Thèses : « Secondary pollution »

1

Meyer, Ben Anton. « An examination of pollution awareness and prevention in Montana secondary agricultural education programs ». Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/meyer/MeyerB0807.pdf.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

2

Baek, Jaemeen. « Improving aerosol simulations : assessing and improving emissions and secondary organic aerosol formation in air quality modeling ». Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37249.

Texte intégral

Résumé :

Both long-term and short-term exposure to fine particulate matter (PM2.5) has been shown to increase the rate of respiratory and cardiovascular illness, premature death, and hospital admissions from respiratory causes. It is important to understand what contributes to ambient PM2.5 level to establish effective regulation, and air quality model can provide guidance based on the best scientific understanding available. However, PM2.5 simulations in air quality models have often found performance less than desirable, particularly for organic carbon levels. Here, some of major shortcomings of current air quality model will be addressed and improved by using CMAQ, receptor models, and regression analysis. Detailed source apportionment of PM2.5 performed using the CMAQ-tracer method suggests that wood combustion and mobile sources are the largest sources of PM2.5, followed by meat cooking and industrial processes. Biases in emission estimates are investigated using tracer species, such as organic molecular markers and trace metals that are used in receptor models. Comparison of simulated and observed tracer species shows some consistent discrepancies, which enables us to quantify biases in emissions and improve CMAQ simulations. Secondary organic aerosol (SOA) is another topic that is investigated. CMAQ studies on organic aerosol usually underestimate organic carbon with larger than a 50% bias. Formation of aged aerosol from multigenerational semi-volatile organic carbon is added to CMAQ, significantly improving performance of organic aerosol simulations.

Styles APA, Harvard, Vancouver, ISO, etc.

3

Wang, Hong. « Field and laboratory investigation of ozone-indoor surface reactions : secondary emissions inventory and implications for indoor air quality ». Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Wang_09007dcc8044137b.pdf.

Texte intégral

Résumé :

Thesis (Ph. D.)--University of Missouri--Rolla, 2007.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 6, 2008) Includes bibliographical references (p. 140-144).

Styles APA, Harvard, Vancouver, ISO, etc.

4

Hennigan, Christopher James. « Properties of secondary organic aerosol in the ambient atmosphere sources, formation, and partitioning / ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26598.

Texte intégral

Résumé :

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Weber, Rodney; Committee Co-Chair: Bergin, Michael; Committee Member: Mulholland, James; Committee Member: Nenes, Athanasios; Committee Member: Russell, Armistead. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Styles APA, Harvard, Vancouver, ISO, etc.

5

Morgan, William Thomas. « Pollution aerosol across Northern Europe : assessing properties, processes and effects on regional climate ». Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/pollution-aerosol-across-northern-europe-assessing-properties-processes-and-effects-on-regional-climate(8c347b7e-baa9-4430-af93-911ad77eef7d).html.

Texte intégral

Résumé :

Atmospheric aerosols are the major component in the shorter-term variability governing the radiative balance of the climate system, particularly on regional scales. However, knowledge of the myriad of properties and processes associated with aerosols is often limited, which results in major uncertainties when assessing their climate effects. One such aspect is the chemical make-up of the atmospheric aerosol burden.Airborne measurements of aerosol properties across Northern Europe are presented here in order to facilitate constraint of the properties, processes and effects of aerosols in this highly populated and industrialised region. An Aerodyne Aerosol Mass Spectrometer (AMS) delivered highly time-resolved measurements of aerosol chemical components, which included organic matter, sulphate, nitrate and ammonium.The chemical composition of the aerosol burden was strongly determined by the dominant meteorological conditions in Northern Europe. Pollution loadings in North- Western Europe were strongly enhanced when air masses originated from Continental Europe. Conversely, much cleaner conditions were associated with air masses from the Atlantic Ocean.Organic matter was found to be ubiquitous across Northern Europe and predominantly secondary in nature, which is consistent with other analyses in polluted regions of the Northern Hemisphere. Furthermore, its concentration was generally comparable to, or exceeded that of, sulphate. Significant chemical processing of the organic aerosol component was observed. Highly oxidised secondary organic aerosol dominated, as the distance from source and photochemical processing increased.Ammonium nitrate was found to be a major component of the aerosol burden in Northern Europe, with peak contributions occurring in North-Western Europe, due to the co-location of its emission precursors (NH3 and NOx) in the region. Ammonium nitrate was found to be the dominant sub-micron chemical constituent during periods associated with enhanced pollution episodes. Its concentration was shown to be modulated by the thermodynamic structure of the lower troposphere, with enhanced concentrations prevalent at the top of the boundary layer. This phenomenon greatly enhanced the radiative impact of the aerosol burden; the increased mass and water uptake by the aerosol significantly amplified the aerosol optical depth in the region.The results presented in this thesis highlight a highly dynamic region, where major changes in emissions have played a significant role in determining the chemical composition of the aerosol burden. As substantial reductions in sulphur dioxide emissions have occurred over the past two decades in Northern Europe, the relative contribution of sulphate aerosols to the regional aerosol burden has decreased. Consequently, it is more pertinent to consider the roles of organic matter and ammonium nitrate, as their influence becomes more pronounced than sulphate on regional and global climate.

Styles APA, Harvard, Vancouver, ISO, etc.

6

Moolman, Tiani. « Environmental reasoning of secondary-level schoolchildren : case study of Okahandja, Namibia ». Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/98100.

Texte intégral

Résumé :

Thesis (MA)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Okahandja has been identified as one of the ‘dirtiest towns’ in Namibia. The town’s location makes it an important node serving as a gateway to the leisure and tourism periphery in Namibia. However, environmental problems such as littering and the burning of household waste are threatening the local cultural and nature-based tourism industry and the aesthetic beauty of the town. These forms of pollution pose various health risks to people living in the area, to those who interact with the spaces as well as for grazing animals and the natural environment. The aim of the study was to explore the environmental reasoning of secondary-level schoolchildren of Okahandja and to establish the main determinants of their environmental knowledge, attitudes and behaviour. The research objectives of the study were (1) to study the literature on and understand the concepts and models related to pro-environmental behaviour (PEB), environmental worldview, environmental concern and place attachment; (2) conduct transect walks through the communities to gain a contextual understanding; (3) question secondary-level schoolchildren at JG van der Wath Secondary School about their environmental knowledge and concern that influence their environmental reasoning; (4) investigate the influences (im)mobility (low access to transport) and place attachment to Okahandja have on the schoolchildren’s views and perceptions of the environment; (5) explore how the children view their local environment and how they want their living environment to change; and (6) examine whether children from different ethnic groups reason differently about the environment and whether these distinctions influence their interactions with their surroundings. The study followed a mixed-methods approach. A questionnaire survey among schoolchildren elicited information supplemented by observations made during transect walks, focus group discussions and participatory drawing exercises. Data was captured and analysed using STATISTICA, Excel and ArcGIS. The findings indicate that the children are aware of and relatively well-informed about the significance of a clean and protected environment. They were also well able to identify the importance of Okahandja within the Namibian landscape. Participants, especially female participants are concerned about protecting the natural environment. Greater emphasis was placed on environmental problems that are apparent and aesthetically unpleasing such as littering, than on other environmental issues such as the chopping down of trees and the burning of household waste. Participants only have a moderate sense of attachment to Okahandja so causing them to have a weak sense of responsibility and desire to behave pro-environmentally. Although community cohesion and social ties are strong within the communities, mistrust and miscommunication between residents and local authorities were identified as major stumbling blocks to PEB. Dissatisfaction with structural opportunities was displayed through a lack of concern and cooperation, leading to high levels of environmental degradation in and around Okahandja. The children seem to possess a ‘balanced’ environmental worldview as they believe that the natural environment should be protected yet used to sustain human life. The importance of positive role models such as parents and teachers was highlighted. It is recommended that environmental education (EE) and awareness should be implemented on three levels, namely parental, school and community.
AFRIKAANSE OPSOMMING:Okahandja staan bekend as een van die ‘vuilste dorpe’ in Namibië. Die ligging van die dorp maak dit ’n belangrike nodus wat dien as ’n poort na die ontspannings- en toerisme-periferie in Namibië. Maar omgewingskwessies soos rommelstrooiing en die verbranding van huishoudelike afval bedreig die plaaslike toerismebedryf en estetiese skoonheid van die dorp wat gegrondves is op sy kultuur en die natuur. Hierdie vorme van besoedeling hou gesondheidsrisiko’s in vir bewoners in die gebied, vir diegene wat beweeg in die ruimte, vir diere wat wei en die natuurlike omgewing. Die doel van die studie was om sekondêre skoolleerlinge van Okahandja se redenering oor die omgewing te ondersoek en die bepalende faktore van hul kennis van die omgewing en hul houding en gedrag teenoor die omgewing vas te stel. Die navorsingsdoelwitte van die studie was (1) om die literatuur oor pro-omgewingsgedrag (POG), die wêreldbeskouing oor die omgewing, besorgdheid oor die omgewing en verbondenheid aan ’n plek te bestudeer en die konsepte en modelle verwant daaraan te verstaan; (2) om deur die gemeenskappe te stap (of te deurkruis) om ’n kontekstuele begrip te verkry; (3) om sekondêre skoolleerlinge van JG van der Wath Sekondêre Skool te ondervra oor hul kennis en besorgtheid vir die omgewing en vas te stel hoe dit hul redenering oor die omgewing beïnvloed; (4) om die invloed wat (im)mobiliteit (beperkte toegang tot vervoer) en plekgehegtheid aan Okahandja het op die skoolleerlinge se omgewingsienings en –persepsies te ondersoek; (5) te ontdek hoe die kinders hul plaaslike omgewing sien en hoe hulle wil hê die omgewing waarin hul leef, moet verander; en (6) om vas te stel of kinders van verskillende etniese groepe verskillend redeneer oor die omgewing en of hierdie onderskeid hul interaksie met hul omgewing beïnvloed. Die studie maak van verskillende metodes gebruik. ’n Vraelys-opname het sekere inligting aan die lig gebring, dit is aangevul deur waarnemings tydens staptogte wat die studiegebied deurkruis het, fokusgroepbesprekings en deelnemende tekenoefeninge. Inligting is opgeteken en geanaliseer deur middel van STATISTICA, Excel en ArcGIS. Die bevindings toon dat die kinders bewus en relatief goed ingelig is oor die belangrikheid van ’n skoon en beskermde omgewing. Hulle was goed in staat om die belangrikheid van Okahandja binne die Namibiese landskap te identifiseer. Deelnemers, veral vroulike deelnemers, is besorg oor die beskerming van die natuurlike omgewing. Respondente het groter klem geplaas op omgewingsprobleme wat duidelik en esteties onaangenaam is soos rommelstrooiing, eerder as ander omgewingskwessies soos die afkap van bome en die verbranding van huishoudelike afval. Deelnemers het slegs ’n redelike sin van gehegtheid aan Okahandja wat veroorsaak dat hulle ’n swak sin van verantwoordelikheid en begeerte om pro-omgewing op te tree, het. Alhoewel gemeenskapsamehorigheid en sosiale bande sterk is binne die gemeenskappe, is wantroue en gebrekkige kommunikasie tussen inwoners en plaaslike owerhede geïdentifiseer as die hoofstruikelblokke van POG. Ontevredenheid met strukturele geleenthede is geopenbaar deur ’n gebrek aan besorgdheid en samewerking wat lei tot hoë vlakke van omgewingsdegradasie in en rondom Okahandja. Dit lyk of die kinders ’n ‘gebalanseerde’ wêreldbeskouing van die omgewing het, want hulle glo dat die natuurlike omgewing beskerm moet word, maar tog gebruik moet word om menselewens te onderhou. Die belangrikheid van positiewe rolmodelle soos ouers en onderwysers het uitgestaan. Daar word aanbeveel dat omgewingsopvoeding en –bewustheid op drie vlakke, naamlik ouer-, skool- en gemeenskapsvlak geïmplementeer moet word.

Styles APA, Harvard, Vancouver, ISO, etc.

7

Couvidat, Florian. « Modélisation des particules organiques dans l'atmosphère ». Phd thesis, Université Paris-Est, 2012. http://pastel.archives-ouvertes.fr/pastel-00778086.

Texte intégral

Résumé :

La formation des aérosols organiques dans l'atmosphère est étudiée via le développement d'un nouveau modèle de formation d'aérosols organiques secondaires nommé H²O (Hydrohilic/Hydrophobic Organics). Dans un premier temps, une paramétrisation de la formation d'aérosols via l'oxydation de l'isoprène est développée. Cette paramétrisation prend notamment en compte l'influence des concentrations d'oxydes d'azote sur la formation d'aérosols et leurs propriétés hydrophiles. Ensuite, H²O incluant cette paramétrisation et d'autres développements est évalué par comparaison aux mesures de carbone organique sur l'Europe. Prendre en compte les émissions de composés semi-volatils primaires gazeux (qui peuvent former des aérosols organiques secondaires après oxydation ou se condenser lors de baisses de température) améliore les performances du modèle de manière significative. En revanche, si les émissions de ces composés ne sont pas prises en compte, il en résulte une très forte sous-estimation des concentrations d'aérosols organiques en hiver. La formation d'aérosols organiques secondaires sur l'Île-de-France durant la campagne d'été de Megapoli (juillet 2009) a aussi été simulée pour évaluer les performances du modèle en zone urbaine. H²O donne de bons résultats sur l'Île-de-France bien que le modèle prévoit un pic d'aérosols organiques, provenant des émissions du trafic durant les heures de pointe, qui n'apparaît pas dans les mesures. La présence de ce pic dans les résultats du modèle peut être due à la sous-estimation de la volatilité des composés semi-volatils primaires. Il est aussi possible que les composés organiques primaires et les composés organiques secondaires ne se mélangent pas et que les composés semi-volatils primaires ne peuvent pas se condenser sur un aérosol organique majoritairement secondaire et très oxydé. Enfin, l'impact de la chimie aqueuse est étudié. Le mécanisme utilisé inclue notamment, la formation d'aérosols organiques secondaires dans la phase aqueuse des nuages par oxydation du glyoxal, du méthylglyoxal, de la méthacroleine et de la méthyl-vinyl-cétone, la formation de méthyltétrols dans la phase aqueuse des particules ou des gouttes d'eau des nuages et le vieillissement des aérosols organiques dans un nuage. L'impact des dépôts humides sur la formation d'aérosols est aussi étudié pour mieux caractériser l'impact des nuages sur les concentrations d'aérosols organiques

Styles APA, Harvard, Vancouver, ISO, etc.

8

Lannuque, Victor. « Formation de l’aérosol organique secondaire dans les modèles de qualité de l’air : développement d’une paramétrisation sur la base de simulations explicites ». Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1129.

Texte intégral

Résumé :

L’oxydation gazeuse des composés organiques émis dans l’atmosphère mène à la formation de milliers de composés organiques secondaires (COS). Une fraction de ces COS est peu volatile, et peut se partager entre la phase gazeuse et la phase particulaire formant ainsi des aérosols organiques secondaires (AOS). Les AOS contribuent majoritairement à la composition des particules, participant entre 20 et 80 % à la masse totale des aérosols fins et influencent ainsi leurs impacts sur l’environnement, en particulier sur la qualité de l’air et le climat. Ces impacts sont quantifiés à l’aide de modèles de chimie-transport (CTM). Les comparaisons avec les mesures in situ montrent que les variations spatiales et temporelles de la masse d’AOS ne sont pas correctement simulées par les CTM. Dans ces modèles, la formation d’AOS est représentée de façon simplifiée à l'aide de paramétrisations empiriques développées sur la base d'observations en chambres de simulation atmosphérique. Il est donc primordial de repenser et d’améliorer la représentation des aérosols organiques dans les CTM pour diagnostiquer l’origine de la pollution atmosphérique par les particules fines, améliorer la fiabilité de la prévision des épisodes de pollution et évaluer l'impact des aérosols sur l'environnement. Les objectifs de cette thèse sont de :• explorer l’influence des conditions environnementales sur la formation et les propriétés des AOS,• développer une nouvelle paramétrisation de formation de l’AOS sur la base d’une représentation déterministe de la chimie atmosphérique,• évaluer cette paramétrisation en CTM par comparaison avec des mesures in-situ.Les modèles déterministes permettent de représenter la non-linéarité des processus de formation de l'AOS. Le modèle déterministe GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) est un outil de modélisation numérique qui intègre les données élémentaires (cinétiques et thermodynamiques) issues des études en laboratoire. Dans le cadre de cette thèse, des scénarios d’oxydation en conditions environnementales ont été développés et GECKO-A a été utilisé pour étudier l’impact des facteurs environnementaux (température, teneur en NOx, ensoleillement...) sur la formation et les propriétés des AOS. Sur la base de ces simulations, une nouvelle paramétrisation pour la formation d’AOS a été développée: VBS-GECKO. L’évaluation de la VBS-GECKO en modèle de boîte a montré une bonne reproduction des concentrations en aérosols organiques (AO) avec une RMSE inférieure à 20%. La VBS-GECKO a été intégrée au CTM CHIMERE pour simuler les concentrations estivales d’AO au dessus de l’Europe. Son utilisation conduit à une sensible amélioration de la masse d’AO simulée par rapport à la paramétrisation de référence utilisée dans CHIMERE. La VBS-GECKO a également été utilisé pour étudier (i) les sources et propriétés des AOS et (ii) différentes représentation des émissions de composés organiques semi-volatils et de volatilité intermédiaire par le trafic routier
The gaseous oxidation of organic compounds emitted into the atmosphere leads to the formation of thousands of secondary organic compounds (SOC). A fraction of these SOC is low volatile, and can partition between the gaseous phase and the particulate phase, forming secondary organic aerosols (SOA). The SOA are a main component of the particles, representing between 20% and 80% of the total mass of fine aerosols. Therefore, SOA contribute to the impact of aerosols on the environment, in particular air quality and climate. The quantification of the SOA impacts is estimated using chemical-transport models (CTM). Comparisons with in situ measurements show that the spatial and temporal variations of SOA mass are not correctly simulated by CTM. In these models, the SOA formation is represented in a simplified way, using empirical parameterizations developed on the basis of observations performed in atmospheric simulation chambers. Improving the representation of organic aerosols in CTM is therefore required to diagnose the origin of air pollution by fine particles, improve the reliability of pollution episode prediction and assess the impact of aerosols on the environment. The objectives of this thesis are :• to explore the influence of environmental conditions on SOA formation and properties,• to develop a new parameterization of SOA formation based on a deterministic representation of atmospheric chemistry,• to evaluate this parameterization in CTM by comparison with in-situ measurements. Deterministic models represent the non-linearity of SOA formation processes. The model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) is a numerical modelling tool that integrates the elementary data (kinetics and thermodynamics) from laboratory studies. In this thesis, oxidation scenarios representative of various environmental conditions were developed and GECKO-A was used to study the impact of environmental factors (temperature, NOx concentrations, solar radiations, etc.) on the formation and the properties of the SOA. On the basis of these simulations, a new parameterization for SOA formation was developed: VBS-GECKO. The evaluation of the VBS-GECKO in box model has shown a good reproduction of the organic aerosol (OA) concentrations with RMSE lesser than 20%.The VBS-GECKO was integrated into the CHIMERE CTM to simulate summer concentrations of OA over Europe. Simulated OA are significantly improved compared to the reference parameterization used in CHIMERE. The VBS-GECKO was also used to study (i) the sources and properties of SOA and (ii) different representations of emissions of semi-volatile and intermediate volatility organic compounds by road traffic

Styles APA, Harvard, Vancouver, ISO, etc.

9

Simon, Leïla. « Détermination des sources de composés organiques (gazeux et particulaires) en Ile-de-France ». Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASJ011.

Texte intégral

Résumé :

Afin d'approfondir les connaissances sur la qualité de l'air et la chimie atmosphérique en Ile-de-France, il est nécessaire de documenter la nature et la variabilité des polluants atmosphériques sur le long terme. La station péri-urbaine du SIRTA (intégrée à l'infrastructure de recherche européenne ACTRIS) héberge des instruments de mesure permettant le suivi en continu des propriétés physico-chimiques des particules en suspension et de certains gaz réactifs inorganiques depuis une dizaine d'années. Des questions restent néanmoins encore ouvertes sur les origines de l'aérosol organique secondaire, et plus particulièrement sur son lien avec ses précurseurs gazeux, les composés organiques volatils (COV). Alors qu'ils jouent un rôle important dans la chimie de l'atmosphère, ces derniers n'étaient jusqu'alors pas mesurés sur le long-terme au SIRTA.Dans ce contexte, cette thèse vise à mieux caractériser la pollution organique en Ile-de-France. Cela passe par la mesure de COV en temps réel venant compléter le panel de mesures existantes, ainsi que l'application et l'évaluation de méthodes pour la détermination des sources de polluants organiques adaptées au long-terme.Pour ce faire, des mesures par spectrométrie de masse (PTR-MS), encore très peu utilisée au sein d'ACTRIS, ont été mises en place au SIRTA dans le cadre de cette thèse. Les chaînes de traitement de données automatisé ont été améliorées et adaptées pour le long terme et un contrôle qualité rigoureux a été appliqué aux données de 2020 et 2021. Ces deux premières années de mesures ont ensuite été étudiées en termes de variabilités journalières et saisonnières. Le rôle joué par les conditions météorologiques et par l'origine des masses d'air est particulièrement illustré par les résultats obtenus lors des confinements de 2020. L'influence de sources anthropiques a été observée pour les monoterpènes, composés habituellement identifiés comme biogéniques en site périurbain.Le modèle source-récepteur Positive Matrix Factorisation (PMF) est classiquement utilisé pour la détermination des sources de polluants atmosphériques (aérosols ou COV), mais certaines limites existent pour son application sur le long-terme. Pour dépasser ces limitations, de nouvelles options existent et ont été testées lors de cette thèse. En particulier, les données COV ont servi de marqueurs pour l'analyse des sources de l'aérosol organique en été, par la création d'un jeu de données combiné unifié. Cette méthodologie complexe a été mise en œuvre ici pour la première fois avec ce type d'instruments. Elle a été adaptée au jeu de données du SIRTA, permettant de mieux déconvoluer l'aérosol organique oxygéné par rapport à une méthode classique, et par conséquent de le relier à ses sources/processus respectifs, notamment en distinguant des processus de jour et de nuit
To refine the knowledge on air quality and atmospheric chemistry in the Paris region, it is essential to document the nature and variability of atmospheric pollutants on the long term. The suburban SIRTA station (integrated to the European infrastructure ACTRIS) has been hosting instruments for the continuous measurement of physicochemical properties of suspended particles and of some inorganic reactive gases for a decade. Nonetheless, questions remain open on the origins of secondary organic aerosol and more specifically the link with its precursor gases, volatile organic compounds (VOC). Although their play an important role in atmospheric chemistry, VOC were hitherto not measured on the long term at SIRTA.In this context, this thesis aims at better characterizing organic pollution in the Paris region. This involves the measurement of VOC in real time to complete the panel of existing measurements, as well as the application and evaluation of methods for the source apportionment of organic pollutants adapted to long term studies.For this purpose, measurements using mass spectrometry (PTR-MS), still very little used within ACTRIS, were setup at SIRTA as part of this thesis. Automated data treatment was improved and adapted for the long term and a rigorous quality control was applied to 2020 and 2021. These first two years of measurements were then studied in terms of diel and seasonal variabilities. The role played by meteorological conditions and air masses was particularly illustrated by results obtained during the lockdowns in 2020. An influence of anthropogenic sources was observed for monoterpenes, compounds usually identified as biogenic in suburban sites.The Positive Matrix Factorization (PMF) source-receptor model is classically used for the source apportionment of atmospheric pollutants (aerosol or VOC), but some limits exist for its long-term application. To overcome these limitations, new options exist and were tested during this thesis. Particularly, VOC were used as organic markers for the analysis of organic aerosol sources in summer, by creating a unified combined dataset. This complex methodology was implemented here for the first time with this type of instruments. It was adapted to the SIRTA dataset, allowing a better deconvolution of oxygenated organic aerosol compared to a classical method, and consequently to link it to its respective sources/processes, especially by distinguishing daytime and nighttime processes

Styles APA, Harvard, Vancouver, ISO, etc.

10

Zhang, Zhenhua. « Plant growth and nutrient removal in simulated secondary-treated municipal wastewater in wetland microcosmos ». University of Western Australia. School of Earth and Geographical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0141.

Texte intégral

Résumé :

[Truncated abstract] The use of constructed wetlands for tertiary purification of municipal wastewater has received increasing attention around the world because direct discharge of secondary-treated municipal wastewater to water bodies has caused eutrophication. Plant species selection and vegetation management may enhance nutrient removal efficiency in constructed wetlands. However, there is a lack of knowledge on the relations between plant growth and nutrient removal efficiency in constructed wetlands. The objective of this study is to better understand how plant growth and resource allocation are influenced by nutrients in wastewater and how nutrient removal efficiencies are affected by plant species and vegetation management. The preliminary experiment was conducted to select macrophytes, especially ornamental species, to grow in the wastewater in the wetland microcosms. Ten plant species, comprising six ornamental species: Alocasia macrorrhiza, Canna indica, Iris louisiana, Lythrum sp., Zantedeschia aethiopica, Zantedeschia sp., and four sedge species: Baumea articulate, Baumea juncea, Carex tereticaulis and Schoenoplectus validus, were planted in the wetland microcosms and fed a simulated wastewater solution in the concentrations similar to the secondary-treated municipal wastewater. C. indica has shown vigorous and healthy growth, and a relatively high potential of rooting-zone aeration and nutrient removal efficiency. B. articulata and S. validus also showed relatively high nutrient removal efficiency. ... The high nutrient availability and optimum N/P ratio were required for stimulating plant growth, resulting in allocation of more resources to above-ground tissues compared to below-ground parts, and enhancing nutrient removal efficiency. Nutrient removal efficiencies were significantly influenced by growth of C. indica and S. validus, nutrient loading rates and N/P ratios in the wastewater. The nutrient uptake kinetics of C. indica and S. validus were investigated to elucidate the differences in nutrient uptake between species. Wetland plant species have shown differential nutrient uptake efficiency and different preferences for inorganic N source, with C. indica preferring NO3-N and S. validus preferring NH4-N. C. indica had greater capacity than S. validus to take up PO4-P when the concentration of PO4-P in the solution was relatively low, whereas S. validus was more capable than C. indica to take up NO3-N when the concentration of NO3-N in the solution was relatively low. The PO4-P uptake capacity was higher in younger than older plants. Overall, the study has suggested that different plant species have differential capacity to take up nutrients. In addition to nutrient uptake, plants have significant other roles in terms of nutrient removal from the wastewater (such as leaking oxygen into the rhizosphere in which oxidation of substances like ammonia can occur). The properly high nutrient availability and optimum N/P ratio are required to stimulate the plant growth, resulting in enhancing the treatment performance in the wetlands. These findings have important implications for improving our ability to engineer ecological solutions to the problems associated with nutrient-rich wastewater.

Styles APA, Harvard, Vancouver, ISO, etc.

11

Lamkaddam, Houssni. « Etude en atmosphère simulée de la formation d'Aérosol Organique Secondaire issue de la photooxydation du n-dodécane : impact des paramètres environnementaux ». Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1128/document.

Texte intégral

Résumé :

L’aérosol organique secondaire (AOS), fraction majoritaire de l’aérosol submicronique, joue un rôle important sur la santé, l’environnement et le climat. L’évaluation de son impact constitue un véritable enjeu pour la communauté scientifique. Toutefois, nos connaissances actuelles sur les processus de formation d’AOS et sa composition chimique sont encore très lacunaires, et en l’occurrence, limitent le développement des modèles atmosphériques permettant de quantifier les impacts des AOS sur la qualité de l’air et le système climatique. Ainsi, l’objectif de ce travail est de produire un ensemble de données expérimentales fournissant des points de contrainte afin d’évaluer et d’améliorer les modèles. Pour ce faire, la formation d’AOS a été étudiée à partir de la photooxydation d’un précurseur modèle, le n-dodécane, dans la chambre de simulation atmosphérique CESAM. La composition chimique a été élucidée par des techniques spectrométriques et chromatographiques permettant d’identifier les différentes espèces constituant la phase gazeuse et particulaire. En particulier, de nouveaux mécanismes en phase condensée ont été proposés afin d’expliquer la formation des acides carboxyliques et des lactones, identifiés pour la première fois dans l’AOS d’un alcane. Ces derniers pourront être implémentés dans les modèles. Une grande diversité de conditions environnementales, telles que la température, l’humidité relative et la présence/absence de particules préexistantes, a été prise en compte dans ces travaux. Notamment, l’étude de l’influence de la température a mis en évidence une faible sensibilité de ce paramètre sur les rendements de production d’AOS. Tandis que l’étude sur l’effet de l’humidité relative, elle, a montré que l’ajout d’eau dans le système réactionnel au-delà de 5% abaisse les rendements d’AOS de près d’un facteur 2 en comparaison à des conditions sèches. Ainsi, la formation potentielle d’AOS sous ces différentes conditions a permis d’aboutir à des paramétrisations directement utilisables par les modélisateurs. Une caractérisation des effets de paroi dans CESAM, i.e. les pertes en phase gazeuse et particulaire, a également été menée
Secondary Organic Aerosol (SOA), the major fraction of the submicron aerosol, plays a key role on health, environment and climate. The evaluation of its impacts is a real challenge for the scientific community. Our current knowledge of SOA formation processes and chemical composition is still very deficient and limit the development of atmospheric models to quantify the impacts of SOA on air quality and climate system. Therefore, the aim of this work is to produce a set of experimental data to use to constrain and improve the models. To do that, the SOA formation has been studied from the photooxidation of a model precursor, n-dodecane, in the CESAM environmental chamber. The chemical composition has been investigated by spectrometric and chromatographic techniques which allowed us to identify the reaction products constituting the gaseous and particulate phases. In particular, new condensed phase mechanisms have been proposed to explain the formation of carboxylic acids and lactones, identified for the first time. These could be implemented in the models. A wide variety of environmental conditions, such as temperature, relative humidity and the presence/absence of preexisting particles, have been taken into account in this work. The study of the temperature influence has shown a low sensitivity of this parameter on the SOA production. While the study relative humidity effect has shown that adding water to the reaction system beyond 5% lowers SOA yields by almost a factor of 2 in comparison to dry conditions. The SOA formation potential, under these conditions, has been evaluated, and resulted in parameterizations which could be useful for modelers. Furthermore, a characterization of the wall effects in CESAM, i.e. gas and particulate phase wall losses, has been carried out

Styles APA, Harvard, Vancouver, ISO, etc.

12

Roskamp, Melissa Jordan. « Characterization of Secondary Organic Aerosol Precursors Using Two-Dimensional Gas Chromatography with Time of Flight Mass Spectrometry (GC×GC/TOFMS) ». PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1411.

Texte intégral

Résumé :

The oxidation of volatile organic compounds (VOCs) plays a role in both regional and global air quality through the formation of secondary organic aerosols (SOA). More than 1000TgC/yr of non-methane VOCs are emitted from biogenic sources (significantly greater than from anthropogenic sources). Despite this magnitude and potential importance for air quality, the body of knowledge around the identities, quantities and oxidation processes of these compounds is still incomplete (e.g., Goldstein & Galbally, 2007; Robinson et al., 2009). Two-dimensional gas chromatography paired with time-of-flight mass spectrometry (GC×GC/TOFMS) is a powerful analytical technique which is explored here for its role in better characterizing biogenic VOCs (BVOCs) and thus SOA precursors. This work presents measurements of BVOCs collected during two field campaigns and analyzed using GC×GC/TOFMS. The first campaign, the Bio-hydro-atmosphere Interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS), took place in a Ponderosa pine forest in Colorado. The second campaign, Particle Investigations at a Northern Ozarks Tower: NOx, Oxidant, Isoprene Research (PINOT NOIR) Study, was conducted in the Ozark region of Missouri. Tens to hundreds of BVOCs were quantified in each set of samples, including primary emissions, atmospheric oxidation products, stress indicators and semi-volatile leaf surface compounds. These findings highlight that there is a largely uncharacterized diversity of BVOCs in ambient samples. Our findings demonstrate that GC×GC can distinguish between compounds with the same molecular weight and similar structures, which have highly variable potentials for production of SOA (Lee et al., 2006). This work represents some of the first analysis of ambient BVOCs with this technology, which is anticipated to contribute greatly to characterization of atmospheric SOA precursors and ultimately, regional and global modeling of SOA and fine particulate matter.

Styles APA, Harvard, Vancouver, ISO, etc.

13

McDonald, Ewan W. « Spatial-temporal analysis of endocrine disruptor pollution, neighbourhood stress, maternal age and related factors as potential determinants of birth sex ratio in Scotland ». Thesis, University of Stirling, 2013. http://hdl.handle.net/1893/16044.

Texte intégral

Résumé :

Background: The human secondary sex ratio has been the subject of long-standing medical, environmental and social scientific curiosity and research. A decline in male birth proportion in some industrialised countries is linked to endocrine disruption and is validated by some empirical studies. Increasing parental age and population stress and associated decreases in sex ratio have also been demonstrated. A thorough literature review of 123 relevant and diverse studies provides context for these assessments. Methods: A spatial-temporal investigation of birth sex ratio in Scotland and potential determinants of endocrine disruptor pollution, socio-economic factors including neighbourhood stress, deprivation, smoking, and maternal age, was conducted. This involved review of national and regional sex ratio time trends, and stratified/spatial analysis of such factors, including the use of GIS tools. Secondary data were sourced from Scottish Government web portals including Scottish Neighbourhood Statistics and the Scottish Environmental Protection Agency. Results: Regional differences in sex ratio between 1973 and 2010 are observed which likely lever the national male birth proportion downwards, with the region of poorest air quality from industrial emissions, the Forth Valley, displaying the greatest sex ratio reduction. Further analysis shows significant upwards skewing in sex ratio for the population cohort experiencing the least and 2nd most deprivation. Localised reductions in sex ratio for areas of high modelled endocrine disruptor pollution within the Central Region in Scotland are also displayed. Discussion: Limitations of the analyses include the danger of ecological fallacy in interpreting from area-based measurement and the simplified pollution modelling adopted. Despite this, and given elevated incidence of testicular cancer in Scottish regions mirrors the study’s results, tentative confirmation of the endocrine disruptor hypothesis can be substantiated. Further, elucidation on advanced parental age as a contributory factor to secondary sex ratio change is also given. Recommendations are made with respect to environmental monitoring and health protection, and preventative health strategies in Scotland.

Styles APA, Harvard, Vancouver, ISO, etc.

14

Martinez, Alvaro. « Contribution des composés organiques volatils (COVs) provenant des émissions des véhicules aux aérosols organiques secondaires (AOS) et à la pollution urbaine ». Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1041.

Texte intégral

Résumé :

Le secteur des transports est fondamental pour le développement économique d'un pays et pour assurer la communication et une bonne qualité de vie. Cependant, le transport routier conduit à une grave dégradation de la qualité de l'air et contribue au réchauffement de la planète. Parmi tous les polluants, les particules fines et ultrafines, émises par les véhicules mais également formées dans l'atmosphère sont considérées toxiques. De nombreuses études montrent que l’exposition chronique aux particules fines favorise le développement de pathologies respiratoires et cardiovasculaires. Les précurseurs gazeux, les principaux mécanismes réactionnels ainsi que les transformations physiques que les Aérosol Organiques Secondaires (AOS) subit dans l'atmosphère restent encore incertains. La présente étude porte principalement sur la caractérisation des polluants primaires émis par les échappements automobiles et les transformations photochimiques des COV / COVI. Les émissions des voitures ont été évaluées à l’aide d’un banc à rouleau au laboratoire de l’IFSTTAR. Les mesures du nombre de particules ont été effectuées directement au niveau de l’échappement. Pour les véhicules GDI, PN0.23 (<23 nm) représentait en moyenne 20- 30% du nombre total de particules émises, alors que pour les voitures diesel, cette fraction était bien inférieure (≈10-15%). Lors des régimes à grande vitesse (autoroutier Artemis) des véhicules diesel, une régénération passive de Filtre à Particules (FAP) a été observée. Les particules émises étaient principalement constituées de suie, de bisulfate et de matière organique. Les particules émises par les voitures essence à injection directe étaient principalement composées de Black Carbon (BC) et de gouttelettes organiques contenant des éléments. Pendant le démarrage à froid, les voitures GDI émettent des concentrations importantes de BC et de matière organique. Les émissions d'hydrocarbures ont également été étudiées. Les véhicules GDI ont émis des concentrations importantes de THC lors du démarrage à froid. Parmi les composés aliphatiques, des composés jusqu’à la C15 ont été identifiés, confirmant l’émission d'hydrocarbures plus lourds par les voitures diesel. La deuxième partie de ce travail consistait à étudier la transformation atmosphérique de certains COV (toluène, naphtalène, cyclohexane, nonane) émis par les véhicules Euro 5 et Euro 6 et à déterminer le potentiel de formation d’AOS de ces composés. Les composés choisis ont été photo-oxydés (seuls et en mélange) dans un réacteur à tube à flux d'aérosol afin de simuler leur vieillissement atmosphérique. Les résultats majeurs suggèrent: (1) des composés aromatiques et des HAP représentent les composés avec le plus fort potentiel de formation d'AOS ; (2) la température a un impact important sur la formation et le rendement d'AOS ; (3) la présence de particules préexistantes a un effet positif sur la formation d'AOS; (4) il a été constaté que la présence des NOx affectaient négativement la formation d'AOS ; (5) la formation d'AOS de mélanges de COV est fortement influencée par la fraction de composé aromatique. Certains des produits identifiés dans la phase particulaire n’ont jamais été signalés auparavant. La dégradation des composés aromatiques en régime de NOx moyen a produit des composés nitro-aromatiques identifiés à la fois en phase gazeuse et en phase particulaire. Cette thèse contribue à enrichir la base de données d’émissions des voitures, encore limitée aux véhicules Euro 5 et Euro 6. La spéciation des composés non réglementés aidera à mieux comprendre le budget atmosphérique d’AOS et les impacts des voitures sur la qualité de l’air. Enfin, l’étude de photoxydation de COV primaires (seuls, mélange et émissions complètes) conduira à une meilleure compréhension de la formation d’AOS
The transport sector is fundamental to the economic development of a country and to ensure communication and a good quality of life. However, road transport contributes significantly to global warming and leads to serious degradation of the air quality. Among all pollutants, fine and ultrafine particles, emitted by vehicles but also formed in the atmosphere are considered as potentially toxic. Many studies show that chronic exposure to fine particles promotes the development of respiratory and cardiovascular diseases. The main gaseous precursors, the atmospheric chemical pathways as well as the chemical composition and the physical transformations that secondary organic aerosol (SOA) undergo in the atmosphere, remain poorly understood. The main aim of this work was on one side to improve the knowledge about primary pollutants emitted from Euro 5 and Euro 6 diesel and gasoline passenger cars and on the other side to investigate the photochemical transformations of the VOCs/IVOCs emitted from these cars. Passenger car emissions have been evaluated on a chassis dynamometer test bench at the IFSTTAR laboratory. Particle number measurements were carried out directly at the tailpipe. For GDI vehicles PN0.23 (< 23 nm) represented on average 20 -30 % of total particle number emitted, while for diesel cars, this fraction was considerably lower (≈10-15%). During high speed regimes (Artemis motorway) of diesel passenger cars Diesel Particulate Filter (DPF) passive regeneration was observed. These periods were characterized by a high particle number concentration; their composition was mainly soot, bisulfate and some organic material. PM emitted from gasoline DI passenger cars was mainly composed by BC and some organic droplets containing traces of other elements. During cold start GDI cars do emit important concentrations of BC and organic material. Emission of hydrocarbons has also been investigated. Gasoline DI emitted important concentration of THCs during cold start. Among the aliphatic compounds, families until C15 have been identified, confirming emission of heavier HCs from diesel cars. The second aim of this work was the study of atmospheric degradation of selected VOCs (toluene, naphthalene, cyclohexane, nonane) emitted from Euro 5 and Euro 6 vehicles and to determine the SOA formation potential of these compounds under different environmental conditions. The chosen compounds have been photoxidized (alone and in mixture) in an Aerosol Flow Tube (AFT) reactor in order to simulate VOCs atmospheric aging. The results suggest: (1) aromatic and PAHs compounds, own highest potential to form SOA; (2) the temperature has an important impact on SOA formation and yield; (3) the presence of pre-existing seed particles has, in general, a positive effect on SOA formation and (4) NOx has been found to negatively affect SOA formation; (5) SOA potential formation of VOC mixtures is highly influenced by the fraction of aromatics. Some of the products identified in the particle phase have never been previously reported. Degradation of aromatic compounds under medium NOx regime produced nitro-aromatic compounds identified both in the gas and particle phase. This PhD contributes to enrich vehicle emissions database, still limited for Euro 5 and Euro 6 cars. Speciation of non-regulated compound will help to better understand atmospheric SOA budget and car emissions air quality impacts. By last, the photoxidation study of primary VOCs (alone, mixture and full emissions) will lead to a better comprehension of SOA formation from vehicles

Styles APA, Harvard, Vancouver, ISO, etc.

15

Varol, Murat. « Combustion And Co-combustion Of Olive Cake And Coal In A Fluidized Bed ». Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607182/index.pdf.

Texte intégral

Résumé :

In this study, combustion performances and emission characteristics of olive cake and olive cake+coal mixture are investigated in a bubbling fluidized bed of 102 mm inside diameter and 900 mm height. The average particle sizes of coal and olive cake used in the experiments were 1.57 mm and 1.52 mm, respectively. Flue gas concentrations of O2, CO, SO2, NOx, and total hydrocarbons (CmHn) were measured during combustion experiments. Operational parameters (excess air ratio, secondary air injection) were changed and variation of pollutant concentrations and combustion efficiency with these operational parameters were studied. The temperature profiles measured along the combustor column was found higher in the freeboard for olive cake than coal due to combustion of hydrocarbons mostly in the freeboard. The location of the maximum temperature in the freeboard shifted to the upper part of the column, as the volatile matter content in the fuel mixture increased. Combustion efficiencies in the range of 83.6-90.1% were obtained for olive cake with the excess air ratio of 1.12-2.30. The corresponding combustion efficiency for coal was 98.4-99.7% under the same conditions. As the CO and hydrocarbon concentration in the flue gas increased, the combustion efficiency decreased. Also co-combustion experiments of olive cake and coal for various mixing ratios were carried out. As the amount of olive cake in the fuel mixture increased, SO2 emissions decreased because of the very low sulfur content of olive cake. In order to increase the combustion efficiency, secondary air was injected into the freeboard which was a good solution to decrease the CO and hydrocarbon emissions, and to increase the combustion efficiency. For the setup used in this study, the optimum operating conditions with respect to NOx and SO2 emissions were found as 1.35 for excess air ratio, and 30 L/min for secondary air flowrate for the combustion of 75 wt% olive cake and 25 wt% coal mixture. Highest combustion efficiency of 99.8% was obtained with an excess air ratio of 1.7, secondary air flow rate of 40 L/min for the combustion of 25 wt% olive cake and 75 wt% coal mixture.

Styles APA, Harvard, Vancouver, ISO, etc.

16

Cropper, Paul Michael. « Determination of Fine Particulate Matter Composition and Development of the Organic Aerosol Monitor ». Thesis, Brigham Young University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10107987.

Texte intégral

Résumé :

Tropospheric fine particulate matter (PM) poses serious health risks and has a significant impact on global climate change. The measurement of various aspects of PM is challenging due to its complex chemical nature. This dissertation addresses various aspects of PM, including composition, measurement, and visibility. The U.S. Environmental Protection Agency (EPA) proposed a new secondary standard based on visibility in urban areas using 24-h averaged measurements of either light scatter or PM concentration. However shorter averaging times may better represent human perception of visibility. Data from two studies conducted in Lindon, UT, 2012, and Rubidoux, CA, 2003, were used to compare different techniques to estimate visibility, particularly the effect of relative humidity on visibility estimations. Particle composition was measured in Salt Lake City during January-February of 2009. One-hour averaged concentrations of several gas phase and particle phase inorganic species were measured. The results indicate ammonium nitrate averages 40% of the total PM2.5 mass in the absence of inversions and up to 69% during strong inversions. Also, the formation of ammonium nitrate is nitric acid limited, while the formation of ozone appears to be oxidant and volatile organic carbon (VOC) limited. Reduction of NOx will reduce ammonium nitrate secondary particle formation, however, a decrease in NOx may increase ozone concentration.

Due to the complexity of PM it is poorly characterized. A large fraction of PM is composed of organic compounds, but these compounds are not regularly monitored due to limitations in current sampling techniques. The GC-MS Organic Aerosol Monitor (OAM) combines a collection device with thermal desorption, gas chromatography and mass spectrometry to quantitatively measure the carbonaceous components of PM on an hourly averaged basis. A compact GC and simple pre-concentrator were developed for the system to decouple separation from manual injection and enhance separation of environmentally-relevant polar organic compounds, such as levoglucosan. The GC-MS OAM is fully automated and has been successfully deployed in the field. It uses a chemically deactivated filter for collection followed by thermal desorption and GC-MS analysis. Laboratory tests show that detection limits range from 0.2 to 3 ng for many atmospherically relevant compounds. The GC-MS OAM was deployed in the field for semi-continuous measurement of the organic markers, levoglucosan, dehydroabietic acid, and several polycyclic aromatic hydrocarbons (PAHs) during winter (January to March), 2015 and 2016. Results illustrate the significance of this monitoring technique to more fully characterize the organic components of PM and identify sources of pollution.

Keywords: air pollution, fine particulate matter, PM_2.5, secondary organic aerosol, organic markers, levoglucosan, PMF.

Styles APA, Harvard, Vancouver, ISO, etc.

17

Varughese, Jincy. « Environmental Inequities in U.S. Public Schooling ». Scholarship @ Claremont, 2016. http://scholarship.claremont.edu/cmc_theses/1416.

Texte intégral

Résumé :

Several studies and local accounts have documented elevated levels of air pollution and toxics on or near US public schools. The low cost of brownfield lands and lands near major sources of air pollution have made siting schools on these areas enticing. Histories of using toxic chemicals in building materials explain their presence in school environments. The impacts to academic achievement associated with air pollution and exposure to lead as well as the health implications of regular, high exposure to air pollution and toxic chemicals necessitate policy changes. In this paper, the extent of these health and achievement impacts will be analyzed along with the current work being done by government and nongovernmental organizations to mitigate pollution in public schools. This study will also offer policy recommendations to address these issues and advance environmental equity in public schools.

Styles APA, Harvard, Vancouver, ISO, etc.

18

Prill, Nadine. « Effects of environmental change on plant performance and plant-herbivore interactions ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:c58761e9-666c-4b7d-a78a-d70de7f253d4.

Texte intégral

Résumé :

Global environmental change fundamentally affects plants and their interactions with other species, and this has profound impacts on communities and ultimately ecosystems. In order to understand the mechanisms involved, we need to elaborate on the combined effects of different global change drivers on multiple levels of plant organization, including the biochemical level (production of defence compounds), the whole organism, the population, and the plant-herbivore interaction level. This thesis investigates (1) the combined effects of factors related to climate change and habitat fragmentation on Brassica nigra and (2) the effects of Zn soil pollution on the heavy metal hyperaccumulator Noccaea caerulescens at these different levels. Common garden and greenhouse experiments with B. nigra applied drought stress and elevated CO₂ to examine climate change impacts, while crossing treatments (inbreeding and between-population outbreeding) were used to investigate habitat fragmentation effects. Heterosis was lost under drought stress, and there were several interactive effects of the experimental treatments that varied within and among populations. In a greenhouse experiment with N. caerulescens, plants were grown on soil with different amounts of zinc. Plants had greater herbivore resistance when grown on Zn-amended soil, and invested more in herbivore tolerance when grown on soil without added Zn. In general, the results indicate that factors related to global environmental change have complex and interactive effects on different levels of plant organization. The findings are discussed in terms of their implications for ecology, evolution and conservation.

Styles APA, Harvard, Vancouver, ISO, etc.

19

Pushpawela, Buddhi G. « The formation and characteristics of new particles in the atmosphere ». Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/122854/2/__qut.edu.au_Documents_StaffHome_StaffGroupH%24_halla_Desktop_Buddhi_Pushpawela_Thesis.pdf.

Texte intégral

Résumé :

Airborne particles play a major role in climate change and human health. Drawing on the results of extensive measurements carried out in the relatively clean environment of Brisbane and the heavily polluted megacity of Beijing, this thesis has significantly furthered our knowledge of the physical mechanisms of new particle formation in the lower atmosphere. Several characteristics of new particle formation events, such as their temporal distribution, the effect of wind speed and the role of atmospheric ions on the particle formation rate, were investigated for the very first time.

Styles APA, Harvard, Vancouver, ISO, etc.

20

Pachon, Quinche Jorge Eduardo. « Development and assessment of environmental indicators for mobile source impacts on emissions, air quality, exposure and health outcomes ». Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42719.

Texte intégral

Résumé :

Environmental indicators were developed and evaluated to assess the impact of mobile sources on emissions, air quality, exposure and health. Different levels of indicators are discussed, from single species to multipollutant indicators. Carbon monoxide (CO), Nitrogen oxides (NOx) and elemental carbon (EC) were chosen as indicators of mobile sources because emissions of these pollutants are largely attributed to mobile sources and ambient concentrations have a close response to the change in mobile source emissions. These pollutants were used in the construction of the integrated mobile source indicators (IMSI). The IMSI have larger spatial representativeness and stronger associations with cardiovascular diseases (CVD) than single pollutants. The use of IMSI in epidemiologic modeling constitutes an alternative approach to assess the health impact of pollutant mixtures and can provide support for the setting of multipollutant air quality standards. The human health benefits of reducing mobile sources emissions were more consistent using multipollutant indicators. Indicator values and uncertainties, in the form of indicator sets, are presented with their associated outcomes and attributes to be useful for policy makers who are interested not only in the value of the indicators, but also in their associated uncertainties and their applicability at other times and other regions.

Styles APA, Harvard, Vancouver, ISO, etc.

21

Brown, Reece. « Development and deployment of novel instrumentation for the real-time monitoring of atmospheric PM-bound ROS ». Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/200736/1/Reece_Brown_Thesis.pdf.

Texte intégral

Résumé :

This thesis details the development and deployment of a novel instrument to quantify particle-bound reactive oxygen species (ROS) in the atmosphere. ROS are significant as they are believed to be one of the underlying mechanisms explaining the link between air pollution exposure and a variety of cardiovascular, respiratory, and neurological diseases. The time resolution, sensitivity and stability of the instrument are higher than any comparable system in literature. In field trials this has allowed first the first ever observations of short-lived ROS species in an atmospheric environment, which has significant implications in the field of atmospheric pollution toxicity.

Styles APA, Harvard, Vancouver, ISO, etc.

22

Hill, Martin. « Essays on environmental policy analysis : computable general equilibrium approaches applied to Sweden ». Doctoral thesis, Stockholm : Economic Research Institute, Stockholm School of Economics (Ekonomiska forskningsinstitutet vid Handelshögsk.) (EFI), 2001. http://www.hhs.se/efi/summary/551.htm.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

23

Young, Dominique Emma. « Characterisation of the chemical properties and behaviour of aerosols in the urban environment ». Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-the-chemical-properties-and-behaviour-of-aerosols-in-the-urban-environment(27de7e50-5069-40a0-b5cd-1370747f646a).html.

Texte intégral

Résumé :

Atmospheric aerosols have adverse effects on human health, air quality, and visibility and frequently result in severe pollution events, particularly in urban areas. However, the sources of aerosols and the processes governing their behaviour in the atmosphere, including those which lead to high concentrations, are not well understood thus limit our ability to accurately assess and forecast air quality. Presented here are the first long-term chemical composition measurements from an urban environment using an Aerodyne compact Time-of-Flight Aerosol Mass Spectrometer (cToF-AMS). Organic aerosols (OA) were observed to account for a significant fraction (44%) of the total non-refractory submicron mass during 2012 at the urban background site in North Kensington, London, followed by nitrate (28%), sulphate (14%), ammonium (13%), and chloride (1%). The sources and components of OA were determined using Positive Matrix Factorisation (PMF) and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2), where HOA, COA, and SFOA were observed to be of equal importance across the year. The concentration of secondary OA increased during the summer yet the extent of oxidation, as defined by the oxygen content, showed no variability during the year. The main factors governing the diurnal, monthly, and seasonal trends observed in all organic and inorganic species were meteorological conditions, specific nature of the sources, and availability of precursors. Regional and transboundary pollution influenced total aerosol concentrations and high concentration events were observed to be governed by different factors depending on season. High-Resolution ToF-AMS measurements were used to further probe OA behaviour, where two SFOA factors were derived from PMF analysis in winter, which likely represent differences in burn conditions. In the summer an OA factor was identified, likely of primary origin, which was observed to be strongly associated with organic nitrates and anthropogenic emissions. This work uses instruments and techniques that have not previously been used in this way in an urban environment, where the results further the understanding of the chemical components of urban aerosols. Aerosol sources are likely to change in the future with increases in solid fuel burning as vehicular emissions decrease, with significant implications on air quality and health. Thus it is important to understand aerosol sources and behaviour in order to develop effective pollution abatement strategies.

Styles APA, Harvard, Vancouver, ISO, etc.

24

Hallemans, Elise. « Étude de la formation, du vieillissement et de la composition chimique de l'aérosol organique secondaire dans le bassin méditerranéen ». Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1122/document.

Texte intégral

Résumé :

L’aérosol organique secondaire (AOS) est issu de processus d’oxydation des précurseurs gazeux, les composés organiques volatils (COV). Des lacunes persistent encore dans la connaissance des voies de formation et d’évolution de l’AOS et de sa composition chimique à l’échelle moléculaire. Ces différents aspects expliquent en partie la sous-estimation de sa concentration globale par les modèles. Pour apporter des éléments de réponse à ces problématiques, le bassin méditerranéen a été sélectionné comme région d’étude. Celui-ci est, en effet, caractérisé par une forte photochimie, notamment en été, et des sources de COV très intenses, à la fois biogéniques et anthropiques, réunissant ainsi les conditions favorables à la formation d’AOS dans l’atmosphère. Dans ce contexte, deux campagnes de mesures ont été réalisées dans le cadre des programmes Canopée et ChArMEx.Grâce au déploiement d’une méthode de prélèvement et d’analyse par TD-GC/MS, la caractérisation de la fraction organique a permis la détermination de plus d’une centaine de composés oxygénés de C2 à C18 en phases gazeuse et particulaire. La complémentarité des jeux de données obtenus avec des méthodes plus traditionnelles (PTR-MS, AMS) a permis d’apporter des éléments de réponse sur la réactivité des composés oxygénés vis-à-vis du radical OH, sur la composition de la matière organique sur deux sites aux caractéristiques contrastées et sur la propension de différents précurseurs biogéniques et anthropiques à former de l’AOS. La détermination des coefficients de partage théoriques et expérimentaux apportent également des éléments de réponse quant à la représentation de l’AOS dans les modèles
Secondary Organic Aerosol or « SOA » is formed in the atmosphere by oxidative process of volatile organic compounds (VOC). Gaps in knowledge of SOA formation and evolution pathways and of molecular characterization still exist. These aspects are an important source of uncertainties and can explain the underestimation of SOA budget calculated by models. In order to give new insights on these issues, the Mediterranean basin appears like an ideal area to study SOA. Actually, this region is characterized by high photochemistry, above all during summer season, and by intense VOC biogenic and anthropogenic emissions implying the formation of SOA in the atmosphere. In this context, two field campaigns have been performed in the frame of Canopée and ChArMEx projects.Thanks to a sampling and analyzing method by TD-GC/MS, the characterization of organic fraction enables one to determine more than one hundred compounds from C2 to C18 in gaseous and particulate phases. In combination with traditional datasets (PTR-MS, AMS), new insights were brought in reactivity of gaseous oxygenated compounds with OH radical, in chemical composition of organic material in particulate phase and about the contribution of various precursors to the capacity to form SOA. The determination of experimental and theoretical partitioning coefficients gives new information on SOA representation in models

Styles APA, Harvard, Vancouver, ISO, etc.

25

Bertrand, Amélie. « Vieillissement atmosphérique de l'aérosol de combustion de biomasse : du potentiel de formation d'aérosol organique secondaire à la modification de l'empreinte chimique à l'échelle moléculaire ». Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0149/document.

Texte intégral

Résumé :

La combustion de bois, ou plus largement de la biomasse, est une source de pollution très importante en particules atmosphériques en hiver, particulièrement en France. Si les émissions primaires ont été étudiées depuis de nombreuses années, il existe de grandes incertitudes sur le devenir de ces émissions dans l’atmosphère. Le travail de thèse a donc porté sur l’étude du vieillissement en chambre de simulation atmosphérique de l’aérosol émis par 3 appareillages pour le chauffage au bois (conçus entre 2000 et 2010 et représentatifs de la politique de renouvellement mis en place par l’ADEME), avec un intérêt particulier pour le potentiel de formation d’aérosol organique secondaire (SOA) et la modification de l’empreinte chimique à l’échelle moléculaire au cours du transport atmosphérique. Les expériences ont montré un potentiel de formation de SOA très important. La concentration en OA peut ainsi être multipliée par 7 (1.5 – 7.1) entre l’émission et après un temps de résidence atmosphérique équivalent à 5 h. Cette étude met également en évidence l’impact de l’efficacité de combustion sur les facteurs d’émission et par conséquent le rôle crucial de l’opérateur. L’étude à l’échelle moléculaire a mis en évidence la formation de composés susceptibles de servir de marqueurs de combustion de biomasse âgée, principalement des nitrocatéchols. Enfin, cette étude démontre le rôle clé de la volatilisation du lévoglucosan, principal marqueur organique de la combustion de biomasse, au cours du processus de dilution dans l’atmosphère, et pose clairement la question de la pertinence des constantes cinétiques de dégradation préalablement calculées en chambre de simulation atmosphérique
Biomass burning is in winter a main source of air pollution by particulate matter, especially in France. While primary emissions have been characterized extensively before, few studies have addressed the aging of these emissions in the atmosphere and large uncertainties remain. Therefore, the objectives of this thesis was to study in a smog chamber the aging of the aerosol emitted by 3 different woodstoves used for residential heating (fabricated from between 2000 and 2010, and representative of the policy engaged by the French environmental agency to renew the appliances across the country), with a specific focus on the Secondary Organic Aerosol (SOA) production potential and the modification of the chemical fingerprint of the emissions at the molecular level during their transport in the atmosphere. The experiments showed the SOA production potential can be significant. The OA concentration can be increased by up to a factor of 7 (1.5 – 7.1) after being aged in the smog chamber with a time equivalent to 5 hours in the atmosphere. The study also further demonstrated the influence of the combustion efficiency on the emissions and implicitly the role of the operator. The study of the composition of the aerosol at the molecular level showed the formation of compounds, likely to serve as markers for aged biomass burning, mainly nitrocatechols. Finally, the work also illustrates the influence of the volatilization of levoglucosan, main marker of biomass burning, during the dilution process occurring in the atmosphere, and challenge the pertinence of the degradation rate constant determined previously in smog chamber

Styles APA, Harvard, Vancouver, ISO, etc.

26

Johansson, Otilia. « Epiphytic lichen responses to nitrogen deposition ». Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43751.

Texte intégral

Résumé :

Nitrogen (N) deposition has increased globally over the last 150 years and further increase is predicted for the future. Nitrogen is an important nutrient for lichens, involved in many processes in both photobiont and mycobiont. However, N can be a stressor, causing many lichens and lichen communities to disappear with increased deposition. The objective of this thesis was to investigate the response of epiphytic lichens to increased N load. This was done by simulating an increased N deposition to lichens in a boreal forest with low background N, including both short term studies with transplanted lichens and long term studies of naturally established lichens. Alectoria sarmentosa was used as a model species for a N-sensitive lichens and Platismatia glauca as a relatively more N-tolerant lichen. Nitrogen deposition was simulated by daily spraying during the growing season with water and isotopically labeled ammonium nitrate (NH4NO3). In Paper I, I found that when N is supplied in realistic doses (equivalent to deposition of 0.6, 6, 12.5, 25 and 50 kg N ha-1), there were no significant differences in uptake of NO3- or NH4+ in either of the lichen species. The results in Paper II indicate that A. samentosa may be limited by phosphorous (P) and not N limited as expected. That study highlights the importance of P, when studying the effects of N deposition, since P can both mitigate and intensify the negative effects of N on epiphytic lichens. Paper III shows that four years of simulated N deposition caused an alteration of the epiphytic lichen community, since A. sarmentosa decreased in the highest N loads (25 and 50 kg ha-1 year-1), Bryoria spp. decreased to 12.5 kg N and higher loads and Hypogymnia physodes decreased over time for all treatments except in 12.5 kg ha-1, where it only decreased during the first treatment year and then increased after 2007. The abundance of Platismatia glauca increased over time, independent of treatment. As hypothesized, responses to the treatments differed among species, reflecting their different N optima. In paper IV, the effects of N on carbon-based secondary compounds were studied. None of the studied species (P. glauca, A. sarmentosa, Lobaria scrobiculata and Xanthoria aureola) reduced their concentration of secondary compounds during the experimental period, but in P. glauca the concentration of all compounds were significantly lower in N treated thalli compared with control thalli. The results are consistent with a high degree of constitutive defence in three of the four studied lichens, and we conclude that all four studied lichens seem to have a robust chemical defence system despite considerable manipulation of the environmental conditions. However, we don't know if these lichens are able to keep up the high protection level over longer periods comprising a number of years when more new tissue is formed. In conclusion, long term experiments are necessary to understand lichen response to environmental changes.

Styles APA, Harvard, Vancouver, ISO, etc.

27

Ashwell, Alice Nicola. « Project water (Grahamstown) : a case study of the development of an environmental education project ». Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1003599.

Texte intégral

Résumé :

Environmental education is an approach to education which emphasises the interrelatedness of people and their human and non-human environments and seeks to encourage environmental awareness, concern and action. This case study documents the implementation and development of Project WATER, Grahamstown, a practical environmental education project dealing with catchment conservation and water quality monitoring. The Grahamstown project is one of a number of local water quality monitoring initiatives affiliated to GREEN (the Global Rivers Environmental Education Network). Participants in the project included student teachers from the Department of Education at Rhodes University and pupils and teachers from three farm schools in the district and four high schools in the town. Project WATER, Grahamstown developed as an Action Research and Community Problem-Solving project. The study focuses on fragmentalist and holistic approaches to education, people's responses to Project WATER and the choice of action research as the research method.

Styles APA, Harvard, Vancouver, ISO, etc.

28

Yan, Bo. « Characterization and source apportionment of ambient PM2.5 in Atlanta, Georgia : on-road emission, biomass burning and SOA impact ». Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37151.

Texte intégral

Résumé :

Characterization and Source Apportionment of Ambient PM2.5 in Atlanta, Georgia: On-Road Emission, Biomass Burning and SOA Impact Bo Yan 260 Pages Directed by Drs. Armistead G. Russell and Mei Zheng Various airborne PM2.5 samples were collected in the metropolitan Atlanta and surrounding areas, which are directly impacted or dominated by on-road mobile and other typical urban emissions, regional transport sources, prescribed burning plumes, wildfire plumes, as well as secondary sources with anthropogenic and biogenic nature in origin. Detailed PM2.5 chemical speciation was conducted including over one hundred of GC/MS-quantified organic compounds, organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), ionic species, and tens of trace metals. Day-night, seasonal and spatial variations of PM2.5 characterization were also studied. Contributions of PM2.5 major sources were identified quantitatively through the receptor source apportionment models. These modeling results, especially on-road mobile source contributions and secondary organic carbon (SOC) were assessed by multiple approaches. Furthermore, new season- and location-specific source profiles were developed in this research to reflect real-world and representative local emission characterizations of on-road mobile sources, aged prescribed burning plumes, and wildfire plumes. Secondary organic aerosol (SOA), a major component of PM2.5 in the summer, was also explored for sources and contributions.

Styles APA, Harvard, Vancouver, ISO, etc.

29

Kammer, Julien. « LANDEX : étude des aérosols organiques secondaires (AOS) générés par la forêt des Landes ». Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0402/document.

Texte intégral

Résumé :

L’objectif de ce travail de thèse est d’améliorer l’état de nos connaissances sur les processus de formation et du devenir de l’AOS, en lien avec la réactivité des COVB avec les oxydants de l’atmosphère et en particulier l’ozone, en utilisant le potentiel de l’écosystème landais en tant que source d'AOS biogénique. Pour cela, des campagnes de terrain ont été menées sur un site de mesure en forêt landaise, écosystème particulièrement approprié pour l’étude de la formation et du devenir des AOS. Au cours de ces campagnes, différents paramètres physico-chimiques complémentaires ont été mesurés, tels que les concentrations et les flux de particules, d’oxydants et de COVB. Des épisodes nocturnes de formation de nouvelles particules ont été mis en évidence, ce qui constitue un résultat original car les évènements rapportés jusqu’ici dans la littérature étaient principalement diurnes. La contribution importante de l’ozonolyse des monoterpènes émis par les pins maritimes, dominés par l’α- et le β-pinène, à la formation nocturne de nouvelles particules a également été démontrée. Les mesures de flux de particules réalisées suggèrent que les particules formées au cours de la nuit sont transférées depuis la canopée vers les plus hautes couches de l’atmosphère. Une production d’ozone a également été démontrée par la comparaison des mesures de flux d’ozone à un modèle physique de dépôt. Cette source d’ozone pourrait être liée à la photooxidation des COVB
Forest ecosystems affect air quality and climate, especially through the emissions and the reactions of biogenic volatile organic compounds (BVOCs) with the atmospheric oxidants, known to generate Secondary Organic Aerosols (SOAs). This work aims to improve our knowledge on the processes involved in biogenic SOA formation and fate. Two field campaigns have been conducted in the Landes forest. In a first step, the measurement site was characterized by a statistical study of local meteorological conditions. During these campaigns, complementary physical and chemical measurements have been carried out, implying measurements of fluxes and concentrations of particles, BVOCs and oxidants. The results evidenced nocturnal new particle formation, which is an original result as this process was usually only reported during daytime. The strong contribution of BVOCs (dominated by α- and β-pinene) ozonolysis to nocturnal new particle formation has been demonstated. Particle flux measurements suggested that particles are transfered from the canopy to the higher atmospheric surface layer. The comparison between ozone fluxes and a physical ozone deposition model also highlighted an ozone production source. This ozone production might be related to BVOC photooxidation

Styles APA, Harvard, Vancouver, ISO, etc.

30

Guilbaud, Sarah. « Etude du vieillissement des aérosols inorganiques industriels en milieu urbain ». Thesis, Littoral, 2018. http://www.theses.fr/2018DUNK0524/document.

Texte intégral

Résumé :

Lors de leur séjour dans l’atmosphère, les aérosols sont soumis, entre autres, à des processus d’agrégation, ainsi que de condensation sur leurs surfaces. Ces processus, dit de vieillissement, dépendent du temps de résidence des particules dans l’atmosphère, des conditions météorologiques et de l’environnement chimique rencontré. Cette étude vise à caractériser l’aérosol inorganique et étudier son évolution physico-chimique sur quelques dizaines de milliers de mètres, dans les panaches industriels et urbains où les concentrations atmosphériques en particules fines (PM₁₀) sont relativement élevées. Il s’agit notamment de rendre compte de l’évolution des particules d’aérosol primaire lors d’épisodes de formation d’aérosols secondaires inorganiques.Dans ce cadre, dans un premier temps, une nouvelle méthodologie d’analyse des aérosols inorganiques, à basse température, par cryo-microscopie électronique (cryo-TSEM-EDX) a été mise au point. L’enjeu était notamment de rendre compte de l’état de mélange des composés atmosphériques d’origine secondaire (composés semi-volatils), avec l’aérosol primaire. Ces développements analytiques ont tout d’abord été réalisés à l’aide de composés modèles, avant d’être validés sur particules environnementales. Dans un second temps, l’étude des processus physico-chimiques mis en jeu lors du vieillissement des aérosols, à l’échelle locale (quelques kilomètres), a été réalisée au cours d’une campagne intensive de terrain sur le dunkerquois, visant à étudier plus particulièrement l’évolution des émissions industrielles en milieu urbain. Des prélèvements ont ainsi été réalisés en bordure de zone industrielle et sur de sites "récepteurs" sous l’influence potentielle des émissions industrielles. Les analyses réalisées sur ces particules par cryo-SEM-EDX ont notamment montré qu’en zone péri-urbaine, à quelques kilomètres de la zone industrielle, des particules émises par la sidérurgie, comme les oxydes de fer, évoluaient rapidement, pour se retrouver, en mélange interne, associés à de la matière organique particulaire. En parallèle, nous avons pu caractériser, sur ces sites récepteurs, la présence d’aérosols inorganiques secondaires absents de la zone source et donc formés au sein de l’air ambiant, lors du survol de l’agglomération dunkerquoise
During their transport in the atmosphere, aerosols are subject, for example, to aggregation and condensation processes on their surfaces. These processes, so-called aging, depend on particle residence time in the atmosphere, meteorological conditions and chemical environment. This study aims to characterize inorganic aerosols and to highlight their physico-chemical evolution on a few tens of thousands meters, from an industrial area to the urban environment of Dunkirk (Northern France), in which PM₁₀ concentrations are quite important. It notably includes reporting on the evolution of primary particles during the formation of secondary inorganic aerosols. First, a new analytical methodology of inorganic aerosols, at low temperature, with cryo-electronic microscopy (cryo-TSEM-EDX) has been developed. Our goal was to characterize the mixing state of secondary atmospheric components (semi-volatile components) with primary aerosols. These analytical developments have been realized with model particles, before validation on real atmospheric particles. In a second time, the study of physico-chemical processes involved in the aging of industrial inorganic aerosols has been undertaken through an intensive field campaign. The objective is to describe the particles evolution between the industrial zone and receptor sites located in the suburb of Dunkirk. Our main results show that Fe-rich particles (Fe oxides), released in the atmosphere by steelworks, incorporate particulate organic matter in a few kilometers, between the source and receptor sites. In addition, the formation of secondary inorganic aerosols (SIA), not present at the source, has been evidenced. Clearly, these SIA have been formed during the transport of air masses over the urban area

Styles APA, Harvard, Vancouver, ISO, etc.

31

Dubois, Diane. « Réalisation et caractérisation d'un réacteur plasma de laboratoire pour des études sur la dépollution des gaz d"échappement ». Toulouse 3, 2006. http://www.theses.fr/2006TOU30139.

Texte intégral

Résumé :

Cette thèse concerne l’étude expérimentale des décharges couronne positives à la pression atmosphérique générées dans un réacteur de laboratoire de type pointe – plan alimenté en régime de tension continue et pulsée. La nature et les caractéristiques de la décharge couronne, notamment dans son régime de « breakdown streamer », sont étudiées en fonction du régime et de l’amplitude de l’alimentation de tension, du rayon de courbure de la pointe, de la distance inter – électrodes ou encore de la composition du mélange gazeux en faisant varier les proportions de N2, de O2 et de CO2. La dynamique et la morphologie des ondes d’ionisation sont finement étudiées à l’aide de diagnostics d’imagerie rapide (ICCD Streak caméras) et de mesures instantanées de courant et de tension (oscilloscope rapide) sur des échelles de temps de quelques centaines de nanosecondes. Les dimensions du réacteur ont été adaptées à la capacité des modèles à le simuler et les premiers résultats de comparaison des courbes instantanées de courant issues des modèles et de l’expérience sont présentés dans le but ultérieure d’estimer la nature et la densité des radicaux formés durant la phase de décharge d’un réacteur de dépollution par décharge couronne
The present thesis is devoted to the experimental study of atmospheric positive corona discharges generated in a point to plane corona reactor under DC or pulsed high voltage conditions. The corona discharge characteristics, in particular during “breakdown streamer” mode, are studied according to the high voltage supply conditions (DC or pulsed), the point radius curvature, the gap distance or the gas mixture following the variation of the N2, O2 and CO2 concentration. The dynamics and the morphology of the streamers are also studied using fast imaging (ICCD and Streak cameras) and electrical (oscilloscope) diagnostics on time scale lower than hundred of nanosecond. As the corona discharge reactor dimensions are well adapted, some preliminary results show the comparison between experimental and simulated results which allow us in the future to estimate the localization, the density and the nature of the radical species created during the discharge phase of a corona reactor devoted to air pollution control

Styles APA, Harvard, Vancouver, ISO, etc.

32

Petit, Marie-Eléonore. « Pérennité, fonctionnalité, efficacité d'une zone humide artificielle (ZHA) en milieu méditerranéen : un nouvel écosystème au service du traitement secondaire des effluents industriels ». Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0439/document.

Texte intégral

Résumé :

Les zones humides naturelles méditerranéennes sont des écosystèmes rares et vulnérables souvent altérés par les pollutions des milieux adjacents. Le développement de zones humides artificielles (ZHA) servant au traitement secondaire des pollutions permettrait de limiter l’impact des activités industrielles sur les milieux naturels. Pour végétaliser ces ZHA et tolérer les contraintes du climat méditerranéen, l’utilisation d’espèces végétales locales éco-adaptées est recommandée. Toutefois ce type de ZHA, utilisant des plantes locales méditerranéennes, a fait l’objet d’un nombre restreint de travaux. Les objectifs de cette thèse sont donc : - de suivre la biocénose implantée et spontanée d’une ZHA pour évaluer la mise en place de ce nouvel écosystème (suivis floristique, faunistique et phytoplanctonique),- d’évaluer ses fonctionnalités et son efficacité épuratoire (suivis physico-chimique et biologique),- de questionner la pérennité de tels systèmes dans une contexte de changements globaux, notamment climatique. Les résultats montrent qu’un nombre restreint d’espèces végétales locales sélectionnées peut permettre la création d’un nouvel écosystème fonctionnel et durable qui soutient l’enjeu de biodiversité, tout en améliorant le traitement des effluents rejetés par le bassin industrialisé. Ces travaux valident l’intérêt des ZHA à hélophytes locales en méditerranée pour traiter les pollutions de bassins versants industrialisés mais un effort de recherche reste à faire pour adapter la conception aux spécificités des sites dans une véritable démarche d’ingénierie écologique
Natural wetlands in Mediterranean areas are rare and vulnerable ecosystems, frequently impacted by various pollutants from nearby environments. In order to decrease industrial activities lethal effects on natural areas, constructed wetlands (CWs) are an interesting opportunity to remediate their pre-treated wastewaters. Such CWs would take advantage with using local plant species, well adapted to Mediterranean climate’s rigors. Nevertheless, CWs planted with Mediterranean plant species are still scarce and poorly studied. Aims of this thesis are thus:• to follow up on planted and adventive biocœnosis of a CW (flora, fauna and phytoplankton), in order to assess a novel ecosystem settlement,• to get better knowledge on its functions and remediation efficiency (physico-chemical and biological parameters),• to question durability of such techno-ecosystems in a context of global changes (with focus on climate).Main result let us know that it only takes a few local plant species, wisely chosen, to allow the settlement of a sustainable and fully functional ecosystem, supporting biodiversity stakes while increasing the remediation of pre-treated wastewaters collected from industrialized catchment. This work assess CWs planted with local helophytes as a powerful tool to treat industrialized catchment wastewaters in Mediterranean area, but researches are still needed to fit each design with each site characteristics, following a sustainable ecological engineering approach

Styles APA, Harvard, Vancouver, ISO, etc.

33

El, Haddad Imad. « Fraction primaire et secondaire de l'aérosol organique : méthodologies et application à un environnement urbain méditerranéen, Marseille ». Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10029.

Texte intégral

Résumé :

La mise en place de politiques efficaces visant à la réduction des niveaux de concentrations en PM exige la connaissance préalable des sources primaires et secondaires de l’aérosol organique, une fraction majoritaire des PM demeurant encore mal appréhendée. Les travaux réalisés au cours de cette thèse s’inscrivent dans le cadre du projet FORMES qui avait pour principal objectif d’évaluer et de contraindre les principales méthodes de quantification de l’influence des différentes sources de la fraction organique de l’aérosol en milieu récepteur et d’en optimiser les procédures. La caractérisation physico-chimique de l’aérosol s’est articulée autour de deux campagnes de mesures intensives de 15 jours chacune dans deux environnements urbains très contrastés : Marseille en été, et Grenoble en hiver. Ce travail de thèse s’est concentré sur le cas de Marseille, un environnement très complexe, combinant une activité photo oxydante très intense à un ensemble d’émissions primaires qui incluent les sources industrielles et les émissions par les bateaux.L’analyse CMB appliquée sur le cas de Marseille a montré que les sources primaires sont dominées par les émissions véhiculaires contribuant à 17 % du carbone organique (OC). Bien que les sources industrielles contribuent faiblement à la masse de l’aérosol (2.5 % de l’OC), ces émissions contrôlent les concentrations des HAP et de certains métaux lourds. Ces sources contribuent également, en moyenne sur la période, à environ 30% du nombre des particules ultrafines (Dp<50 nm), ce qui augmente probablement leurs effets sanitaires. Contrairement à Grenoble, où la combustion de bois est une source prépondérante (environ 70 % de l’OC), à Marseille ces émissions ne constituent qu’une source minoritaire, contribuant à 0.8 % de l’OC. Toutefois, la principale information révélée par la déconvolution de sources par CMB est que les sources primaires considérées ne permettent d’expliquer, que 22 % de l’OC mesuré ; 78 % du carbone restant non expliqué. Cette fraction est associée majoritairement à l’aérosol organique secondaire (SOA). En combinant les résultats CMB aux mesures 14C, il a été montré que plus que 70% de cet aérosol est très vraisemblablement d’origine biogénique. En conséquence, les contributions du SOA formé à partir de l’isoprène, l’α-pinène et le β-caryophyllène ont été examinées moyennant une approche basée sur les marqueurs de cet aérosol. Le SOA issu de ces précurseurs a été estimé comme contribuant uniquement à 4.3 % de l’OC, laissant une grande fraction de ce carbone non-attribuée. Cette sous-estimation est la conséquence de trois causes : (i) les incertitudes associées à l’approche utilisée, (ii) des précurseurs biogéniques non-considérés et (iii) le vieillissement de l’aérosol secondaire au cours de son transport dans l’atmosphère, comme suggéré par les mesures d’organosulfates et de la fraction polycarboxylique de type HULIS. Cette dernière fraction peut contribuer à près de 40% de l’OC non-attribué
Tougher particulate matter regulations around the world and especially in Europe point out the need of source apportionment studies in order to better understand the different primary and secondary sources of organic aerosol, a major fraction of particulate matter that remains not well constrained. The work carried out in this thesis takes part of the FORMES project whose main objective is the source apportionment of the organic aerosol using different approaches, including mainly CMB modelling, AMS/PMF and radiocarbon (14C) measurements. The aerosol characterisation was performed within two intensive field campaigns conducted in two contrasted urban environments: Grenoble during winter and Marseille during summer. The present work focuses on the Marseille case study that presents a particularly complex environment, combining an intense photochemistry to a mixture of primary emissions including shipping and industrial emissions. Primary organic carbon (POC) apportioned using CMB modelling contributed on average for only 22% and was dominated by vehicular emissions accounting on average for 17% of OC. Even though, industrial emissions contribute for only 2.3% of the total OC, they are associated with ultrafine particles and high concentrations of Polycyclic Aromatic Hydrocarbons and heavy metals such as Pb, Ni and V, which most likely relate them with acute health outcomes. Whereas in Grenoble the organic aerosol was dominated by wood burning smoke (70% of OC), this source was negligible in Marseille contributing for less than 1% of OC. The main result from this source apportionment exercise is that 78% of OC mass cannot be attributed to the major primary sources and remains un-apportioned; this fraction is mostly associated with secondary organic aerosol. Radiocarbon measurements suggest that more than 70% of this fraction is of modern origins, assigned predominantly to biogenic secondary organic carbon (BSOC). Therefore, contributions from three traditional BSOC precursors, isoprene, α-pinene and β-caryophellene, were considered using a marker based approach. The aggregate contribution from BSOC derived from these precursors was estimated at only 4.2% of total OC. As a result, these estimates underpredict the high loading of OC. This underestimation can be associated with (i) uncertainties underlying the marker-based approach, (ii) presence of other SOC precursors and (iii) further processing of fresh SOC, as indicated by organosulfates (RSO4) and HUmic LIke Substances (HULIS) measurements. This HULIS can contribute up to 40% of the unattributed OC

Styles APA, Harvard, Vancouver, ISO, etc.

34

Michel, Christelle. « L'aérosol de combustion dans une région en grande mutation, l'Asie ». Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00069797.

Texte intégral

Résumé :

Une source majeure d'incertitude dans l'estimation de l'impact climatique des aérosols est directement liée à notre connaissance des émissions gazeuses et particulaires. Ceci est particulièrement vrai en Asie, où une forte empreinte régionale est observée, avec différents types d'émissions, dépendant de la grande hétérogénéité de végétations et climats (émissions de feux de biomasse) et de l'évolution rapide de la population, de l'urbanisation et de l'industrialisation (émissions de fuels fossiles et de biofuels).
Mon travail de thèse a eu pour but, tout d'abord, de développer un inventaire d'émissions de gaz et particules issues des feux de biomasse pour les campagnes ACE-Asia (Aerosol Characterization Experiment) et TRACE-P (Transport and Chemical Evolution over the Pacific), de mars à mai 2001. Pour ce faire, j'ai mis en œuvre une méthodologie la plus adaptée à mon étude, qui repose sur la cartographie des surfaces brûlées (projet GBA2000 (Global Burnt Area 2000) [Tansey et al., 2003]).
Les résultats de cette étude, ABBI (Asian Biomass Burning Inventory) [Michel et al., 2005] ont été comparés avec un autre inventaire d'émissions de feux de végétation (ACESS : ACE-Asia and TRACE-P Modelling and Emission Support System) [Streets et al., 2003], construit, non pas à partir des surfaces brûlées, mais à partir des pixels de feux actifs. Cette comparaison illustre les limitations de l'utilisation des pixels de feux dans l'établissement des cartes d'inventaires d'émissions par les feux de biomasse, tout en soulignant l'importance et la pertinence de la méthode retenue dans mon étude. Une comparaison avec les données de l'année 2000, obtenues selon la même procédure, souligne toute l'importance des variations interannuelles.
L'inventaire ABBI a été introduit dans le modèle méso-échelle MésoNH-C couplé au module aérosol ORISAM (ORganic and Inorganic Spectral Aerosol Module) [Bessagnet, 2000]. Une attention particulière a porté sur l'étude du transport des émissions de feux de végétation à travers le continent asiatique. Des comparaisons entre les données simulées et les mesures in-situ et aéroportées ont montré des résultats satisfaisants dans certains cas, mais ont également fait encore apparaître certaines limitations. Des tests de sensibilités ont été effectués pour comprendre l'origine de ces différences, avec tout d'abord une deuxième simulation avec MésoNH-C-ORISAM effectuée avec l'inventaire ACESS pour étudier l'impact des émissions de feux. Le module ORISAM dans sa version 0D a été ensuite utilisé pour mettre en évidence de manière détaillée les paramètres contrôlant la formation de l'aérosol secondaire au sein du modèle.
Au total, tout en faisant ressortir l'importance majeure des inventaires d'émissions gazeuses et particulaires à l'échelle continentale, ce travail va au delà de ce thème, en montrant notamment l'apport du modèle d'aérosol ORISAM à l'analyse et la compréhension des processus de chimie hétérogène dans les épisodes de pollution affectant l'Asie.

Styles APA, Harvard, Vancouver, ISO, etc.

35

Chen, Chi-Yan, et 陳奇言. « A Study of Vehicle Exhaust Pollution by Adding Secondary Air ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/az6t2k.

Texte intégral

Résumé :

碩士
國立虎尾科技大學
機械與機電工程研究所
102
The objective of this paper is to explore the best way of reducing pollution from the automobile exhaust. In order to find out the best way, the writer of this paper tries to do two types of experiments. The first one is to add catalytic converter and four different quantities of secondary air into gasoline engine exhaust manifold, and to cover it with thermal insulation material, and the second one is to add four different quantities of secondary air into diesel engine exhaust manifold, and spray it with water. According to the numerical values of doing analysis and comparison from the experiments of automobile exhaust, adding 100 L/min of secondary air into gasoline engine exhaust manifold is the most effective way to reduce pollution from the automobile exhaust. Besides, the numerical values of CO, HC and CO2 are the best, and effectively promote the temperature ascension of the catalytic converter, and to purify the exhaust. As for diesel engine exhaust manifold, adding 50 L/min of secondary air is the best condition.

Styles APA, Harvard, Vancouver, ISO, etc.

36

Chun-Hsien, Shih, et 施純賢. « Secondary Pollution by Volatile Organic Compounds in Wastewater Treatment Plant of Petrochemical Industry ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/14956952668176205636.

Texte intégral

Résumé :

碩士
國立高雄海洋科技大學
海洋環境工程研究所
101
The wastewater of wastewater treatment plants in petrochemical industry contains large quantity of VOCs (Volatile Organic Compounds), and the domestic regulatory standards of VOCs for the industry in early years was less developed; therefore, wastewater without proper treatment was wantonly discharged, causing pollution problems came out one after the other, coupled with volatile characteristics of such pollution substances, so a superior emission condition was formed under the high perturbation of treatment process. Therefore, wastewater treatment plants in petrochemical industry have both of: (1) liquid phase secondary pollution caused by improperly treated wastewater; and (2) gas phase secondary pollution through emission pathway resulted from factors such as water body perturbation caused by wastewater treatment process. Therefore, this study took a wastewater treatment plant in northern Kaohsiung petrochemical factory as an example and conducted a ten day-times collection and analysis of water and gas samples to monitor the pollution species and concentration trends in liquid phase and gas phase in the factory site, and explore the current situation of secondary pollution caused by water flow and gas emission pathways. This study then coordinated with relevant regulatory standards to develop secondary pollution preventive and control measures for reducing pollutants entering into environment, and actually achieved the objective of pollution reduction. The study results reveal that: (1) this factory site receives three kinds of manufacturing process wastewater with PVC manufacturing process as main contributing source, and the concentration of the wastewater is between 685-123,000 μg/L, overall speaking, the concentration is very unstable and thus increases the workload of subsequent treatment units; (2) the main compounds in wastewater in sequence are dichloromethane (1,786 μg/L), 1,2-dichloroethane, vinyl chloride, chloroform, and methylene chloride, showing that the most major pollutant in the studied factory site is Cl-VOCs and it accounts for 96% of overall pollutants; (3) the gas sample analysis shows a consistent result with the water body analysis, with methylene chloride (787 μg/m3) as the most major pollutant, and the monitoring results in various treatment units show that an emission problem really exists and the most major emission source comes from the pre-treatment unit with bio-reacting tank having an additional aeration system (4,377 μg/m3); (4) through the result of comparison between dynamic sampling equipment and CANISTER sampling, revealed that using a dynamic sampling equipment is indeed better than directly using CANISTER sampling and can better approach the theoretical value, the ratio is between 1~4.12, this not only corroborates that the emission problem is actually serious than expected, but also can even provide as sampling correction for future studies; and (5) coordinated with relevant regulatory standards to conduct comparison and exploration, in terms of liquid phase it can not fully comply with emission control standards, which exceeds the standard by up to 44%, and in terms of gas phase it is also unable to comply with the regulatory standards, so the treatment units are required to carry out secondary preventive and control measures including tank body closing and emission gas recycling processing against top emission gases. Through this study, it is understood that the major pollution problem of wastewater treatment plants in petrochemical industry lies in the secondary pollution caused by emission side. Although it can be improved by establishing relevant secondary pollution preventive and control measures against gas emission, however, these measures can only be partially applied, and yet more accurate simulations and researches are required for various compounds. So if want to fundamentally get rid of all pollution problems through tracing to their origins, it is also required to proceed from water body, such that not only can sustainably resolve pollution problems, and also can help to reduce the requirement of building additional secondary pollution preventive control measures.

Styles APA, Harvard, Vancouver, ISO, etc.

37

Yao, Yi-Ling, et 姚御凌. « A Study on the effect of secondary air in motorcycle to the exhaust pollution and catalytic converter ». Thesis, 2009. http://ndltd.ncl.edu.tw/handle/keny26.

Texte intégral

Résumé :

碩士
崑山科技大學
機械工程研究所
97
This paper is mainly to discuss the effect of secondary air in motorcycles to the exhaust pollution and catalytic converter during the engine warm-up period. We measured the exhaust emissions and catalytic converter’s temperature during engine warm-up and the idle/high engine speed. Under the warm-up transient condition, the engine and catalytic converter are both not reach the working temperature. The pollution during this period is heavy. So in this experiment, we controlled different flows of high-pressure’s secondary air into the exhaust pipe to make exhaust emission to burn continuously. This operation will lower the amount of CO and HC in exhaust, it also can make exhaust temperature higher to heat the catalytic converter and oxygen sensor rapidly.The converting efficiency of the catalytic converter was improved and the exhaust pollution was reduced. In this experiment we used active secondary air and the test engine is G5 Fi engine of KYMCO company. The secondary air flow was controlled electronically. The high-pressure secondary air into exhaust manifold near the cylinder head was controlled with the amount of 10、20、30、40、50 L/min respectively. By this method, the exhaust continue to burn the HC and CO in exhaust pipe. Then the emission to the environment was reduced. Through a series of experiments, we found that the operation of the active secondary air is better than the passive one to lower the CO and HC amount in exhaust. But it needs large amount of active secondary air to reduce the CO and HC in exhaust. In the experiment under the stable operation of engine, we found that if the secondary air amount is over 20 L/min, it can reduce the CO and HC amount in exhaust at the same time. If under the warm-up operation of engine, we found that the larger amount the secondary air is, the lower amount the HC in exhaust. But the amount of CO only reduce obviously when the secondary air is over 30 L/min

Styles APA, Harvard, Vancouver, ISO, etc.

38

Yun-Jui et 吳昀叡. « Secondary aerosols with hourly measurements of air pollution events in Taichung the association with the atmospheric transmission ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/43378954914854813751.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

39

Wichmann, Janine. « Probing secondary exposure and health data as a tool to improve public health in South Africa ». Thesis, 2005. http://hdl.handle.net/2263/29941.

Texte intégral

Résumé :

The usefulness of secondary exposure and health data to improve public health in South Africa will be assessed. Given the tremendous health impact of air pollution exposure the focus of this thesis is on primary prevention, that is the identification of outdoor air pollution and the use of dirty fuels (wood, animal dung, crop residues, coal, paraffin) for cooking and heating as risk factors, whilst controlling for confounding. Hourly averaged outdoor PM10 mass, NO2, NO, SO2, O3 data (1 August 1998 - 31 July 2003) from Cape Town were analysed in a nonparametric Spearman’s Rho correlation analysis to determine the seasonal spatial correlation between the monitoring sites. Trend and descriptive analyses were conducted on the outdoor hourly and daily PM10 mass data to investigate the current and future health implications in the Khayelitsha sub-district, Cape Town. The 1998 South African Demographic and Health Survey (SADHS) data were analysed. The survey involved 13 826 individuals in 12763 households. Univariate and multivariate logistic regression analyses generated crude and adjusted odds ratios and 95% confidence intervals in order to assess the influence of dirty fuel use for cooking and heating on adult (> 15 years) respiratory health, childhood (< 59 months) respiratory health and 1-59 month mortality. It was found that outdoor air pollution is not homogenously distributed in Cape Town during all seasons. Elevated PM10 mass concentrations are frequently present in the Khayelitsha sub-district. There is a strong case for acknowledging the large public health risk arising from air pollution exposure in South Africa, despite the limitations of the 1998 SADHS data. Not much progress has been made in air pollution epidemiology in the country during this investigation due to the identified limitations. Secondary exposure and health data are thus only useful in improving public health in South Africa by supplying baseline data for trend analysis or hypotheses generation. It is recommended that the country must develop environmental public health tracking networks, which incorporates various data sources from multi-sectoral collaborative intervention projects with analytic study designs, in all major cities in the country.
Thesis (PhD)--University of Pretoria, 2006.
School of Health Systems and Public Health (SHSPH)
PhD
Unrestricted

Styles APA, Harvard, Vancouver, ISO, etc.

40

Τσιμπίδη, Αλεξάνδρα. « Simulating the atmospheric primary and secondary organic aerosols ». Thesis, 2009. http://nemertes.lis.upatras.gr/jspui/handle/10889/2402.

Texte intégral

Résumé :

Until recently, organic particulate material was simply classified as either primary or secondary with the primary component being treated in models as nonvolatile and inert. This framework is used to simulate the organic aerosol formation, growth and composition in the eastern United States during the four seasons of the year. The model predictions are evaluated against daily average PM2.5 (particulate matter smaller than 2.5 μm) measurements taken throughout the eastern United States by the Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Speciation Trends Network (STN) monitoring networks. The performance of the model in reproducing organic mass concentrations is average during all four seasons of the year. The agreement between the predicted and observed temporal profiles suggests a reasonable understanding and depiction in the model of the corresponding processes. However, this oversimplified view fails to explain the observed highly oxygenated nature of ambient organic aerosols (OA), the relatively small OA concentration gradients between large urban areas and their surroundings, and the concentrations of OA during periods of high photochemical activity. To address the above issues new primary and secondary organic aerosol modules have been added to a three dimensional chemical transport model (PMCAMx) based on recent smog chamber studies. The new modeling framework is based on the volatility basis-set approach: both primary and secondary organic components are assumed to be semivolatile and photochemically reactive and are distributed in logarithmically spaced volatility bins. The resulting PMCAMx-2008 was applied in Mexico City Metropolitan Area (MCMA) for approximately a week during April of 2003. The model predictions are compared with Aerosol Mass Spectrometry (AMS) observations and their Positive Matrix Factorization (PMF) analysis. The final goal of this work is to provide information to the policy makers regarding the response of fine PM to emission controls. PMCAMx is used to investigate changes in PM2.5 concentrations in response to 50% emissions changes of oxides of nitrogen and anthropogenic volatile organic compounds during July 2001 and January 2002 in the Eastern United States.
Τα ατμοσφαιρικά οργανικά σωματίδια συνηθίζεται να χωρίζονται σε δυο κατηγορίες: πρωτογενή και δευτερογενή. Τα πρώτα εκπέμπονται κατευθείαν στην ατμόσφαιρα ενώ τα δευτερογενή δημιουργούνται με την μεταφορά μάζας αερίων χαμηλής πτητικότητας, που προκύπτουν από την οξείδωση πρωτογενών οργανικών αερίων, στα ατμοσφαιρικά σωματίδια. Ένα τρισδιάστατο χημικό μοντέλο (PMCAMx), βασιζόμενο σε αυτό το διαχωρισμό, χρησιμοποιήθηκε για την προσομοίωση της σύνθεσης και της μάζας των οργανικών σωματιδίων της ατμόσφαιρας, στις ανατολικές Ηνωμένες Πολιτείες της Αμερικής κατά τη διάρκεια των τεσσάρων εποχών του χρόνου. Οι προβλέψεις του μοντέλου αξιολογήθηκαν έναντι μετρήσεων που πραγματοποιήθηκαν από τα δίκτυα παρακολούθησης IMPROVE και STN στις ανατολικές ΗΠΑ. Η απόδοση του μοντέλου, όσον αφορά τον προσδιορισμό της συγκέντρωσης των οργανικών ενώσεων κατά τη διάρκεια όλων των εποχών είναι ιδιαίτερα ικανοποιητική. Ωστόσο, αν και οι προβλέψεις του μοντέλου για τη συγκέντρωση της οργανικής μάζας είναι ενθαρρυντικές, δεν είναι ξεκάθαρο εάν το μοντέλο προβλέπει τις σωστές τιμές για τους σωστούς λόγους. Συγκεκριμένα το μοντέλο δεν μπορεί να εξηγήσει την πολύ οξυγονωμένη χημική μορφή των ατμοσφαιρικών οργανικών σωματιδίων όπως αυτή αποτυπώθηκε σε μετρήσεις πεδίου. Για να αντιμετωπιστούν τα ανωτέρω ζητήματα αναπτύσσουμε μια νέα μέθοδο προσομοίωσης των διεργασιών σχηματισμού και χημικής γήρανσης των πρωτογενών και δευτερογενών οργανικών σωματιδίων της ατμόσφαιρας, στο τρισδιάστατο χημικό μοντέλο PMCAMx βασιζόμενοι σε πρόσφατα πειραματικά δεδομένα. Στο νέο αυτό πλαίσιο μοντελοποίησης τόσο τα πρωτογενή, όσο και τα δευτερογενή οργανικά συστατικά θεωρούνται ότι είναι ημιπτητικά και φωτοχημικά ενεργά και κατανέμονται λογαριθμικά σε ομάδες ενώσεων διαφορετικής πτητικότητας. Το βελτιωμένο PMCAMx (PMCAMx-2008) έχει εφαρμοστεί στην ευρύτερη περιοχή της πόλης του Μεξικού για περίπου μια βδομάδα τον Απρίλιο του 2003. Οι προβλέψεις του μοντέλου συγκρίνονται με μετρήσεις φασματογράφου μάζας αεροζόλ και άλλες μετρήσεις που πραγματοποιήθηκαν κατά τη διάρκεια της καμπάνιας MCMA-2003. Τέλος το PMCAMx έχει χρησιμοποιηθεί για να μελετηθούν διεξοδικά οι αλλαγές στη συγκέντρωση των οργανικών σωματιδίων διαμέτρου έως 2.5 μm που προκύπτουν από αλλαγές των εκπομπών NOx και VOCs κατά τη διάρκεια των μηνών του Ιουλίου 2001 και του Ιανουαρίου 2002 στις ανατολικές Ηνωμένες Πολιτείες της Αμερικής.

Styles APA, Harvard, Vancouver, ISO, etc.

41

Olufemi, A. C. « Investigates the levels of awareness, knowledge and attitude of South African secondary school learners and educators about environmental pollution in a coal mining area ». 2013. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001338.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

42

Liu, Yang. « Comparative analysis of Unmix/PMF modeling for PM₂.₅ source apportionment in rural and urban Kansas and a review of life cycle assessment on carbon footprint of beef production ». Diss., 2018. http://hdl.handle.net/2097/39285.

Texte intégral

Résumé :

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

Styles APA, Harvard, Vancouver, ISO, etc.

43

Ashford, Nicholas. « The Encouragement of Technological Change for Preventing Chemical Accidents : Moving Firms from Secondary Prevention and Mitigation to Primary Prevention ». 1993. http://hdl.handle.net/1721.1/1561.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

44

Παπασάββας, Άγγελος. « Βελτιστοποίηση των φυσικών αντιοξειδωτικών παραγόντων των φυτών μέσω του ελέγχου των θρεπτικών συστατικών ». Thesis, 2014. http://hdl.handle.net/10889/8564.

Texte intégral

Résumé :

Η ρύπανση από τα χημικά λιπάσματα είναι έντονη στα ελληνικά εδάφη (ιδιαίτερα από τα νιτρικά άλατα) και επομένως είναι κρίσιμη η μείωση των εισροών αγροχημικών στο περιβάλλον. Η μείωση της λίπανσης αυξάνει την συγκέντρωση αντιοξειδωτικών ουσιών στους φυτικούς ιστούς. Πολλές επιστημονικές μελέτες μέχρι σήμερα συσχετίζουν την διατροφή με φυτικά προϊόντα υψηλής διατροφικής αξίας που περιέχουν φαινολικές-αντιοξειδωτικές ουσίες με την πρόληψη καρδιαγγειακών παθήσεων, πολλών μορφών καρκίνου αλλά και την γήρανση. Έτσι η έρευνα αυτή είχε διπλό στόχο: τη μείωση της ρύπανσης του περιβάλλοντος μέσω της μείωσης των λιπασμάτων που χορηγούνται στις καλλιέργειες, και την παραγωγή φυτικών προϊόντων υψηλής βιολογικής και διατροφικής αξίας, αφού θα παρέχουν μεγαλύτερες ποσότητες αντιοξειδωτικών ουσιών στον ανθρώπινο οργανισμό. Επίσης θα πρέπει να αναφερθεί ότι η μείωση των ποσοτήτων των λιπασμάτων που θα απαιτούνται για την καλλιέργεια των φυτών θα επιφέρει και οικονομικό όφελος προς τους καλλιεργητές και τους καταναλωτές, αφού θα μειωθεί το κόστος παραγωγής των φυτικών προϊόντων. Για το σκοπό αυτό μελετήθηκε για πρώτη φορά η επίδραση της μεταβολής της συγκέντρωσης των χορηγούμενων νιτρικών ιόντων μέσω του θρεπτικού διαλύματος υδροπονικής καλλιέργειας στο ρυθμό παραγωγής πολυφαινολικών ενώσεων σε λαχανικά ευρείας κατανάλωσης (παντζάρι και μαρούλι) και διαπιστώθηκε ότι η μεγιστοποίηση της παραγωγής των φυσικών αντιοξειδωτικών παραγόντων είναι δυνατή μέσω του ελέγχου της αζωτούχου θρέψης. Παράλληλα, διαπιστώθηκε και ποσοτικοποιήθηκε η ύπαρξη ενός κρίσιμου σημείου στη συγκέντρωση του χορηγούμενου αζώτου που ενεργοποιεί τον δευτερογενή μεταβολισμό των καλλιεργούμενων φυτών παντζαριού και μαρουλιού, αυξάνοντας σημαντικά το ρυθμό παραγωγής των ιδιαίτερα ευεργετικών για την υγεία φυτοχημικών ενώσεων όπως φαινολικών και μπετακυανινών. Η αύξηση όχι μόνο της περιεκτικότητας αλλά και της ενεργότητας των αντιοξειδωτικών παραγόντων επιβεβαιώθηκε με τη χρήση προηγμένων μεθόδων προσδιορισμού όπως το EPR. Τέλος προσδιορίστηκαν και ποσοτικοποιήθηκαν με σύγχρονη μέθοδο φασματομετρίας μαζών (LC-MS/MS) στα διαφορετικά μέρη των φυτών παντζαριού και στα φύλλα του μαρουλιού συνολικά επτά διαφορετικές πολυφαινολικές ενώσεις.
The pollution from chemical fertilizers is pronounced in Greek soils (particularly nitrates) and is therefore critical to reduce inputs of agrochemicals in the environment. The decrease of fertilization increases the concentration of antioxidants in plant tissues. Many scientific studies to date relate the diet with plant products of high nutritional value containing phenolic-antioxidants with the prevention of cardiovascular disease, number of cancers and aging. So the aims of the present research are: to reduce environmental pollution by reducing fertilizer applied to crops, and the production of crops with high biological and nutritional value, providing greater amounts of antioxidants in the human body. It should also be noted that the decrease in the quantities of fertilizer that will be required for the cultivation of plants will also lead to economic benefits to farmers and consumers, as it will reduce the cost of production of plant products. For this purpose the effect of varying concentration of nitrate granted via hydroponic nutrient solution, in the production rate of polyphenolic compounds in vegetables (lettuce and beetroot) was studied. It was found that maximizing the production of natural antioxidants is possible through the control of nitrogen nutrition. Also, it was ascertained that a critical point in the concentration of the administered nitrogen exists below which the secondary metabolism of the studied crops i.e. beetroot and lettuce is activated, significantly increasing the rate of production of the highly beneficial for the health compounds such as phenolic phytochemicals and betacyanins. The augmentation of the activity of antioxidants was confirmed by using advanced methods such as EPR. Finally seven different polyphenolic compounds were identified and quantified by the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS), in different plant parts of beetroot and lettuce leaves.

Styles APA, Harvard, Vancouver, ISO, etc.

45

Κωστενίδου, Ευαγγελία. « Usage of aerosol mass spectrometry for the measurement of the physical and chemical properties of the atmospheric nanoparticles ». Thesis, 2010. http://nemertes.lis.upatras.gr/jspui/handle/10889/3343.

Texte intégral

Résumé :

The Aerosol Mass Spectroscopy (AMS) is a recently developed method that provides on-line measurements of the chemical composition, mass spectrum and mass distributions of the atmospheric aerosol. Using the AMS with a thermodenuder in smog chamber experiments of ozonolysis of α-pinene, β-pinene and limonene, the mass spectrum of the secondary organic aerosols (SOA) is deconvoluted in low, medium and high volatility mass spectra. The spectrum of the surrogate component with the lower volatility for α-pinene and β-pinene is quite similar to that of ambient oxygenated organic aerosol (OOA). This could explain part of the difference between the AMS mass spectrum in the lab and the field. Combining an AMS and a Scanning Mobility Particle Sizer (SMPS) in smog chamber experiments of α-pinene, β-pinene and limonene ozonolysis, the density of the SOA is calculated and estimated between 1.4 and 1.65 g cm-3. This high density implies that the SOA is likely in a solid or a waxy state. The method is applied on field measurements at Finokalia, Crete during the FAME. For the summer campaign (FAME-08) the organic density is in the range of 0.8 and 1.8 g cm-3 with a mean value of 1.35±0.22 g cm-3¬, while for the winter (FAME-09) the average organic density is 1.14±0.36 g cm-3. This technique can also calculate the Collection Efficiency (CE) of the AMS, since AMS does not measure all the particles that enter the instrument. Applying the estimated CE, the AMS is in a good agreement with other instrumentation. The CE and the organic density of the thermodenuded samples are calculated as well. The CE and the organic density both for the ambient and the themodenuded samples are used as post corrections in the volatility estimation. For FAME-08 the organic aerosol is one order of magnitude less volatile than laboratory-generated α-pinene SOA. Furthermore they are highly oxidized due to the photochemistry conditions (especially in the summer) and the station location (away from detectable sources of pollution). Finally, modifying the steam-jet aerosol collector (SJAC) method both particulate and gas phase of the main inorganic species can be measured. Testing the approach at ambient conditions at the ICE-FORTH Institute, we were able to measure together with the inorganic aerosol composition the gas-phase concentrations of NH3, HONO and very low HNO¬3. The results are consistent with the predictions of the thermodynamic model ISORROPIA.
Τα αεροζόλ είναι σωματίδια που αιωρούνται στην ατμόσφαιρα. Η Φασματομετρία Μάζας Αεροζόλ (AMS) είναι μία νέα μέθοδος που μπορεί να δώσει ταυτόχρονα και σε πραγματικό χρόνο τη χημική σύσταση, το φάσμα μάζας και τις κατανομές μάζας των ατμοσφαιρικών σωματιδίων. Χρησιμοποιώντας το AMS με έναν θερμικό απογυμνωτή σε πειράματα οζονόλυσης α-πινενίου, β-πινενίου και λεμονενίου σε περιβαλλοντικό θάλαμο, το φάσμα μάζας των δευτερογενών οργανικών σωματιδίων (SOΑ) αναλύεται σε 3 επιμέρους φάσματα, ανάλογα με την πτητικότητα των οργανικών σωματιδίων. Το φάσμα που αντιστοιχεί στις ενώσεις με τη χαμηλότερη πτητικότητα για το α- και β-πινένιο είναι αρκετά όμοιο με αυτό των οξυγονωμένων οργανικών σωματιδίων (ΟΟΑ) από το περιβάλλον. Αυτό εξηγεί και μέρος της διαφοράς του φάσματος μάζας AMS μεταξύ εργαστηρίου και πεδίου. Συνδυάζοντας το AMS με ένα σαρωτή μεγέθους κινούμενων σωματιδίων (SMPS) υπολογίζεται η πυκνότητα των SOA από οζονόλυση α-πινενίου, β-πινενίου και λεμονενίου μεταξύ 1.4 και 1.65 g cm-3. Η σχετικά υψηλή τιμή της πυκνότητας μάλλον σημαίνει ότι τα παραγόμενα σωματίδια είναι στερεά ή κερώδη.Η παραπάνω μέθοδος εφαρμόζεται σε μετρήσεις πεδίου στη Φινοκαλιά, στην Κρήτη (FAME). Για το FAME-08 (καλοκαίρι) η πυκνότητα των οργανικών σωματιδίων είναι μεταξύ 0.8 και 1.8 g cm-3 με μέση τιμή 1.35±0.22 g cm-3, ενώ για το FAME-09 (χειμώνας) η μέση τιμή είναι 1.14±0.36 g cm-3. Η τεχνική αυτή υπολογίζει και το ποσοστό συλλογής (CE) σωματιδίων του AMS, καθώς το AMS μετράει ένα ποσοστό αυτών. Εφαρμόζοντας την CE που υπολογίζεται, η συμφωνία μεταξύ του AMS και άλλων οργάνων είναι αρκετά καλή. Υπολογίζεται επίσης η CE και η πυκνότητα των οργανικών για τα δείγματα που έχουν θερμανθεί στον θερμικό απογυμνωτή. Οι CE και οι οργανικές πυκνότητες χρησιμοποιούνται ως διορθώσεις για την αποφυγή υποεκτίμησης της πτητικότητας του οργανικού αεροζόλ. Για το FAME-08 οι οργανικές ενώσεις είναι περισσότερο από μία τάξη μεγέθους λιγότερο πτητικές από τα SOA που δημιουργούνται σε συνθήκες εργαστηρίου. Επίσης είναι υψηλά οξειδωμένες λόγω της φωτοχημείας (καλοκαίρι) και της τοποθεσίας της δειγματοληψίας (μακριά από πρωτογενείς ρύπους). Τέλος τροποποιώντας τη μέθοδο δειγματοληψίας υγροποιημένων σωματιδίων (SJAC) είναι δυνατό να μετρηθεί και η σωματιδιακή αλλά και η αέρια φάση των κυρίως ανόργανων ενώσεων. Πειράματα που έγιναν από δειγματοληψία στο ΕΙΧΗΜΥΘ δείχνουν την ύπαρξη ΝΗ3 αλλά σχεδόν μηδενικού ΗΝΟ3. Τα αποτελέσματα συγκρίνονται με ένα θερμοδυναμικό μοντέλο (ISΟRROPIA) και η συμφωνία είναι καλή.

Styles APA, Harvard, Vancouver, ISO, etc.

Thèses sur le sujet « Secondary pollution »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres