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Energy saving policies applied to modem buildings and air recirculation systems promote the build up of high levels of VOCs in indoor air. The growing concern related to the air quality in indoor environments requires the replacement of ineffective traditional purification methods, with an efficient and cost effective technology. Photocatalytic oxidation that utilise TiO2, represents a promising candidate for this purpose. However, the formulation of photocatalysts that can efficiently utilise a sustainable energy source (i.e. solar light), still represents an ambitious target in this field. In this study, different TiO2-based photocatalysts were synthesised by modified sol-gel and/or hydrothermal routes. The materials were characterised by XRD, SEM, N2 sorption (BET and BJH methods), UV-vis Spectroscopy and XPS. The photocatalytic activity of TiO2-based materials was systematically investigated at different light intensities, in a gas-phase flatplate photoreactor, using trichloroethylene (TCE) as model pollutant, and compared with that of the commercial product TiO2 Degussa P-25. This research provides insights into the influence of preparation parameters on different synthetical pathways for the preparation of highly active TiO2- based photocatalysts. The general approach to this investigation is based on the study of the influence of several processing parameters on morphological, textural and crystallographic properties of the photocatalysts, in order to correlate the material's features with their photocatalytic properties. The preparation of a wide range of pristine TiO2 allowed assessing a clear correlation between phase composition and crystal size and the photocatalytic performance. A series of highly active anatase photocatalysts was prepared. The best photocatalyst has an optimum crystal size of 28 nm and exhibits a photocatalytic activity that exceeds that of P-25 by a factor of over 2 times. A new TiO2/WO3 nanocomposites with peculiar crystallographic properties of the W component was developed by a novel one-step hydrothermal synthesis. The synthesis conditions were optimised with respect to the photocatalytic activity. Overall, the optimisation of the properties that enable an efficient interfacial charge transfer rate at the catalyst surface was found to be of fundamental importance for the design of improved TiO2-based photocatalysts.

This thesis presents the research on direct-fuel-injection (DFI) performance analyses of the two-stroke engine using computational fluid dynamics (CFD). The aims of this research are: (1) to generate a finite volume mesh that can be used to simulate the moving of the piston and opening and closing the ports of the cylinder, (2) to achieve an numerical flow pattern of the scavenging process and (3) to study the DFI process using the mesh and the flow pattern obtained from the first two parts. The three parts in the analyses, therefore, are the engine geometry modelling, scavenging process modelling and DFI modelling. CFD software STAR-CD was used to write the programme and perform the analysis. The geometry model used a moving mesh mechanism with variable openings to simulate the piston motion and port area changes. The scavenging model was constructed to calculate 3D, compressible, turbulent, transient flow with heat transfer and changing volume. Results of the calculation provided a large number of data, including flow patterns, pressure and temperature distributions and fresh-charge concentrations. The DFI process was simulated as a gasliquid two-phase flow. Fuel droplets dispersed in the continuous gas phase were calculated using the Lagrangian model. Four DFI cases that differ in position and number of injectors were simulated. Fuel droplet distribution, including droplet size, velocity, temperature and position, and fuel-vapour concentration were obtained. The result of the geometry modelling shows that the finite volume programme performed well for this particular task. Because of the limitation of the computer hardware used, this programme was restricted to be used for the simulation of the engine process before the ignition, i. e., cold running condition, therefore, combustion process was not included. The findings from the analyses, with very limited resources, would help improve the engine design. The results of all four cases indicate that, even only for the period of engine process before the ignition, the DFI two-stroke engine can significantly reduce hydrocarbon emissions compared with the conventional carburettor engine.

La nuisance olfactive perçue au voisinage de zones industrielles est souvent le résultat de la combinaison de plusieurs sources odorantes. L’objectif de ce travail de thèse est de quantifier simultanément la participation de chacune de ces sources à la nuisance globale afin de pouvoir prendre les mesures correctives adaptées. Pour cela, deux approches sont étudiées : la mesure des effluents gazeux par un nez électronique composé de capteurs de gaz peu spécifique, et l’analyse physico-chimique des Composés Organiques Volatils (COV) présents dans ces effluents gazeux à l’aide de techniques chromatographiques. L’aspect novateur de la thèse provient plus particulièrement de la méthode d’analyse des données utilisées lors des deux méthodes :- les signaux du nez électronique issus de mélanges de sources odorantes sont interprétés en calculant leur proximité aux signaux issus des sources prises individuellement : la proximité d’une source peut être corrélée avec sa teneur relative dans l’échantillon.- l’utilisation d’un modèle « site-récepteur » de type « Chemical Mass Balance » (CMB) permet d’interpréter les teneurs en COV d’un mélange de sources. En effet, chaque source possédant une signature (ou motif) propre, en effectuant différentes combinaisons linéaires des sources, il est possible de faire converger ces combinaisons vers la signature du mélange. / The odor perceived in the vicinity of industrial areas is often the result of a combination of several odor sources. The objective of this thesis is to quantify simultaneously the contribution of each of these sources to the overall nuisance, in order to take appropriate corrective actions. In order to do so, two approaches are studied: the measurement of gaseous effluents using an electronic nose containing 6 non-specific gas sensors, and the chemical analysis of Volatile Organic Compounds (VOCs) in the gaseous effluent using chromatographic techniques. The innovative aspect of the thesis comes particularly from the data analysis used in the two methods:- For the electronic nose, the signals obtained from the measurements of mixtures of odor sources are interpreted by calculating their proximity to the signals obtained from the measurement of individual sources: the proximity of a source can be correlated with its portion in the sample.- The use of a receptor model (the "Chemical Mass Balance", or “CMB” model) allows to interpret the concentrations of VOC in a mixture of sources. Indeed, each source having its own unique signature (or pattern), by performing different linear combinations of sources, it is possible to fit these combinations to the pattern of the mixture.

The occurrence of hydrogen sulphide in the environment, the reasons for concern about the levels which may be present, particularly on off-shore installations, and methods for determining the gas in air are reviewed. The original aim of this project was to explain the reasons for the variations in the levels of naturally occurring hydrogen sulphide over the estuary of the Don at Aberdeen. The monitoring work required a reliable method: as the published methods were all problematical, much effort was expended in improving the Ethylene Blue method and investigating the range of trapping solutions. The final optimised method has been published (Analyst 1988, 113, 1635). An alternative method for standardising H2S in air gas mixes has also been developed and used on commercial samples. Microbiological studies have shown that sulphate-reducing bacteria were not present in the sediments of the Don estuary in 1988 (but were present in sediments from the Forth estuary) and further, that the Don sediments would not support growth of SRB's, which in part explains why there has been effectively no release of H2S from the estuary in recent years. Attempts have been made to correlate the H2S emission events with changes in river water quality over the last ten years, but no obvious clues have become evident.

Soil samples were collected from the major horizons of Scottish upland Calluna moorland podzols derived from quartzite, Devonian and Torridonian sandstone, or granite or granitic tills. All soil was subjected to routine chemical analysis and the soil derived from granite was also mineralogically analysed. The results were studied in relation to finding evidence for potential acidification effects of atmospheric deposition. Strong relationships were observed between acid deposition parameters, particularly the mobile anion concentrations, and soil pH measured in water and soil extractable Al in all the horizons from podzols derived from sandstones and quartzites. These are discussed in Chapter 2. When looking for ameliorative effects, less clear trends were observed between atmospheric base cation inputs and soil "damage" parameters, possibly due to the distribution of the data. Soils derived from granite or granitic till showed relationships between soil pH in water or in CaCl2 pastes and H+ deposition, and between soil extractable Al and H+ deposition (Chapter 3). In addition, atmospheric inputs of base cations showed strong acid ameliorative properties in these soils. The relative importance of marine- and non-marine base cations in the calculation of critical loads for soil is examined in Chapter 4. The accumulation of N in the surface horizons along a pollution gradient is discussed in Chapter 5. At low to moderate total and NH4+ deposition (i.e., 10 and 5 kg ha-1 yr-1 respectively), soil total N and soil C:N ratio increased linearly with atmospheric N deposition. In spite of the N accumulation, C accumulated relatively faster than N, to increase the C:N ratio at sites with low to moderate N deposition. At total N or NH4+ deposition values above 8.8 and 4.0 kg ha-1 yr-1 respectively, the C:N ratio declined with increasing N deposition.

A variety of approaches, spanning a range of spatial and temporal scales, were applied to the investigation of the effects of low dose SO₄^2- deposition, at rates comparable to those experienced in acid rain impacted areas, on methane (CH₄) emissions from natural wetlands. Over two years of experimental manipulation of SO₄^2- deposition to a peatland in northeast Scotland, CH₄ emissions were suppressed by around 40%. There was no significant difference in suppression of CH₄ flux within the sol- deposition range of 25-100 kg-S ha^-1yr^-1. In a similar short-term controlled environment SO₄^2- manipulation experiment, the suppressive effect of SO₄^2- was found to be independent of the simulated SO₄^2- deposition rate within a range of 15-100 kg-S ha^-1yr^-1. The possibility that suppression of CH₄ fluxes may have been the result of a 'salt effect' was ruled out. Both temperature and water table controlled the extent of CH₄ flux suppression in acid rain impacted wetlands. Sulfate reduction potential in SO₄^2- treatments were found to be 10 times larger than in control plots, suggesting that long-term suppression of CH₄ fluxes is the result of the formation of an enlarged population of competitively superior sulfate reducing bacteria. SO₄^2- concentrations were smaller in peat pore water from SO₄^2- treatments than from controls. This is possibly the result of a stimulated SO₄^2- reducing community scavenging available SO₄^2-, thereby decreasing concentrations to below ambient levels. In northern peatlands (>50°) the effect of SO₄^2- deposition at 1990 rates may have been sufficient to reduce emissions from these systems by around 15% annually. Globally, the effect of acid rain SO₄^2- deposition may be sufficient to reduce CH₄ emissions by as much as 22-28 Tg by 2030, which places this interaction within the same size category as many other components of the global CH₄ budget that have received far greater attention.

La nature et l’intensité des impacts environnementaux et sanitaires des particules d’aérosols atmosphériques sont fortement dépendantes de leur composition chimique. Cette composition est corrélée avec la nature des sources d’émission et du temps de transport dans l’atmosphère où les particules peuvent subir de nombreuses transformations physico-chimiques, appelées vieillissement. Les objectifs de la thèse sont d’une part d’étudier en laboratoire les premières étapes du vieillissement atmosphérique de particules organiques et, d’autre part, d’affiner la modélisation de la composition chimique des aérosols atmosphériques. Le premier volet de ce travail a été consacré à l’étude de la réactivité de particules organiques modèles au sein d’un réacteur à écoulement d’aérosols pour deux systèmes chimiques : acide oléique + ozone et acide palmitique + radical chlore. Des analyses chimiques en phase gazeuse et particulaire nous ont permis de quantifier les produits de réaction et de déterminer les mécanismes de réaction. Dans la seconde partie de la thèse, nous avons mis au point un modèle de génération d’émission de polluants anthropiques pour la modélisation de la qualité de l’air par le modèle de chimie-transport WRF-Chem. La spéciation chimique des aérosols primaires nous a permis de modéliser la composition chimique des aérosols sur la région Nord-Pas de Calais. Les sorties du modèle ont été validées par comparaison statistique avec des données issues des réseaux de mesures (ATMO Nord-Pas de Calais) ainsi que des mesures réalisées par un spectromètre de masse pour aérosols lors de campagnes de terrain. / The intensity of environmental and health impacts of atmospheric aerosol depend on their chemical composition. This composition varies as function of their emission source and transport time in the atmosphere where many chemical and physical transformations occur. The objectives of this thesis are, firstly, to study the initial steps of the atmospheric aging of organic aerosol in laboratory and, secondly, to provide with information on the modelling of the chemical composition of atmospheric aerosol. The first part of this work has been dedicated to the study of the reactivity of model organic aerosol in an aerosol flow tube for two heterogeneous chemical systems: oleic acid + ozone; palmitic acid + chlorine radical. Chemical analyses in both gas phase and particle phase were performed to quantify the products and determine the chemical mechanisms.In the second part of the thesis, we have built a model to generate anthropogenic pollutant emission data for the chemistry weather forecast with the WRF-Chem model. The chemical speciation of primary aerosol permits us to model the chemical composition of aerosol over the French northern region. The model results have been validated by statistical comparison with data coming from measurements network (ATMO Nord-Pas de Calais) and also measurement campaigns performed with an Aerosol Mass Spectrometer.

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Les systèmes autonomes de traitement de l’air intérieur présentant une fonction photocatalytique ont conquis un marché important en France. La norme XP B 44 013, norme en vigueur pour tester les performances de ces systèmes, propose des conditions expérimentales éloignées des conditions réelles de mise en œuvre du point de vue (i) du volume de l’enceinte de test et (ii) de la diversité des COV modèles considérés. Ainsi, l’étude des performances des systèmes de traitement dans une pièce expérimentale de volume réaliste et face à différents mélanges de COV qui pourront être rencontrés en air intérieur s’avère crucial pour proposer une évaluation pertinente des performances de systèmes de traitement et déterminer leur influence réelle sur la qualité de l’air intérieur. L’objectif principal de cette thèse est d’évaluer les performances et l’innocuité de systèmes commerciaux de traitement d’air présentant une fonction photocatalytique dans des situations de fonctionnement types, proches des conditions réelles d’utilisation ; c'est-à-dire, prenant en compte de la diversité des espèces présentes dans l’air intérieur et des faibles concentrations de COV. Pour atteindre cet objectif une pièce expérimentale nommée IRINA est développée et validée. Les performances des systèmes de traitements sont évaluées dans IRINA (i) en utilisant cinq matrices spécifiques de différentes pollutions d’air intérieur, (ii) face à un évènement de pollution ponctuel due aux nettoyages et (iii) à une source d’émission continu de pollution liée à des matériaux bois. A partir des résultats obtenus dans ces travaux, des recommandations pour l’évolution des normalisations en photocatalyse sont formulées. / Autonomous devices presenting a photocatalytic function designed for VOCs treatment in indoor air have conquered a large market in France. The current standard, named XP B 44 013, for testing the performances of such systems provides experimental conditions that are far from realistic conditions of implementation from the point of view of (i) the test chamber volume and (ii) the considered diversity of the VOCs. Thus, the study of devices treatment performances in an experimental room of realistic volume and facing different VOC mixtures that may be encountered in indoor air is crucial to propose a relevant evaluation of the performances of treatment devices and to determine their real influence on indoor air quality.The main objective of this thesis is to evaluate the performance and safety of commercial air treatment devices with a photocatalytic function in typical operating situations, close to actual conditions of use; that is to say, taking into account, on one hand, the diversity of species present in indoor air and, on the other hand, the low concentrations of VOCs. To achieve this objective, an experimental room called IRINA is developed and validated. Then, the performances of the treatment systems are evaluated in IRINA (i) using five artificial specific matrices of different indoor air pollution, (ii) facing a point pollution event due to cleanings and (iii) a source of continuous emission of pollution related to wood materials.Based on the obtained results in this work, recommendations for the evolution of photocatalysis standardizations are formulated.