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1
Ponczek, Milena. "Understanding Atmospheric Mineral Dust Photochemistry." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1190.
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Les minéraux absorbent la lumière proche des UV (comme TiO2, Fe2O3, MgO) présents dans les aérosols minéraux interagissent avec les gaz traces présents dans l'atmosphère et peuvent initier une nouvelle chimie hétérogène photo-induite potentiellement significative et actuellement peu documentée. Cette thèse vise à aborder différentes questions sur la réactivité des poussières minérales vers les composés organiques et évaluer l'impact de ces interactions sur plusieurs aspects des sciences de l'atmosphère. Nous avons étudié expérimentalement l'interaction physico-chimique d'aérosols minéraux, purs ou revêtus de matériaux organiques/inorganiques avec des gaz traces de plusieurs familles chimiques (alcools, cétones, acides carboxyliques), dans des conditions simulées proches de l'environnement reel (concernant l'humidité, la concentration en phase gazeuse, la longueur d'onde et l'intensité de l'irradiation, la pression et la température) évaluant les effets des conditions ambiantes sur la cinétique de capture et la génération de produits en phase gazeuse. Dans l'ensemble, nos résultats montrent clairement que les reactions photochimique des poussières minérales doit être considéré comme une source de composés réactifs et comme un processus clé affectant leur action sur la nucléation de la glace et les noyaux de condensation des nuagesMinerals that absorb light near UV/Vis present in dust aerosols interact with trace gases in the atmosphere and can initiate a new and potentially significant photo-induced heterogeneous chemistry, which is currently poorly documented. This thesis aims to address different issues of mineral dust reactivity towards organic compounds and, therefore, assesses the impact of these interactions on several aspects of atmospheric sciences. We investigated experimentally the physicochemical interaction of mineral aerosols (synthetic and natural), pure or coated with organic/inorganic materials with trace gases from several chemical families (alcohols, ketones, carboxylic acids, etc.), under simulated conditions close to the real environment (regarding to humidity, concentration in the gas phase, wavelength and intensity of irradiation, pressure and temperature). In a first approach, we studied the uptake of oxygenated organics onto different dust proxies such as SiO2, TiO2 and Arizona test dust (ATD) evaluating the effects of ambient conditions on the uptake kinetics and product generation. Then, we discussed the chemistry of 5 dicarboxylic acids (C4-C8) on ATD particles upon UV-A irradiation monitoring products in the gas phase as well as those whose stay adsorbed on the particulate phase. Lastly, we investigated the influence of nitrate anions on the uptake of acetone on ATD and SiO2 and in the photochemical product formation of glutaric acid on ATD. Overall, our results clearly show that photochemical processing of dust aerosols should be considered as a source of reactive compounds and as a key process affecting their action as ice nucleation and cloud condensation nuclei
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Goodman, Michael Max. "Wasatch Front Atmospheric Deposition Reflects Regional Desert Dust and Local Anthropogenic Sources." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8256.
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Dust originating from dry lakes contributes harmful and toxic elements to downwind urban areas and mountain snowpack that is compounded by local contaminant inputs from anthropogenic sources. To evaluate dust contributions to an urban area from regional playas, we sampled playa dust sources, urban dust deposition, and snow dust deposition in central Utah, USA. Samples were analyzed for grain size, mineralogy, and chemistry. Bulk mineralogy between playa, urban, and snow dust samples was similar, with silicate, carbonate, and evaporite minerals. Grain size distribution between fine playa, urban, and snow dust particles was also similar. Elements found at high concentrations in playas include Li, Na, Mg, Ca, Sr, and U, and most other elements were found at higher concentrations in urban and snow deposition samples. Particularly enriched elements in dust deposition include Cu, Se, Ag, Cd, Sb, and La, which are sourced from industrial activity, mining, and vehicular emissions and wear. Based on results from mass balance modeling, a large majority of the dust mass deposited on the Wasatch Front is from playa sources. Urban and playa dust sources largely remain constant seasonally, although spikes in playa-associated element concentrations during a particular seasonal sample may indicate frequent and/or more intense dust events. Among the highly environmentally available elements B, Ca, Sr, and U, are Cd and Se, both of which present toxicity concerns for humans and environments. This is the first study describing heavy metal contamination and sources in Utah, USA.
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Eastwood, Michael Logan. "Ice nucleation on uncoated and coated atmospheric mineral dust particles." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1613.
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An optical microscope coupled to a flow cell was used to investigate ice nucleation on five atmospherically relevant mineral dusts at temperatures ranging from 233 to 247 K. Kaolinite and muscovite particles were found to be efficient ice nuclei in the deposition mode, requiring relative humidities with respect to ice (RHi) below 112% in order to initiate ice crystal formation. Quartz and calcite particles, by contrast, were poor ice nuclei, requiring relative humidities close to water saturation before ice crystals would form. Montmorillonite particles were efficient ice nuclei at temperatures below 241 K, but poor ice nuclei at higher temperatures. In several cases, there was a lack of quantitative agreement between these data and previously published work. This can be explained by several factors including mineral source, particle size, observation time and surface area available for nucleation.
Heterogeneous nucleation rates (Jhet) were calculated from the onset data. Jhet values ranged from 60 to 1100 cm-²s-¹ for the five minerals studied. These values were then used to calculate contact angles (θ) for each mineral according to classical nucleation theory. The contact angles measured for kaolinite and muscovite ranged from 6 to 12º; for quartz and calcite the contact angles were much higher, ranging from 25 to 27º. The contact angles measured for montmorillonite were less than 15º at temperatures below 241 K, and above 20º at higher temperatures. The reported Jhet and θ values may allow for a more direct comparison between laboratory studies and can be used when modeling ice cloud formation in the atmosphere.
The roles of H₂SO₄ and (NH4)₂SO₄ coatings on the ice nucleating properties of kaolinite were also investigated. Onset data was collected for H₂SO₄ coated and (NH4)₂SO₄ coated kaolinite particles at temperatures ranging from 233 to 247 K. In contrast to uncoated kaolinite particles, which were effective ice nuclei, H₂SO₄ coated particles were found to be poor ice nuclei, requiring relative humidities close to water saturation before nucleating ice at all temperatures studied. (NH4)₂SO₄ coated particles were poor ice nuclei at 245 K, but effective ice nuclei at 236 K.
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Shannon, Sarah R. "Modelling the atmospheric mineral dust cycle using a dynamic global vegetation model." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520308.
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Sullivan, Ryan Christopher. "Heterogeneous chemistry of atmospheric mineral dust particles and their resulting cloud-nucleation properties." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3331170.
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Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed Dec. 11, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Tang, Mingjin [Verfasser]. "Atmospheric heterogeneous reactions of N2O5 and NO3 radicals with mineral dust particles / Mingjin Tang." Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1019194278/34.
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Cavazos, Guerra C. d. C. "Modelling the atmospheric controls and climate impact of mineral dust in the Sahara Desert." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1322565/.
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Mineral dust aerosols play an important role in climate and the Earth's energy budget. The effect of dust on the radiative forcing is uncertain due to the complexity of particle properties and the complexity to quantify and discriminate preferential dust sources. This research considers the potential of two Regional Climate Models (RCM’s): The Weather Research and Forecasting model (WRF-Chem) and the Regional Climate Model (RegCM3) both with an integrated dust module. Numerical sensitivity experiments are performed to quantify the ability of both models to simulate sources, the magnitude of dust emission, the transport in 3-dimensions and the subsequent impact on the radiative forcing. Particular emphasis is given to preferential source regions within the Sahara and Sahel in North Africa including the Bodélé Depression in Northern Chad. To account for the distribution of preferential dust source regions, soil texture characteristics were modified in dust source regions in RegCM3. As for WRF-Chem GOCART scheme, a new higher resolution erodible fraction map is tested. Moreover, the sensitivity of the results to the specification of aerosol optical properties to evaluate the impacts of optical characteristics on the radiative forcing was considered for the RegCM3. Finally, model outputs are compared to in-situ data: weather stations (WMO) and AERONET and satellite estimates: MODIS, MISR, OMI, CALIPSO and SEVIRI. Results show that both models represent the space/time structure of near-surface meteorology well. The tuning of preferential dust sources tested in this research provides a more realistic representation of local dust sources, emissions and resulting AOT. This suggest that in the absence of truly accurate soil maps at high resolution, further refinements to preferential sources map and its implementation in dust models can lead to useful improvements in simulation of dust processes and dust forecast accuracy.
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Sjöström, Jenny. "Reconstruction of Holocene atmospheric mineral dust deposition from raised peat bogs in south–central Sweden." Licentiate thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-153723.
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Atmospheric mineral dust plays a dynamic role in the climate system acting both as a forcing and a feedback mechanism. To date, the majority of paleodust studies have been conducted on marine sediments or polar ice cores, while terrestrial deposition has been less studied. As such, it is important to produce new terrestrial Holocene paleo–dust records and fill existing regional gaps. Ombrotrophic (atmospherically–fed) peat bogs can be used to reconstruct dust deposition through elemental chemistry analysis. Multi–elemental data sets are commonly used infer net dust deposition rates, source changes, grain size, and mineral composition. Mineralogical identification of dust particles is particularly important because it allows both provenance tracing and increased understanding in climate and ecosystem feedbacks. Establishing mineralogy from elemental data of mixed mineral matrixes can however be challenging. X–ray diffraction analysis (XRD) is a standard technique for mineral identification which ideally requires removal of organic matter (OM). Therefore, a test procedure was undertaken where common OM removal methods were evaluated on bulk peat samples was therefore undertaken. The results showed that combustion at 500°C was most efficient in removing OM, while leaving the majority of minerals intact, but not all. In this Licenciate thesis, early result of a paleodust study from Draftinge Mosse, southern Sweden, are also outlined. Here, the method development mentioned above was applied, enabling a combination of elemental data with mineralogy. Future work includes minor and trace element analysis by ICP–AES and ICP–MS, evaluation of the reproducibility of single core reconstructions, tests of some of the methodological assumptions used in previous paleodust studies, source tracing and paleodust reconstruction from a second site (Gällsered Mosse).Atmosfäriskt mineraldamm, mineralpartiklar som lyfts upp i atmosfären och avsätts via eoliska processer, spelar en komplex roll i klimatsystemet då partiklarna påverkar klimatet, samtidigt som rådande klimat också påverkar partikelmängden. De flesta hittills genomförda mineraldamms- studier har utförts på marina sediment eller iskärnor trots att mineraldammspartiklar i störst utsträckning deponeras på kontinenterna. Ombrotrofa mossar (högmossar) kan användas för att rekonstruera avsättning av mineraldamm över tid genom geokemiska analyser på olika djup i torvkärnor. Den kemiska sammansättningen ger information som kan användas för att härleda variationer i partikelmängd, källområden, kornstorlek, samt mineralogisk sammansättning. Bestämning av mineralen är av särskild vikt då det möjliggör identifikation av partiklarnas källområden samt ger kunskap om partiklarnas del i klimat- och ekosystem processer. Att via geokemiska data identifiera mineral prover av blandad sammansättning är dock utmanande, särskilt då många mineral har en liknande kemisk sammansättning. Röntgen diffraktions analys (XRD) är en standardmetod inom berggrundsgeologi för att identifiera mineral, som här används på torvprover. Metoden är icke-destruktiv, men kräver att provet är relativt rent från amorfa faser, så som organiskt material. Då torv innehåller stora mängder organiskt material (>98 %), som dessutom karaktäriseras av att vara svårnedbrutet, utformades ett testprotokoll för att studera vilken metod som är bäst lämpad för att ta bort organiskt material från denna specifika jordtyp. Resultaten från genomförda tester visade att förbränning (500°C) är mest effektivt och även lämnade en majoritet av mineralen intakta, dock inte alla. I denna licenciatavhandling beskrivs även de övergripande målen med min forskning samt tidiga resultat från en mineraldammstudie från Draftinge mosse (Småland), där resultaten från metodstudien ovan applicerats och kombinerats med andra geokemiska data. Vidare arbete inom detta doktorandprojekt kommer innefatta ytterligare geokemiska analyser (spårämnesanalys med ICP-MS och ICP-AES) samt identifiering av källområden. Dessutom kommer ytterligare en mosse (Gällsered mossse) att studeras för förändringar i avsättning av mineraldamm under de senaste 7000 åren.
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Gankanda, Aruni. "Heterogeneous and multiphase chemistry of trace atmospheric gases with mineral dust and other metal containing particles." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3090.
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Particulate matter in the atmosphere emitted from various natural and anthropogenic sources is important due to their effects on the chemical balance of the atmosphere, the Earth's climate, human health and biogeochemical cycles. Although there have been many studies performed to understand the above effects, there still remains substantial uncertainty associated with processes involved and thus it is difficult for current atmospheric chemistry and climate models to reconcile model results with field measurements. Therefore, it is important to have better agreement between models and observations as the accuracy of future atmospheric chemistry and climate predictions depends on it.
In this research, a greater understanding of the role of mineral dust chemistry was pursued through focused laboratory studies in order to better understand fundamental processes involved. In particular, studies to further understand the photochemistry of adsorbed nitrate, an important inorganic ion associated with particulate matter exposed to gas-phase nitrogen oxides, were conducted using Al2O3, TiO2 and NaY zeolite to represent non-photoactive components, photoactive components and aluminosilicate respectively, present in mineral dust. These studies reveal that photochemistry of nitrate adsorbed on mineral dust is governed by wavelength of light, physicochemical properties of dust particles and adsorption mode of nitrate. Gas phase NO2, NO and N2O are the photolysis products of nitrate on oxide particles under dry conditions. In contrast, nitrate adsorbed on zeolite is converted mainly to adsorbed nitrite upon irradiation. This nitrite yield is decreased with increasing relative humidity. Gas phase N2O is the main photolysis product of nitrate adsorbed in zeolite in the presence of co-adsorbed ammonia. Water adsorbed on semiconducting TiO2 can be photochemically converted to hydroxyl radicals. These hydroxyl radicals can be involved in surface mediated as well as gas phase oxidation reactions in the presence of cyclohexane. Another focus of this dissertation was to investigate the oxidation of sulfur dioxide oxidation in the presence of mineral aerosol, particularly, coal fly ash (FA), γ-Fe2O3 and Arizona test dust (AZTD), a model for mineral dust aerosol. Depending on the temporal evolution of Fe(II), we proposed that S(IV) oxidation in the presence of FA and γ-Fe2O3 initially occurs through a heterogeneous pathway and a homogeneous pathway is also possible over later time scales. S(IV) oxidation in the presence of AZTD appears to be mostly heterogeneous and does not lead to iron dissolution. Overall, these studies suggest that the rate, extent and products of atmospheric S(IV) oxidation can be highly variable and heavily dependent upon the nature of aerosol sources, thereby precluding simple generalizations about this reaction when modeling atmospheric processes involving diverse mineral dust aerosols. With the recent development in nanotechnology, nanoparticles are becoming a major fraction of atmospheric particulate matter. These particles can undergo aging under ambient conditions at any stage of their life cycle. This impacts the fundamental properties of these materials and therefore the behavior in the environment and interactions with biomolecules and biological systems. ZnO and CuO nanoparticles form adsorbed carbonate phases upon exposure to CO2 and water vapor. These carbonates become more solvated as the relative humidity is increased. Presence of carbonate phases on ZnO particles increases their water solubility. Thus, overall the work reported in this dissertation provides insights into heterogeneous and multiphase atmospheric chemical reactions in the presence of mineral aerosol and atmospheric aging of nanoparticles.
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BACCOLO, GIOVANNI. "Atmospheric mineral dust in ice cores: application of Neutron Activation and Synchrotron Radiation X-ray fluorescence." Doctoral thesis, Università di Siena, 2017. http://hdl.handle.net/11365/1006205.
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It is estimated that several million of tons of mineral dust are constantly transported in the atmosphere. Such a massive burden has a great influence on many dynamics of our planet, from biogeochemistry, to radiative processes, to sedimentology. An important aspect concerns the tight relationship between dust and climate, at different spatial and temporal scales. Ice cores allowed reconstructing the more detailed and extended records related to atmospheric dust deposition and transport. Measuring the physical and chemical properties of mineral particles, it was possible to understand the influence of climate on the dust cycle and vice versa, i.e. the influence of mineral particles on climate.
In this thesis recent advancements about the understanding of the dust cycle in different contexts (Antarctica and the Alps) will be presented. A significative part of the work is dedicated to the development of new methods for the geochemical investigation of ice cores. Applying these new methods and other established ones, it was possible to draw new insights about the provenance of dust during different climatic periods in Antarctica, focusing on the different response associated to local and distal dust sources in relation to climate changes and on the effect of climate on dust geochemistry. In particular new evidences concern dust properties during Holocene, when dust deposition in Antarctica reaches its lower levels. Turning the attention to the Alps it was possible to highlight the influence of anthropic emission on dust composition, with anomalous values for many elements related to industrial and domestic activities. In addition the construction of a high resolution record allowed studying in detail the phenomenon of Saharan dust deposition in Southern Europe, a process with many and different environmental consequences.
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Jeong, Gill-Ran. "Investigation of Mineral Dust Aerosols - Chemistry Intractions in the Marine Environments." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19805.
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Mineral dust aerosols play an important role in atmospheric chemistry through photolysis and heterogeneous uptake. Both mechanisms strongly depend on the size and composition of mineral dust. Because of the complex nature of dust, chemistry modeling commonly relies on simplified assumptions about the properties of dust particles relevant to physiochemical processes. The goal of this thesis is to investigate the impact of size-resolved composition of dust aerosols on atmospheric photochemistry. The relative importance of dust characteristics in photolysis and heterogeneous loss and the relative roles of the two mechanisms on atmospheric photochemistry are investigated.
A new block of spectral aerosol optical properties was developed and incorporated into the tropospheric ultraviolet and visible radiation transfer code in order to calculate spectral actinic fluxes and photolysis rates, J-values. The Fuchs-Sutugin approximation was employed to compute mass transfer from gas to dust mineral species and heterogeneous loss rate, kloss,j. The J-values and kloss,j were incorporated into a one-dimensional photochemistry model to simulate the diurnal cycle of a vertical profile of photochemical species. Several cases of dust loading were considered in the clean and polluted marine environments. A size-resolved mineralogical composition was constructed by selecting a range of the mass fraction of the three main mineral species such as iron oxide-containing clay minerals, carbonate-containing species, and quartz.
This work demonstrates that differences in microphysical and chemical properties of mineral dust lead to the important changes in spectral optical properties, J-values, and kloss,j. It also shows that non-linear relationships of photochemical species with two mechanisms result in various changes in the photochemical oxidant fields and that the most important factor controlling the photochemistry field is the dust size distribution, followed by the amount of mineral species with high uptake coefficients and the amount of iron oxide-clay aggregates.
This work demonstrates that accounting for regional differences in microphysical and chemical properties of mineral dust will improve the assessment of the impact of mineral dust on tropospheric photochemistry. In addition, it suggests that the size and composition of mineral dust will lead to a deeper understanding of the impact of mineral dust on the global climate system.
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Garimella, Sarvesh. "Cloud condensation nucleus activity comparison of dry- and wet-generated mineral dust aerosol : the significance of soluble material." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90821.
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Thesis: S.M. in Atmospheric Science, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.70
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 60-65).
This study examines the interaction of clay mineral particles and water vapor to determine the conditions required for cloud droplet formation. Droplet formation conditions are investigated for two common clay minerals, illite and sodium-rich montmorillonite, and an industrially derived sample, Arizona Test Dust. Using wet and dry particle generation coupled to a differential mobility analyzer (DMA) and cloud condensation nuclei counter, the critical activation of the clay mineral particles as cloud condensation nuclei is characterized. Electron microscopy (EM) is used to determine non-sphericity in particle shape. EM is also used to determine particle surface area and account for transmission of multiply charged particles by the DMA. Single particle mass spectrometry and ion chromatography are used to investigate soluble material in wet-generated samples and demonstrate that wet and dry generation yield compositionally different particles. Activation results are analyzed in the context of both K-Köhler theory (K-KT) and Frenkel, Halsey, and Hill (FHH) adsorption activation theory. This study has two main results: (1) K-KT is the suitable framework to describe clay mineral nucleation activity. Apparent differences in K with respect to size arise from an artifact introduced by improper size-selection methodology. For dust particles with mobility sizes larger than ~ 300 nm, i.e. ones that are in an atmospherically relevant size range, both K-KT and FHH theory yield similar critical supersaturations. However, the former requires a single hygroscopicity parameter instead of the two adjustable parameters required by the latter. For dry-generated particles, the size dependence of K is likely an artifact of the shape of the size distribution: there is a sharp drop-off in particle concentration at ~300 nm, and a large fraction of particles classified with a mobility diameter less than -300 nm are actually multiply charged, resulting in a much lower critical supersaturation for droplet activation than expected. For wet-generated particles, deviation from K-KT is likely a result of the dissolution and redistribution of soluble material. (2) Wet-generation is found to be unsuitable for simulating the lofting of fresh dry dust because it changes the size-dependent critical supersaturations by fractionating and re-partitioning soluble material.
by Sarvesh Garimella.
S.M. in Atmospheric Science
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Gierlus, Kelly M. "Laboratory studies of the physicochemical properties of mixed organic/mineral dust atmospheric aerosols: hygroscopicity and cloud condensation nuclei activity." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2704.
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Mineral dust aerosol generated from windblown soil can participate in climate forcing either directly through scattering or absorbing solar radiation or indirectly through acting as cloud condensation nuclei (CCN). In recent field studies organic material, such as oxalic acid and humic-like substances (HULIS), has been shown to be present in mineral dust aerosol. The presence of these internally mixed organic compounds can alter the physicochemical properties of the dust particles in the Earth's atmosphere. Thus, in this dissertation research the hygroscopic growth and CCN activity of model humic and fulvic acids and of calcite (CaCO3) particles coated with humic and fulvic acids has been measured. Furthermore, the CCN activity of calcite aerosol reacted with oxalic acid (H2C2O4) has been measured and compared to that of the humic and fulvic acids. The CCN measurements indicate that humic- or fulvic acid-coated calcite particles are significantly more CCN active than uncoated calcite particles, whereas reacted oxalate/calcite particles are not significantly more CCN active than the unreacted calcite particles, because the enhancement in CCN activity is reduced due to the reaction of calcite with oxalic acid to yield calcium oxalate. These results show that atmospheric processing of mineral dust through surface adsorption and/or heterogeneous reactions can alter hygroscopicity and CCN activity to an extent which depends on mineralogy and chemical speciation.
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Rockhold, Thomas Hall Jr. "Development of a Knudsen Cell Reactor for Measuring the Uptake of Atmospheric Gases on Particulate Matter." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32194.
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Heterogeneous reactions between mineral dust aerosols and gas phase volatile
organic compounds have the potential to impact important atmospheric chemical
processes. However, little is known about the uptake and reactivity of volatile organic
compounds on particulates found in the environment. A Knudsen cell was designed and
constructed for providing precise measurement of reaction probabilities within these
systems. The instrument was validated through a series of experiments. After validating
the Knudsen cell against several key benchmarks, the instrument was used to measure the
uptake coefficient for ethanol on particulate silicon dioxide. The uptake coefficient of
ethanol on silicon dioxide, a common compound in mineral dust aerosols, was
determined to be 7 x 10-7. Therefore, uptake of ethanol on silicon dioxide would be
competitive with the loss of other volatile organic compounds on silicon dioxide, which
show similar rates of uptake. The Knudsen cell was validated and measured the uptake
of ethanol on silicon dioxide, and future work with the Knudsen cell will study the uptake
of chemical warfare agent simulants on metal oxides.Master of Science
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Nanayakkara, Charith Eranga. "Heterogeneous chemistry and photochemistry of atmospherically relevant gases on oxide surfaces." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/4705.
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Metal oxides in the atmosphere emitted from various natural and anthropogenic processes alter the chemical balance of the Earth's atmosphere due to heterogeneous and photochemical processes with atmospheric trace gases. Therefore, understanding the heterogeneous chemistry and heterogeneous photochemistry of atmospheric trace gases on these oxide surfaces has become vital to precisely predict the effect of mineral dust loading on the Earth's atmosphere. Among the various components of mineral dust, light absorbing oxides play a significantly important role during the daytime.
The work reported herein has focused mainly on TiO2 and Α-Fe2O3. These are light adsorbing components found in atmospheric mineral dust. Apart from being a component of mineral dust, TiO2 is heavily used in a number of industrial applications ranging from uses in self-cleaning, water purification to cosmetics. These applications have led to their presence in the atmosphere as anthropogenic dust particles and in contact with the atmosphere as a stationary phase. Iron-containing particles are transferred to the atmosphere mainly from wind and volcanic activities in the form of iron-containing mineral dust and volcanic ash aerosols. Α-Fe2O3 is the most stable iron containing compound found in the Earths' crust which constitutes in significant amounts in mineral dust. The presence of these oxide surfaces in the atmosphere can play a major role in heterogeneous chemistry and photochemistry.
In this dissertation research, transmission FTIR spectroscopy and X-ray photoelectron spectroscopy are used to probe the details of heterogeneous chemistry and photochemistry of CO2, SO2, NO2, HCOOH, and HNO3 on titanium dioxide and hematite surfaces. Adsorption sites, surface speciation and surface species stability have been determined from analysis of FTIR and XPS spectra. Isotope labeling experiments were also carried out in order to obtain mechanistic information about the details of surface hydroxyl group reactivity on these oxide particle surfaces. Furthermore, heterogeneous photochemical reactions of adsorbates from atmospheric trace gas adsorption on TiO2 and Α-Fe2O3 were investigated under the conditions pertinent to troposphere. The role of adsorbed water on the stability of adsorbed species that form as a result of heterogeneous reactions and the effect of relative humidity on photochemistry on these oxide particles surfaces has also been investigated due to its important implications in the atmospheric chemistry of oxide surfaces. The research adds to our overall scientific understanding of the molecular level details of heterogeneous chemistry and photochemistry of light absorbing components in the atmosphere.
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Waza, Andebo Abesha [Verfasser], Konrad [Akademischer Betreuer] Kandler, and Sergio [Akademischer Betreuer] Rodriguez. "Development of a technique for measuring atmospheric dry deposition and its application to mineral dust / Andebo Abesha Waza ; Konrad Kandler, Sergio Rodriguez." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1205880771/34.
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Ashpole, Ian. "Patterns and causes of spatial and temporal variability of dust presence in the central and western Sahara." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:1b071769-d3a4-42ac-8960-43f990383bc8.
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Dust is a critical component of the Earth System. The central and western Sahara (CWS) is the dustiest place on Earth during the northern hemisphere summer. Understanding patterns and causes of spatial and temporal variability of dust presence here is essential for its reliable simulation in numerical models of weather and climate. Four papers in this thesis contribute to that objective, utilising a combination of high temporal resolution satellite data and global atmospheric reanalyses for June – August 2004 – 2010 inclusive. The first paper develops an objective dust detection scheme for the CWS using data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI), which are available every 15 minutes around the clock. These data have shed valuable insight on CWS dust processes, but their subjective application has to date limited their range of applications. The SEVIRI dust flag (SDF) developed here is evaluated against other widely used surface and satellite derived indicators of dustiness and it is found to reliably detect the presence of moderate-heavy dust loadings. The distribution of dust each summer is presented, revealing a high degree of interannual variability in overall dust coverage. The second paper utilises SDF to create an objective, high spatial resolution dust source map, based on the automated tracking of individual dust plumes. The most active sources are associated predominantly with palaeo-lakes and outwash plains, typically around the Saharan mountains. There is a clear intraseasonal progression of active source areas, controlled by regional climatology. The tracking scheme describes the transport trajectory of dust events following their initiation and the spatial association with deep convection at this time, revealing a clear regional divide in the relative importance of known meteorological mechanisms that drive dust emission from the dominant sources. The third paper uses an unsupervised clustering algorithm to classify maps of daily dust presence frequency and identify patterns of intraseasonal variability in CWS dust coverage. The resulting idealised dust states vary according to frequency of dust occurrence and its location, demonstrating a clear progression in preferred dust location from June – August and preferred state transitions from one day to the next. High daily dust occurrence frequency corresponds to an advanced West African Monsoon flow and low daily dust occurrence frequency corresponds to a Harmattan-dominated CWS. The overall location of the dust is linked to the location of the Sahara Heat Low, which changes as the summer progresses. The final paper addresses interannual variability in summertime dust presence frequency by comparing the 2 years with highest (2005) and lowest (2008) dust presence. The key difference is the occurrence of 3 multi-day periods in 2005 characterised by anomalously high dust presence. Case study comparison with the 3 periods of highest dust presence in 2008 identifies the anticyclonic circulation of the midtroposphere as a key control on dust duration over the CWS, dictating whether emitted dust is efficiently transported away from the CWS or whether it remains in suspension over the region for prolonged periods of time, up to several days in the anomalously dusty periods of 2005.
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Zuluaga-Arias, Manuel D. "Spatio-temporal variability of aerosols in the tropics relationship with atmospheric and oceanic environments." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41202.
Full textAbstract:
Earth's radiation budget is directly influenced by aerosols through the absorption of solar radiation and subsequent heating of the atmosphere. Aerosols modulate the hydrological cycle indirectly by modifying cloud properties, precipitation and ocean heat storage. In addition, polluting aerosols impose health risks in local, regional and global scales.
In spite of recent advances in the study of aerosols variability, uncertainty in their spatial and temporal distributions still presents a challenge in the understanding of climate variability. For example, aerosol loading varies not only from year to year but also on higher frequency intraseasonal time scales producing strong variability on local and regional scales. An assessment of the impact of aerosol variability requires long period measurements of aerosols at both regional and global scales.
The present dissertation compiles a large database of remotely sensed aerosol loading in order to analyze its spatio-temporal variability, and how this load interacts with different variables that characterize the dynamic and thermodynamic states of the environment. Aerosol Index (AI) and Aerosol Optical Depth (AOD) were used as measures of the atmospheric aerosol load. In addition, atmospheric and oceanic satellite observations, and reanalysis datasets is used in the analysis to investigate aerosol-environment interactions. A diagnostic study is conducted to produce global and regional aerosol satellite climatologies, and to analyze and compare the validity of aerosol retrievals. We find similarities and differences between the aerosol distributions over various regions of the globe when comparing the different satellite retrievals. A nonparametric approach is also used to examine the spatial distribution of the recent trends in aerosol concentration. A significant positive trend was found over the Middle East, Arabian Sea and South Asian regions strongly influenced by increases in dust events.
Spectral and composite analyses of surface temperature, atmospheric wind, geopotential height, outgoing longwave radiation, water vapor and precipitation together with the climatology of aerosols provide insight on how the variables interact. Different modes of variability, especially in intraseasonal time scales appear as strong modulators of the aerosol distribution. In particular, we investigate how two modes of variability related to the westward propagating synoptic African Easterly Waves of the Tropical Atlantic Ocean affect the horizontal and vertical structure of the environment. The statistical significance of these two modes is tested with the use of two different spectral techniques. The pattern of propagation of aerosol load shows good correspondence with the progression of the atmospheric and oceanic synoptic conditions suitable for dust mobilization over the Atlantic Ocean. We present extensions to previous studies related with dust variability over the Atlantic region by evaluating the performance of the long period satellite aerosol retrievals in determining modes of aerosol variability. Results of the covariability between aerosols-environment motivate the use of statistical regression models to test the significance of the forecasting skill of daily AOD time series. The regression models are calibrated using atmospheric variables as predictors from the reanalysis variables. The results show poor forecasting skill with significant error growing after the 3rd day of the prediction. It is hypothesized that the simplicity of linear models results in an inability to provide a useful forecast.
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Qu, Zihan. "Chemical properties of continental aerosol transported over the Southern Ocean : Patagonian and Namibian sources." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066002/document.
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Patagonie et la Namibie sont deux sources importantes d'aérosol minéral qui alimente la section Atlantique Sud de l'océan Austral avec les micronutriments.L'objet de ma thèse est d'étudier 1) la concentration atmosphérique et la variation temporel de la poussière en Patagonie, 2) l'hétérogénéité spatiale de composition élémentaire de poussière en Patagonie et en Namibie, et 3) la solubilité élémentaire de poussière en Patagonie et en Namibie. Ces trois aspects sont les principaux enjeux pour modéliser les inventaires des émissions de micronutriments biodisponibles à partir de sources de poussière.La concentration en poussière mesurée en Patagonie montre une variation saisonnière avec un niveau plus bas en hiver. Les données météorologiques suggèrent que cette variation saisonnière est associée à la variation de l'humidité du sol dans les zones source plutôt qu'à la vitesse du vent. Des échantillons d'aérosol minéral ont été générés à partir des sols de Patagonie et de Namibie. La composition élémentaire des poussières diffère de celles des sols parents, en particulier en Namibie en raison de l'effet de dilution par le quartz dans les sols. Des compositions élémentaires varient spatialement aux échelles continentale et régionale en Patagonie et Namibie. Les variations de Ca et Mg sont les principales raisons conduisant à l'hétérogénéité spatiale de la composition élémentaire des poussières. Les solubilités élémentaires des aérosols minéraux de Patagonie et de Namibie augmentent avec l'acidité de la solution altérante. Les poussières riches en calcium présentent une solubilité plus élevée pour les éléments les plus solubles (Ca, etc.) en raison de la présence de carbonate. Le suivi de la concentration en poussières obtenu en Patagonie peut aider à mieux en quantifier les émissions dans la région subantarctique et ainsi à mieux contraindre les modèles. La base de données que nous avons obtenue sur les poussières et leur solubilité contribue également à l'évaluation des émissions d'éléments solubles dans la région AustraleMineral dust is considered to be an important supplier of micronutrient for the Southern Ocean where the primary production is limited by insufficient supply of micronutrients. Patagonia (South America) and Namibia (Southern Africa) are two main dust sources for the South Atlantic section of the Southern Ocean. Emission inventories of bioavailable micronutrients from these two regions regulate the final biological impact on marine ecosystem in the South Atlantic Ocean. This thesis is mainly focused on the investigation of 1) the atmospheric dust concentration and its temporal pattern in Patagonia, 2) the spatial heterogeneity of dust elemental composition in Patagonia and Namibia, and 3) the pH dependence of elemental solubility in Patagonian and Namibian dust. These three aspects are the key issues to model the emission inventories of bioavailable micronutrients from dust sources. Dust concentration measurements were conducted in Patagonia-Atlantic Coast and revealed a seasonal pattern of dust concentration with lower dust level in winter than the other three seasons. Meteorological records suggest that this seasonal pattern is associated with the variation of soil moisture in source areas rather than the recurrently high wind speed. Dust samples were generated from Patagonian and Namibian soils to investigate the elemental composition and the elemental solubility of source dust. Dust elemental composition differs to different degrees from their parents soils, particularly in Namibia due to the dilution effect of quartz in soil. Spatial variability of dust elemental composition was observed at both continental scale and regional scale in Patagonia and Namibia. Variations in Ca and Mg content are the main reasons for the spatial heterogeneity of dust elemental composition. Elemental solubility of Patagonian and Namibian dust increased with acidity of leaching solution. More soluble elements namely Ca, K, Mg, Mn, Sr and Ba showed much higher solubility in calcium-rich dust due to the presence of carbonate. The dust concentration record obtained in Patagonia may help to better quantify the dust emission in subantarctic region and to constrain dust models. Database of dust elemental composition and elemental solubility in Patagonia and Namibia also contributes to the evaluation of emission inventories of soluble elements from dust sources to the Southern Ocean
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Silva, Marcio Cataldo Gomes da. "Características biogeoquímicas da interação atmosfera criosfera na Antártica ocidental." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=3339.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoO manto polar antártico retêm informação paleoclimatologica por entres suas camadas de neve e gelo. O gelo antártico tem revelado a base de dados paleoclimática de maior resolução para os últimos 800 mil anos. Os padrões de transporte atmosférico refletem a composição e a fonte do particulado encontrado na neve e no gelo do continente Antártico. Estando relacionado a processos climáticos, as características desse transporte alteram em quantidade e qualidade as espécies químicas que se depositam sobre o manto de gelo. Dessa forma, o estudo dos depósitos de particulado ao longo das camadas de neve/gelo na Antártica pode sugerir mudanças nos padrões de transporte atmosférico. Atualmente a comunidade científica discute as diferenças de padrões climáticos entre o leste e o oeste antártico. Enquanto de forma geral observa-se instabilidade no setor oeste, o clima da antártica oriental demonstra relativa estabilidade climática. Neste estudo, analisamos dois testemunhos de gelo recente de duas regiões com características climáticas diferentes do continente Antártico. No Platô Detroit situado na Península Antártica (6410′S/0600′O), analisamos a variabilidade de Black Carbon (BC) ao longo de 20 metros de neve. O BC encontrado na Península Antártica apresentou baixas concentrações comparáveis as encontradas no gelo do Artico período pré-industrial. Nossos resultados sugerem que sua variabiliade corresponde à sazonalidade dos períodos de queimada nos continentes do Hemisfério Sul. No interior do continente Antártico, analisamos o particulado em geral por um processo de microanálise ao longo de um testemunho de 40 metros extraído em Mont Johns (79o55′S/09423′O). Encontramos uma tendência negativa na deposição de poeira mineral (AlSi) entre 1967 e 2007. Nossos resultados sugerem que esta tendência seja resultado de um crescente isolamento atmosférico da região central do continente antártico pelo aumento da intensidade dos ventos ao redor da Antártica. Este aumento na intensidade dos ventos reflete por sua vez o resfriamento da alta atmosfera no centro antártico causado pela depleção da camada de ozônio na região. Adicionalmente, amostras de diferentes microambientes de Patriot Hills (8018′S/08121′O) foram coletadas de maneira asséptica para análise microbiológica. As amostras foram cultivadas em meio R2 e paralelamente o DNA total extraído foi sequenciado pela técnica de pirosequenciamento. Os resultados preliminares desta analise mostram grande riqueza de espécies dos mais variados grupos. Os resultados deste trabalho caracterizam três diferentes parâmetros relacionados a deposição atmosférica em duas áreas pouco exploradas e de grande interesse científico do continente antártico.
The antarctic ice cap stores paleoclimatological information within layers of snow and ice. Antarctic ice has revealed the higher resolution paleoclimactic database for the last 800 kyr. Atmospheric transport plays a fundamental role on the composition and sources of particulate matter found in the Antarctic ice. It has been related to several climatic processes that changes the quantity and quality of exogenous aerosols reaching Antarctica. Therefore, studies of the particulate matter deposits along the snow/ice layers may suggest changes on atmospheric transport patterns. This work, analyze two recent ice cores from two climatic distinct regions of the Antarctic continent. One retrieved from Detroit Plateau/Antarctic Peninsula (6410′S/0600′W), in which we have analyze Black Carbon (BC) deposition and variability along 20 meters of snow. BC found in the Antarctic Peninsula showed low concentrations (varing between 0,014 and 3,733ppb), comparable to the concentrations found on Arctic ice dated from before the industrial revolution period. Our results suggest that peaks of BC detected correspond, mostly, to biomass burning seasons in the South Hemisphere, not speficically from South America. The second one, of 40 m, was retrieved from Central-West Antarctica, Mont Johns (79o55′S/094 23′W), in which we analyzed the mineral dust abundance thought M.E.V. E.D.X. technique. In this study we found negative trends in mineral dust (inferred from Fe, Ti and AlSi) deposition between 1967 and 2007, in contrast to similar works in Sub-antarctic regions. We demonstrate that this trend is a consequence of the persistent atmospheric isolation that encloses the Central and East Antarctic regions due to the increasing winds around Antarctica within this period. It has been documented that westerlies intensification reflect the upper atmosphere cooling above Central Antarctica caused by the stratospherical ozone layer depletion. As part of the polar site characterization, we additionally have performed sampling for microbiological purpose from distinct microenvironments at Patriot Hills (8018′S/08121′W). Samples were cultivated on R2 media and at the same time total DNA on samples was extracted and sent to a pyrosequencing analysis. Preliminary results show richness and diversity of bacterial species distributed on five phyla.
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Zeineddine, Mohamad Nour. "Heterogeneous Interactions of Volatile Organic Compounds with Natural Mineral Dust Samples." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2018. http://www.theses.fr/2018MTLD0005/document.
Full textAbstract:
Ce travail de thèse vise à caractériser l’interaction entre composés organiques volatils et poussières minérales atmosphériques. Les COV sélectionnés sont l’isopropanol (IPA), l’isoprène (ISP) et l’acide acétique (AcA). Cinq échantillons naturels de poussières minérales provenant de zones désertiques situées dans plusieurs régions du globe ont été retenus.Il a été mis en évidence que l’origine et donc la composition chimique des poussières naturelles joue un rôle majeur dans la nature de leur interaction avec les COV. Plus particulièrement, les coefficients de capture tendent à croître avec les rapports élémentaires Al/Si et Fe/Si. De plus, il est montré que l’interaction entre COV et poussières est fortement impactée par l’humidité relative et la température.Plusieurs modes d’interaction entre les COV et les poussières étudiés ont été mis en évidence : physisorption, chimisorption ou adsorption réactive. Ils dépendent de la composition chimique des poussières et de la structure des COV. En fonction du mode d’interaction, ces processus hétérogènes peuvent être considérés comme des puits de COV primaires voire des sources de COV secondaires en phase gazeuse. Ce travail met en lumière la contribution des processus hétérogènes dans l’atmosphèreThis thesis investigates the interactions of volatile organic compounds (VOCs) with natural mineral dust samples. The VOCs used are isopropanol (IPA), isoprene (ISP) and acetic acid (AcA). Five natural mineral dust samples originating from various desert regions all over the world are used in this study.It is evidenced that the origin, I.E. the chemical composition, of the natural dust sample plays a significant role in defining the nature of its interaction with the VOCs. In particular, an increase of uptake is observed with increasing Al/Si and Fe/Si elemental rations. Moreover, the dust-VOC interaction is evidenced as being highly impacted by relative humidity and temperature.Various interactions modes have been evidenced between dust and VOCs such as physisorption, chemisorption and reactive sorption depending on the chemical composition of the dust and the structure of the VOC. Depending on the interaction mode, heterogeneous processes can act as a sink of primary VOCs or even a soure of secondary oxygenated VOCs in the gas phase. This work emphasiez the contribution of heterogeneous processes to the atmosphere
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Alizadeh, Choobari Omid. "Modelling the spatial distribution, direct radiative forcing and impact of mineral dust on boundary layer dynamics." Thesis, University of Canterbury. Geography, 2013. http://hdl.handle.net/10092/7700.
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Mineral dust aerosols, the tiny soil particles in the atmosphere, play a key role in the atmospheric radiation budget through their radiative and cloud condensation nuclei effects. It is therefore important to evaluate the radiative forcing of mineral dust and subsequent changes in atmospheric dynamics. The Weather Research and Forecasting with Chemistry (WRF/Chem) regional model with the integrated dust modules and available observations have been used to investigate the three-dimensional distribution of mineral dust over Australia. Additionally, the WRF/Chem model was used to estimate the direct radiative forcing by mineral dust over Australia. Particular emphasize has been given to direct
radiative feedback effect of mineral dust on boundary layer dynamics. Two dust emission schemes embedded within the WRF/Chem model have been utilized in this study: the dust transport (DUSTRAN) and the Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) schemes. The refractive index of mineral dust depends on the mineralogy, size and composition of dust over a given region. The refractive index of mineral dust for shortwave radiation was considered to be wavelength independent and set based on previous mineralogical studies over North Africa and Australia. However, the refractive index of mineral dust for longwave radiation was considered to be wavelength dependent and to vary for 16 longwave spectral bands. Model results were compared with observations to validate the performance of the model, including satellite datasets
from the Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging SpectroRadiometer (MISR) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), as well as ground-based measurements obtained from air quality monitoring sites over Australia. The major results can be summarized as follows: (1) Lake Eyre Basin
is the most important source of dust in Australia, with a peak activity identified to be during austral spring and summer, and dust emission within the basin is often associated with the passage of dry cold fronts; (2) Mineral dust from Lake Eyre Basin can be transported long distances to southeastern Australia in association with eastward propagating frontal
systems, reaching as far as New Zealand and beyond, and to northern tropical Australia by postfrontal southerly winds, and subsequently towards northwestern Australia and the Indian Ocean by southeasterly trade winds; (3) Australian dust plumes are mainly transported in the lower atmosphere, although variation of boundary layer depth during the passage of cold frontal systems, as well as ascending motion at the leading edge of these
systems and descending motion where postfrontal anticyclonic circulation is dominant contribute to the vertical extent of mineral dust aerosols; (4) the shortwave direct radiative effect of mineral dust results in cooling of the atmosphere from the surface to near the boundary layer top, but warming of the boundary layer top and lower free atmosphere; (5)
changes in the vertical profile of temperature result in an overall decrease of wind speed in the lower boundary layer and an increase within the upper boundary layer and lower free atmosphere; (6) the longwave warming effect of mineral dust partly offsets its shortwave cooling effect at the surface. This compensation is significantly larger over and immediately downwind of dust source regions where coarse particles are more abundant, as they have stronger interaction with longwave radiation emitted from the Earth’s surface; (7) both shortwave and longwave radiative forcing by mineral dust was found to have a diurnal variation in response to changes in solar zenith angle and in the intensity of longwave
radiation, respectively; (8) the absorptive nature of dust was shown to be associated with the shortwave heating of the atmosphere; (9) on the other hand, longwave cooling of the atmosphere was identified because absorption of longwave radiation by dust is less than its emission to the surface and top of the atmosphere (TOA).
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Haga, Donna. "Ice nucleation by mineral dusts, fungal spores, and bacteria : implications for climate and the long-distance transport of these aerosols in the atmosphere." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45241.
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In the atmosphere, ice can form on solid aerosol particles called ice nuclei. This research focuses on the ice nucleation properties of mineral dusts and biological particles. The motivation for this research is two-fold. First, ice nucleation on these aerosols may influence cloud formation, cloud reflectivity and precipitation patterns in what is an indirect climate effect. This effect is one of the largest uncertainties in current climate models. Second, ice nucleation may be an important removal mechanism for these particles from the atmosphere and may influence their long-distance transport. Currently, ice nucleation is represented in a simplistic manner or not at all in models used to predict the long-distance transport of aerosols.
A temperature and humidity controlled flow cell coupled to an optical microscope was used to study the ice nucleation properties of four mineral dusts, eighteen fungal spores, and six bacteria. It was found that acidic coatings reduce the ice nucleating ability of the mineral dusts. The fungal spores showed a wide range of ice nucleating properties and there was no inherent difference in the ice nucleation ability of spores belonging to different taxonomic groups. Four of the bacteria studied were very poor ice nuclei and the fifth bacterium was an excellent ice nucleus.
The results from the flow cell experiments on fungal spores were used to describe ice nucleation in two modeling studies that simulated atmospheric transport. One study found that a significant fraction of large fungal spores (20 micrometers in diameter) can reach high altitudes where they could act as ice nuclei. The other study focused on smaller spores (3 to 8 micrometers) and found that ice nucleation on these spores effects their long-distance transport to polar and marine regions.
The laboratory results were used to show that mineral dusts are more important than the fungal spores or bacteria that were studied on a global annual scale. These results can be used to improve parameterizations of ice nucleation on mineral dusts and biological particles in future modeling studies investigating the indirect effect of aerosols on climate or the long-distance transport of aerosols in the atmosphere.
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Borunda, Alejandra. "Tracing dust in the Southern Hemisphere over the last glacial cycle." Thesis, 2019. https://doi.org/10.7916/d8-rmak-qn20.
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Mineral dust both influences and is influenced by climate on many timescales, from seconds to epochs. Its complex interactions with the climate system are still being unraveled. For example, dust fluxes change in tandem with other records of past changes in climate, and dust source is often presumed to change as well, in response to shifts in climate conditions in source regions; changes in wind regimes; or changes in atmospheric transport pathways. In this work, I investigate dust records from the Southern Hemisphere from ice core and marine sediment core climate archives, looking at both flux and provenance in order elucidate the conditions that allowed for those particles to travel from source to sink. Using multiple radiogenic isotope systems as tracers (87Sr/86Sr, εNd(0), 206Pb/207Pb, and 208Pb/207Pb), I geochemically “fingerprint” of dust particles from Southern Hemisphere climate archives over the last glacial cycle. I compare the dust fingerprints to potential source areas (PSA’s) from across the Southern Hemisphere in order to identify the sources of dust found in the WAIS Divide and Taylor Glacier ice cores from West Antarctica, as well as from marine sediment core ELT39.75 in the Tasman Sea. I use endmember mixing theory to determine the relative contribution of different sources to the climate archives over time. In West Antarctica, I geochemically identify specific local volcanoes from Marie Byrd Land as significant particle contributors to the WAIS Divide ice core during the previous glacial period. In the Tasman Sea, I identify a specific region of southeastern Australia as primary the dust source over the past glacial cycle, with the source remaining constant across glacial-interglacial climate transitions. This clarifies that the “fingerprint” of Australian dust is relatively invariant over time and allows a single Australian signature to be used as an endmember for identifying dust provenance in climate archives downwind. I also identify the dust sources in the WAIS Divide during the Last Glacial Maximum and through the early deglacial, identifying southern South America as the predominant source during cold stages. WAIS Divide and Taylor Glacier dust records do not record dust source changes across millennial-scale climate events, suggesting that a) the source regions did not change, b) the transport pathways remained pinned, or c) the proxy is not sensitive to changes in these variables. Contributions from local volcanoes are also inferred from the WAIS dust record using mixing theory. In summary, I find that the radiogenic isotope fingerprint of dust samples from the archives analyzed show subtle or no changes in source over climate transitions, and therefore the strategy of dust particles as a tracer of past atmospheric circulation pathways should be approached cautiously.
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Styler, Sarah Anne. "Heterogeneous Photochemistry of Atmospheric Dusts and Organic Films." Thesis, 2014. http://hdl.handle.net/1807/65753.
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Little is currently known regarding the nature and consequences of interactions between photoactive surfaces, including mineral dust and ‘urban film’, and gas-phase pollutants in urban environments. In order to address this knowledge gap, this thesis explores the photochemical reactivity of these environmental surfaces in controlled laboratory settings.
The photoenhanced ozonation of pyrene, a toxic product of incomplete combustion, proceeds at different rates and via different mechanisms at three model ‘urban film’ surfaces. These results are important because they suggest that the reactivity of a molecule on simplified surfaces may not accurately reflect its reactivity in the real environment.
The photooxidation of isopropanol at the surface of TiO2, here used as a proxy for the photoactive component of mineral dust, yields gas-phase acetone. This chemistry is amplified by nitrate, a major surficial component of atmospherically processed dust. These results suggest that dust has the potential to convert non-absorbing species to photochemically active species, and thereby serve as a source of reactive organic radicals for further gas- or surface-phase chemistry.
Oxalic acid, the most atmospherically abundant dicarboxylic acid, is efficiently oxidized to gas-phase CO2 at the surface of Mauritanian sand and Icelandic volcanic ash. These experiments indicate that the lifetime of oxalic acid may be limited in arid regions by Fe and Ti-catalyzed aerosol-phase photochemistry.
Fluorotelomer alcohols (FTOHs), a class of industrial chemicals used in the production of surface coatings, undergo photooxidation at the surface of sand and ash to yield toxic and persistent perfluorinated carboxylic acids (PFCAs). These results provide the first evidence that the metal-catalyzed heterogeneous oxidation of FTOHs may act as a local source of aerosol-phase PFCAs.
Illumination of Nigerien sand in the presence of gas-phase SO2 leads to the formation of surface-sorbed sulfate. This chemistry proceeds more efficiently on fine sand than on coarse sand. In chamber experiments, the illumination of SO2 in the presence of realistically produced dust aerosol results in new particle formation. Together, these results suggest that SO2 photochemistry at the dust surface has the potential to change not only dust hygroscopicity but also the net scattering potential of dust-containing air masses.
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Bangalath, Hamza Kunhu. "Direct Radiative Effect of Mineral Dust on the Middle East and North Africa Climate." Diss., 2016. http://hdl.handle.net/10754/621965.
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Dust-climate interaction over the Middle East and North Africa (MENA) has long been studied, as it is the "dustiest" region on earth. However, the quantitative and qualitative understanding of the role of dust direct radiative effect on MENA climate is still rudimentary. The present dissertation investigates dust direct radiative effect on MENA climate during summer with a special emphasis on the sensitivity of climate response to dust shortwave absorption, which is one of the most uncertain components of dust direct radiative effect. Simulations are conducted with and without dust radiative effect, to differentiate the effect of dust on climate. To elucidate the sensitivity of climate response to dust shortwave absorption, simulations with dust assume three different cases of dust shortwave absorption, representing dust as a very efficient, standard and inefficient shortwave absorber. The non-uniformly distributed dust perturb circulations at various scales. Therefore, the present study takes advantage of the high spatial resolution capabilities of an Atmospheric General Circulation Model (AGCM), High Resolution Atmospheric Model (HiRAM), which incorporates global and regional circulations. AMIP-style global high-resolution simulations are conducted at a spatial resolution of 25 km. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet and West African Monsoon circulation. Consistent with these dynamic responses at various scales, the tropical rainbelt across MENA strengthens and shifts northward. Similarly, the temperature under rainbelt cools and that over subtropical deserts warms. Inter-comparison of various dust shortwave absorption cases shows that the response of the MENA tropical rainbelt is extremely sensitive to the strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. Importantly, the summer precipitation over the semi-arid strip south of Sahara, including Sahel, increases in response to dust radiative effect. The maximum response and sensitivity are predicted over this region. The sensitivity of the responses over Sahel, especially that of precipitation, is comparable to the mean state. Locally, the precipitation increase reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. As the region is characterized by the "Sahel drought", the predicted precipitation sensitivity to the dust loading over this region has a wide-range of socioeconomic implications. The present study, therefore, suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the MENA climate in general, and of Sahel in particular.
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Bachelder, Jill. "Characterization of mineral dust emitted from an actively retreating glacier in Yukon, Canada." Thèse, 2019. http://hdl.handle.net/1866/22446.
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Yang, Mingxi. "Separation of aerosol light absorption to black carbon, brown carbon, and mineral dust : interpretatins of atmospheric measurements near Beijing." Thesis, 2007. http://hdl.handle.net/10125/20810.
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Bi, Lei. "Light Scattering by Ice Crystals and Mineral Dust Aerosols in the Atmosphere." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9319.
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Modeling the single-scattering properties of nonspherical particles in the atmo¬sphere (in particular, ice crystals and dust aerosols) has important applications to climate and remote sensing studies. The first part of the dissertation (Chapters II¬V) reports a combination of exact numerical methods, including the finite-difference time-domain (FDTD), the discrete-dipole-approximation (DDA), and the T-matrix methods, and an approximate method-the physical-geometric optics hybrid (PGOH) method-in the computation of the optical properties of the non-spherical particles in a complete range of size parameters. The major advancements are made on the modeling capabilities of the PGOH method, and the knowledge of the electromag¬netic tunneling effect – a semi-classical scattering effect. This research is important to obtain reliable optical properties of nonspherical particles in a complete range of size parameters with satisfactory accuracy and computational efficiency.
The second part (Chapters VI-VII) of the dissertation is to investigate the de¬pendence of the optical properties of ice crystals and mineral dust aerosols in the atmosphere on the spectrum, the particle size and the morphology based on compu¬tational models. Ice crystals in the atmosphere can be classified to be simple regular faceted particles (such as hexagon columns, plates, etc.) and imperfect ice crystals. Modeling of the scattering by regular ice crystals is straightforward, as their morphologies can be easily defined. For imperfect ice crystals, the morphology is quite diverse, which complicates the modeling process. We present an effective approach of using irregular faceted particle to characterize the imperfectness of ice crystals. As an example of application, less-than-unity backscattering color ratio of cirrus clouds is demonstrated and explained theoretically, which provides guidance in the calibra¬tion algorithm for 1.064-µm channel on the Calipso lidar. Dust aerosols have no particular morphology. To develop an approach to modeling the optical properties of realistic dust particles, the principle of using simple shapes (triaxial ellipsoids and nonsymmetric hexahedra) to represent irregular dust particles is explored. Simulated results have been compared with those measured in laboratory for several realistic aerosol samples. Agreement between simulated results and measurement suggests the potential applicability of the two aforementioned aerosol models. We also show the potential impact of the present study to passive and active atmospheric remote sensing and future research works.
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Sapkota, Atindra [Verfasser]. "Mineralogical, chemical, and isotopic (Sr, Pb) composition of atmospheric mineral dusts in an ombrotrophic peat bog, southern South America / vorgelegt von Atindra Sapkota." 2006. http://d-nb.info/982377444/34.
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