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Dissertations / Theses on the topic 'Gaseous environment'
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Bremer, Malcolm Neal. "The gaseous environment of quasars." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281988.
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Chaves, Tara A. "Neutral hydrogen in NGC 2613, probing the dynamic gaseous environment of spiral galaxies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63280.pdf.
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Torresi, Eleonora <1981>. "The gaseous environment of radio galaxies: a new perspective from high-resolution x-ray spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3820/1/Torresi_Eleonora_tesi.pdf.
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It is known that massive black holes have a profound effect on the evolution of galaxies, and possibly on their formation by regulating the amount of gas available for the star formation. However, how black hole and galaxies communicate is still an open problem, depending on how much of the energy released interacts with the circumnuclear matter.
In the last years, most studies of feedback have primarily focused on AGN jet/cavity systems in the most massive galaxy clusters. This thesis intends to investigate the feedback phenomena in radio--loud AGNs from a different perspective studying isolated radio galaxies, through high-resolution spectroscopy. In particular one NLRG and three BLRG are studied, searching for warm gas, both in emission and absorption, in the soft X-ray band. I show that the soft spectrum of 3C33 originates from gas photoionized by the central engine. I found for the first time WA in 3C382 and 3C390.3. I show that the observed warm emitter/absorbers is not uniform and probably located in the NLR.
The detected WA is slow implying a mass outflow rate and kinetic luminosity always well below 1% the L(acc) as well as the P(jet).
Finally the radio--loud properties are compared with those of type 1 RQ AGNs.
A positive correlation is found between the mass outflow rate/kinetic luminosity, and the radio loudness.
This seems to suggest that the presence of a radio source (the jet?) affects the distribution of the absorbing gas.
Alternatively, if the gas distribution is similar in Seyferts and radio galaxies, the M(out) vs rl relation could simply indicate a major ejection of matter in the form of wind in powerful radio AGNs.
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Torresi, Eleonora <1981>. "The gaseous environment of radio galaxies: a new perspective from high-resolution x-ray spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3820/.
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It is known that massive black holes have a profound effect on the evolution of galaxies, and possibly on their formation by regulating the amount of gas available for the star formation. However, how black hole and galaxies communicate is still an open problem, depending on how much of the energy released interacts with the circumnuclear matter.
In the last years, most studies of feedback have primarily focused on AGN jet/cavity systems in the most massive galaxy clusters. This thesis intends to investigate the feedback phenomena in radio--loud AGNs from a different perspective studying isolated radio galaxies, through high-resolution spectroscopy. In particular one NLRG and three BLRG are studied, searching for warm gas, both in emission and absorption, in the soft X-ray band. I show that the soft spectrum of 3C33 originates from gas photoionized by the central engine. I found for the first time WA in 3C382 and 3C390.3. I show that the observed warm emitter/absorbers is not uniform and probably located in the NLR.
The detected WA is slow implying a mass outflow rate and kinetic luminosity always well below 1% the L(acc) as well as the P(jet).
Finally the radio--loud properties are compared with those of type 1 RQ AGNs.
A positive correlation is found between the mass outflow rate/kinetic luminosity, and the radio loudness.
This seems to suggest that the presence of a radio source (the jet?) affects the distribution of the absorbing gas.
Alternatively, if the gas distribution is similar in Seyferts and radio galaxies, the M(out) vs rl relation could simply indicate a major ejection of matter in the form of wind in powerful radio AGNs.
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Merlin, Jérémie. "Study of long-term sustained operation of gaseous detectors for the high rate environment in CMS." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE005/document.
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Le spectromètre à muons de CMS doit permettre l'identification rapide et efficace des muons produits lors des collisions proton-proton au LHC. Cependant, à cause d'un environnement de détection extrême, seules les chambres à pistes cathodiques équipent actuellement les bouchons de CMS. Cette faiblesse dans le système de détection pourrait devenir problématique après l'amélioration du LHC. L'augmentation du taux de particules dans les bouchons va dégrader les performances du système de déclenchement L1 ainsi que l'efficacité de sélection des phénomènes physiques intéressants. Le but du programme d'amélioration de CMS est de maintenir le taux de déclenchement L1 tout en gardant une efficacité de sélection maximale. La collaboration CMS GEM propose d'équiper les régions vacantes des bouchons avec des détecteurs basés sur la technologie d'amplification des électrons dans un gaz (GEM), appelés GE1/1. Le sujet de thèse proposé par la collaboration CMS GEM a pour but de justifier le choix de la technologie GEM pour l'amélioration de CMS. Trois projets ont été suivis pendant la thèse. La première partie du projet de thèse consistait à mesurer précisément les caractéristiques fondamentales et les performances de détection des détecteurs triple-GEM produit par la technique simple-masque. Ces éléments sont essentiels pour s'assurer que les détecteurs GE1/1 pourront fonctionner en toute sécurité dans l'environnement des bouchons de CMS. Le deuxième projet consistait à prouver que les excellentes performances des détecteurs GE1/1 ne vont pas se dégrader pendant leur utilisation dans CMS. Cette étape comprend l'étude du fonctionnement à long terme des détecteurs GE1/1, en particulier le phénomène de vieillissement, qui inclue tous les processus physiques et chimiques qui provoquent la dégradation graduelle et permanente des performances de détection. Plusieurs tests de vieillissement ont été menés dans des zones d'irradiations spécifiques au CERN pour reproduire un minimum de 10 ans de fonctionnement réel dans l'environnement de CMS après la montée en puissance du LHC. Enfin, les excellentes propriétés mesurées lors de la phase de R&D ont permis de valider la technologie triple-GEM, qui fut ensuite approuvée par la collaboration CMS et le comité du LHC. La production de 144 grands détecteurs GE1/1 sera partagée entre différents sites de production à travers le monde. Le troisième projet de thèse fut donc le développement des principales étapes du contrôle qualité nécessaire pour assurer une production uniforme et une même qualité pour tous les détecteurs GE1/1The muon system of CMS aims to provide an efficient and fast identification of the muons produced in the proton-proton collisions. However, the forward region of the end-caps is only instrumented with Cathode Strip Chambers. This lack of redundancy will be problematic after the high-luminosity upgrade of the LHC (HL-LHC), for which the increase of the background rate would degrade the Level-1 trigger performance and thus the selection of interesting physics channels. The goal of the CMS muon upgrade is to maintain the L1 trigger rate with maximum selection efficiency in order to fully exploit the HL-LHC. The CMS GEM Collaboration has proposed to instrument the vacant highetaregion of the muon end-caps with Gas Electron Multiplier (GEM) detectors, called GE1/1chambers.The Ph.D. subject proposed by the CMS GEM Collaboration aims to demonstrate that the GE1/1technology is the most suitable choice for the upgrade of the muon end-caps. Three main researchprojects were conducted in this context. The first project included the precise measurement of the fundamental characteristics and the detection performance of the triple-GEM detectors produced with the single-mask technique. Those characteristics are essential to ensure that the detectors can operate in the forward region of CMS. The second project was focused on the long-term operation of GE1/1 detectors, in particular the study of the aging phenomenon, which includes all the processes that lead to a significant and permanent degradation of the performance of the detectors. Several aging tests were performed at the CERN irradiation facilities to prove that the GE1/1 chambers can operate during at least 10 yearsat HL-LHC without suffering from performance losses. The excellent properties measured during the R&D phase led to the approval of the GE1/1 project by the CMS Collaboration. The third project, conducted in the framework of the mass production,consisted of developing of the main steps of the Quality Control of the GE1/1 chambers
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Zhang, Yunbo. "Effect of microstructure on oxidative wear of a dual-phase low-alloy steel under different gaseous atmospheres, sliding speeds, and oxidation temperatures." Electronic Thesis or Diss., Compiègne, 2022. http://www.theses.fr/2022COMP2699.
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Le comportement tribologique des aciers à double phase a été étudié aux effets de différentes fractions volumiques de martensite (MVF), d'environnements gazeux et de vitesses de glissement, à l'aide d'un tribomètre à bille sur disque, dans des conditions de charge constante et de glissement par friction sèche. Par ailleurs, le comportement tribologique des couches d'oxyde formées à différentes températures et MVF a été étudié par nanoindentation et par des expériences de grattage. Les expériences de glissement à sec ont démontré qu'une MVF plus faible, des vitesses de glissement plus élevées et des environnements CO2 réduisent considérablement les taux d'usure en raison d'une meilleure oxydation ainsi que de la formation de couches d'oxyde protectrices sur les surfaces usées. Les essais de grattage des couches d'oxyde ont montré que le taux d'usure des couches d'oxyde de même composition diminuait à mesure que le MVF augmentait. La résistance à l'usure de la couche d'oxyde dominée par FeO est la plus mauvaise. Dans les mêmes conditions, la couche d'oxyde formée sur la martensite présente une résistance spécifique à l'usure plus élevée que celle formée sur la ferriteThe tribological behavior of dual-phase steels was investigated at the effects of different martensite volume fraction (MVF), gaseous environments, and sliding velocities, using a ball-on-disk tribometer, under constant load and dry friction sliding conditions. Furthermore, the tribological behavior of oxide layers formed at different temperatures and MVF was investigated by nanoindentation and scratching tests. Dry sliding experiments demonstrated that lower MVF, higher sliding velocities, and CO2 environments significantly reduce wear rates due to improved oxidation as well as the formation of protective oxide layers on the worn surfaces. Scratch tests of oxide layers revealed that the wear rate of same composition oxide layers decreased with increasing MVF. The wear resistance of the FeO-dominated oxide layer is the worst. Under the same conditions, the oxide scale formed on martensite has higher specific wear resistance than that formed on ferrite
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Wilman, Richard John. "The gaseous environments of powerful active objects." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.622002.
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RAGUSA, ENRICO. "THE EVOLUTION OF BINARY SYSTEMS IN GASEOUS ENVIRONMENTS." Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/604177.
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Systems where a binary, that is two gravitationally bound objects orbiting their centre of mass, interacts with the surrounding gas or dust are extremely common in the Universe and involve a wide variety of different astrophysical objects (star + star, black hole + black hole, star + planet, or planet + moon). Among them, protoplanetary systems and black hole binaries (BHBs) are currently capturing the attention of the scientific community.
Despite their very different nature and EM appearance, both protoplanetary and BHB systems are characterized by the presence of a gaseous accretion disc surrounding the binary. As a consequence, the dynamics of these systems is very similar and can be described in one unique theoretical framework: the disc-satellite interaction theory.
This project is meant to deepen our knowledge of the theory of circumbinary discs, approaching it in a multidisciplinary way from both the protoplanetary and the BHBs perspective.
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Maheras, Anastasia Francis. "Elemental and reactive gaseous mercury deposition and diurnal cycles over terrestrial environments." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/114365.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 88-93).
The atmospheric component of the global biogeochemical mercury cycle was studied to determine the mechanisms behind diurnal trends and amplitudes in elemental and reactive gaseous mercury concentrations over terrestrial environments. This analysis was done using the 3D GEOS-Chem chemical transport model and the creation of a simple one-box model. Mercury is a significant neurotoxin for humans and other species that has been addressed in the policy realm on both national and international levels. Being able to model atmospheric mercury processes correctly is an important part of regulation and policy drafting. GEOS-Chem model results were compared with Weiss-Penzias et al. [2009] measurements for three Nevada, USA sites. The magnitude of elemental mercury concentrations differed by 0.07-0.2 ng/m3 , with GEOS-Chem underestimating concentrations due to an under-representation of mercury emissions at naturally enriched sites. The amplitude of reactive gaseous mercury diurnal variations differed by a factor of 3-4, with GEOS-Chem underestimating the diurnal trend. Based on the diurnal nature of this error, it is hypothesized that GEOS-Chem under represents the magnitude of elemental mercury emissions, the amount of oxidation occurring in the atmosphere, and the scale of entrainment from the free troposphere.
by Anastasia F. Maheras.
S.B.
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O'Driscoll, Nelson James. "Dissolved gaseous mercury dynamics and mercury volatilization in freshwater lakes." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/29035.
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This thesis examines the production and distribution of dissolved gaseous mercury (DGM) in freshwater ecosystems and its relationship to mercury volatilization. The importance of volatilization was assessed within a multidisciplinary mercury mass balance for Big Dam West Lake (BDW) Kejimkujik Park, Nova Scotia. The magnitude of volatilization was found to be approximately double the direct wet deposition over lake and wetlands, and 27% of the direct wet deposition to the terrestrial catchment. Over the entire basin area the mass of mercury volatilized is 46% of the mass deposited by wet deposition.
A new method of continuous (5 minute) DGM analysis was developed and tested. The detection limit for DGM was 20 fmol L-1 with 99% removal efficiency. Control experiments showed that there was no interference due to methyl mercury, which is present in similar concentrations to DGM. Experiments comparing continuous DGM analysis with discrete DGM analysis showed that the results are not significantly affected by typical variations in water temperature (4--30°C), oxidation-reduction potential (135--355 mV), dissolved organic carbon (4.5--10.5 mg L-1), or pH (3.5--7.8). The continuous analysis was within 4.5% of the discrete analysis when compared across 12 samples analyzed in triplicate.
Diurnal patterns for dissolved gaseous mercury (DGM) and mercury flux were measured (using this new DGM method and a Teflon flux chamber method) in two lakes with contrasting dissolved organic carbon (DOC) concentrations in Kejimkujik Park, Nova Scotia. Consistently higher DGM concentrations were found in the high DOC lake as compared to the low DOC lake. Cross-correlation analysis indicated that DGM dynamics changed in response to solar radiation with lag-times of 65 and 90 minutes. An examination of current mercury flux models using this quantitative data indicated some good correlations between the data and predicted flux (r ranging from 0.27 to 0.83) but generally poor fit (standard deviation of residuals ranging from 0.97 to 3.38). This research indicates that DOC and wind speed may play important roles in DGM and mercury flux dynamics that have not been adequately accounted for in current predictive models.
The distribution of DGM in the water columns of shallow and deep freshwater lakes was investigated in Lake Ontario and several small freshwater lakes. When DGM concentrations were expressed on an areal basis, DGM concentrations above the thermocline in Lake Ontario average 1.5 ng m-2 and in small freshwater lakes it ranged between 0.1 and 0.8 ng m -2. Further, it was demonstrated that the majority of DGM in large freshwater lakes such as Lake Ontario exists below the thermocline where photochemical oxidation and reduction processes cannot occur. The depth profiles indicate that vertical mixing in the water column may alter the DGM concentration in the upper epilimnion, and that turn over in deep lakes may result in a transfer of large concentrations of DGM from the hypolimnion into the epilimnion. In addition, the results indicate that microbial processes may be an important factor regulating DGM in the water column of freshwater lakes, particularly in the hypolimnion. (Abstract shortened by UMI.)
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Morgan, Scott Warwick. "Gaseous secondary electron detection and cascade amplification in the environmental scanning electron microscope /." Electronic version, 2005. http://adt.lib.uts.edu.au/public/adt-NTSM20060511.115302/index.html.
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Renninger, Neil Stephen. "Modeling cometabolic in situ groundwater bioremediation utilizing gaseous nutrient and substrate delivery." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/9922.
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Ekpe, Ngozi Chinwe. "Novel co-precipitated oxygen carriers for chemical looping combustion of gaseous fuel." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39557/.
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Carbon Capture and Storage (CCS) is one option to meet the increasing energy demand as well as reduce net CO2 emissions to the atmosphere. Chemical Looping Combustion (CLC) is a promising CCS technology proposed to meet the challenge of mitigating the carbon dioxide (CO2) emissions. CLC process can be based on interconnected fluidized beds, consisting of air reactor, fuel reactor and oxygen carrier (OC) which undergoes redox reactions while it circulates between the reactors. The main products are CO2 and water, thus eliminating the need of an additional energy intensive CO2 separation. The feasibility of CLC depends on the oxygen carrier's (OC) ability to transfer O2 from air reactor to fuel reactor and have sufficient oxygen capacity, high reactivity and withstand a high number of redox cycles without significant loss in performance. OCs based on transition metal oxides of Cu, Co, Fe, Mn and Ni has been explored. Nevertheless, research is focused on improving the OCs performance with the aim to overcome their various practical limitations. Mechanical mixing and impregnation which fails to provide a high degree of dispersion and high metal loading respectively are commonly used for OC synthesis. Very few works have been reported for Mn-oxide and co-precipitated oxygen carriers. The few studies on co-precipitated OCs mainly use strong base as precipitants. One drawback to this is the repetitive washing of precipitate to remove excess alkali ions and controlled loading of active components cannot be easily obtained. In this study, weak base instead of strong base was used in the synthesis of OCs. This is the first time this controlled approach has been applied to prepare oxygen carrier in CLC for manganese and iron. This thesis is a novel research on development and detailed investigation of co-precipitated Mn-oxide and Fe-oxide OCs with ZrO2 and combined ZrO2–CeO2 support. The reaction kinetics, stability and oxygen transfer capacity (OTC) of the OCs were studied by TGA up to 1173 K in H2, CO and CH4. Characterization of physical and chemical structures of particles was obtained by SEM-EDX, XRD, BET and pycnometer. The result reveals that regardless of the composition of the co-precipitated oxygen carriers, there was no interaction of the metal oxides with the support material which could have altered the thermodynamics of the redox system. Furthermore, co-precipitated Mn/Zr and Fe/Zr OCs were more reactive than their counterpart prepared by impregnation and mechanical mixing. Also, changes in reactivity and OTC suggest that the synergistic effect varies with ratios of the single oxides in the bimetallic OCs. Co-precipitated Mn-rich oxygen carriers were more reactive than Fe-rich OCs. Interestingly, OCs with zirconia-ceria support exhibited activation tendency behaviour. Moreover, the use of combined zirconia-ceria for bimetallic Mn-Fe oxide reversed the characteristic progressive decrease in the performance of the OC with equimolar composition. For co-precipitated Mn-Fe Oxide oxygen carriers, zirconia content of 44 wt. % is sufficient to maintain the mechanical integrity of the particles during redox reactions compared to a zirconia content of 20 wt. %. This research has resulted in the development of highly reactive and stable oxygen carriers, which are promising for CLC. Mn/Zr OC reached full conversion in less than 48 secs and bimetallic Mn-Fe OCs reached 30% conversion in less than 43 secs in CH4 and maintained stability in a thirty multicycle test. The redox reaction kinetics of the most reactive oxygen carrier using CH4, H2, CO and air was investigated at isothermal conditions (973-1173 K) to determine the kinetic parameters. Models of the reduction and oxidation reactions were selected by using a model fitting method. The nucleation model was the most statistically significant and suitable model for describing the reduction and oxidation behaviour of the oxygen carrier. The values of activation energy obtained for the reduction reaction in CH4, H2 and CO were 142.8 KJ/mol, 32.95 KJ/mol and 26.37 KJ/mol respectively. Whereas, for the oxidation reaction, the activation energy obtained using air was 28.83 KJ/mol. In the application of co-precipitation technique for the synthesis of multicomponent materials, a heterogeneous product could be obtained from using improper preparation conditions. Results from this research have demonstrated that, the application of the well-designed co-precipitation procedure effectively produced composite materials (up to four co-precipitated mixed metal oxides) with controlled compositions and homogeneous dispersion. Furthermore, this study provides insight into the fundamental behaviours of co-precipitated manganese and iron based oxygen carriers to aid the design and optimization of future materials development.
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Wilson, Sam T. "The production of biogenic gases in the marine environment." Thesis, Open University, 2007. https://pure.uhi.ac.uk/portal/en/studentthesis/the-production-of-biogenic-gases-in-the-marine-environment(932c755e-35e5-46f0-823d-426afa30d3a2).html.
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The biogenic trace gases dimethylsulphide (DMS) and methane play a major role in the Earth’s climate and atmospheric chemistry. DMS makes a significant negative contribution to radiative forcing and methane is an important greenhouse gas. The marine environment is an important source of both DMS and methane and this thesis investigated the interactions between methylated sulphur compounds and methanogenesis within micro-environments in the upper-water column. The production of DMS is closely associated with dimethylsulphoniopropionate (DMSP) and dimethylsulfoxide (DMSO) although comparatively little is known about the dynamics of DMSO in the marine environment. This study analysed the production of DMSO by a range of marine phytoplankton species in comparison with DMSP. Algal concentrations of DMSO were taxon-dependent and an average DMSPp:DMSOp ratio of 4.85 was calculated for the phytoplankton species analysed. The consistent presence of DMSO at ~20 % of total intracellular methylated sulphur (DMSP + DMSO) suggests it is an important algal consituent. The fate of DMSP and DMSO produced by algal cells was analysed in a series of grazing experiments with the copepods Temora longicornis and Acartis clausi, and the dinoflagellate Scrippsiella trochoidea. The relative importance of assimilation, sloppy feeding, DMS production and excretion of faecal pellets as sinks for algal-DMSP was calculated. In comparison to the ambient marine environment, both algal cells and copepod faecal pellets were identified as micro-habitats of elevated DMSP and DMSO concentrations. Millimolar concentrations of DMSP were measured in algal cells and micromolar concentrations of DMSP were recorded in copepod faecal pellets. These hotspots of DMSP and DMSO may be associated with chemical processes that differ from bulk seawater characteristics, such as the transformation of DMSO as revealed in coastal pelagic particulate material. Furthermore, oxygen depletion at the micro-scale could facilitate the presence of anaerobic bacteria, or anaeorobic bacterial activity, in the predominantly aerobic pelagic environment. The occurrence of methanogenic Archaea specifically associated with copepod faecal pellets from mono-species cultures of copepods, environmental samples and total pelagic particulates was investigated using 16S rRNA gene libraries. Clusters of sequences closely related to Methanogenium, Methanobacterium and Methanolobus were recovered. This work revealed that CO2-reducing methanogens can exist in the pelagic environment where it was previously assumed methylotrophic methanogenesis dominated. This work demonstrated that the methylated sulphur compounds represent a metabolic substrate for methanogens in the upper water column. The addition of DMSP, DMSO and DMS to samples collected from the upper water column stimulated methanogenesis when incubated under anaerobic conditions. The addition of inhibitors suggest that other anaerobic bacteria e.g. sulphate-reducing bacteria, may play a key role in this process. The potential for DMSP and DMSO to serve as precursors for methane, a potent greenhouse gas, as well as DMS, has important implications when considering the emissions of these compounds from the marine environment and their role in the Earth’s climate.
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Boereboom, Thierry. "Greenhouse gases investigations in ice from periglacial environments." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209673.
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L’environnement périglaciaire en général et les régions de permafrost en particulier, connus pour être très sensibles au changement climatique actuel, sont le sujet de beaucoup d’études sur les émissions de gaz à effet de serre. En effet, le dégel de ces milieux engendre la mobilisation d’une quantité importante de matière organique, précédemment piégée par le froid, favorisant les émissions de dioxyde de carbone et/ou de méthane. L’objectif premier, du présent travail, est de contribuer à l’étude des gaz enfermés dans certains types de glace de ces régions afin de mieux quantifier leur impact potentiel sur le climat.Dans un premier temps, une analyse multiparamétrique a été menée sur deux coins de glace du nord de la Sibérie dans la cadre d’une collaboration avec l’Alfred Wegener Institut (Allemagne). Cette première approche a révélé que l’analyse conjointe de la cristallographie, de l’orientation des axes optiques, du contenu en gaz total et de la composition en gaz des coins de glace est un outil puissant, complémentaire aux analyses des isotopes stables, pour comprendre les conditions paléo-climatiques qui ont régi la construction des coins de glace. Cette étude soutient également l’hypothèse de variations spatiales importantes de l’origine des masses d’air durant les variations climatiques du Pléistocène.
Dans un deuxième temps, une analyse des caractéristiques de la glace annuelle de 4 lacs du nord de la Suède a été réalisée afin d’étudier le rôle de la couverture de glace sur les émissions de gaz à effet de serre. En effet, les lacs de ces régions contribuent fortement aux émissions de méthane durant la période d’eau libre et très peu d’études ont analysé la quantité de méthane emprisonnée dans la glace hivernale et relâchée au printemps. Ce projet nous a amené à établir une nouvelle classification des bulles dans la glace de lac basée sur leur contenu en méthane, leur origine, leur forme et leur densité. Il nous a également permis de montrer que plusieurs facteurs interviennent sur le contenu en gaz dans la couverture de glace :le système hydrologique, la variation de la pression atmosphérique, la variabilité des émissions et potentiellement la proximité des sédiments sont autant de facteurs qui déterminent le contenu en gaz. L’analyse de la composition des gaz a révélé que la composition observée dans la glace est sensiblement différente de celle observée durant les périodes d’eau libre. Nous avons également, pour la première fois, établit un budget des émissions de méthane relâchées par la fonte de la couverture de glace au niveau mondial.
Cette étude a été complétée par l’analyse des isotopes 13C des gaz des différents types de bulles de notre classification en collaboration avec l’Université d’Utrecht. Nous avons alors mis en évidence que la couverture de glace influence l’équilibre biogéochimique dans l’eau en favorisant l’oxydation du méthane en dioxyde de carbone.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Jachym, Anne-Laure. "Economic Growth, Greenhouse Gases and Environmental Regulation." Master's thesis, Université Laval, 2020. http://hdl.handle.net/20.500.11794/38154.
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Dans cette étude, nous cherchons à mesurer l’impact des émissions anthropogéniques de gaz à effet de serre sur la croissance économique dans un modèle de convergence conditionnelle. Nous nous intéressons au dioxyde de carbone, au méthane, au protoxyde d’azote et au groupe des "gaz F", ainsi qu’à l’effet de la somme de ces polluants, c’est-à-dire la quasi totalité des gaz à effet de serre. Notre échantillon est composé de 81 pays, avec une variété de niveaux de revenu par habitant, entre 1993 et 2012. Nous définissons deux sous-périodes de 10 ans et nous régressons la croissance économique sur la croissance des émissions de chaque polluant séparément, sur le PIB de la première année de la période et sur plusieurs variables de contrôle. Face au risque de biais de causalité inversée entre les émissions de pollution et la croissance économique, et entre l’investissement et la croissance économique, nous décidons d’utiliser les données passées comme variables instrumentales. Plus précisément, les données de la première année de la période sont utilisées comme instruments pour la pollution et l’investissement. Mis à part le CO2, nous trouvons qu’aucun des gaz à effet de serre n’a d’impact significatif sur la croissance économique. La croissance des émissions de CO2 semble avoir un impact positif sur la croissance économique. Cet impact apparaît moins fort sur la seconde période (2003-2012) que sur la première (1993-2002). De plus, il semble plus fort pour la moitié la plus riche des pays de notre échantillon.In this study, we investigate the effect of anthropogenic greenhouse gas emissions on economic growth in a conditional convergence framework. We look at carbon dioxide, methane, nitrous oxide and the group of "F gases", as well as the effect of the sum of these pollutants, i.e. almost all greenhouse gases. Our sample is composed of 81 countries with a variety of per capita income levels and covers the period between 1993 and 2012. We define two ten-year periods and regress economic growth on emissions growth of each pollutant separately, on the first-year GDP of the period and on several control variables. To address the issue of inverse causality bias between pollution emissions and economic growth, as between investment and economic growth, we use an instrumental variable methodology. We use past data to instrument pollution and investment. More precisely, the data of the first year of the period are used as instruments. We find that, except for CO2, greenhouse gas emissions growth does not generate economic growth. CO2 emissions growth has a positive impact on economic growth. Interestingly, this impact is less pronounced between 2003 and 2012, as compared to the 1993-2002 period. In addition, the impact of CO2 emissions growth is stronger in the richer half of countries in our sample.
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Moore, Jude Arthur Hamilton. "Internal environment of badger (Meles meles) setts." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360488.
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Woodworth, Ashley. "Integration of Regulatory Requirements for the Creation of a Remediation Tool at the Portsmouth Gaseous Diffusion Plant." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397233188.
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SAIYASITPANICH, PHIRUN. "CONTROL OF DIESEL PARTICULATE AND GASEOUS EMISSIONS USING A SINGLE-STAGE TUBULAR WET ELECTROSTATIC PRECIPITATOR." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1163607234.
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YU, JINSONG. "Development of Microfabricated Electrochemical Sensors for Environmental Parameter Measurements Applicable to Corrosion Evaluation and Gaseous Oxygen Detection." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1206981091.
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Douglas, Boma. "Environmental impact of green house gases on Nigeria." Thesis, London South Bank University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313004.
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An analysis of climate change in Nigeria has been carried out. The aim was to investigate the environmental impact of Green house gases. The three zones of the country namely the extreme North, the middle zone and the extreme South have all been separately examined with respect to changes in solar radiation, temperature, precipitation and evaporation. The agricultural productivity for each zone was compiled, and trend plots over time carried out. Correlation tests were done between productivity and climatic changes and it was found that each zonal area reacted differently to changes in climate. The emission of carbon dioxide, methane and the oxides of nitrogen in Nigeria were calculated and trends plotted. A correlation test was also carried out between carbon dioxide emission and temperature change for each zone. The relationship between temperature change and productivity was shown in a regression model. An economic appraisal for Nigeria involving the GDP, pollution and population was examined in terms of the productivity- pollution index. This was also extended to some of the Western countries
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Gustafson, Kurt E. "Gaseous flux and distribution of polycyclic aromatic hydrocarbons across the air-water interface of southern Chesapeake Bay." W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539616678.
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Gaseous fluxes of polycyclic aromatic hydrocarbons (PAHs) across the air-water interface of Southern Chesapeake Bay were calculated for the period January 1994 through May 1995 using a modified two-film model. Additionally, the distributions of PAHs between the vapor and aerosol phase in the atmosphere, and between the freely dissolved and suspended particulate phase in the water column were investigated. Net instantaneous gaseous fluxes of PAHs were determined to vary in direction and magnitude both spatially and temporally across the air-water interface of Southern Chesapeake Bay at four sites ranging from remote to urban and highly industrialized. The magnitude of gas exchange fluxes was of the same order as wet and dry atmospheric depositional fluxes. Spatial variations in gaseous fluxes resulted from differences in the air-water concentration gradients between sites. Temporal variations in gas exchange fluxes resulted from seasonal changes in both water temperatures and vapor concentrations. Atmospheric PAH vapor concentrations increased exponentially with temperature at the non-rural sites suggesting volatilization from contaminated surfaces (soils, roads, vegetation) during warmer weather; whereas, PAH vapor concentrations at the rural site decreased with time. All sites experienced increased loadings of particulate-associated PAHs during winter. Mean total atmospheric PAH concentrations ranged from 7.87 ng/m&\sp3& at a rural (Haven Beach) site to 92.8 ng/m&\sp3& at an urban (Elizabeth River) site. Plots of the logarithm of the particle-vapor partitioning coefficient (C&\rm\sb{lcub}p{rcub}/TSP\sp\* C\sb{lcub}v{rcub})& versus inverse temperature indicate different particle characteristics or atmospheric partitioning processes at the urban and rural sites. Three methods (gas sparging, semipermeable membrane devices, filtration with sorption of the dissolved contaminant fraction to XAD-2 resin) for determining freely dissolved contaminant concentrations in estuarine waters were investigated. Mean total PAH concentrations in surface waters ranged from 24.2 ng/l at a mainstem bay site to 91.1 ng/l at the industrialized Elizabeth River site. Dissolved-particulate partitioning of PAHs approximated equilibrium theory at all sites and sampling periods. The results of this study support the hypothesis that gas exchange is a major transport process affecting concentrations and exposure levels of PAHs in the southern Chesapeake Bay Region.
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Ansuategi, Alberto. "Economic growth and environmental quality : a critical assessment of the environmental Kuznets curve hypothesis." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326770.
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Devine, Gerard Majella. "The behaviour of trace gases and aerosol particles in a cumulonimbus environment." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486393.
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Cumulonimbus clouds perturb their local environment in such a way that subsequent clouds may experience dramatically different fields of gas and aerosol species. A full understanding of the behaviour of these species in a convective environment therefore requires examination beyond single-cloud studies. This study uses a cloud-resolving model to examine the evolution of species typical of the remote marine atmosphere over a period of several days and across a domain size that encompasses several cloud systems· at once. Using a series of gas and aerosol sub-models that have been developed in the cloud-resolving model, the full effect of an evolving field of convective clouds on gas and aerosol formation, transport, and eventual removal is examined. The knowledge gained from these simulations will ultimately aid representation in global models where such processes are not explicitly resolved. Sea salt aerosol and dimethyl sulphide gas, or DMS, both exhibit large temporal and spatial variability in the convective environment. This variability is inextricably linked to the 'cold pool' outflow from convective systems. Resolving the interaction between the cold pool and the chemical species is shown to be important for various aspects of the species behaviour. An inability to resolve such features, such as in a global model, leads to inaccuracies in both species concentration and vertical transport. In the case of DMS, the abundance as well as the amount vented to the free troposphere is enhanced significantly in comparison to a global model estimate. Emissions into the domain are greater in the CRM because it resolves the localised intense winds embedded in cold pools. Additionally, secondary convection occurs through dynamical lifting at the leading edges of cold pools. Because DMS concentrations are high in these regions, the ability to resolve such features enhances the transport to the free troposphere by up to 50% in comparison to using a mean gas field, typical of a global model. In the case of sea salt aerosol, it is found that precipitation is co-located with regions of maximum and minimum sea salt. This feature arises due to a build up of sea salt inside the cold pool head, a region wh~re precipitation from secondary cono vection tends to occur. Aerosol is also found to be scavenged in localised regions faster than the precipitation lifecycle itself. An inability to resolve these features is shown to have a significant influence on the amount of aerosol scavenged from the domain. The examination of the marine sulphur cycle around convective clouds shows that an anti-correlation exists between 802 and its precursor gas, DMS. Although concentrations of DMS are high around convection due to enhanced surface fluxes, the efficient scavenging of S02 dominates over its formation. Also, it is found that the concentration of accumulation mode sulphate particles falls dramatically during convection. The reason for this is the dominance of nucleation scavenging events. Additionally, it is shown that although aqueous-phase oxidation of S02 is significant, a large majority of the sulphate generated in this way is precipitated to the ground in rain drops.
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Kutlaca, Alex. "Environmental issues associated with landfill-generated methane /." Title page, table of contents and abstract only, 1992. http://web4.library.adelaide.edu.au/theses/09ENV/09envk97.pdf.
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Sohl, Lukas. "Development of PICOSEC-Micromegas for fast timing in high rate environments." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP084.
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Les futures expériences de physique des particules devront être opérationnelles pour un flux de particules et une luminosité croissants. Plus particulièrement, les détecteurs proches du point d'interaction devront présenter une très bonne robustesse pour faire face à un flux de particules très élevé. De plus, une résolution temporelle de quelques dizaines de picosecondes pour les particules au minimum d’ionisation sera nécessaire pour assurer une séparation nette des vertex reconstruits et réduire l'empilement d’événements. Ce manuscrit a pour sujet l’instrument PICOSEC-Micromegas, un détecteur de particules innovant basé sur la lecture d’un détecteur Micromegas couplé à un radiateur Cherenkov et une photocathode. Dans ce dispositif, chaque électron primaire étant produit à la surface de la photocathode, l’étalement en temps du signal est minimal, alors qu’il peut atteindre plusieurs nanosecondes lorsque les ionisations primaires ont lieu sur le passage d'une particule dans l’espace de dérive. La hauteur de ce dernier est ici du même ordre de grandeur que celle de la région d'amplification (100-200 μm) afin de minimiser l'ionisation directe du gaz. L’espace de dérive est également utilisée comme espace de pré-amplification. Un modèle mathématique, basé sur des simulations GARFIELD++, a été développé pour décrire le développement de l'avalanche de pré-amplification. Il a permis de montrer que la longueur et la multiplication de l'avalanche dans l’espace de dérive sont les facteurs dominants dans la résolution temporelle. Le concept PICOSEC-Micromegas a été étudié avec plusieurs prototypes optimisant les champs électriques, la distance de dérive et le mélange gazeux auprès de l’installation laser du LIDYL (Laboratoire Interactions, Dynamiques et Lasers). Une résolution temporelle de ~44 ps a été obtenue pour un photo‑électron unique. Par ailleurs, des mesures effectuées en faisceau test au CERN ont permis d'obtenir une résolution temporelle de 24 ps pour des muons de 150 GeV, avec un espace de dérive de 200 μm et une photocathode en CsI (10 photoélectrons par MIP). Afin de passer du concept de détection à un démonstrateur plusieurs prototypes ont été développés, en se concentrant sur les propriétés spécifiques nécessaires aux applications futures: segmentation de l'anode, annulation des étincelles, efficacité de la photocathode et robustesse à haut flux de particules. Un prototype à pads hexagonaux a été testé en faisceau et montré une résolution temporelle de ~36 ps dans le pad central. Les performances à haut flux sont testées avec des détecteurs résistifs dans des faisceaux de muons et de pions. Des résolutions temporelles nettement inférieures à 100 ps et un fonctionnement stable en faisceau de pions sont obtenus avec tous les prototypes résistifs. Des matériaux de photocathode robustes, comme alternative au CsI, sont étudiés pour réduire la dégradation due au retour des ions. Les matériaux les plus prometteurs sont le “diamond-like carbon” (DLC) et le carbure de bore (B4C). Compte tenu des résultats obtenus, deux cas d'application sont considérés pour les perspectives de ce programme de R&D. La première application considérée est l'utilisation du détecteur PICOSEC à l'intérieur d'un calorimètre comme couche de synchronisation ou de nombreuses particules secondaires sont produites dans un calorimètre électromagnétique après quelques longueurs de radiation. Une résolution temporelle de ~5 ps est attendue avec le PICOSEC-Micromegas. La seconde application est l'identification des particules par des mesures de temps de vol (TOF) ou PICOSEC-Micromegas devrait permettre de doubler la plage d’impulsion des détecteurs TOF actuels pour la séparation π/Κ avec 3σFuture particle physics experiments will face an increasing particle flux with rising beam luminosity. Detectors close to the interaction point will need to provide robustness against the high particle flux. Moreover, a time resolution of tens of picosecond for Minimum Ionising Particles will be necessary to ensure a clear vertex separation of the reconstructed secondary particles and to reduce pile-up. This manuscript focusses on the PICOSEC-Micromegas, an innovative particle detector based on the Micromegas readout coupled to a Cherenkov radiator and a photocathode in front of the gaseous volume. In this way, each primary electron is located on the surface of the photocathode, suppressing thus the inevitable time jitter of several nanoseconds, due to the different ionisation positions created by the passage of a particle from the drift region of a gaseous detector. The drift region length is reduced to the same order of magnitude as the amplification region (100-200 μm) to minimise direct gas ionisation, and it is additionally used as a pre-amplification stage. A mathematical model, based on GARFIELD++ simulations, is developed to describe the propagation of the pre-amplification avalanche showing that the length and multiplication of the avalanche in the drift region is the dominant factor in the timing performance. The PICOSEC-Micromegas concept is studied with several prototypes optimising the electric fields, the drift distance, and the gas mixture in the LIDYL (Laboratoire Interactions, Dynamiques et Lasers) UV laser facility. A single photoelectron time resolution of ~44 ps is measured with the shortest tested drift region length of 119,μm and the highest stable field setting. Measurements performed in the secondary particle beam at CERN have resulted in a time resolution of 24 ps for 150 GeV muons with a drift region length of 200 μm and a CsI photocathode providing 10 photoelectrons per MIP. In order to evolve from the detection concept to a versatile instrument, several prototypes are developed, focusing on specific properties needed for future applications: anode segmentation, spark quenching, photocathode efficiency and robustness for higher particle flux. An hexagonal segmented multipad prototype is tested in the beam with a time resolution of ~36 ps in the central pad. The operation in high rate environments is studied with different resistive strip and floating strip anodes resistive detectors in muon and pion beams. Time resolutions significantly under 100 ps and stable operation in the pion beam are achieved with all resistive prototypes. Robust photocathode materials, as an alternative to CsI, are investigated to reduce degradation from the ion-backflow generated in the pre-amplification avalanche. The most promising materials are diamond-like carbon (DLC) and boron carbide (B4C). Considering all the results achieved, two application cases are projected with the PICOSEC-Micromegas detector. The first one is the use in a calorimeter as a timing layer. Many secondary particles are produced in an electromagnetic calorimeter after few radiation lengths and a time resolution down to ~5 ps is expected with the PICOSEC-Micromegas. The second one is particle identification trough time-of-flight (TOF) measurements. The PICOSEC-Micromegas is expected to double the momentum range of current TOF detectors for π/Κ separation with 3σ
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Sagheby, Seyed Hossein [Verfasser], Martin [Akademischer Betreuer] Kriegel, Birgit [Akademischer Betreuer] Müller, Birgit [Gutachter] Müller, and Martin [Gutachter] Kriegel. "Density effects of gaseous contaminants in low velocity indoor environments / Seyed Hossein Sagheby ; Gutachter: Birgit Müller, Martin Kriegel ; Martin Kriegel, Birgit Müller." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/115618312X/34.
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Matta, Anand. "Laser Spectroscopy Sensor for Measurements of Trace Gaseous Sulfur Dioxide (SO2)." Connect to resource online, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1229541167.
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Bradford, Mark Alexander. "The response of methane oxidation to environmental change." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286477.
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Lohmann, Martin. "Herstellung von Partikeln durch elektrostatische Zerstäubung von Flüssigmetallen in gasförmiger Umgebung - Production of particles via electrostatic atomization of liquid metals in gaseous environments." Gerhard-Mercator-Universitaet Duisburg, 2001. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-05282001-115418/.
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Fine solid particles, especially nano-particles, are of great interest for the synthesis of new materials. There is also a strong demand for newer and more precise contact technologies of electronic components due to the higher getting integration of electronic devices. These new technologies may be based on submicron conducting particles, e.g. for producing solder pastes. In the present thesis a process was developed for the production of micron and submicron conducting particles by the use of electrostatic atomisation of liquid metals. The atomization process is based on the instability of conducting liquids in a strong inhomogenous electric field. The free liquid surface is transformed into a cone shape, from where a thin liquid jet is emitted. This jet breaks up into a spray of fine unipolary charged droplets immediately after the emission. Under defined circumstances the droplets have a narrow size distribution and can be extracted for other applications without additional classification methods. The rapid solidification leads to defined spherical particles, depending on the used metal, and the unipolar charge to a low agglomeration. The high electrical field, which is necessary for the atomization, causes electrical discharges of the ambient gas and disturbes the atomization process. To reduce these discharges a special pressure chamber was constructed, which is filled with quenching gas as SF6 with over-pressures of up to 12 bar. The electrostatic atomisation was applicated for liquid metals only in an ultra high vacuum up to now. The production of aerosol particles may have advantages not only due to available cheaper online measurement techniques. By the use of aerosol measurement techniques a direct statement about the particle size, the particle number concentration and the mean charge on the particles is possible. The atomization was investigated for metals as well as for eutectic alloys with a low melting point and a low surface tension. The results show, that spherical particles with a diameter down to a few hundred nanometer could be produced. In addition the production of thin and homogenous granular films was possible. To compare and verify the experimental results a simplified numerical model of the spraying process with respect to the space charge was developed. By calculating the particle trajectories from the emission source to the collector plate an estimation of the spray cloud geometry and the emitted electrical current was possible. An interesting observation was the self induced size segregation of the particles, which occurred in the experiments and in the numerical simulations. This effect can be used for a defined expansion or focussing of the deposition area on the target. Here there may be found some interesting applications for the point spraying.
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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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Niap, Damian Tien Foo, and e58018@ems rmit edu au. "Environmental Management Accounting for an Australian Cogeneration Company." RMIT University. Accounting and Law, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080102.102723.
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This research explores whether Environmental Management Accounting can be applied to assist an Australian cogeneration company in improving both its financial performance as well as its environmental performance. Cogeneration or 'combined heat and power', in this particular case, involves the simultaneous production of heat and electricity using a single fuel, that is, natural gas. The heat generated is then used to produce steam to meet the customers' requirements as well as boost the production of electricity. Therefore, cogeneration provides greater efficiencies compared to traditional electricity generation methods because it utilizes heat that would otherwise be wasted. In addition, greenhouse gases emissions can be reduced substantially. The approach taken in this research is to assess whether an improvement in the energy efficiency of the cogeneration plant can lead to a reduction in greenhouse gases emissions. An improvement in energy efficiency means that either: less gas is consumed, thus leading to cost savings; or more electricity is generated for the same quantity of gas consumed, which leads to an increase in income and consequently profit. Therefore, an improvement in energy efficiency means an improvement in the financial performance. In addition, a reduction in the quantity of gas consumed or generating as much electricity as possible from a given quantity of gas can lead to a reduction in greenhouse gases emissions which means an improvement in the company's environmental performance. A case study method, which involves an Australian cogeneration company, is adopted because this would provide valuable in-depth practical insight into the operations and mechanisms of a company that is involved in combined heat and power generation. A review of the literature and the evidence collected indicated that a cogeneration plant's efficiency can be improved at least back to near the plant's designed efficiency. And, further improvements may be achieved by utilizing the latest technology although this involves capital investment. It is also established that an improvement in plant efficiency can reduce greenhouse gases emissions. This research then concludes that Environmental Management Accounting can help the case study company improve its financial and environmental performances. An Environmental Management Accounting system can provide the physical information that is not available in the existing management accounting system. Physical information such as the physical quantities of gas consumed, electricity and steam produced, and greenhouse gases emitted, can help the company in decision-making relating to improving plant efficiency as well as reducing greenhouse gases emissions.
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Rodríguez-Navas, González Carlos. "Exploiting novel automated analytical methodologies for the monitoring of environmental organic pollutants, and its potential incorporation to environmental monitoring regulations." Doctoral thesis, Universitat de les Illes Balears, 2012. http://hdl.handle.net/10803/98297.
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Se han desarrollado métodos analíticos basados en cromatografía y detección por espectrometría de masas para la detección de múltiples compuestos orgánicos a niveles traza en muestras de interés ambiental. Se han determinado compuestos volátiles en aire atmosférico de Mallorca y varias plantas de tratamiento de residuos y vertederos, y fármacos de consumo humano en muestras del medioambiente acuático de Mallorca, plantas de tratamiento de aguas y lixiviados de vertederos. Con estos datos se ha evaluado la necesidad de modificar los planes de vigilancia ambiental para asegurar la calidad del medioambiente de Mallorca.We have developed analytical methodologies based on chromatography and mass spectrometry for the detection of multiple different organic compounds in the trace levels in samples of environmental interest. Volatile organic compounds have been determined in the atmospheric air of Mallorca as well as some waste treatment plants and landfills. Pharmaceuticals for human consumption have been investigated in several samples of the aquatic environment of Mallorca as well as some wastewater treatment plants and landfill leachates. Based on these data it has been evaluated the necessity to modify the environmental monitoring regulations to save the quality of the Mallorca’s environment.
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Melnik, Y., and T. Linnik. "Chemtrails impact on the environment and human brains." Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/30866.
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Humans have undeniably affected the atmosphere and air quality of our planet. However, because most gasses are invisible to the human eye, it can be hard to physically see some of the changes we've brought about. Smog, exhaust from cars and trucks and smoke from chimneys and fires are a few of the visible signs, but one of the most intriguing visual manifestation of how we've changed the atmosphere are the jet trails left behind by airplanes.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/30866
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Quesada-Kimzey, Jaime F. "Tropospheric carboxylic acids in tropical rainforest environments a study of their presence in the gaseous and aqueous phases under maritime to continental transport regimes /." [S.l. : s.n.], 2003. http://ArchiMeD.uni-mainz.de/pub/2003/0029/diss.pdf.
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Ahmad, Abo Markeb Ahmad Mohamed. "Environmental applications of engineered nanomaterials: synthesis and characterization." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/454768.
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Aquesta tesi es basa en el desenvolupament (síntesi) de diferents nanomaterials per a la seva aplicació com a materials adsorbents per a l'eliminació de contaminants en aigua (anions inorgànics, metalls pesats i pesticides) i per l'adsorció de gas metà. El desenvolupament dels diferents materials s'ha basat en una extensa recerca bibliogràfica de l'estat de l'art dels materials utilitzats actualment per a aquesta aplicació, i s'ha tractat de millorar l'eficiència del procés mitjançant l'ús de nanomaterials. Amb aquest objectiu s’han sintetitzat materials magnètics per diferents mètodes. En alguns casos, aquests han estat funcionalitzats amb grups orgànics per adaptar i/o millorar la seva funció d'adsorció o estabilitzar-los en suports (polímers, zeolites, esponges, etc.) per millorar la seva aplicació a una escala real en un futur. A més, es va desenvolupar un nou mètode per a la formació de nanopartícules core-shell amb un nucli de magnetita. Tots els nanomaterials sintetitzats s'han caracteritzat en profunditat, utilitzant les tècniques més avançades per a la caracterització dels nanomaterials. Tècniques com ara la microscòpia electrònica, difracció de raigs X, entre d'altres, permeten conèixer les característiques i propietats dels materials (mida, dispersió, estructura cristal·lina, etc.) i per tant concloure la seva contribució a l'eficàcia de cada un dels materials adsorbents.
Pel que fa als contaminants en aigua, el treball se centra en el fluorur, el fosfat, el nitrat, els metalls cadmi i níquel i pesticides, destacant l'obtenció de resultats excepcionals per a les nanopartícules de Ce-Ti@Fe3O4.
En el cas de tractament de gas, per una banda s'ha desenvolupat un nou nanomaterial basat en nanopartícules magnètiques estabilitzades en esponges de poliuretà que ha presentat resultats interessants per a l'adsorció de metà. A més, s'ha col·laborat amb la Institut Català de Nanotecnologia per a l'aplicabilitat dels Metal Organic Frameworks en l'oxidació de CO.
Una altra aplicació que s'ha donat a les nanopartícules magnètiques ha estat la seva utilització en la separació de algues procedents de processos de tractament d’aigües, per tal de substituir el procés actual de decantació.
Amb tot això, la tesi ofereix una gamma de nanomaterials per a diferents usos en enginyeria ambiental, amb la possibilitat d'investigar i desenvolupar en la seva aplicabilitat a gran escala. Amb aquesta finalitat, es proporcionen diferents solucions per a la millora del medi ambient.This thesis is based on the development (synthesis) of different nanomaterials for their application as adsorbent materials for the removal of pollutants from water (inorganic anions, heavy metals and pesticides) and for the adsorption of methane gas. The development of the different materials has been based on an extensive bibliographical search of the state of the art of the materials currently used for this application, and it has been tried to improve the efficiency of the process by using nanomaterials. Thus, magnetic (magnetite) nanoparticles are synthesized by different methods. These are functionalized with organic groups to adapt and/or improve their adsorption function or stabilize in supports (polymers, zeolites, sponges, etc.) to improve their application on a real scale. In addition, a new method for the formation of core-shell nanoparticles with a magnetite core is developed. All the synthesized nanomaterials have been characterized in depth, using the most advanced techniques for the characterization of nanomaterials. Techniques such as electron microscopy, X-ray diffraction, among others, allow to know the characteristics and properties of the materials (size, dispersion, crystallinity, structure, etc.) and thus conclude their contribution to the efficiency of their application with adsorbent material. As for the contaminants in water, the work focuses on fluoride, phosphates, nitrates, cadmium, nickel and pesticides, obtaining outstanding results for the nanoparticles of Ce-Ti @Fe3O4. In the case of gas treatment, on the one hand has developed a new nanomaterial based on magnetic nanoparticles stabilized in polyurethane sponges which present interesting results for the adsorption of methane and great applicability on a real scale. In addition, we have collaborated with the Institut Català de Nanotecnologia for the applicability of Metal Organic Frameworks in the oxidation of CO. Another application that has been given to magnetic nanoparticles has been its use to separate algae from wastewater treatment processes, in order to substitute the current sedimentation processes. With all this, the thesis offers a range of nanomaterials for different uses in environmental engineering, with the possibility of investigating and developing on its applicability on a large scale. To this end, different solutions are provided for the improvement of the environment.
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Coe, Jeffrey Ellis. "In vivo human ocular responses to irritant gases." Thesis, London School of Hygiene and Tropical Medicine (University of London), 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362322.
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Christensen, Torben Rojle. "Exchange of radiatively active trace gases in tundra environments, with particular attention to methane." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319526.
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Sjoeberg, Tristan Nenne. "The distribution and cycling of dissolved carbon monoxide in estuarine, coastal and shelf break environments." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302077.
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Stein, Antoinette Weil. "Investigation of the Chemical Pathway for Gaseous Nitrogen Dioxide Formation during Flue Gas Desulfurization with Dry Sodium Bicarbonate Injection." Cincinnati, Ohio : University of Cincinnati, 2001. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin997940666.
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Nkongolo, Nsalambi Vakanda. "Quantification of greenhouse gas fluxes from soil in agricultural fields." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1474.
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Field studies were conducted at Lincoln University of Missouri (USA) and Hokkaido University (Japan) to: (i) study the relationships between greenhouse gases emissions and soil properties, (ii) assess the influence of agricultural practices on greenhouse gas fluxes and soil properties and (iii) improve the quantification of greenhouse gases from soil in agricultural fields using geospatial technologies. Results showed that besides soil temperature (T), soil thermal properties such as thermal conductivity (K), resistivity (R) and diffusivity (D) and soil pore spaces indices such as the pore tortuosity factor and the relative gas diffusion coefficient (Ds/Do) are controlling factors for greenhouse gases emissions. Soil thermal properties correlated with greenhouse gases emissions when soil temperature could not. The study has found that predicted Ds/Do and correlate with greenhouse gas fluxes even when the air-filled porosity and the total porosity from which they are predicted did not. We have also showed that Ds/Do and can be predicted quickly from routine measurements of soil water and air and existing diffusivity models found in the literature. Agricultural practices do seriously impact greenhouse gases emissions as showed by the effect of mechanized tillage operations on soil physical properties and greenhouse gas fluxes in a corn and soybean fields. In fact, our results showed that tractor compaction increased soil resistance to penetration, water, bulk density and pore tortuosity while reducing air-filled porosity, total pore space and the soil gas diffusion coefficient. Changes in soil properties resulted in increased CO2, NO and N2O emissions. Finally, our results also confirmed that greenhouse gas fluxes vary tremendously in space and time. As estimates of greenhouse gas emissions are influenced by the data processing approach, differences between the different calculation approaches leads to uncertainty. Thus, techniques for developing better estimates are needed. We have showed that Geographic Information Systems (GIS), Global Positioning System (GPS), computer mapping and geo-statistics are technologies that can be used to better understand systems containing large amounts of spatial and temporal variability. Our GIS-based approach for quantifying CO2, CH4 and N2O fluxes from soil in agricultural fields showed that estimating (extrapolating) total greenhouse gas fluxes using the “standard” approach – multiplying the average flux value by the total field area – results in biased predictions of field total greenhouse gases emissions. In contrast, the GIS-based approach we developed produces an interpolated map portraying the spatial distribution of gas fluxes across the field from point measurements and later process the interpolated map produced to determine flux zones. Furthermore, processing, classification and modeling enables the computation of field total fluxes as the sum of fluxes in different zones, therefore taking into account the spatial variability of greenhouse gas fluxes.
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Chen, Yuan, and 陳源. "An embodied GHG emissions auditing and benchmarking model for assessing the environmental impacts of buildings." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/195969.
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Climate change constitutes one of the greatest challenges facing the world today, as it will influence the way we live and work in future decades. Excessive greenhouse gas (GHG) emissions are recognized as the key contributor to climate change, and the construction sector has an indispensable role to play in emission reduction, as building facilities are energy- and emission-intensive to construct and operate. Previous research indicates that up to 30 percent of buildings’ lifecycle emissions can be minimized through the careful selection of low-carbon materials. Although building environmental assessment (BEA) tools have been widely used in identifying and mitigating the lifecycle environmental impacts of building facilities, the existing BEA tools provide no rigorous regime for assessing the embodied GHG emissions of building materials. Therefore the aim of this research is to bridge the research and practical gaps by developing an integrated BEA assessment model that comprehensively audits and benchmarks the embodied GHG emissions of building materials at product level.
The research began by examining the limitations of current BEA tools, in particular their means of evaluating the embodied GHG emissions of buildings. Then, an embodied GHG emissions evaluation module model under an existing BEA scheme was proposed. The proposed model comprised (i) product category, (ii) product-based GHG auditing framework, and (iii) emissions benchmarking measure. After that, a thorough review of the relevant literature and international classification systems was carried out to establish a systematic product categorization regime for building materials. An auditing framework comprising system boundary, process map, emission sources, and a carbon auditing tool in Microsoft TM Excel has been developed by reviewing international standards on product carbon footprint assessments and eliciting knowledge from domain experts through a series of interviews. The emission benchmarks for each product category have been determined through the application of fuzzy set theory to facilitate easy comparison and decision-making. Finally, the developed product categorization regime, GHG auditing framework, and benchmarks were validated through a Delphi study, a discussion of which concluded the thesis.
The research outcomes confirm that the GHG emissions embodied in a building facility can be meticulously analyzed and integrated into the BEA. The research also improves the understanding of how the materials’ embodied emissions can be accurately calculated at the product level. More importantly, it enhances existing BEA tools by incorporating embodied GHG emissions into the analysis, thus makes the lifecycle emission assessment of building facilities possible. The proposed integrated BEA model will enable clients and design teams to minimize the carbon footprints of buildings and assist users and the general public in identifying green building facilities.
The originality of this research lies in the establishment of a set of emissions benchmarks for five most emission-intensive building materials using fuzzy set theory. These benchmarks provide a seamless platform allowing the assessment of materials’ embodied emissions to be integrated with the existing BEA model, thereby not only encouraging the adoption of low-carbon building materials but also fostering ongoing product carbon footprint reductions.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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Shaver, Elizabeth M. "Predicting the trajectories of hazardous discharges of dense gases." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/10245.
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Yu, Bin. "Environmental Implications of Pavements: A Life Cycle View." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4619.
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Environmental aspect of pavement, unlike its economic counterpart, is seldom considered in the theoretical study and field practices. As a highly energy and material intensive infrastructure, pavement has great potential to contribute to the environment protection, which, in root, depends on the in-depth understanding of the environmental impacts, holistically and specifically. A life cycle assessment (LCA) model is used to fulfill the goal.
This research firstly carried out extensive literature review of LCA studies on pavement to identify the major research gaps, including: incompleteness of the methodology, controversy of the functional unit, and unawareness of feedstock energy of asphalt, etc. Based on that, a comprehensive methodology to apply the LCA model in the context of pavement engineering was developed. The five-module methodology, including material module, maintenance and rehabilitation (M&R) module, construction module, congestion module, and end of life module, covers almost every stage of pavement for a life time. The unique contribution of the proposed methodology lies in the deep-going modeling of the congestion module due to construction and M&R activities and the great efforts on the usage module. Moreover, the proposed methodology is a complex structure, demanding many sub-models to enrich the model bank and therefore another three contributions are made accordingly. Specifically, the environmental damage costs (EDCs) were calculated based on the estimates of the marginal damage cost of involved air pollutants; a function describing the relationship of pavement roughness and average vehicle speed was established; and an improved pavement M&R optimization algorithm was developed with the incorporation of EDCs.
To demonstrate how the proposed methodology can be implemented, a case study of three overlay systems, including hot mixture asphalt (HMA), Portland cement concrete (PCC), and crack, seat and overlay (CSOL), was performed. Through the case study, the PCC option and CSOL options are found to have less environmental burdens as opposed to the HMA option while the comparison between the former two is indeterminate due to the great uncertainties associated with usage module, especially pavement structure effect; and the material, congestion, and usage modules are the three major sources of energy consumptions and air pollutant emissions. Traditionally, cost evaluation of pavement does not refer to EDC while the developed M&R optimization algorithm suggests that EDC occupies a significant fraction of the total cost constitution. And the M&R algorithm leads to a reduction from 8.2 to 12.3 percent and from 5.9 to 10.2 percent in terms of total energy consumptions and costs compared to the before optimization results.
On the other aspect, pavement communities seem to prefer long life pavement because they believe small increase of pavement thickness prolongs the service life and thus leads to a smaller marginal cost while the study in Chapter 5 suggests that it may not be always true, at least in terms environmental impacts. Specially, frequently used pavement designs in the U.S. of two design lives, 20 years and 40 years, at three levels of traffic, are evaluated for their environmental impacts using the proposed methodology. It is found that only at high traffic volumes, the 40-year designs carry environmental advantages over their 20-year counterparts while the opposite is true at the low or medium traffic volumes. Unfortunately, it is not possible to determine the watershed traffic volumes due to the disturbance of many external factors.
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Rubasinghege, Gayan Randika S. "Chemical and photochemical reactions on mineral oxide surfaces in gaseous and liquid phases: environmental implications of fate, transport and climatic impacts of mineral dust aerosol." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1173.
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Mineral dust aerosols emitted from the Earth crust during various natural and anthropogenic processes continuously alter the chemical balance of the atmosphere via heterogeneous processes and thus, impact on the global climate. Understanding of heterogeneous chemistry and photochemistry on mineral dust has become vital to accurately predict the effect of mineral dust loading on the Earth's atmosphere. Here, laboratory measurements are coupled with model studies to understand heterogeneous chemistry and photochemistry in the atmosphere with the specific focus on reactions on mineral oxide surfaces.
Heterogeneous uptake of gas phase HNO3 on well characterized metal oxides, oxyhydroxides and carbonates emphasized binding of nitric acid to these surfaces in different modes including monodentate, bidentate and bridging under dry conditions. It is becoming increasingly clear that the heterogeneous chemistry, including uptake of HNO3, is a function of relative humidity (RH) as water on the surface of these particles can enhance or inhibit its reactivity depending on the reaction. All the studied model systems showed a significant uptake of water with the highest uptake by CaCO3. Quantitative analysis of water uptake indicated formation of multilayers of water over these reactive surfaces. Under humid conditions, two water solvated nitrate coordination modes were observed that is inner-sphere and outer-sphere, which differ by nitrate proximity to the surface.
Photochemical conversion of nitric acid to gas phase nitrous oxide, nitric oxide and nitrogen dioxide through an adsorbed nitrate intermediate under different atmospherically relevant conditions is shown using transmittance FTIR and XPS analysis. The relative ratio and product yields of these gas phase products change with relative humidity. Photochemistry of adsorbed nitrate on mineral aerosol dust may be influenced by the presence of other distinct gases in the atmosphere making it complicated to understand. This thesis converses formation of active nitrogen, NOx and N2O, and chlorine, ClOx, species in the presence of co-adsorbed trace gases, that could potentially regulate the peak concentration and geographical distribution of atmospheric ozone. Here we report formation of atmospheric N2O, from the photodecomposition of adsorbed nitrate in the presence of co-adsorbed NH3 via an abiotic mechanism that is favorable in the presence of light, relative humidity and a surface. Estimated annual production of N2O over the continental United States is 9.3+0.7/-5.3 Gg N2O, ~5% of total U.S. anthropogenic N2O emissions. Not only NH2 but also gaseous HCl react with adsorbed nitrate to activate "inert" N and Cl reservoir species, yielding NOCl, NOx, Cl and Cl2, through adsorbed nitrate under different atmospherically relevant conditions.
Mineral dust aerosol is a major source of bioavailable iron to the ocean with an annual deposition of ~ 450 Tg of dust into the open ocean waters. In this study, we report enhanced Fe dissolution from nano scale Fe-containing minerals, i.e.alpha-FeOOH, beyond the surface area effects that can be attributed to the presence of more reactive sites on specific crystal planes exposed. We further report with clear evidence that aggregation impacts on dissolution. Proton-promoted dissolution of nanorods is nearly or completely quenched in the aggregated state. Acid type, presence of oxyanions and light are several other key factors responsible for regulating for iron dissolution. The work reported in this thesis provides insight into the heterogeneous chemistry and photochemistry of mineral dust aerosol under different atmospherically relevant conditions.
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Moore, Keara Bevin. "Nitrate source history for Livermore, California using environmental isotopes, noble-gases, and major ions." Thesis, The University of Arizona, 2004. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0118_sip1_w.pdf&type=application/pdf.
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Mata, Ricardo Manuel Reis. "Assessment of the environmental impact of yeast waste application to soil: an integrated approach." Master's thesis, ISA-UL, 2016. http://hdl.handle.net/10400.5/12979.
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Mestrado em Engenharia do Ambiente - Instituto Superior de Agronomia - ULThe yeast production industry (e.g. distillery, brewing, baking industries) has been growing globally over the last years generating a large amount of sub-products. Laboratory experiments, under controlled conditions, were performed to investigate the impact of yeast waste application to a sandy texture soil. Experimental treatments were: surface application of yeast and decanted-yeast (CMSs and CMSds), surface application of yeast and decantedyeast followed by incorporation in the 0-5 cm soil layer (CMSm and CMSdm), surface application of ammonium nitrate (AN) (not applied in short-term experiment) and a control (soil only) (CTR). The amount of yeast applied was 2 g in the short-term experiment and equivalent to 170 kgN.ha-1 in the long-term experiment. A short-term (38-day period) leaching experiment was performed with 5 weekly irrigation events (5 treatments × 3 replications) to assess N, P, K losses. Results showed that yeast application increased NH4+, PT and KT leaching relative to control while decreased NO3- leaching relative to a high initial content of control, during first irrigation events. Incorporation treatments increased NH4+, NO3- and PT losses earlier. KT losses were higher in surface treatments. A long-term leaching experiment (73-day period) with 6 irrigation events every two weeks was then performed (6 treatments × 4 replicates) to assess N, P losses. A two parallel incubation experiment (6 treatments × 3 replicates) were simultaneously performed to measure GHG emissions (CO2, N2O, CH4) and to assess the N mineralization in each treatment. Results showed that yeast application increased initial NH4+ concentration in leachates and soil relative to control and NO3- increased afterwards. N2O and CO2 increased significantly relative to control on the first days after yeast application. AN treatment emissions were very similar to control but had a small increase of N2O. CH4 emissions were insignificant. The global warming potential (GWP) of yeast and AN were 6× and 2× times higher than control, respectively
N/A
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Mtetwa, Lawrence. "Africa as a regional and global source of atmospheric gases and particulates." W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539624015.
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The role of the continent of Africa as a source of gaseous and particulate emissions to the atmosphere is investigated in this study. Sources of gases and particulates from Africa include fossil fuel combustion, biomass burning, and biogenic soil emissions of nitric oxide. This study represents the first comprehensive database of gaseous and particulate emissions developed for the continent of Africa on a country by country basis and establishes the framework for country-by-country, assessment of greenhouse gases emissions as required by the Kyoto Conference on Global Warming, which was attended by representatives from more than 100 countries. Calculations of gases and particulates resulting from fossil fuel combustion were based on the Intergovernmental Panel on Climate Change (IPCC) guidelines. Calculations of gases and particulates resulting from biomass burning were based on fire counts obtained from the Defense Meteorological Satellite Program (DMSP). Block 5 satellites and emission ratios for various gaseous and particulate fire products obtained during the recent Southern African Fire-Atmosphere Research Initiative (SAFARI), an activity of the international Global Atmospheric Chemistry (IGAC) Project, part of the international Geosphere-Biosphere Program (IGBP). The calculations of biogenic soil emissions of nitric oxide were obtained with the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) Biogenic Soil NO&\rm\sb{lcub}x{rcub}& Model. Africa was found to be a significant global source of the following gases: carbon dioxide (CO&\sb{lcub}2{rcub}&), carbon monoxide (CO), methyl chloride (CH&\sb{lcub}3{rcub}&Cl), oxides of nitrogen &\rm(NO\sb{lcub}x{rcub}),& and carbon particulates. The results indicate that Africa is the world's single largest continental source of emissions due to biomass burning and that these emissions are likely to increase with time. The study established that on a global scale, Africa was the largest source of soil biogenic NO&\rm\sb{lcub}x{rcub}&. The importance of Africa as a key global source of trace gases and aerosols has been underestimated in the past. This research offers a new picture of gaseous and particulate emissions from Africa. Africa's global significance as a source of atmospheric gases is very important, i.e., more than 11% of the world's total anthropogenic CO&\sb{lcub}2{rcub}& production results from biomass burning in Africa. Africa contributes nearly a third of the global anthropogenic CH&\sb3&Cl, a third of the global anthropogenic &\rm NO\sb{lcub}x{rcub},& and almost 20% to the world's global carbon particles anthropogenic budget.
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Calle, Laguna Alvaro Jesus. "Isolated Traffic Signal Optimization Considering Delay, Energy, and Environmental Impacts." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74238.
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Traffic signal cycle lengths are traditionally optimized to minimize vehicle delay at intersections using the Webster formulation. This thesis includes two studies that develop new formulations to compute the optimum cycle length of isolated intersections, considering measures of effectiveness such as vehicle delay, fuel consumption and tailpipe emissions. Additionally, both studies validate the Webster model against simulated data. The microscopic simulation software, INTEGRATION, was used to simulate two-phase and four-phase isolated intersections over a range of cycle lengths, traffic demand levels, and signal timing lost times. Intersection delay, fuel consumption levels, and emissions of hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and carbon dioxide (CO2) were derived from the simulation software. The cycle lengths that minimized the various measures of effectiveness were then used to develop the proposed formulations. The first research effort entailed recalibrating the Webster model to the simulated data to develop a new delay, fuel consumption, and emissions formulation. However, an additional intercept was incorporated to the new formulations to enhance the Webster model. The second research effort entailed updating the proposed model against four study intersections. To account for the stochastic and random nature of traffic, the simulations were then run with twenty random seeds per scenario. Both efforts noted its estimated cycle lengths to minimize fuel consumption and emissions were longer than cycle lengths optimized for vehicle delay only. Secondly, the simulation results manifested an overestimation in optimum cycle lengths derived from the Webster model for high vehicle demands.Master of Science
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Moore, Kori D. "Measurement of Agriculture-Related Air Pollutant Emissions using Point and Remote Sensors." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6907.
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Measuring air pollution emissions from agricultural activities is usually difficult because of their large area and variability. Traditional air quality sensors, called point samplers, measure conditions in one location, which may not adequately measure a plume. Remote sensors, instruments that measure pollution along a line rather than at a single point, are better able to measure conditions around large areas. This dissertation reports on four agricultural air emissions studies that used both point and remote sensors for comparison. The methods used to calculate the emissions are based on previous work and are further developed in these studies. In particular, an atmospheric dispersion model was developed and tested that can account for a particle behaving different than the surrounding gas due to gravity and inertia and depositing out of the flow. Particulate matter (PM) emissions values are reported for two agricultural tillage conservation management practices (CMPs)and the corresponding traditional tillage methods in order to determine how well the CMP reduces emissions. In addition, gas-phase ammonia (NH3) emissions for a dairy operation and PM emissions from a feedlot operation are reported. These studies can help us better measure emissions from agricultural operations and understand how much air pollution is being emitted.