC in the atmosphere.

Les mécanismes de formation des nuages de glace arctiques durant la nuit polaire sont encore mal définis en raison de l’absence d’observations et de l’éloignement de cette région. Pourtant, leur influence sur les conditions météorologiques et sur le climat dans l’hémisphère nord est d’une importance primordiale ; et les connaissances sur la modification de leurs propriétés, liées à des processus d’interaction aérosol-nuage, doivent être améliorées. Les fortes concentrations d’aérosols en Arctique durant la nuit polaire sont associées au transport des aérosols anthropiques des latitudes moyennes jusqu’au pôle Nord. Les observations et les modèles montrent que cela peut conduire à un transport important de particules d’aérosol acidifiées. Les mesures en laboratoire et in situ montrent qu’à basse température (< -30°C), le revêtement d’acide sur les noyaux glaçogènes (IN) peut réduire leurs propriétés de nucléation de la glace. Par conséquent, leur concentration est réduite dans ces régions entraînant une plus faible concentration de plus gros cristaux de glace en raison d’une diminution de la compétition pour une humidité disponible similaire. De nombreuses mesures de terrain et par télédétection par satellite (CloudSat et CALIPSO) révèlent l’existence de deux types de nuages de glace (TIC) en Arctique durant la nuit polaire. Les nuages de glace de type 1 (TIC-1) ne sont visibles que par le lidar tandis que les nuages de glace de type 2 (TIC-2) sont perçus à la fois par le lidar et le radar. Les TIC-2 sont divisés en TIC-2A et TIC-2B. Les TIC-2A sont recouverts d’une fine couche de petits cristaux de glace non-précipitant (invisible par le radar) (TIC-1), tandis que les TIC-2B ne le sont pas. Ils sont caractérisés par une faible concentration de gros cristaux de glace. On suppose que la microstructure des TIC-2B est liée à l’acidification des aérosols. Pour vérifier cette hypothèse, des études de cas et des approches statistiques ont été combinées afin d’analyser le transport des aérosols et les propriétés des nuages de glace en Arctique. La première partie de la thèse enquête sur les propriétés microphysiques des TIC-1/2A et TIC-2B, en analysant des mesures aéroportées et satellitaires de cas spécifiques observés durant la campagne de mesures ISDAC (Alaska, Avril 2008). Pour la première fois, les microstructures des TIC-1/2A et TIC-2B en Arctique sont comparées en utilisant les observations in-situ des nuages. (...) La deuxième partie de la thèse enquête sur l’origine des masses d’air formant deux cas spécifiques de TICs ISDAC : TIC-1/2A (1 Avril 2008) et TIC-2B (15 Avril 2008), en utilisant des outils de trajectoire et des données satellitaires. / Arctic ice cloud formation during winter is poorly understood mainly due to the lack of observations and the remoteness of this region. Yet, their influence on Northern Hemisphere weather and climate is of paramount importance, and the modification of their properties, linked to aerosol-cloud interaction processes, needs to be better understood.Large concentration of aerosols in the Arctic during winter is associated to long-range transport of anthropogenic aerosols from the mid-latitudes to the Arctic. Observations and models show that this may lead to a significant transport of acidified aerosol particles. Laboratory and in-situ measurements show that at cold temperature (< -30°C), acidic coating may reduce the ice nucleating properties of ice nuclei (IN). Therefore, the IN concentration is reduced in these regions, resulting to a smaller concentration of larger ice crystals and because of the reduced competition for the same available moisture.Extensive measurements from ground-based sites and satellite remote sensing (CloudSat and CALIPSO) reveal the existence of two Types of Ice Clouds (TICs) in the Arctic during the polar night and early spring. The first Type of Ice Clouds (TIC-1) are visible only by the lidar while the second Type of Ice Clouds (TIC-2) are detected by both the lidar and radar. TIC-2 are divided into TIC-2A and TIC-2B. TIC-2A are topped by a cover of non-precipitating very small (radar-unseen) ice crystals (TIC-1), while TIC-2B are not. They are characterized by a low concentration of large ice crystals. It is hypothesized that the observed low concentration of large ice crystals, leading to precipitation (e.g. cloud regime TIC-2B), is linked to the acidification of aerosols. To check this, we are combining case studies and statistical approaches to analyse aerosol transport and cloud properties in the Arctic.The first part of the thesis investigate the microphysical properties of TIC-1/2A and TIC-2B, analysing airborne in-situ and satellite measurements of specific cases observed during the ISDAC campaign (Alaska, April 2008). For the first time, Arctic TIC-1/2A and TIC-2B microstructures are compared using in-situ cloud observations. Results show that the differences between them are confined in the upper part of the clouds where ice nucleation occurs. TIC-2B were characterized by fewer (< 10 L-1) and larger (> 110 μm) ice crystals, a larger ice supersaturation (> 15 %) and a fewer ice nuclei (IN) concentration (< 2 order of magnitude) when compared to TIC-1/2A. Ice crystal growth in TIC-2B clouds seems explosive whereas it seems more gradual in TIC-1/2A. It is hypothesized that these differences are linked to the number concentration and the chemical composition of aerosols. The second part of the thesis investigate the origin of air masses forming two specific cases ; TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008), using trajectory tools and satellite data.(...)

Atmospheric trace components play a critical role in the earth–atmosphere system through their interaction and perturbation to global atmospheric chemistry. They perturb the climate through scattering and absorbing of solar radiation (direct effects), thereby impacting on the heat energy balance of the atmosphere, and alter cloud microphysical properties affecting cloud formation, cloud lifetime and precipitation formation (indirect effects). These trace components can also have adverse effects on human health, visibility and air quality (AQ) composition, including various feedback processes on the state of the atmosphere. As well as their direct and indirect effects, aerosols are important for cloud formation. They serve as cloud condensation and ice nuclei (CCN and IN) during cloud droplet and ice crystal formations. Although many connections between clouds and aerosol effects have been established in cloud physics and climate modelling, aerosol–cloud interaction (ACI) is still one of the areas of large uncertainties in modern climate and weather projections. Different models have been developed placing much emphasis on ACIs, to have robust and more consistent description processes within the meteorological and chemical variables to account for ACIs and feedback processes. Because pollutant distributions are controlled by a specific meteorology that promotes residence times and vertical mixing in the atmosphere, reliable chemical composition measurements are required to understand the changes occurring in the earth–atmosphere system. Also, because atmospheric pollution is a combination of both natural and man-made (anthropogenic) sources, to direct controlled and/or mitigation procedures efficiently, contributions of different sources need to be considered. Occasionally these are explored from a particular region or global environment, depending on a specific area of interest. A fully coupled online meteorology–chemistry model framework (WRF-Chem) is used to investigate atmospheric ACIs over southern Africa –a region characterized by a strong and intense seasonal biomass burning (BB) cycle. The large transport of aerosol plumes originating from the seasonal burning from agriculture, land-use management and various activities give rise to a unique situation warranting special scrutiny. Simulations are conducted for the 2008 dry season BB episode, implementing a chemical dataset from various emission sources (anthropogenic, BB, biogenic, dust and sea salt) with the meteorological conditions. A base line (CNTRL) simulation was conducted with all emission sources from 26 August to 10 September 2008. To probe the contribution of BB on the regional pollution and influence on ACIs, a sensitivity (TEST) simulation was conducted without BB emissions and compared to the base line. The impact of natural and anthropogenic aerosol particles is studied and quantified for the two simulations, focusing on aerosol concentration and cloud responses under different model resolutions. A statistical analysis of pollutant concentration of major regulated species and cloud variables is conducted and the percentage difference used to assess the contribution due to BB emissions. Results confirm the high variability of spatial and temporal patterns of chemical species, with the greatest discrepancies occurring in the tropical forests whereas the subtropics show more urban/industrial related emissions. Whilst CO and O3 show statistically significant increases over a number of cities/towns, the trend and spatial variability is much less uniform with NO2 and PM in most urban and populous cities. Statistical analysis of major chemical pollutants was mainly influenced by BB emissions. O3, NOx, CO and PM increase by 24%, 76%, 51%, 46% and 41% over the main source regions, whereas in the less affected regions concentrations increased by 5%, 5%, 5%, 3% and 2% when BB emissions are included. This study sheds new light on the response of cloud processes to changing aerosol concentrations and different model resolutions. In the parameterised case (dx = 20 km), clouds become more cellular, correlated with high supersaturations, whereas in the resolved case (dx = 4 km), they become more faint with relatively lower supersaturations. Aerosol effects on cloud properties were further studied and statistical analysis conducted on CCN, cloud droplet number concentration (CDNC), supersaturation and aerosol optical depth (AOD) at two different grid spacings. Most clouds occur to the west of the domain coincident with increase in aerosol concentration and AOD, while single scattering albedo (SSA) decreases. A considerable cloud ‘burn-off’ occurs in tropical west Africa, where aerosols can also be lofted up to 500-hPa level when BB emissions are included in the simulation. Due to BB, absorbing aerosol increased by 76% and 23% over tropical west and subtropical southeast, while tropical east shows no change. The study shows that tropical central Africa is characterized by an increased build-up in biomass burning aerosols (BBAs), forming a regional haze with high AOD; this becomes stronger near active burning areas with a significant proportion occurring to the west. AOD enhancement increases up to 38%, 31% and 11% in the west, east and south respectively. Although CDNC increased in areas with high aerosol concentration, supersaturation decreases (in the small domains) since increase in aerosol number concentration decreases maximum supersaturation Smax. Changes in absorbed radiation increased by +56 Wm-2, +23 Wm-2 and +14 Wm-2 in the west, east and southeast. To further evaluate the model sensitivity and its skill, an analysis was conducted by comparing the model performance with measurement data. Simulated AOD, surface concentrations of CO and O3, ozonesondes and liquid water path (LWP) were compared with measured data from MODIS satellite, SAFARI2000 field study and Cape Point WMO. The model shows a good skill in capturing and reproducing the trends as that measured. However, a severe lack of measurement data over southern Africa makes it more difficult to effectively evaluate WRF-Chem over southern Africa. There is a need for increased availability of measurements to adequately compare with models. This study is one of the first WRF-Chem studies conducted over southern Africa to simulate the weather and pollution interaction. The novelty of the present study is the combined analysis of ACI sensitivity to aerosol loading and cloud response in a regime-based approach. The study concludes with a brief discusssion of future directions for work on AQ and modelling interactions between pollution and weather over southern Africa.

abstract: Particulate trace metals can enter the atmosphere as mineral dust, sea spray, anthropogenic emissions, biomass burning, etc. Once in the atmosphere they can undergo a variety of transformations including aqueous phase (cloud) processing, photochemical reactions, interact with gases, and ultimately deposit. Metals in aerosols are of particular interest because of their natural and anthropogenic sources as well as their effects on local (human health) and global (climate change) scales. This work investigates the metal component of atmospheric particles and how it changes during physical and chemical processes at local, regional and global scales, through laboratory and field studies. In the first part of this work, the impact of local dust storms (haboobs) on ambient metal concentrations and speciation is investigated in Tempe, AZ. It was found that metal concentrations substantially increase (> 10 times) during these events before returning to pre-storm levels. In a second part of this work, the impact of fog processing on metal concentrations, solubility and speciation is examined through field observations in California’s Central Valley. The observations show that fog processing has a profound effect on local metal concentrations but the trends are not consistent between sites or even between events, indicating complex processes that need further investigation. For example, fogs have an effect on scavenging and solubility of iron in Davis, while in Fresno soluble iron content is indicative of the source of the aerosol. The last part of the thesis investigates the role of particle size on the solubilization of iron from mineral dust aerosols during global atmospheric transport through laboratory experiments. The experiments showed that mineralogy and pH have the greatest effect on iron solubility in atmospheric aerosols in general while particle size and photochemistry impact mainly the solubility of iron oxides. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

abstract: Nanomaterials exhibit unique properties that are substantially different from their bulk counterparts. These unique properties have gained recognition and application for various fields and products including sensors, displays, photovoltaics, and energy storage devices. Aerosol Deposition (AD) is a relatively new method for depositing nanomaterials. AD utilizes a nozzle to accelerate the nanomaterial into a deposition chamber under near-vacuum conditions towards a substrate with which the nanomaterial collides and adheres. Traditional methods for designing nozzles at atmospheric conditions are not well suited for nozzle design for AD methods. Computational Fluid Dynamics (CFD) software, ANSYS Fluent, is utilized to simulate two-phase flows consisting of a carrier gas (Helium) and silicon nanoparticles. The Cunningham Correction Factor is used to account for non-continuous effects at the relatively low pressures utilized in AD. The nozzle, referred to herein as a boundary layer compensation (BLC) nozzle, comprises an area-ratio which is larger than traditionally designed nozzles to compensate for the thick boundary layer which forms within the viscosity-affected carrier gas flow. As a result, nanoparticles impact the substrate at velocities up to 300 times faster than the baseline nozzle. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

Les aérosols atmosphériques jouent un rôle important à la surface de la Terre. Ils influencent les propriétés radiatives de l'atmosphère et représentent des composés importants pour les questions de qualité de l'air et de santé publique dans les régions polluées. Suite à la forte diminution de la pollution soufrée survenue au cours des trois dernières décennies, l'aérosol organique représente maintenant une part importante de l'aérosol atmosphérique. Cette fraction a une nature complexe et jusqu'à présent, moins de la moitié de ses constituants chimiques ont été identifiés. La fraction soluble des HUmic LIke Substances (HULISWS) représente une des familles importantes de l'aérosol organique soluble avec une contribution en masse comprise entre 20 et 50%. L'objectif de cette thèse est de développer une méthode de mesure des HULISWS dans la glace. L'étude de ces archives environnementales, ici une carotte de glace extraite au col du Dôme (4250 m, massif du Mont-Blanc, France), permet de remonter aux concentrations en HULISWS en Europe au cours de la période 1920-1988. L'étude des concentrations et de l'absorbance spécifique des HULISWS dans la carotte de glace a permis d'identifier deux sources distinctes suivant la saison et de suivre leur évolution au cours du XXème siècle. Les HULISWS sont issus de la combustion du bois en hiver, leur absorbance est forte et leurs concentrations sont faibles et stables tout au long du XXème siècle. En été, les HULISWS sont formés par des processus secondaires ayant pour précurseurs des espèces biogéniques organiques, leur absorbance spécifique est plus faible qu'en hiver et leurs concentrations plus fortes. Les teneurs estivales en HULISWS montrent une stabilité entre 1920 et 1950 puis une tendance à l'augmentation entre 1951 et 1970 associée vraisemblablement à une augmentation des émissions de composés organiques volatils depuis la biosphère. / Atmospheric aerosols play an important role on the radiative properties of the atmosphere. They are also key factors for air quality and public health in polluted areas. As a result of the strong decrease of SO2 emissions over the last three decades, organic aerosol now represents a more important part of atmospheric aerosol. The nature of this organic fraction is complex and until now less than a half of it has been chemically identified. Water Soluble HUmic LIke Substances (HULISWS) are an important contributor to water soluble organic aerosol with a mass fraction ranging from 20 to 50%. The aim of this work is to design a method to measure HULISWS in ice cores. The application of this method to an ice core extracted at the col du Dôme (4250 m, Mont-Blanc massif, France) enables to investigate changes in HULISWS over Europe since 1920. The study of their concentrations and specific absorbance in ice core samples reveals well-marked differences in the sources of HULISWS depending on the season. In winter, HULISWS are primarily emitted by wood burning, their specific absorbance is high and their concentrations are low and remained stable over the 20th century. In summer, HULISWS are producted from biogenic precursors by secondary processes, their specific absorbance is lower and their concentrations higher than in winter. Summer concentrations of HULISWS were stable between 1920 and 1950, and have increased from 1951 to 1970. This recent trend probably results from an increase of volatile organic compounds emissions by the biosphere.