Dissertations / Theses on the topic 'Atmospheric Compounds'
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Yin, Fangdong Seinfeld John H. "Atmospheric photooxidation of organosulphur compounds /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-11192007-092214.
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Gunawardena, Rohith. "Atmospheric methyl iodide." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,91.
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Kahnt, Ariane. "Semivolatile compounds from atmospheric monoterpene oxidation." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-93492.
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This PhD thesis aims to improve the knowledge on the processes and chemical species in the gas- and particle-phases that are involved in the production of secondary organic aerosol (SOA) from monoterpene oxidation in the atmosphere.
A denuder/filter technique that enabled the simultaneous sampling of gaseous and particulate compounds was applied in the present study. The sampling technique was comprehensively characterised and optimised using twelve atmospherically relevant carbonyl compounds. The present study improved the denuder coating procedure and the sampling performance. An additional coating with the derivatisation reagent, 2,4‑dinitrophenylhydrazine (DNPH), reduced the break-through potential (e.g., from 98% to 0.9% for methyl vinyl ketone) and the fraction of carbonyl compounds on the filter material (e.g., from 8.7% to 0% for acetone).
Calibration experiments against an aerosol chamber were performed to reduce the relative standard deviation (RSD) of the calibration points in the denuder measurements. The RSDs were reduced by half for acetone, acetaldehyde, methyl vinyl ketone, glyoxal, benzaldehyde and campholenic aldehyde using a XAD‑4/DNPH denuder, and the quantification error was also reduced.
This sampling technique was then applied to a series of α- and β-pinene ozonolysis experiments. The present study examined the influence of an OH radical scavenger (CO), and hence the HO2/RO2 ratio, on the SOA formation, product distribution and partitioning behaviour of selected oxidation products in conjunction with different seed particle acidities.
It was shown that SOA yields increased by about 8% in α-pinene ozonolysis when CO and acidic seed particles co-existed, whereas only a marginal difference was observed (increase of 2%) for β-pinene compared to neutral seed particles.
From the denuder/filter sample analysis, it was possible to tentatively identify a new compound from the α-pinene ozonolysis, i.e., terpenylic aldehyde. Gas- and particle-phase yields were estimated for the first time for this compound (i.e., 1% and 0.4%, respectively). The atmospheric relevance of terpenylic aldehyde was demonstrated based on ambient filter measurements and a possible formation pathway was suggested.
Furthermore, the present study provided an additional explanation for enhanced SOA formation when acidic seed particles are used in monoterpene ozonolysis. It was demonstrated that the isomerisation of monoterpene oxides on acidic seed particles leads to the formation of highly reactive SOA precursors, whose subsequent reaction with ozone contributes significantly to SOA formation.
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Arsene, Cecilia. "Atmospheric degradation mechanisms of organic sulphur compounds." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96417023X.
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Grira, Asma. "Atmospheric degradation of oxygenated Volatile Organic Compounds." Thesis, Rennes 1, 2021. http://www.theses.fr/2021REN1S017.
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Les composés organiques volatils oxygénés (COVO), principalement émis par des sources biogènes, jouent un rôle majeur dans la chimie de l'atmosphère, le changement climatique, l'environnement et la santé. Il a été récemment démontré que ces émissions augmentent en cas de stress biotique et/ou abiotique. Les COVO biogéniques peuvent subir une variété de réactions, tant chimiques que photolytiques, et ils sont impliqués dans la formation d'Aérosols Organiques Secondaires (AOS). Ces composés ont été détectés dans diverses régions, mais il y a très peu d’informations sur leurs processus de dégradation sous conditions troposphériques. La compréhension des mécanismes d'oxydation de ces espèces est d'un intérêt fondamental et fournit des données cruciales pour les modèles atmosphériques qui sont utilisés par les responsables politiques pour formuler et décider des stratégies d'amélioration de la qualité de l'air. Cette thèse vise à améliorer les connaissances actuelles sur le comportement de ces COVO, pour une meilleure compréhension de leur impact sur la chimie atmosphérique. Dans ce travail, nous avons présenté une étude détaillée de la dégradation atmosphérique des aldéhydes insaturés en C5-C7 et des alcools insaturés en C5-C8 par ozone, l’atome Cl et le radical OH. Les principaux objectifs étaient de mieux comprendre le mécanisme de réaction et de mettre en évidence leur potentiel à former des AOS. Pour atteindre ces objectifs, nous nous sommes concentrés sur quatres volets : (i) détermination du spectre IR et UV des aldéhydes insaturés en C5-C7, (ii) détermination de la constante de vitesse pour les systèmes COVO + Oxydant étudiés à température ambiante, (iii) identification et quantification des produits en phase gazeuse, (iv) détermination des rendements en AOS. Les études sur les produits ont été menées avec et sans ajout d'un piégeur des radicaux OH. Les expériences ont été réalisées dans huit réacteurs différents, statiques (chambres) ou dynamiques (flux), et diverses techniques analytiques ont été utilisées pour étudier les produits de réaction (FTIR, GC-FID/MS, SPME-GC/MS, HPLC, PTR-ToF-MS, SIFT-MS, PLP-LIF) et la formation de SOA (SMPS, FMPS)Oxygenated Volatile Organic Compounds (OVOCs), mainly released from biogenic sources, play a major role in atmospheric chemistry, climate change, environment, and health. These emissions have been recently shown to increase in the case of biotic and/or abiotic stresses. Biogenic OVOCs may undergo a wide variety of reactions, both chemical and photolytic, and they contribute in the formation of Secondary Organic Aerosols (SOAs). These compounds have been detected in various areas, but little is known about their degradation processes under tropospheric conditions. Understanding the oxidation mechanisms of these species is of fundamental interest and yields crucial data for atmospheric models used by policymakers in formulating and deciding strategies for improving air quality. This dissertation aims to improve the current knowledge of those OVOCs behaviors to better understand their impact on atmospheric chemistry. This work reports a detailed study of the atmospheric degradation of C5-C7 unsaturated aldehydes and C5-C8 unsaturated alcohols by ozone, Cl atom, and OH radical. The main objectives were to better understand the reaction mechanism and to feature the SOA formation potential. To achieve these objectives, we focused on four topics: (i) determination of IR and UV spectrum of C5-C7 unsaturated aldehydes, (ii) determination of the rate constant for the studied OVOCs + Oxidant at room temperature, (iii) identification and quantification of the gas-phase products, (iv) determination of the SOA yields. The product studies were investigated both with and without adding an OH radical scavenger. Experiments were performed in eight different static (chambers) or dynamic (flow) reactors, and various analytical techniques were used to investigate the reaction products (FTIR, GC-FID/MS, SPME-GC/MS, HPLC, PTR-ToF-MS, SIFT-MS, PLP-LIF) and SOA formation (SMPS, FMPS)
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Han, Dawei. "Atmospheric Hydrocarbon Analysis." PDXScholar, 1993. https://pdxscholar.library.pdx.edu/open_access_etds/4588.
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This treatise studied two correlated important issues in atmospheric chemistry: real-time monitoring of ambient air and removal mechanisms of atmospheric hydrocarbons. An analytical system was designed for the purpose of identification and measurement of sub-ppb level hydrocarbons of different reactivities in air samples. This analytical system was then applied to a series of smog-chamber studies which simulated the removal of reactive hydrocarbons from the atmosphere by reaction with hydroxyl radicals. Six representative atmospheric hydrocarbons ( hexane, octane, toluene, m-xylene, a-xylene and mesitylene) were selected for these experiments. The experimental data indicated that the decay of atmospheric hydrocarbons under laboratory conditions is entirely due to reaction with hydroxyl radicals. The conclusion drawn from a time-resolved plume study that aromatic molecules decay much faster than could be accounted for solely by reaction with hydroxyl radicals was not verified; this indicates a difference between laboratory study and the study in the real atmosphere, and some physical factors besides chemical mechanism might take a more significant role in removing aromatics faster from the atmosphere.
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Connell, Richenda K. "Tropospheric degradation of halogenated compounds." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320615.
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Sengupta, Kamalika. "Climate impacts of atmospheric low volatility organic compounds." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/20146/.
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There exist huge gaps in the knowledge of how cloud-aerosol interaction affects climate. Consequently global models estimating the radiative forcing by anthropogenic aerosols show considerable discrepancy. Especially challenging to quantify is the role of volatile organic compounds in forming aerosol particles which can act as cloud condensation nuclei. Volatile organic compounds are emitted into the atmosphere in large quantities by biogenic and anthropogenic sources. In the atmosphere they undergo chemical oxidation reactions and typically produce products that are highly oxygenated and have lower volatility. Volatility of these highly oxygenated molecules span a wide range and determine the ease with which they transfer to the aerosol phase - either via participation in new particle formation or by contributing to the growth of bigger particles. The extent to which the highly oxygenated molecules contribute to new particle formation or their subsequent growth impacts the number concentration of cloud condensation nuclei in the atmosphere. Hence to accurately estimate cloud condensation nuclei, global models need to take into account the role of highly oxygenated molecules of varying volatility in modulating the atmospheric aerosol size distribution. In this thesis a new nucleation parameterisation based solely on highly oxygenated species of extremely low volatility is added to the model and its impact on the estimated cloud albedo effect is assessed. The nucleation mechanism is based on the findings of the CLOUD Experiment at CERN. The implementation of this new parameterisation reduces previous model estimates of cloud albedo forcing through its impact on the pre-industrial atmosphere. The thesis then goes on to introduce a new secondary aerosol formation scheme from highly oxygenated organic molecules based on the understanding of recent scientific advancements and assesses the effect of implementing the scheme on the estimated cloud albedo effect. Results show highly oxygenated molecules of semi-volatile nature play a significant role in determining the number concentration of cloud relevant particles. Although their higher volatility renders them incapable of new particle formation, their atmospheric abundance and contribution to the growth of particles which are relatively larger, provide an efficient pathway for producing cloud condensation nuclei in the atmosphere. Further, an ensemble of simulations are produced and analysed to explore a 6-D parameter space based on pre-defined uncertainty ranges of these highly oxygenated molecules. The work identifies plausible and implausible regions within the 6-D space, based on model-observation comparison against three model outputs - number concentration of all particles, number concentration of CCN-relevant sized particles and organic aerosol concentration. The work provides a top-down estimate of yields of highly oxygenated molecules (that contribute to SOA formation) based on model skill score against ground-based observations. Such yields are typically based on laboratory experiments and is broadly considered to be an important reason behind the failure of global models to estimate realistic mass of secondary organic aerosols produced in the atmosphere. The work particularly highlights the importance of simulating cluster growth from low-volatility organic compounds to account for atmospheric cloud droplets.
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Ligocki, Mary Peterson. "The scavenging of atmospheric trace organic compounds by rain /." Full text open access at:, 1986. http://content.ohsu.edu/u?/etd,101.
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Price, Benjamin Suresh John. "The atmospheric consequences of the photolysis of carbonyl compounds." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522964.
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Szabó, Emese. "Atmospheric kinetics and photochemistry of oxygenated volatile organic compounds." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10099/document.
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Les composés organiques volatils oxygénés (COVOs) sont des espèces chimiques importantes de l’atmosphère. Ils incluent, par exemple, les alcools aliphatiques, les aldéhydes, les cétones et les acides organiques. Dans la troposphère libre, l’abondance des COVOs est plus importante que celle des hydrocarbures non méthaniques et leur réactivité globale avec OH est comparable avec celle du méthane. En revanche le méthane est présent à une concentration plus élevée. La dégradation des COVOs dans l’atmosphère s’effectue soit par la réaction avec le radical OH, soit par photolyse. La dégradation des COVOs produit des radicaux libres qui vont influencer la capacité oxydante de l’atmosphère, les concentrations en oxydes d’azotes, en radical OH et en ozone troposphérique. L’ozone est le troisième plus important gaz à effet de serre dans l’atmosphère et est l’un des composants toxiques principaux des pollutions urbaines et intervient donc dans des problèmes environnementaux graves comme le réchauffement climatique et la dégradation de la qualité de l’air. L’objectif de ce travail est de contribuer à la compréhension du comportement atmosphérique de quelques COVOs en mesurant leurs paramètres cinétiques et photochimiques apportant des donnés afin de permettre la réalisation de modélisations informatiques et l’amélioration de la connaissance des mécanismes chimiques ayant lieu dans l’atmosphèreOxygenated volatile organic compounds (OVOCs) are important constituents of the atmosphere. They include, e.g., aliphatic alcohols, aldehydes, ketones, and organic acids. In the free troposphere, the abundance of OVOCs is higher than that of the non-methane hydrocarbons and their overall reactivity with OH is comparable with that of methane, in contrast that methane is present in much higher concentration. Degradation of OVOCs in the atmosphere takes place via the reaction with OH radicals and, in the case of photochemically active molecules, via photolysis. Free radicals are formed in the photooxidative degradations of the oxygen containing organics which basically determine the oxidative capacity of the atmosphere, the transformation of nitrogen oxides and the concentration of OH radicals and tropospheric ozone. Ozone is the third most important greenhouse gas in the atmosphere, it is one of the toxic components of urban smog and so it is related to such grave environmental problems as global warming and the quality of air. The aim of this work is to contribute to the understanding of the atmospheric behaviour of a few OVOCs by measuring their kinetic and photochemical parameters. One of the major goals of a laboratory basic research in atmospheric chemistry is to provide kinetic and photochemical data for computer modelling and to deduce atmospheric transformation mechanisms in the case of some important chemicals
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Jiang, Zhaohui. "Atmospheric measurements of a series of volatiles organic compounds." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2014.
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Les composes carbonyles et BTEX (benzène, toluène, éthylbenzène et xylène) sont deux groupes importants de composés organiques volatils (COV) présents dans l'atmosphère. Ils ont une contribution significative à la formation d'oxydants tels que l'ozone, PAN et d'autres photo-oxydants dans la troposphère. En outre, ils ont des effets néfastes sur la santé humaine. Dans ce travail, les concentrations atmosphériques de carbonyles et d’hydrocarbures aromatiques ont été mesurées et quantifiées en utilisant des techniques HPLC et GC-MS sur un site de mesure semi-urbain à Orléans (ICARE, France), de juin 2010 à août 2011. D’autres mesures ont été conduites à Pékin (CAS-RCEES, Chine) du 6 au 28 Juin 2013 en utilisant les mêmes techniques expérimentales. Les résultats obtenus dans ces deux sites sont présentés, comparés et discutésCarbonyls and BTEX (benzene, toluene, ethyl-benzene and xylene) are two important groups of Volatile Organic Compounds (VOCs) present in the atmosphere. They have a significant contribution to the formation of oxidants such as ozone, PAN and other photooxidants in the troposphere. In addition, they have adverse effects on human health. In this work, atmospheric concentrations of carbonyls and aromatic hydrocarbons were measured and quantified using GC-MS and HPLC techniques at a semi-urban site in Orleans (ICARE, France), from June 2010 to August 2011. Urban ambient air sampling was also performed in 6-28th June 2013 in Beijing (RCEES-CAS, China). It has been conducted in order to compare the measured concentrations of the investigated species in two different sites using the same analytical techniques. All results are presented and discussed
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Huang, Xiaofeng. "Formation mechanisms of water-soluble organic compounds in atmospheric aerosols /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202005%20HUANG.
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Lee, Robert George Marlor. "Factors that influence atmospheric concentration of semi-volatile organic compounds." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302364.
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Hunter, James Freeman. "Oxidation of atmospheric organic carbon : interconnecting volatile organic compounds, intermediate-volatility organic compounds, and organic aerosol." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97794.
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Thesis: Ph. D. in Environmental Chemistry, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-110).
.Organic molecules have many important roles in the atmosphere, acting as climate and biogeochemical forcers, and in some cases as toxic pollutants. The lifecycle of atmospheric organic carbon is extremely complex, with reaction in multiple phases (gas, particle, aqueous) and at multiple timescales. The details of the lifecycle chemistry (especially the amount and properties of particles) have important implications for air quality, climate, and human and ecosystem health, and need to be understood better. Much of the chemical complexity and uncertainty lies in the reactions and properties of low-volatility oxidized intermediates that result from the oxidation of volatile organic precursors, and which have received comparatively little study thus far. This thesis describes three projects that link together the entire chain of oxidation (volatile to intermediate to condensed) in an effort to improve our understanding of carbon lifecycle and aerosol production. Laboratory studies of atmospherically relevant aerosol precursors show that the slow oxidation of intermediates is critical to explaining the yield and properties of aerosol under highly oxidized ("aged") conditions, and that the production of organic particles is significantly increased when intermediates are fully oxidized. This aging process is a strong function of molecular structure, and depends on aerosol concentration through the phenomenon of condensational trapping. Further laboratory studies of a series of (poly)cyclic 10 carbon alkanes show that structural effects are largely explained through fragmentation reactions, and that more generally, carbon-carbon bond scission is a ubiquitous and important reaction channel for oxidized intermediates. Finally, direct measurement of oxidized intermediate compounds in field studies shows that these compounds are abundant and important in the ambient atmosphere, with concentrations and properties in between those of volatile and particulate organic compounds. Together with other co-located measurements and complementary techniques, this enables estimates of emission, oxidation, and deposition to be constructed. The results from this thesis can be used to inform more sophisticated models of atmospheric organic carbon cycling, and to improve prediction of organic particulate matter concentrations.
by James Freeman Hunter.
Ph. D. in Environmental Chemistry
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Tang, Apollo Teck Choon. "A computer simulation of polar sunrise ozone depletion in the planetary boundary layer." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ59206.pdf.
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Jacobson, Michael. "Integrated theoretical and experimental studies of organic atmospheric aerosols /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/11594.
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Chan, Man Nin. "Experimental measurements of phase transition and hygroscopic growth of water-soluble organic compounds in atmospheric aerosols /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?EVNG%202004%20CHAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 54-62). Also available in electronic version. Access restricted to campus users.
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Bortoli, Daniele. "Spatram: Spectrometer for atmospheric tracers measurements. A prototype equipment for the monotoring of minor compounds of the atmosphere." Doctoral thesis, Universidade de Évora, 2005. http://hdl.handle.net/10174/11219.
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O presente trabalho desenvolveu-se para atingir dois objectivos; um de vertente tecnológica e o segundo de vertente científica: o primeiro, que visou o desenvolvimento de um novo espectrómetro que opera nas regiões espectrais do ultravioleta (UV) e visível (Vis), com as tecnologias mais avançadas disponíveis, assim como a realização do equipamento e a sua instalação no Centro de Geofísica de Évora (CGE); o segundo objectivo, visou o estudo dos algoritmos da Espectroscopia de Absorção óptica Diferencial (DOAS) e da sua aplicação às medidas espectrais das secções eficazes de absorção de gases traçadores atmosféricos (principalmente dióxido de azoto – NO2 e ozono – 03 presentes na estratosfera) a partir dos quais se pode obter as quantidades colunares desses gases. Finalmente, e ainda inserido nos objectivos científicos, foi possível comparar valores colunares de gases atmosféricos, quimicamente relevantes obtidos a partir de observação à superfície (SPATRAM, com valores correspondentes obtidos a partir de observações de satélite. Foi ainda investigada a relação entre episódios de aerossóis (aerossóis do deserto do Sahara) e os conteúdos colunares de gases traçadores atmosféricos.
O primeiro objectivo da tese de Doutoramento foi completamente alcançado. Os estudos de física da atmosfera e dos diferentes tipos de equipamento usado para efectuar as medições e para a caracterização da radiação solar, permitiram o desenvolvimento de um protótipo, o espectrómetro denominado SPectrometer for Atmospheric TRAcers Measurements (SPATRÁAO. O SPATRAM opera no UV e Vis (250-950nm) com uma resolução típica de 0.5 nm e está equipado com três possíveis entradas da radiação, uma delas correspondente à observação no zénite . O SPATRAM encontra-se instalado no observatório do CGE desde Abril 2004 e é presentemente utilizado para fazer medições da radiação difusa no zénite. Os estudos da metodologia DOAS permitiram a implementação de uma ferramenta para a determinação da concentração ao longo do percurso óptico da medição de alguns dos componentes atmosféricos com características de absorção muito marcadas (principalmente NO2 e 03) na região espectral coberta pelo SPATRAM. Este objectivo foi também atingido e esta ferramenta foi aplicada tanto a medidas espectrais obtidas com o SPATRAM como com um equipamento semelhante (GASCOD - Gas Analyzer Spectrometer Correlating Optical Differences) instalado na Estação Italiana na Antárctica, desde 1995. Foi ainda possível com o desenvolvimento da metodologia DOAS investigara influência das diferentes temperaturas da secção eficaz do mesmo composto.
/Abstract - The goals of this research can be divided in two main subjects: the
technological one, regarding the development of a new UV-Visible spectrometer with
the most advanced available technologies, the realization of the equipment and
is installation at the Geophysics Centre of Évora (CGE). The scientific topic
concerning both the deep studies of the Differential Optical Absorption
Spectroscopy (DOAS) algorithms and their application to the measured spectral data
as well as the measurements and the monitoring of some atmospheric gases (mainly
stratospheric NO2 and 03) and the comparison of the obtained results with satellite data.
In addition, a relation between episodes of aerosol contamination and the content of
atmospheric trace gases is expected to be found.
The first goal of the doctorial project was completely reached. The studies on
the atmospheric physics and on the different types of equipment used for the measurements
and for the characterization of the solar radiation, allowed for the development
of a spectrometer prototype called SPectrometer for Atmospheric TRAcers Measurements
(SPATRAM. The SPATRAM is a multi purpose UV-Vis. Spectrometer (250-950 nm), with a typical
spectral resolution of 0.5nm; it is equipped with three radiation input, one pointing
the zenith direction. The SPATRAM is installed at the CGE Observatory since April 2004
and it is presently utilized to carry-out measurements of the zenith scattered
radiation.
The studies of the DOAS methodology are aimed to the implementation of a tool for the
determination of the Slant Column Density (SCD) of some atmospheric compounds with
marked absorption spectral features (mainly nitrogen dioxide - NO2 and ozone - 03) in the
spectral range covered by SPATRAM. Also this goal was reached, and the tool was applied to
the spectral measurements obtained as with the SPATRAM as well as with similar
equipment (the GASCOD - Gas Analyzer Spectrometer Correlating Optical Differences)
installed at the Antarctic Italian Station since 1995. Also the influence of the
different temperatures of the same absorbers cross section utilized in the retrieval was
investigated.
/Riassunto - Gli obiettivi di questo progetto di ricerca possono essere suddivisi in due diversi tipologia: quella tecnológica che prevede la progettazione, sviluppo e realizzazione di un nuova spettrometro operante nelle regioni spettrali del visibile e delVultravioletto, munito delia piá avanzate soluzioni tecnologiche disponibili e la sua installazione al centro di geofísica dell'Universitá di Evora. L'aspetto scientifico di questa ricerca prevede sia lo studio approfondito degli algoritmi della Spettroscopia ad Assorbimento Ottico Différenziale (DOAS), a la loro applicazione alie serie spettrali misurate con lo spettrometro, sia la misura ed il monitoraggio di alcuni composti minori dell'atmosphera ( principalmente biossido di azoto – NO2, e ozono – 03, in questa prima fase della ricerca) e il confronto dei risultati ottenuti con la strumentazione al suolo con quelli ottenuti da strumenti installati su satelliti. Inoltre, ci si aspetta di ottenere una relazione Ira il contenuto di gas atmosferici ed episodi di contaminazione da particolato (aerosoli).
E primo obiettivo del progetto di dottorato è stato completamente raggiunto. Gli studi condotti sui processi fisici in atmosfera e sui diversi tipi di strumenti utilizzati per Ia misura e la caratterizzazione della radiazione solara, hanno permesso di progettare e realizzare un protótipo di spettrometro che è stato chiamato SPATRAM (SPectrometer for Atmospheric TRAcers Measurements). Al fine di ottenere uno strumento multi funzione lo SPATRAM è dotato di ire diversi ingressi (uno punia direitamente lo zenith con un campo di vista di 1.1-10-5 sr, e due ingressi via fibra ottica), che consistono in una serie di specchi piani e sferici che focalizzano la radiazione in ingresso sulla fenditura dIngresso al monocromatore. SPATRAM è uno spettrometro UV-Vis. che opera nella regione spettrale da 250 a 950nm, con una risoluzione ottica típica di 0.5nm. L'intero intervallo spettrale é indagato in finestre successive di 60nm ognuna, grazie all'uso di un motora passo-passo che variando la posizione del reticolo, modifica Vintervallo spettrale che raggiunge il sensore. Quest'ultimo è un CCD (Charged Coupled Device – dispositivo ad accoppiamento di carita) che permette di ottenere prestazioni molto m~ di quella ottenibili con i rivelatori CMOS (Complementary Metal Oxide Semiconductor). Il maggior vantaggio nell'uso dei CCD risiede nell'alto rapporto segnale rumore che puó essere ottenuto.
Lo SPATRAM è installato all’osservatorio del CGE dal’Aprile dei 2004 ed è attualmente utilizzato per la misura di radiazione solara dessa fungo la verticale.
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Goris, Nadine [Verfasser]. "Singular vector based targeted observations of atmospheric chemical compounds / Nadine Goris." Köln : Universitäts- und Stadtbibliothek Köln, 2010. http://d-nb.info/1013735617/34.
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Allen, Andrew G. "A physico-chemical investigation of atmospheric sulphur, nitrogen and chlorine compounds." Thesis, University of Essex, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235717.
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Abd, Allah Zaenab. "Non-thermal atmospheric pressure plasma for remediation of volatile organic compounds." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/nonthermal-atmospheric-pressure-plasma-for-remediation-of-volatile-organic-compounds(2826f483-e29f-402e-93a7-5f73818c4292).html.
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Non-thermal plasma generated in a dielectric barrier packed-bed reactor has been used for the remediation of chlorinated volatile organic compounds. Chlorinated VOCs are important air pollutant gases which affect both the environment and human health. This thesis uses non-thermal plasma generated in single and multiple packed-bed plasma reactors for the decomposition of dichloromethane (CH2Cl2, DCM) and methyl chloride (CH3Cl). The overall aim of this thesis is to optimize the removal efficiency of DCM and CH3Cl in air plasma by investigating the influence of key process parameters. This thesis starts by investigating the influence of process parameters such as oxygen concentration, initial VOC concentration, energy density, and plasma residence time and background gas on the removal efficiency of both DCM and CH3Cl. Results of these investigations showed maximum removal efficiency with the addition of 2 to 4 % oxygen to nitrogen plasma. Oxygen concentrations in excess of 4 % decreased the decomposition of chlorinated VOCs as a result of ozone and NOx formation. This was improved by adding an alkene, propylene (C3H6), to the gas stream. With propylene additives, the maximum remediation of DCM was achieved in air plasma. It is thought that adding propylene resulted in the generation of more active radicals that play an important role in the decomposition process of DCM as well as a further oxidation of NO to NO2. Results in the single bed also showed that increasing the residence time increased the removal efficiency of chlorinated VOCs in plasma. This was optimized by designing a multiple packed-bed reactor consisting of three packed-bed cells in series, giving a total residence time of 4.2 seconds in the plasma region of the reactor. This reactor was used for both the removal of DCM, and a mixture of DCM and C3H6 in a nitrogen-oxygen gas mixture. A maximum removal efficiency of about 85 % for DCM was achieved in air plasma with the use of three plasma cells and the addition of C3H6 to the gas stream. Nitrogen oxides are air pollutants which are formed as by-products during the decomposition of chlorinated VOCs in plasmas containing nitrogen and oxygen. Results illustrate that the addition of a mixture of DCM and C3H6 resulted in the formation of the lowest concentration of nitric oxide, whilst the total nitrogen oxides concentrations did not increase. A summary of the findings of this work is presented in chapter eight as well as further work. To conclude, the maximum removal efficiency of dichloromethane was achieved in air plasma with the addition of 1000 ppm of propylene and the use of three packed-bed plasma cells in series. The lowest concentration of nitric oxide was formed in this situation.
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Zhu, Lei. "Aqueous phase reaction kinetics of organic sulfur compounds of atmospheric interest." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-11172004-142820/unrestricted/zhu%5Flei%5F200412%5Fphd.pdf.
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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2005.Davis, Douglas, Committee Member ; Huey, Greg, Committee Member ; Nenes, Athanasios, Committee Member ; Weber, Rodney, Committee Member ; Whetten, Robert, Committee Member ; Wine, Paul H., Committee Chair. Includes bibliographical references.
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Thompson, Katherine C. "Aspects of the tropospheric chemistry of halogenated compounds and chlorine atoms." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302490.
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Darbyshire, Megan Louise. "The measurement and transport of volatile organic compounds in the troposphere." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270934.
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Heathfield, Adam Edward. "Potential contributions to global warming from several partially fluorinated ether compounds." Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296566.
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Nagai, M., M. Hori, and T. Goto. "Decomposition and polymerization of perfluorinated compounds in microwave-excited atmospheric pressure plasma." American Institute of Physics, 2005. http://hdl.handle.net/2237/7053.
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Huang, Wei [Verfasser], and S. [Akademischer Betreuer] Norra. "Molecular Level Analysis of Atmospheric Organic Compounds / Wei Huang ; Betreuer: S. Norra." Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/1192373650/34.
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Pongpiajun, Siwatt. "Atmospheric chemistry of semi-volatile organic compounds in urban and rural air." Thesis, Birmingham City University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479120.
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Kleiman, Gary 1969. "Measurement and deduction of emissions of short-lived atmospheric organo-chloride compounds." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/59644.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999.Includes bibliographical references (leaves 84-88).
Atmospheric studies of halogenated organics have centered on long lived halocarbons due to their effect on stratospheric ozone. Now that controls have been put in place to curb emissions of longer lived halocarbons through the Montreal Protocol, and speculation about the safety of many short-lived chlorinated organic molecules has been raised, there has been more consideration given to the efforts aimed at determining the levels of human exposure to all types of halogenated organics. Most previous studies of reactive chlorine compounds have focused solely on quantifying their ambient levels in urban and rural regions. However, for many of these organo-chlorine molecules a detailed knowledge of emissions levels, transport, and final environmental disposition still does not exist. The present work was designed to aid in understanding the emissions patterns for several reactive halogenated organic compounds including trichloromethane (chloroform, CHCl3), trichloroethene (TCE, CHClCCl2), and tetrachloroethene (perchloroethylene, CCl2CCl2). A high temporal frequency (hourly) measurement campaign in Nahant, Massachusetts (approximately 10 km. northeast of Boston) provided automated gas-chromatographic measurements for these species as well as the somewhat more stable 1,1,1 trichloroethane (methyl chloroform, CH3CCl3). Cryogenic preconcentrations, daily calibrations, and weekly linearity tests insure high precision (by Gary Kleiman.
Ph.D.
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Zhang, Yujie. "Atmospheric measurements and degradation mechanisms of a number of volatile organic compounds." Thesis, Orléans, 2012. http://www.theses.fr/2012ORLE2048.
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Les composés organiques carbonylés et les BTEX (Benzène, Toluène, Éthylbenzène et Xylènes) représentent une classe importante de composés organiques volatils dans l’atmosphère. Ils sont émis par des sources anthropogénique et biogéniques. Leur dégradation atmosphérique conduit à la formation d’ozone, de phooxidants et d’aérosols organiques affectant ainsi la qualité de l’air aux échelles locales et régionales ainsi que la santé humaine. Il est donc important de mesurer leurs concentrations et évaluer leur devenir atmosphérique. Dans la présente thèse, nous avons conduit une étude systématique qui a permis de mesurer les concentrations de ces composés et identifier leurs sources à Pékin (Juillet 2008-Août 2010) et évaluer l’importance des caractéristiques météo. Nous avons aussi mené des études sur la dégradation atmosphérique de trois formates (isoproyle, isobutyle et n-propyle) en utilisant la chambre de simulation atmosphérique d’ICARE (CNRS, Orléans)Carbonyls and BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) represent an important class of VOCs (volatile organic compounds) in the atmosphere. They are emitted into the atmosphere through anthropogenic and biogenic sources. Their atmospheric degradation leads to the formation of ozone, photooxidants and organic aerosols affecting the air quality at the local and regional scales and human health. It is, hence, of importance to measure their atmospheric concentrations and investigate their fate. In the present thesis, we have conducted a systematic measurement study of carbonyls and BTEX in Beijing during the period of Jul 2008-Aug 2010 in order to evaluate their ambient levels, possible sources and the influence of characteristic weather conditions. In a separate work, we performed a series of experimental studies on the OH-initiated oxidation of isopropyl formate, isobutyl formate, and n-propyl isobutyrate using the ICARE-CNRS (Orleans) simulation chamber from which we derived the product yields. The data obtained are presented and discussed
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Berlanga, Jesus Alejandro. "Kinetic Modeling of the Atmospheric Photooxidation of Reduced Sulfur and Nitrogen Compounds." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2686.
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Atmospheric aerosols encapsulate a wide variety of particles with different compositions, sizes and sources of origin. They also directly and indirectly affect climate by their interactions with sunlight, clouds, atmospheric chemical species, and even other suspended particles. To understand the atmospheric aerosol processes and the effects they have in global and regional climate is of utmost importance for the future establishment of environmental regulations and emission policies that affect aerosol precursor compounds in an effective and beneficial manner. In particular, aerosols are known to be formed from emissions from human activities, such as fossil fuel burning, agriculture, or concentrated animal feeding operations (CAFOs). Secondary organic aerosols (SOA) constitute a type of atmospheric aerosols that are formed from the atmospheric oxidation of organic compounds that are released from various sources into the atmosphere. Due to the complexity of the atmosphere and variability of its conditions, the direct study of SOA formation is a challenging task, but the implementation of atmospheric chamber facilities to study aerosol formation and growth under controlled conditions has provided a way to study the formation and growth of SOA. However, chamber experiments cannot study specific reactions or individual compounds from the aerosol formation mechanisms in isolation, they can only provide insight on what is produced and what it is produced from, and under what conditions. Thus, kinetic modeling of the mechanisms of gas-phase atmospheric oxidation of the compounds of interest is used to develop reliable and accurate chemical models that will help have precise estimations and determine the mechanisms by which volatile organic compounds interact to produce aerosol particles. Dimethyl sulfide (DMS), dimethyl disulfide (DMDS) and trimethylamine (TMA) are three relevant atmospheric compounds, due to their emissions from many natural and anthropogenic sources and recent studies on emissions of these compounds from animal waste from CAFOs has triggered the interests on the study of SOA formation from these and other similar compounds. In this study, kinetic modeling of the atmospheric oxidation mechanisms of DMDS, DMS and TMA is used to simulate atmospheric chamber studies of aerosol formation to develop accurate models and help determine the mechanisms of aerosol formation.
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Gunawardena, Rohith. "Global distribution of organo-bromine gases /." Full text open access at:, 1989. http://content.ohsu.edu/u?/etd,245.
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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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Vimal, Deepali. "Laboratory investigations of the hydroxyl radical-initiated oxidation of atmospheric volatile organic compounds." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3324041.
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Thesis (Ph.D.)--Indiana University, School of Public and Environmental Affairs, 2008.Title from PDF t.p. (viewed on May 13, 2009). Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4637. Adviser: Philip S. Stevens.
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Roddis, Tristan. "A laboratory investigation of the heterogeneous reactions of atmospheric halogen and nitrogen compounds." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266730.
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Broomfield, Mark. "Spectra, kinetics and mechanisms of organic sulphur radicals and compounds of atmospheric interest." Thesis, University of York, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316167.
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Zhou, Li. "Atmospheric chemistry of NO₃ : reactions with a series of organic and inorganic compounds." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2055/document.
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Le radical nitrate NO₃ est un intermédiaire clé dans la chimie atmosphérique nocturne. Il peut réagir avec un certain nombre de composés organiques volatils (COV) initiant leur dégradation pendant la nuit. Dans cette thèse, la cinétique de NO₃ avec plusieurs de ces composés a été étudiée à température ambiante (298 ± 2K) et à pression atmosphérique (1000 ± 5 hpa) dans une chambre de simulation atmosphérique en Téflon(ICARE-7300L) couplée à des outils analytiques tels que : FTIR, PTR-ToF-MS and CRDS etc. Nous avons déterminé les constantes de vitesse pour les réactions du radical NO3 avec sept esters de méthacrylate à température ambiante: méthacrylate de méthyle, méthacrylate d'éthyle, méthacrylate de propyle,méthacrylate d'isopropyle, méthacrylate de butyle, méthacrylate d'isobutyle, méthacrylate de méthyle deutéré. Les résultats obtenus, suggèrent que la réaction de NO₃ avec les esters de méthacrylate procède par addition sur la double liaison du groupe méthacrylate. Ensuite, une méthode absolue a été utilisée pour déterminer les constantes de vitesse de réaction de NO₃ avec une série d'alcanes et de gaz inorganiques importants dans les processus atmosphériques : le méthane, l'éthane, le pentane, le n-butane, l’isobutane, le2, 3-diméthylbutane, le cyclopentane, le cyclohexane, l'oxyde nitreux, le monoxyde de carbone et le dioxyde de soufre. Avec l’ensemble des données cinétiques obtenues, les durées de vie atmosphériques de ces composés vis à vis des radicaux NO₃ ont été calculées et comparées à celles déterminées pour d’autres oxydants de l’atmosphère. Ces résultats améliorent également les connaissances de base sur les réactions impliquant le radical NO₃NO₃ is a key intermediate in the chemistry of the night-time atmosphere. NO₃ radical can react with anumber of VOCs initiating their night-time degradation. In this thesis, the kinetics of NO₃ with different kinds of compounds was studied at room temperature (298 ± 2 K) and atmospheric pressure (1000 ± 5 hpa) in a Teflon simulation atmospheric chamber (ICARE-7300L) coupled to analytical tools including Fourier Transform Infrared Spectroscopy, Proton Transfer Reaction-Time of Flight-Mass Spectrometer and CavityRing Down Spectrometer etc. The rate coefficients for the reactions of NO₃ radical with seven methacrylate esters are firstly reported: methyl methacrylate; ethyl methacrylate; propyl methacrylate; isopropylmethacrylate, butyl methacrylate, isobutyl methacrylate, and deuterated methyl methacrylate. The trends in the measured rate coefficient with the length and nature of the alkyl group strongly suggest that the reaction proceeds via addition to the double bond on the methacrylate group. Then, an absolute method was used to determine the upper limits or rate coefficients for the reactions of NO₃ radicals with a series of alkanes and some important inorganic gases: methane, ethane, pentane, n-butane, iso-butane, 2,3-dimethybutane,cyclopentane, cyclohexane, nitrous oxide, carbon monoxide and and sulfur dioxide. With the obtained kinetics data, the atmospheric lifetimes of these compounds toward NO₃ radicals were calculated and compared with those due to loss via reactions with the other major atmospheric oxidants. The kinetics results also enhance the available database on NO₃ reactions
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Storey, John Morse Elliot. "Gas/particle partitioning of semi-volatile organic compounds to model atmospheric particulate material /." Full text open access at:, 1993. http://content.ohsu.edu/u?/etd,647.
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Schofield, Daniel Paul, and n/a. "Hydrated complexes in the earth�s atmosphere." University of Otago. Department of Chemistry, 2005. http://adt.otago.ac.nz./public/adt-NZDU20070427.120933.
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The interaction between sunlight and our atmosphere is one of the most fundamental processes affecting weather and climate. The majority of the Sun�s radiation is produced in the ultraviolet, visible and near-infrared regions of the electromagnetic spectrum. These spectral regions correspond to the energies of vibrational overtone and electronic transitions. The composition of our atmosphere is complex, and many trace species have a large influence on its chemistry and dynamics. Hydrogen bound hydrated complexes are trace species that could play an important role in the Earth�s atmosphere. However, before this role can be quantified, spectral identification and characterisation of these complexes is essential.
We have developed vibrational local mode Hamiltonians to simulate the absorption spectra of hydrated complexes. To test the approximations made in the vibrational model, we have peformed calculations on the diatomics OH, HF and CO, which can be considered to act as pure local modes. When highly correlated ab initio methods and large basis sets are used to calculate the potential energy and dipole moment curve, the simulated vibrational transitions of the diatomics are in excellent agreement with experiment.
We have derived approximate vibrational Hamiltonians which describe the OH-stretching and HOH-bending modes of vibration in the complexes H₂O�H₂O, H₂O�HO₂ and H₂O�HO. The calculated spectrum of H₂O�H₂O has been used to assess its atmospheric importance, and to succesfully guide experimental efforts to detect H₂O�H₂O in the laboratory and the Earth�s atmosphere. The calculated transition energies and intensities of H₂O�H₂O and H₂O�HO are in good agreement with experimental matrix isolation and gas-phase studies.
To investigate the effect of low frequency modes on OH-stretching overtone spectra we have simulated the spectrum of HOONO. We have derived a Hamiltonian that couples the NOOH-torsional mode to the high frequency OH-stretching and OOH-bending modes. The simulated spectrum is in good agreement with the experimentally observed spectrum. We find that the OH-stretching spectra are perturbed strongly only if the barrier to torsion is low.
We have also investigated changes in the electronic spectrum of hydrated complexes and the corresponding parent monomers. Upon complex formation, the lowest-lying electronic transition in the hydroxyl radical is strongly redshifted outside the region of monomeric absorption.
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Johnson, David. "The kinetics and mechanisms of the gas-phase reactions of ozone with unsaturated compounds." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340021.
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Slater, Daniel. "Predicting the impacts of cloud processing on aerosol properties /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10175.
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Sartin, John Henry. "Volatile organic compounds in the maritime atmosphere at Mace Head, Ireland : C8-C16 n-alkanes and oxygenates." Thesis, Lancaster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289049.
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Miya, Senzo Simo. "Atmospheric pressure metal-organic vapour phase epitaxial growth of InAs/GaSb strained layer superlattices." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020866.
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The importance of infrared (IR) technology (for detection in the 3-5 μm and 8-14 μm atmospheric windows) has spread from military applications to civilian applications since World War II. The commercial IR detector market in these wavelength ranges is dominated by mercury cadmium telluride (MCT) alloys. The use of these alloys has, however, been faced with technological difficulties. One of the materials that have been tipped to be suitable to replace MCT is InAs/InxGa1-xSb strained layer superlattices (SLS’s). Atmospheric pressure metal-organic vapour phase epitaxy (MOVPE) has been used to grow InAs/GaSb strained layer superlattices (SLS’s) at 510 °C in this study. This is a starting point towards the development of MOVPE InAs/InxGa1-xSb SLS’s using the same system. Before the SLS’s could be attempted, the growth parameters for GaSb were optimised. Growth parameters for InAs were taken from reports on previous studies conducted using the same reactor. Initially, trimethylgallium, a source that has been used extensively in the same growth system for the growth of GaSb and InxGa1-xSb was intended to be used for gallium species. The high growth rates yielded by this source were too large for the growth of SLS structures, however. Thus, triethylgallium (rarely used for atmospheric pressure MOVPE) was utilized. GaSb layers (between 1 and 2 μm thick) were grown at two different temperatures (550 °C and 510 °C) with a varying V/III ratio. A V/III ratio of 1.5 was found to be optimal at 550 °C. However, the low incorporation efficiency of indium into GaSb at this temperature was inadequate to obtain InxGa1-xSb with an indium mole fraction (x) of around 0.3, which had previously been reported to be optimal for the performance of InAs/InxGa1-xSb SLS’s, due to the maximum splitting of the valence mini bands for this composition. The growth temperature was thus lowered to 510 °C. This resulted in an increase in the optimum V/III ratio to 1.75 for GaSb and yielded much higher incorporation efficiencies of indium in InxGa1-xSb. However, this lower growth temperature also produced poorer surface morphologies for both the binary and ternary layers, due to the reduced surface diffusion of the adsorbed species. An interface control study during the growth of InAs/GaSb SLS’s was subsequently conducted, by investigating the influence of different gas switching sequences on the interface type and quality. It was noted that the growth of SLS’s without any growth interruptions at the interfaces leads to tensile strained SLS’s (GaAs-like interfaces) with a rather large lattice mismatch. A 5 second flow of TMSb over the InAs surface and a flow of H2 over GaSb surface yielded compressively strained SLS’s. Flowing TMIn for 1 second and following by a flow of TMSb for 4 seconds over the GaSb surface, while flowing H2 for 5 seconds over the InAs surface, resulted in SLS’s with GaAs-like interfacial layers and a reduced lattice mismatch. Temperature gradients across the surface of the susceptor led to SLS’s with different structural quality. High resolution x-ray diffraction (HRXRD) was used to determine the thicknesses as well as the type of interfacial layers. The physical parameters of the SLS’s obtained from simulating the HRXRD spectra were comparable to the parameters obtained from cross sectional transmission electron microscopy (XTEM) images. The thicknesses of the layers and the interface type played a major role in determining the cut-off wavelength of the SLS’s.
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Yoshida, Yasuko. "Global sources and distribution of atmospheric methyl chloride." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-06232006-151220/.
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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.Robert Dickinson, Committee Member ; Athanasios Nenes, Committee Member ; David Tan, Committee Member ; Armistead Russell, Committee Member ; Yuhang Wang, Committee Chair.
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Chadwick, Michael Andrew Joseph. "Effects of Nitrogen Deposition and Flow Permanence on Stream Organic Matter Dynamics." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/ChadwickMAJ2003.pdf.
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Shaw, Jacob T. "Multivariate relative rate measurements of reactions between volatile organic compounds (VOCs) and atmospheric radicals." Thesis, University of York, 2018. http://etheses.whiterose.ac.uk/21989/.
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Knowledge of the reactions between VOCs and atmospheric radicals and oxidants is fundamental to understanding atmospheric chemistry and the formation of air pollution in urban environments. This work describes the development of a new experimental technique for the simultaneous measurement of gas-phase rate coefficients for reactions between multiple VOCs and different atmospheric radicals. The technique is based on the traditional relative rate approach and succeeds in markedly increasing the rate of throughput of target reactions; an improvement necessary when considering the vast number of organic compounds observed in the atmosphere for which experimental oxidation data are not available. New rate coefficients are derived using a suite of the available kinetic literature as reference reactions to calibrate the results over a range of reactivity, thereby reducing the reliance on any single rate coefficient value. This new multivariate method was applied to mixtures containing multiple VOCs with a range in functionalities and under different experimental conditions. Two different atmospherically relevant radicals were tested (OH and Cl) and the technique was adapted to allow for temperature controlled measurements. Rate coefficients for the reactions of eight VOCs (1,2-, 1,3- and 1,4-diethylbenzene, n-pentylbenzene, 2-methylheptane, 2-methylnonane, ethylcyclohexane and 2,3-dimethylpent-1-ene) with OH at room temperature were derived for the first time. Rate coefficients for the reactions of 44 other VOCs with OH were also assessed concurrently with the derivation of these eight new results. A rate coefficient for the reaction between 2-methylheptane and Cl was measured for the first time, alongside the measurement of rate coefficients for the reactions of seven other VOCs with Cl.
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Lee, Alex King Yin. "Investigation of heterogeneous reactions of organic aerosols using single particle levitation and Raman spectroscopy /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CBME%202009%20LEE.
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Waterman, Daniel Stephen. "Electron spin resonance studies of transient radicals from VOCs." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361406.
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Baasandorj, Munkhbayar. "Experimental and theoretical studies of the kinetics of the hydroxyl radical-initiated oxidation of oxygenated volatile organic compounds." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3297937.
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Thesis (Ph. D.)--Indiana University, School of Public and Environmental Affairs, 2008.Title from dissertation home page (viewed Sept. 30, 2008). Source: Dissertation Abstracts International, Volume: 69-03, Section: B, page: 1537. Adviser: Philip S. Stevens.