Tesi sul tema "Emission de particule"

Réduire les émissions de particules, notamment les PM10, les PM2.5 et les ultrafines (<100nm) est devenu un enjeu environnemental et de santé publique. Leur dispersion dans l'environnement proche au cours du freinage à friction est liée, d'une part, aux sollicitations thermomécaniques à l'interface garniture – disque, et d'autre part, à l'encombrement sous véhicule qui va influencer leur trajectoire initiale. Cette thèse fait partie du projet BREAQ visant à réduire l'exposition aux particules fines issues du freinage ferroviaire. Les travaux présentés dans ce mémoire s'intéressent plus particulièrement à relier la production de particules aux paramètres thermomécaniques dans le contact d'un frein à disque et à évaluer leur trajectoire par une technique de visualisation. Un banc d'essai de freinage à échelle réduite est dimensionné de sorte à conserver une équivalence sur la densité de flux thermique dissipée et est intégré dans une soufflerie pour émuler le déplacement d'un train. Les conditions d'écoulement d'air sont combinées à celles de freinages afin d’être représentatives de trajets urbains réels. Les particules de différentes tailles sont quantifiées par des compteurs et spectromètres en temps réel, en fonction des paramètres de freinage et d’écoulement. Les données montrent une influence des conditions tribologiques sur le profil des émissions. Les résultats mettent en évidence des phases d'émission de particules (mise en contact, maintien de l’effort, retrait). Une analyse PIV (Particule Imaging Velocimetry), habituellement utilisée pour calculer le champ de vitesse d’un fluide ensemencé, est adaptée à notre étude pour estimer la dispersion des particules proche du système de freinage. Les champs de vitesse estimés des particules sont en cohérence avec les mesures des compteurs. L’analyse PIV a permis de proposer un indicateur de présence, temporel et spatial des particules émises, au cours des différentes phases d'un freinage
Reducing particulate emissions, particularly PM10, PM2.5, and ultrafine particles, has become a critical environmental and public health issue. Their dispersion in the nearby environment during friction braking is linked, on one hand, to the thermomechanical stresses at the pad-disc interface, and on the other hand, to the under-vehicle clearance, which affects their initial trajectory. This thesis is part of the BREAQ project, aimed at reducing exposure to fine particles generated by railway braking. The work presented in this dissertation specifically focuses on correlating particle production with thermomechanical parameters in the contact of a disc brake and evaluating their trajectory through visualization techniques. A scaled-down braking test bench was designed to maintain equivalency in dissipated heat flux density and was integrated into a wind tunnel to simulate train movement. Airflow conditions were combined with braking conditions to accurately represent real urban journeys. Particles of various sizes were quantified in real-time using counters and spectrometers, based on braking and airflow parameters. The data show that tribological conditions influence the emission profile. The results highlight phases of particle emission (contact initiation, force maintenance, release). A Particle Imaging Velocimetry (PIV) analysis, usually employed to calculate the velocity field of a seeded fluid, was adapted to estimate the dispersion of particles near the braking system. The estimated particle velocity fields are consistent with counter measurements. The PIV analysis enabled the proposal of a temporal and spatial presence indicator of emitted particles during different braking phases

La detection des produits de fusion (3. 5mev) sera d'importance majeure pour la realisation d'une decharge continue dans les reacteurs de fusion thermonucleaire. Du fait de leur giration cyclotronique, les particules emettent dans la bande radiofrequence rf: 10-500mhz. Notre but est de determiner dans quelle mesure la detection du rayonnement rf issu d'un plasma de reacteur peut renseigner sur ces produits de fusion. Experimentalement, nous avons montre que le rayonnement rf emis par des particules rapides situees au centre de la decharge est detectable. Nous proposons ensuite deux modeles complementaires de cette emission. Le premier procede d'une description locale des echanges d'energie entre les photons et le plasma. Les particules ne sont pas les seules a intervenir et la prise en compte de toutes les especes du plasma est necessaire. Il apparait neanmoins que le diagnostic de la fonction de distribution des particules est possible dans une bande de frequence situee au voisinage des trois premiers harmoniques cyclotroniques et a condition de selectionner les modes de faible k#. Dans ce premier modele, la description des modes est realisee en supposant que l'onde est localement plane. Cette hypothese condamne la possibilite de decrire la propagation des photons dans certaines regions singulieres ou le vecteur d'onde ne peut plus etre defini. En pareil cas, l'ecriture d'une equation de continuite sur l'energie necessite la connaissance du champ electrique, et implique la resolution complete des equations de champ. Notre seconde modelisation realise numeriquement la resolution du systeme maxwell-vlasov a partir d'une formulation variationnelle. Une fois le champ calcule, la mesure de correlation entre plusieurs sondes donne acces a la densite de particules. Pour finir nous proposons ume experience pour demontrer la faisabilite d'un diagnostic fournissant la densite centrale de particules dans un reacteur

Cette etude porte sur la desintegration de mesons dans des modeles de quarks constituants. Ces derniers sont presentes ainsi que les differents potentiels d'interaction qq employes. La desintegration forte d'un meson en deux ou trois mesons fait l'objet de la seconde partie. Le modele 3p 0 original est presente ainsi que la recherche d'une fonction de vertex (p) dependant de l'impulsion de la paire qq creee. On montre qu'une fonction (p) de type constante + gaussienne se revele superieure a la constante utilisee habituellement. La deuxieme partie est consacree aux transitions electromagnetiques etudiees a travers l'emission d'un photon reel ou virtuel. Dans le cadre de l'emission d'un photon reel les approximations rencontrees dans la litterature sont passees en revue puis comparees a un formalisme depassant l'approximation des grandes longueurs d'ondes. Des angles de melange sont testes pour certains mesons. Pour les photons virtuels, l'expression de la largeur obtenue par vanroyen et weisskopf est redemontree puis etendue en prenant compte la distribution des impulsions des quarks au sein du meson. Un habillage electromagnetique est ajoute aux quarks aboutissant a une amelioration des resultats. Tout au long de cette etude, des fonctions d'onde de divers degres de sophistication sont utilisees. Les resultats de largeurs de desintegration sont compares avec un large eventail de donnees experimentales.

Vehicle emitted particles are of significant concern based on their potential to influence local air quality and human health. Transport microenvironments usually contain higher vehicle emission concentrations compared to other environments, and people spend a substantial amount of time in these microenvironments when commuting. Currently there is limited scientific knowledge on particle concentration, passenger exposure and the distribution of vehicle emissions in transport microenvironments, partially due to the fact that the instrumentation required to conduct such measurements is not available in many research centres. Information on passenger waiting time and location in such microenvironments has also not been investigated, which makes it difficult to evaluate a passenger’s spatial-temporal exposure to vehicle emissions. Furthermore, current emission models are incapable of rapidly predicting emission distribution, given the complexity of variations in emission rates that result from changes in driving conditions, as well as the time spent in driving condition within the transport microenvironment. In order to address these scientific gaps in knowledge, this work conducted, for the first time, a comprehensive statistical analysis of experimental data, along with multi-parameter assessment, exposure evaluation and comparison, and emission model development and application, in relation to traffic interrupted transport microenvironments. The work aimed to quantify and characterise particle emissions and human exposure in the transport microenvironments, with bus stations and a pedestrian crossing identified as suitable research locations representing a typical transport microenvironment. Firstly, two bus stations in Brisbane, Australia, with different designs, were selected to conduct measurements of particle number size distributions, particle number and PM2.5 concentrations during two different seasons. Simultaneous traffic and meteorological parameters were also monitored, aiming to quantify particle characteristics and investigate the impact of bus flow rate, station design and meteorological conditions on particle characteristics at stations. The results showed higher concentrations of PN20-30 at the station situated in an open area (open station), which is likely to be attributed to the lower average daily temperature compared to the station with a canyon structure (canyon station). During precipitation events, it was found that particle number concentration in the size range 25-250 nm decreased greatly, and that the average daily reduction in PM2.5 concentration on rainy days compared to fine days was 44.2 % and 22.6 % at the open and canyon station, respectively. The effect of ambient wind speeds on particle number concentrations was also examined, and no relationship was found between particle number concentration and wind speed for the entire measurement period. In addition, 33 pairs of average half-hourly PN7-3000 concentrations were calculated and identified at the two stations, during the same time of a day, and with the same ambient wind speeds and precipitation conditions. The results of a paired t-test showed that the average half-hourly PN7-3000 concentrations at the two stations were not significantly different at the 5% confidence level (t = 0.06, p = 0.96), which indicates that the different station designs were not a crucial factor for influencing PN7-3000 concentrations. A further assessment of passenger exposure to bus emissions on a platform was evaluated at another bus station in Brisbane, Australia. The sampling was conducted over seven weekdays to investigate spatial-temporal variations in size-fractionated particle number and PM2.5 concentrations, as well as human exposure on the platform. For the whole day, the average PN13-800 concentration was 1.3 x 104 and 1.0 x 104 particle/cm3 at the centre and end of the platform, respectively, of which PN50-100 accounted for the largest proportion to the total count. Furthermore, the contribution of exposure at the bus station to the overall daily exposure was assessed using two assumed scenarios of a school student and an office worker. It was found that, although the daily time fraction (the percentage of time spend at a location in a whole day) at the station was only 0.8 %, the daily exposure fractions (the percentage of exposures at a location accounting for the daily exposure) at the station were 2.7% and 2.8 % for exposure to PN13-800 and 2.7% and 3.5% for exposure to PM2.5 for the school student and the office worker, respectively. A new parameter, “exposure intensity” (the ratio of daily exposure fraction and the daily time fraction) was also defined and calculated at the station, with values of 3.3 and 3.4 for exposure to PN13-880, and 3.3 and 4.2 for exposure to PM2.5, for the school student and the office worker, respectively. In order to quantify the enhanced emissions at critical locations and define the emission distribution in further dispersion models for traffic interrupted transport microenvironments, a composite line source emission (CLSE) model was developed to specifically quantify exposure levels and describe the spatial variability of vehicle emissions in traffic interrupted microenvironments. This model took into account the complexity of vehicle movements in the queue, as well as different emission rates relevant to various driving conditions (cruise, decelerate, idle and accelerate), and it utilised multi-representative segments to capture the accurate emission distribution for real vehicle flow. This model does not only helped to quantify the enhanced emissions at critical locations, but it also helped to define the emission source distribution of the disrupted steady flow for further dispersion modelling. The model then was applied to estimate particle number emissions at a bidirectional bus station used by diesel and compressed natural gas fuelled buses. It was found that the acceleration distance was of critical importance when estimating particle number emission, since the highest emissions occurred in sections where most of the buses were accelerating and no significant increases were observed at locations where they idled. It was also shown that emissions at the front end of the platform were 43 times greater than at the rear of the platform. The CLSE model was also applied at a signalled pedestrian crossing, in order to assess increased particle number emissions from motor vehicles when forced to stop and accelerate from rest. The CLSE model was used to calculate the total emissions produced by a specific number and mix of light petrol cars and diesel passenger buses including 1 car travelling in 1 direction (/1 direction), 14 cars / 1 direction, 1 bus / 1 direction, 28 cars / 2 directions, 24 cars and 2 buses / 2 directions, and 20 cars and 4 buses / 2 directions. It was found that the total emissions produced during stopping on a red signal were significantly higher than when the traffic moved at a steady speed. Overall, total emissions due to the interruption of the traffic increased by a factor of 13, 11, 45, 11, 41, and 43 for the above 6 cases, respectively. In summary, this PhD thesis presents the results of a comprehensive study on particle number and mass concentration, together with particle size distribution, in a bus station transport microenvironment, influenced by bus flow rates, meteorological conditions and station design. Passenger spatial-temporal exposure to bus emitted particles was also assessed according to waiting time and location along the platform, as well as the contribution of exposure at the bus station to overall daily exposure. Due to the complexity of the interrupted traffic flow within the transport microenvironments, a unique CLSE model was also developed, which is capable of quantifying emission levels at critical locations within the transport microenvironment, for the purpose of evaluating passenger exposure and conducting simulations of vehicle emission dispersion. The application of the CLSE model at a pedestrian crossing also proved its applicability and simplicity for use in a real-world transport microenvironment.

Canon a electron fournissant un faisceau dans la gamme 5 ev-50 ev: resolution en vecteur d'onde de 0,2 a**(-1), courant maximal de 25 microamperes a 20 ev. Les spectres de photoemission inverse resolue angulairement presentent des effets angulaires a 30 ev. A 10 ev les effets angulaires devraient etre plus marques mais de faible rendement du spectrometre a cette energie rend les experiences difficiles. Caracterisation de nouvelles sources d'electrons: electrons emis par effet du champ par une cathode comprenant un grand nombre de micropointes. Ces cathodes fonctionnent a basse temperature. Description du spectrometre uv du vide et de la multidetection des photons

Conventional charged-particle imaging techniques--such as autoradiography--provide only two-dimensional (2D) images of thin tissue slices. To get volumetric information, images of multiple thin slices are stacked. This process is time consuming and prone to distortions, as registration of 2D images is required. We propose a direct three-dimensional (3D) autoradiography technique, which we call charged-particle emission tomography (CPET). This 3D imaging technique enables imaging of thick sections, thus increasing laboratory throughput and eliminating distortions due to registration. In CPET, molecules or cells of interest are labeled so that they emit charged particles without significant alteration of their biological function. Therefore, by imaging the source of the charged particles, one can gain information about the distribution of the molecules or cells of interest. Two special case of CPET include beta emission tomography (BET) and alpha emission tomography (𝛼ET), where the charged particles employed are fast electrons and alpha particles, respectively. A crucial component of CPET is the charged-particle detector. Conventional charged-particle detectors are sensitive only to the 2-D positions of the detected particles. We propose a new detector concept, which we call particle-processing detector (PPD). A PPD measures attributes of each detected particle, including location, direction of propagation, and/or the energy deposited in the detector. Reconstruction algorithms for CPET are developed, and reconstruction results from simulated data are presented for both BET and 𝛼ET. The results show that, in addition to position, direction and energy provide valuable information for 3D reconstruction of CPET. Several designs of particle-processing detectors are described. Experimental results for one detector are discussed. With appropriate detector design and careful data analysis, it is possible to measure direction and energy, as well as position of each detected particle. The null functions of CPET with PPDs that measure different combinations of attributes are calculated through singular-value decomposition. In general, the more particle attributes are measured from each detection event, the smaller the null space of CPET is. In other words, the higher dimension the data space is, the more information about an object can be recovered from CPET.

The behaviour of particulate matter emissions from a Ford XLD 4T, passengercar diesel engine through a practical exhaust system in place was investigated during transient conditions, namely cold start and fast acceleration. Particulate emissions were measured at four sampling points through the exhaust system and the changes in particulate total mass concentration, total number concentration, particle size distribution and Carbon/SOF fractions were determined for various engine operating conditions. Each cold start test consisted of a step-change cold-start with fast acceleration, reaching one of the following target operation conditions: Idle, 1500rpm - 15kW, 2250rpm - 15kW, 2250rpm-35kW and 3500rpm - 15kW. Two preconditioning procedures were designed to provide repeatable cold start tests. These consisted of a) Idle operation for 4 hours the day before the test, followed by overnight soak; and b)10 minutes at high engine speed operation. Fast acceleration tests consisted of idle preconditioning followed by a step change to the target operation conditions. The particulate matter changes through the exhaust system were shown to be dependent on the previous operational history of the engine, idle conditions being effective at forming particle deposits. The amount of particulate deposited or blown out from the exhaust system constituted a significant fraction of the total engine exhaust emissions in a significant number of cold start and acceleration tests. The changes in particle concentration did not occur throughout the system in the same fashion. The catalyst produced predominantly particle number and mass reduction and the second silencer was a more efficient particle collector than the first silencer. From the first silencer, particles were resuspended more easily and in many more cases. Regarding the chemical composition, high-load conditions produced lower Solvent Organic Fraction (SOF) than their low load counterpart. However, the SOF did not change significantly through the exhaust system. Part of this work consisted of examining the use of the Electrical Low Pressure Impactor (ELP1) to estimate particulate mass emissions. It was observed that the ELP1 tended to overestimate the number of particles in the large (>0.1 (im) size range. This greatly affected the conversion from total particle number concentration to particle mass concentration. A correction based on comparison between the electrical and gravimetric methods (ELPI vs. Andersen Impactors) in the common size range for both techniques was proposed. Transient and steady-state tailpipe emission factors, expressed as grams of particulate per unit of engine work in kWh, were calculated from the test results and used to estimate the effect of transients on total cycle emissions in cycles with a different design from those followed in this work. The ELPI proved to be useful, yet limited for particle collection on Transmission Electron Microscope (TEM) grids in several size ranges. TEM images of particles were analysed and their fractal dimension determined.

Doctor of Philosophy
Department of Biological & Agricultural Engineering
Ronaldo G. Maghirang
Emissions of particulate matter (PM) are an increasing concern for large open beef cattle feedlots. Research is needed to develop science-based information on PM emissions and abatement measures for mitigating those emissions. This research was conducted to (1) measure PM concentrations emitted from large cattle feedlots, (2) compare different samplers for measuring concentrations of PM with equivalent aerodynamic diameter of 10 µm or less (PM10), (3) evaluate the relative effectiveness of pen surface treatments in reducing PM10 emissions, and (4) predict PM control efficiency of vegetative barriers. Concentrations of PM with equivalent aerodynamic diameter of 2.5 µm or less (PM2.5), PM10, and total suspended particulates (TSP) upwind and downwind of two large cattle feedlots (KS1, KS2) in Kansas were measured with gravimetric samplers. The downwind and net concentrations generally decreased with increasing water content (WC) of the pen surface; for effective control of PM emissions from feedlots, it appears that pen surface WC should be at least 20% (wet basis). Three types of samplers for measuring PM10 concentrations in feedlots KS1 and KS2 were compared: Tapered Element Oscillating Microbalance™ (TEOM), high-volume (HV), and low-volume (LV) PM10 samplers. Measured PM10 concentration was generally largest with the TEOM PM10 sampler and smallest with the LV PM10 sampler. A laboratory apparatus was developed for measuring the PM10 emission potential of pen surfaces as affected by surface treatments. The apparatus was equipped with a simulated pen surface, mock cattle hooves that moved horizontally across the pen surface, and PM10 samplers that collected emitted PM10. Of the surface treatments evaluated, application of water (6.4 mm) and hay (723 g/m2) exhibited the greatest percentage reduction in PM10 emission potential (69% and 77%, respectively) compared with the untreated manure layer. Computational fluid dynamics (CFD) was applied to predict airflow and particle collection by a row of trees (2.2 m high × 1.6 m wide). Predicted particle collection efficiencies generally agreed with published data and ranged from less than 1% for 0.875-µm particles to approximately 32% for 15-µm particles.

Biomass burning started to attract attention since the last decade because of its impacts on the atmosphere and the environmental air quality, as well as significant potential effects on human health and global climate change. Knowledge of particle emission characteristics from biomass burning is crucially important for the quantitative assessment of the potential impacts. This thesis presents the results of study aimed towards comprehensive characterization of particle emissions from biomass burning. The study was conducted both under controlled laboratory conditions, to quantify the particle size distribution and emission factors by taking into account various factors which may affect the particle characteristics, and in the field, to investigate biomass burning processes in the real life situations and to examine vertical profile of particles in the atmosphere. To simulate different environmental conditions, a new technique has been developed for investigating particle emissions from biomass burning in the laboratory. As biomass burning may occur in a field at various wind speeds and burning rates, the technique was designed to allow adjustment of the flow rates of the air introduced into the chamber, in order to control burning under different conditions. In addition, the technique design has enabled alteration of the high particle concentrations, allowing conducting measurements with the instrumentations that had the upper concentration limits exciding the concentrations characteristic to the biomass burning. The technique was applied to characterize particle emissions from burning of several tree species common to Australian forests. The aerosol particles were characterized in terms of size distribution and emission factors, such as PM2.5 particle mass emission factor and particle number emission factor, under various burning conditions. The characteristics of particles over a range of burning phases (e.g., ignition, flaming, and smoldering) were also investigated. The results showed that particle characteristics depend on the type of tree, part of tree, and the burning rate. In particular, fast burning of the wood samples produced particles with the CMD of 60 nm during the ignition phase and 30 nm for the rest of the burning process. Slow burning of the wood samples produced large particles with the CMD of 120 nm, 60 nm and 40 nm for the ignition, flaming and smoldering phases, respectively. The CMD of particles emitted by burning the leaves and branches was found to be 50 nm for the flaming phase and 30 nm for the smoldering phase, under fast burning conditions. Under slow burning conditions, the CMD of particles was found to be between 100 to 200 nm for the ignition and flaming phase, and 50 nm for the smoldering phase. For fast burning, the average particle number emission factors were between 3.3 to 5.7 x 1015 particles/kg for wood and 0.5 to 6.9 x 1015 particles/kg for leaves and branches. The PM2.5 emission factors were between 140 to 210 mg/kg for wood and 450 to 4700 mg/kg for leaves and branches. For slow burning conditions, the average particle number emission factors were between 2.8 to 44.8 x 1013 particles/kg for wood and 0.5 to 9.3 x 1013 particles/kg for leaves and branches, and the PM2.5 emissions factors were between 120 to 480 mg/kg for wood and 3300 to 4900 mg/kg for leaves and branches. The field measurements were conducted to investigate particle emissions from biomass burning in the Northern Territory of Australia over dry seasons. The results of field studies revealed that diameters of particles in ambient air emissions were within the size range observed during laboratory investigations. The laboratory measurements found that the particles released during the controlled burning were of a diameter between 30 and 210 nm, depending on the burning conditions. Under fast burning conditions, smaller particles were produced with a diameter in the range of 30 to 60 nm, whilst larger particles, with a diameter between 60 nm and 210 nm, were produced during slow burning. The airborne field measurements of biomass particles found that most of the particles measured under the boundary layer had a CMD of (83 ± 13) nm during the early dry season (EDS), and (127 ± 6) nm during the late dry season (LDS). The characteristics of ambient particles were found to be significantly different at the EDS and the LDS due to several factors including moisture content of vegetation, location of fires related to the flight paths, intensity of fires, and burned areas. Specifically, the investigations of the vertical profiles of particles in the atmosphere have revealed significant differences in the particle properties during early dry season and late dry season. The characteristics of particle size distribution played a significant role in these differences.

Biomass burning started to attract attention since the last decade because of its impacts on the atmosphere and the environmental air quality, as well as significant potential effects on human health and global climate change. Knowledge of particle emission characteristics from biomass burning is crucially important for the quantitative assessment of the potential impacts. This thesis presents the results of study aimed towards comprehensive characterization of particle emissions from biomass burning. The study was conducted both under controlled laboratory conditions, to quantify the particle size distribution and emission factors by taking into account various factors which may affect the particle characteristics, and in the field, to investigate biomass burning processes in the real life situations and to examine vertical profile of particles in the atmosphere. To simulate different environmental conditions, a new technique has been developed for investigating particle emissions from biomass burning in the laboratory. As biomass burning may occur in a field at various wind speeds and burning rates, the technique was designed to allow adjustment of the flow rates of the air introduced into the chamber, in order to control burning under different conditions. In addition, the technique design has enabled alteration of the high particle concentrations, allowing conducting measurements with the instrumentations that had the upper concentration limits exciding the concentrations characteristic to the biomass burning. The technique was applied to characterize particle emissions from burning of several tree species common to Australian forests. The aerosol particles were characterized in terms of size distribution and emission factors, such as PM2.5 particle mass emission factor and particle number emission factor, under various burning conditions. The characteristics of particles over a range of burning phases (e.g., ignition, flaming, and smoldering) were also investigated. The results showed that particle characteristics depend on the type of tree, part of tree, and the burning rate. In particular, fast burning of the wood samples produced particles with the CMD of 60 nm during the ignition phase and 30 nm for the rest of the burning process. Slow burning of the wood samples produced large particles with the CMD of 120 nm, 60 nm and 40 nm for the ignition, flaming and smoldering phases, respectively. The CMD of particles emitted by burning the leaves and branches was found to be 50 nm for the flaming phase and 30 nm for the smoldering phase, under fast burning conditions. Under slow burning conditions, the CMD of particles was found to be between 100 to 200 nm for the ignition and flaming phase, and 50 nm for the smoldering phase. For fast burning, the average particle number emission factors were between 3.3 to 5.7 x 1015 particles/kg for wood and 0.5 to 6.9 x 1015 particles/kg for leaves and branches. The PM2.5 emission factors were between 140 to 210 mg/kg for wood and 450 to 4700 mg/kg for leaves and branches. For slow burning conditions, the average particle number emission factors were between 2.8 to 44.8 x 1013 particles/kg for wood and 0.5 to 9.3 x 1013 particles/kg for leaves and branches, and the PM2.5 emissions factors were between 120 to 480 mg/kg for wood and 3300 to 4900 mg/kg for leaves and branches. The field measurements were conducted to investigate particle emissions from biomass burning in the Northern Territory of Australia over dry seasons. The results of field studies revealed that diameters of particles in ambient air emissions were within the size range observed during laboratory investigations. The laboratory measurements found that the particles released during the controlled burning were of a diameter between 30 and 210 nm, depending on the burning conditions. Under fast burning conditions, smaller particles were produced with a diameter in the range of 30 to 60 nm, whilst larger particles, with a diameter between 60 nm and 210 nm, were produced during slow burning. The airborne field measurements of biomass particles found that most of the particles measured under the boundary layer had a CMD of (83 ± 13) nm during the early dry season (EDS), and (127 ± 6) nm during the late dry season (LDS). The characteristics of ambient particles were found to be significantly different at the EDS and the LDS due to several factors including moisture content of vegetation, location of fires related to the flight paths, intensity of fires, and burned areas. Specifically, the investigations of the vertical profiles of particles in the atmosphere have revealed significant differences in the particle properties during early dry season and late dry season. The characteristics of particle size distribution played a significant role in these differences.

Diesel Particulate Matter (DPM) and coal dust samples were characterised using Raman microscopy, X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Thermo-Gravimetric Analysis (TGA), X-ray Fluorescence (XRF) spectrometry and Scanning electron Microscopy. The sp2/sp3 carbon bonding ratios for DPM and coal dust were determined as 6.1 and 0.7, respectively, from XPS. Principal Component Analysis (PCA) was successfully implemented as a tool for distinguishing between the very similar DPM and coal dust Raman spectra, with over 99% of the variance contained in the first principal component. DPM and coal dust mixtures with known compositions were produced. Raman instrumental parameters were systematically optimised by varying the objective lenses, acquisition times and laser powers, to improve spectral and obtain the most reproducible integrated spectral areas. A rotation stage was developed and employed to spin the specimens during analysis, resulting in a larger sampling area. This resulted in a more representative sampling regime for the heterogeneous specimens and a considerable improvement in the reproducibility of integrated spectral areas. The error in the integrated spectral areas of 10 replicate spectra of different mixtures ranged from 5-22% before implementation of the rotating stage and was notably reduced to 2 -6% due to the action of spinning. Raman spectra of mixtures were used to construct a Partial Least Squares (PLS) model. The R2 values for the DPM and coal dust were 0.865 and 0.763, respectively. The differential bum-off of volatile organics during the Raman analysis due to localised heating from the laser hindered the ability to gain highly reproducible spectra and thus markedly affected the PLS model. A method development stage aimed at improving the R2 values was applied to the samples. This involved heat-treating the specimens to 625°C in an inert nitrogen atmosphere, before the Raman analysis. The resultant PLS model, after heat-treatment, dramatically improved the R2 values such that the DPM and coal dust were 0.974 and 0.907, respectively. This model was used to predict the composition of a test sample with known amounts of DPM and coal dust. The concentrations predicted by the model were 166 ± 3.9pg for the DPM and 68 ± 7.8jxg for the coal dust. The model slightly overestimated the amount of DPM present in the sample but gave a large underestimation of the coal dust content. The diagnostics of the model were investigated and recommendations for the improvement of future models were given.

An optical and infrared observing programme which provides the most detailed information yet available for blazars is described. From this it is possible to make progress in understanding the physical processes which are occurring on the smallest scales within the emission region. Later theoretical calculations including a treatment of synchrotron emission incorporating losses and a realistic source geometry are presented together with a model of particle acceleration at relativistic shocks in disordered magnetic fields. The work contained in this thesis can explain the radiation and make predictions regarding future observations. The conclusion is that the observations support the idea that the synchrotron emitting electrons are being accelerated at a collisionless shock front in a disordered field.

Crankcase ventilation contributes significantly to diesel engine particulate emissions. Future regulations will not only limit the mass of particulate matter, but also the number of particles. Controlling the source of crankcase emissions is critical to meeting the perennial legislation. Deficiency in the understanding of crankcase emissions generation and the contribution of lubricating oil has been addressed in detail by the experimental study presented in this thesis. A plethora of high speed laser optical diagnostics techniques have been employed to deduce the main mechanisms of crankcase oil aerosol generation. Novel images have captured oil atomisation and passive oil distribution around the crankcase of an optically accessed, motored, four cylinder, off highway, heavy duty, diesel engine. Rayleigh type ligament breakup of oil films present on the surface of dynamic components, most notably the crankshaft, camshaft and valve rockers generated oil drops below 10 micrometers. Data illustrated not only crankcase oil aerosol generation at source, but it has provided valuable information on methods to control oil aerosol generation and improve oil circuit efficiency. The feasibility of utilising computational fluid dynamics to predict crankcase oil aerosol generation has been successfully assessed using the experimental data. Particle sampling has characterised the crankcase emissions from both a fired and motored diesel engine crankcase. The evolution of submicron crankcase particles down to 5 nm has been recorded from both engines, including the isolated contribution of engine oil, at a wide range of engine test points. Results have provided constructive insight into the generation and control of this complex emission. The main mechanism of crankcase oil aerosol generation was found to be crankshaft oil atomisation. This atomisation process has been analysed in detail, involving high speed imaging of primary and satellite drop generation and high speed digital particle image velocity of the crankshaft air flow. A promising mechanism of regulating and controlling crankcase oil aerosol emissions at source has been studied experimentally.

The technique of Positron Emission Particle Tracking (PEPT), developed at University of Birmingham in the late 1980s has become a powerful tool to track particles flowing in various industrial engineering applications. Hydrocyclones are extensively used in a widespread amount of applications for many industries, but are predominantly used in closed circuit grinding operations as classifiers in mineral processing. Many attempts have been made to capture the key relationships between hydrocyclone operating and geometrical variables in models, but hydrocyclone characterization is still heavily empirical and on a case-by-case basis. Due to their simplistic design, easy operation, low cost and maintenance, hydrocyclones have gained a widespread positive reputation for solid-liquid separations. Despite their wide use and long history in industry, the internal flow field of the hydrocyclone is complex in nature and remains a challenge to visualize under standard operating conditions. The work presented in this thesis project has looked at the feasibility and potential of PEPT to examine the flow in hydrocyclones. This study presents views of the real-time particle motion within small diameter hydrocyclones by PEPT. There is a need to develop a visualization method by which the velocity distributions can be quantified under realistic industrial conditions. Therefore, this thesis project will give an overview on current hydrocyclone flow field theory, and presents the experimental results of particle flow visualization inside two inch standard and stub hydrocyclones using PEPT under water and water-silica conditions.
La technique de localisation des particules par l'émission de positons (PEPT), développée à l'université de Birmingham dans les années 1980s, est un outil puissant dans diverses applications de génie industriel. Les hydrocyclones sont largement utilisés dans une quantité répandue des applications pour de nombreuses industries, mais sont principalement utilisés dans les opérations de broyage en circuit fermé de classification dans le traitement des minerais. De nombreuses tentatives ont été faites pour capturer les relations clés entre hydrocyclone des variables géométriques et fonctionnement mais la caractérisation de l'hydrocyclone est encore largement empirique et au cas par cas. En raison de leur conception simpliste, l'opération facile et faible coût de maintenance, les hydrocyclones ont acquis une bonne réputation répandue pour les séparations solide-liquide. Malgré leur large utilisation et longue histoire dans l'industrie, le champ d'écoulement interne de l'hydrocyclone est de nature complexe et demeure un défi de visualiser dans des conditions d'utilisation normales. Les travaux présentés dans ce projet se sont penché sur la faisabilité et le potentiel de PEPT d'examiner le movement fluide des hydrocyclones. Cette étude présente le mouvement des particules en temps réel de petits hydrocyclones par PEPT. Il est nécessaire de développer une méthode de visualisation par lequel les distributions de vitesse peuvent être quantifiées dans des conditions industrielles réelles. Par conséquent, ce projet donnera un aperçu sur la théorie du champ d'écoulement de l'hydrocyclone actuel et présente les résultats expérimentaux de visualisation de movement de particules à l'intérieur de hydrocyclones en utilisant PEPT pour deux conditions : l'eau et la silice en suspension.

Whilst the compression ignition (CI) engine exhibits many design advantages relative to its spark ignition engine counterpart; such as: high thermal efficiency, fuel economy and low carbon monoxide and hydrocarbon emissions, the issue of Diesel Particulate Matter (DPM) emissions continues to be an unresolved problem for the CI engine. Primarily, this thesis investigates a range of DPM mitigation strategies such as alternative fuels, injection technologies and combustion strategies conducted with a view to determine their impact on the physico-chemical properties of DPM emissions, and consequently to shed light on their likely human health impacts. Regulated gaseous emissions, Nitric oxide (NO), Carbon monoxide (CO), and Hydrocarbons (HCs), were measured in all experimental campaigns, although the major focus in this research program was on particulate emissions...

Emissions from airport operations are of significant concern because of their potential impact on local air quality and human health. The currently limited scientific knowledge of aircraft emissions is an important issue worldwide, when considering air pollution associated with airport operation, and this is especially so for ultrafine particles. This limited knowledge is due to scientific complexities associated with measuring aircraft emissions during normal operations on the ground. In particular this type of research has required the development of novel sampling techniques which must take into account aircraft plume dispersion and dilution as well as the various particle dynamics that can affect the measurements of the aircraft engine plume from an operational aircraft. In order to address this scientific problem, a novel mobile emission measurement method called the Plume Capture and Analysis System (PCAS), was developed and tested. The PCAS permits the capture and analysis of aircraft exhaust during ground level operations including landing, taxiing, takeoff and idle. The PCAS uses a sampling bag to temporarily store a sample, providing sufficient time to utilize sensitive but slow instrumental techniques to be employed to measure gas and particle emissions simultaneously and to record detailed particle size distributions. The challenges in relation to the development of the technique include complexities associated with the assessment of the various particle loss and deposition mechanisms which are active during storage in the PCAS. Laboratory based assessment of the method showed that the bag sampling technique can be used to accurately measure particle emissions (e.g. particle number, mass and size distribution) from a moving aircraft or vehicle. Further assessment of the sensitivity of PCAS results to distance from the source and plume concentration was conducted in the airfield with taxiing aircraft. The results showed that the PCAS is a robust method capable of capturing the plume in only 10 seconds. The PCAS is able to account for aircraft plume dispersion and dilution at distances of 60 to 180 meters downwind of moving a aircraft along with particle deposition loss mechanisms during the measurements. Characterization of the plume in terms of particle number, mass (PM2.5), gaseous emissions and particle size distribution takes only 5 minutes allowing large numbers of tests to be completed in a short time. The results were broadly consistent and compared well with the available data. Comprehensive measurements and analyses of the aircraft plumes during various modes of the landing and takeoff (LTO) cycle (e.g. idle, taxi, landing and takeoff) were conducted at Brisbane Airport (BNE). Gaseous (NOx, CO2) emission factors, particle number and mass (PM2.5) emission factors and size distributions were determined for a range of Boeing and Airbus aircraft, as a function of aircraft type and engine thrust level. The scientific complexities including the analysis of the often multimodal particle size distributions to describe the contributions of different particle source processes during the various stages of aircraft operation were addressed through comprehensive data analysis and interpretation. The measurement results were used to develop an inventory of aircraft emissions at BNE, including all modes of the aircraft LTO cycle and ground running procedures (GRP). Measurements of the actual duration of aircraft activity in each mode of operation (time-in-mode) and compiling a comprehensive matrix of gas and particle emission rates as a function of aircraft type and engine thrust level for real world situations was crucial for developing the inventory. The significance of the resulting matrix of emission rates in this study lies in the estimate it provides of the annual particle emissions due to aircraft operations, especially in terms of particle number. In summary, this PhD thesis presents for the first time a comprehensive study of the particle and NOx emission factors and rates along with the particle size distributions from aircraft operations and provides a basis for estimating such emissions at other airports. This is a significant addition to the scientific knowledge in terms of particle emissions from aircraft operations, since the standard particle number emissions rates are not currently available for aircraft activities.

Emissions from airport operations are of significant concern because of their potential impact on local air quality and human health. The currently limited scientific knowledge of aircraft emissions is an important issue worldwide, when considering air pollution associated with airport operation, and this is especially so for ultrafine particles. This limited knowledge is due to scientific complexities associated with measuring aircraft emissions during normal operations on the ground. In particular this type of research has required the development of novel sampling techniques which must take into account aircraft plume dispersion and dilution as well as the various particle dynamics that can affect the measurements of the aircraft engine plume from an operational aircraft. In order to address this scientific problem, a novel mobile emission measurement method called the Plume Capture and Analysis System (PCAS), was developed and tested. The PCAS permits the capture and analysis of aircraft exhaust during ground level operations including landing, taxiing, takeoff and idle. The PCAS uses a sampling bag to temporarily store a sample, providing sufficient time to utilize sensitive but slow instrumental techniques to be employed to measure gas and particle emissions simultaneously and to record detailed particle size distributions. The challenges in relation to the development of the technique include complexities associated with the assessment of the various particle loss and deposition mechanisms which are active during storage in the PCAS. Laboratory based assessment of the method showed that the bag sampling technique can be used to accurately measure particle emissions (e.g. particle number, mass and size distribution) from a moving aircraft or vehicle. Further assessment of the sensitivity of PCAS results to distance from the source and plume concentration was conducted in the airfield with taxiing aircraft. The results showed that the PCAS is a robust method capable of capturing the plume in only 10 seconds. The PCAS is able to account for aircraft plume dispersion and dilution at distances of 60 to 180 meters downwind of moving a aircraft along with particle deposition loss mechanisms during the measurements. Characterization of the plume in terms of particle number, mass (PM2.5), gaseous emissions and particle size distribution takes only 5 minutes allowing large numbers of tests to be completed in a short time. The results were broadly consistent and compared well with the available data. Comprehensive measurements and analyses of the aircraft plumes during various modes of the landing and takeoff (LTO) cycle (e.g. idle, taxi, landing and takeoff) were conducted at Brisbane Airport (BNE). Gaseous (NOx, CO2) emission factors, particle number and mass (PM2.5) emission factors and size distributions were determined for a range of Boeing and Airbus aircraft, as a function of aircraft type and engine thrust level. The scientific complexities including the analysis of the often multimodal particle size distributions to describe the contributions of different particle source processes during the various stages of aircraft operation were addressed through comprehensive data analysis and interpretation. The measurement results were used to develop an inventory of aircraft emissions at BNE, including all modes of the aircraft LTO cycle and ground running procedures (GRP). Measurements of the actual duration of aircraft activity in each mode of operation (time-in-mode) and compiling a comprehensive matrix of gas and particle emission rates as a function of aircraft type and engine thrust level for real world situations was crucial for developing the inventory. The significance of the resulting matrix of emission rates in this study lies in the estimate it provides of the annual particle emissions due to aircraft operations, especially in terms of particle number. In summary, this PhD thesis presents for the first time a comprehensive study of the particle and NOx emission factors and rates along with the particle size distributions from aircraft operations and provides a basis for estimating such emissions at other airports. This is a significant addition to the scientific knowledge in terms of particle emissions from aircraft operations, since the standard particle number emissions rates are not currently available for aircraft activities.

Transient emission of a particle in inductively coupled plasma-atomic emission spectrometry (ICP-AES) depends on the fundamental processes of aerosol desolvation, particle vaporization and atomization, ionization, excitation and diffusion of the analyte. Ideally, the rate of the above processes can be determined from the evolution of the transient emission as the ion plume moves along the central channel of the ICP. However, the dimension of the ion plume is significantly smaller than the central channel. The signal-to-background and signal-to-noise ratios suffer when the entire channel is imaged. Deconvolution of the temporal profile is required to determine the emission intensity of the ion plume versus observation height. Small aperture can be used to locate the vertical emission position accurately, but the evolution of the plume emission is lost. In this study, a double-slit method has been developed to pin-point two vertical positions of an ion plume. An ion plume travelling along the ICP central channel produces two peaks in the temporal emission profile. The temporal evolution of emission intensity can be correlated to delineate the degree of particle vaporization at the two positions. The relative widths and separation of the two peaks in a double-peak can be used to determine the analyte diffusion rate and particle velocity in the ICP, respectively. An unicellular green algae, chlorella vulgaris, was used as the test particles. The average Mg content of the algae is equivalent to MgO particles of diameter of 265nm. The strong ionic emission at wavelength of 279.55nm was monitored using a ¼ -m monochromator equipped with a PMT detector. Method of curve fitting was used to filter out the noise with minimum distortion of the peak shape for accurate determination of peak height and peak width. The merits of curve fitting versus methods of smoothing such as moving average and Savitzky-Golay filtering will be discussed. All transient emissions from the algal cells were detected with sufficient signal-to-noise ratio using a single-slit setup with slit height of 1mm at observation height of 18 mm above the load coil and ICP forward power of 1400 W. However, using the double-slit setup, less than half of the expected double-peaks were observed. One of the peaks in the double-peak can be below the detection limit and the double-peak is lost. An innovative development of this study is that the relative sensitivity corresponding to the 2 slits can be varied to enhance the intensity of the weaker emission peak. The peak with insufficient signal-to-noise ratio for detection can be enhanced to a level above the limit of detection. The number of observed double-peaks in increased and the observed particles are more representative of the population. Two types of double-peaks are categorized according to the relative intensity of the first peak to the second peak. A computer model was used to estimate the intensity ratio of the two emission peaks at different observation position of the ICP. The experimental and theoretical ratios agree generally. The theoretical ratio also shows the bias in the population sampled by the double-slit setup.
published_or_final_version
Chemistry
Master
Master of Philosophy

The estimation of energy dissipated during multiple particle impact is a key aspect in evaluating the abrasive potential of particle-laden streams. A systematic investigation of particle impact energy using acoustic emission (AE) measurements is presented in this thesis with experiments carried out over a range of particle sizes, particle densities and configurations. A model of the AE impact time series is developed and validated on sparse streams where there are few particle overlaps and good control over particle kinetic energies. The approach is shown to be robust and extensible to cases where the individual particle energies cannot be distinguished. For airborne particles, a series of impact tests was carried out over a wide range of particle sizes (from 125 microns to 1500 microns) and incident velocities (from 0.9 ms-1 to 16 ms-1). Two parameters, particle diameter and particle impact speed, both of which affect the energy dissipated into the material, were investigated and correlated with AE energy. The results show that AE increases with the third power of particle diameter, i.e. the mass, and with the second power of the velocity, as would be expected. The diameter exponent was only valid up to particle sizes of around 1.5mm, an observation which was attributed to different energy dissipation mechanisms with the higher associated momentum. The velocity exponent, and the general level of the energy were lower for multiple impacts than for single impacts, and this was attributed to particle interactions in the guide tube and/or near the surface leading to an underestimate of the actual impact velocity in magnitude and direction. In order to develop a model of the stream as the cumulation of individual particle arrival events, the probability distribution of particle impact energy was obtained for a range of particle sizes and impact velocities. Two methods of time series processing were investigated to isolate the individual particles arrivals from the background noise and from particle noise associated with contact of the particles with the target after their first arrival. For the conditions where it was possible to resolve individual impacts, the probability distribution of particle arrival AE energy was determined by the best-fit lognormal probability distribution function. The mean and variance of this function was then calibrated against the known nominal mass and impact speed. A pulse shape function was devised for the target plate by inspection of the records, backed up by pencil lead tests and this, coupled with the energy distribution functions allowed the iv records to be simulated knowing the arrival rate and the nominal mass and velocity of the particles. A comparison of the AE energy between the recorded and simulated records showed that the principle of accumulating individual particle impact signatures could be applied to records even when the individual impacts could not be resolved. For particle-laden liquid, a second series of experiments was carried out to investigate the influence of particle size, free stream velocity, particle impact angle, and nominal particle concentration on the amount of energy dissipated in the target using both a slurry impingement erosion test rig and a flow loop test rig. As with airborne particles, the measured AE energy was found overall to be proportional to the incident kinetic energy of the particles. The high arrival rate involved in a slurry jet or real industrial flows poses challenges in resolving individual particle impact signatures in the AE record, hence, and so the model has been further developed and modified (extended) to account for different particle carrier-fluids and to situations where arrivals cannot necessarily be resolved. In combining the fluid mechanics of particles suspended in liquid and the model, this model of AE energy can be used as a semi-quantitative diagnostic indicator for particle impingement in industrial equipments such as pipe bends.

The disposal of used tires represents an environmental and health hazard, especially when large stockpiles of tires start on fire. This study focuses on ambient particulate matter samples collected during the Iowa City landfill tire fire and laboratory emissions of tire combustion. Levels of elemental (EC) and organic carbon (OC), metals, polycyclic aromatic hydrocarbons (PAH), azaarenes and oxygenated PAH (oxy-PAH) were determined by thermo-optical analysis, high precision mass, inductively-coupled plasma mass spectrometry and gas chromatography mass spectrometry. Results demonstrate that tire combustion emissions are enriched in elemental carbon and PAH. Levels of hazardous metals, such as lead and zinc, are not enhanced in particulate emissions 4.2 km from the fire. In addition, fresh tire combustion emissions have increased amounts of lower molecular weight PAH in the particle phase when compared to diluted real world emissions. This is due to gas phase partitioning of lower molecular weight PAH in plume transport. To build on the prior, qualitative understanding of organic compounds in tire emissions, 15 total azaarenes and oxy-PAH were identified, including four azaarenes and three oxy-PAH that were identified in tire combustion emission for the first time. The combustion of tires has significant health implications, particularly when open burning occurs near populations. This study serves to characterize the major chemical components of tire smoke and to quantify emissions of select chemicals with known carcinogenic, mutagenic, and toxic effects.

The understanding of human exposure to indoor particles of all sizes is important to enable exposure control and reduction, but especially for smaller particles since the smaller particles have a higher probability of penetration into the deeper parts of the respiratory tract and also contain higher levels of trace elements and toxins. Due to the limited understanding of the relationship between particle size and the health effects they cause, as well as instrument limitations, the available information on submicrometer (d < 1.0 µm) particles indoors, both in terms of mass and number concentrations, is still relatively limited. This PhD project was conducted as part of the South-East Queensland Air Quality program and Queensland Housing Study aimed at providing a better understanding of ambient particle concentrations within the indoor environment with a focus on exposure assessment and control. This PhD project was designed to investigate comprehensively the sources and sinks of indoor aerosol particles and the relationship between indoor and outdoor aerosol particles, particle and gaseous pollutant, as well as the association between indoor air pollutants and house characteristics by using, analysing and interpreting existing experimental data which were collected before this project commenced, as well as data from additional experiments which were designed and conducted for the purpose of this project. The focus of this research was on submicrometer particles with a diameter between 0.007 - 0.808 µm. The main outcome of this project may be summarised as following: * A comprehensive review of particle concentration levels and size distributions characteristics in the residential and non-industrial workplace environments was conducted. This review included only those studies in which more general trends were investigated, or could be concluded based on information provided in the papers. This review included four parts: 1) outdoor particles and their effect on indoor environments; 2) the relationship between indoor and outdoor concentration levels in the absence of indoor sources for naturally ventilated buildings; 3) indoor sources of particles: contribution to indoor concentration levels and the effect on I/O ratios for naturally ventilated buildings; and 4) indoor/outdoor relationship in mechanically ventilated buildings. * The relationship between indoor and outdoor airborne particles was investigated for sixteen residential houses in Brisbane, Australia, in the absence of operating indoor sources. Comparison of the ratios of indoor to outdoor particle concentrations revealed that while temporary values of the ratio vary in a broad range from 0.2 to 2.5 for both lower and higher ventilation conditions, average values of the ratios were very close to one regardless of ventilation conditions and of particle size range. The ratios were in the range from 0.78 to 1.07 for submicrometer particles, from 0.95 to 1.0 for supermicrometer particles and from 1.01 to 1.08 for PM2.5 fraction. Comparison of the time series of indoor to outdoor particle concentrations showed a clear positive relationship existing for many houses under normal ventilation conditions (estimated to be about and above 2 h-1), but not under minimum ventilation conditions (estimated to be about and below 1 h-1). These results suggest that for normal ventilation conditions and in the absence of operating indoor sources, outdoor particle concentrations could be used to predict instantaneous indoor particle concentrations but not for minium ventilation, unless air exchange rate is known, thus allowing for estimation of the "delay constant". * Diurnal variation of indoor submicrometer particle number and particle mass (approximation of PM2.5) concentrations was investigated in fifteen of the houses. The results show that there were clear diurnal variations in both particle number and approximation of PM2.5 concentrations, for all the investigated houses. The pattern of diurnal variations varied from house to house, however, there was always a close relationship between the concentration and human indoor activities. The average number and mass concentrations during indoor activities were (18.2±3.9)×10³ particles cm-³ and (15.5±7.9) µg m-³ respectively, and under non-activity conditions, (12.4±2.7)x10³ particles cm-³ (11.1±2.6) µg m-³, respectively. In general, there was a poor correlation between mass and number concentrations and the correlation coefficients were highly variable from day to day and from house to house. This implies that conclusions cannot be drawn about either one of the number or mass concentration characteristics of indoor particles, based on measurement of the other. The study also showed that it is unlikely that particle concentrations indoors could be represented by measurements conducted at a fixed monitoring station due to the large impact of indoor and local sources. * Emission characteristics of indoor particle sources in fourteen residential houses were quantified. In addition, characterizations of particles resulting from cooking conducted in an identical way in all the houses were measured. All the events of elevated particle concentrations were linked to indoor activities using house occupants diary entries, and catalogued into 21 different types of indoor activities. This enabled quantification of the effect of indoor sources on indoor particle concentrations as well as quantification of emission rates from the sources. For example, the study found that frying, grilling, stove use, toasting, cooking pizza, smoking, candle vaporizing eucalyptus oil and fan heater use, could elevate the indoor submicrometer particle number concentration levels by more than 5 times, while PM2.5 concentrations could be up to 3, 30 and 90 times higher than the background levels during smoking, frying and grilling, respectively. * Indoor particle deposition rates of size classified particles in the size range from 0.015 to 6 µm were quantified. Particle size distribution resulting from cooking, repeated under two different ventilation conditions in 14 houses, as well as changes to particle size distribution as a function of time, were measured using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS), and a DustTrak. Deposition rates were determined by regression fitting of the measured size-resolved particle number and PM2.5 concentration decay curves, and accounting for air exchange rate. The measured deposition rates were shown to be particle size dependent and they varied from house to house. The lowest deposition rates were found for particles in the size range from 0.2 to 0.3 µm for both minimum (air exchange rate: 0.61±0.45 h-1) and normal (air exchange rate: 3.00±1.23 h-1) ventilation conditions. The results of statistical analysis indicated that ventilation condition (measured in terms of air exchange rate) was an important factor affecting deposition rates for particles in the size range from 0.08 to 1.0 µm, but not for particles smaller than 0.08 µm or larger than 1.0 µm. Particle coagulation was assessed to be negligible compared to the two other processes of removal: ventilation and deposition. This study of particle deposition rates, the largest conducted so far in terms of the number of residential houses investigated, demonstrated trends in deposition rates comparable with studies previously reported, usually for significantly smaller samples of houses (often only one). However, the results compare better with studies which, similarly to this study, investigated cooking as a source of particles (particle sources investigated in other studies included general activity, cleaning, artificial particles, etc). * Residential indoor and outdoor 48 h average levels of nitrogen dioxide (NO2), 48h indoor submicrometer particle number concentration and the approximation of PM2.5 concentrations were measured simultaneously for fourteen houses. Statistical analyses of the correlation between indoor and outdoor pollutants (NO2 and particles) and the association between house characteristics and indoor pollutants were conducted. The average indoor and outdoor NO2 levels were 13.8 ± 6.3 ppb and 16.7 ± 4.2 ppb, respectively. The indoor/outdoor NO2 concentration ratio ranged from 0.4 to 2.3, with a median value of 0.82. Despite statistically significant correlations between outdoor and fixed site NO2 monitoring station concentrations (p = 0.014, p = 0.008), there was no significant correlation between either indoor and outdoor NO2 concentrations (p = 0.428), or between indoor and fixed site NO2 monitoring station concentrations (p = 0.252, p = 0.465,). However, there was a significant correlation between indoor NO2 concentration and indoor submicrometer aerosol particle number concentrations (p = 0.001), as well as between indoor PM2.5 and outdoor NO2 (p = 0.004). These results imply that the outdoor or fixed site monitoring concentration alone is a poor predictor of indoor NO2 concentration. * Analysis of variance indicated that there was no significant association between indoor PM2.5 and any of the house characteristics investigated (p > 0.05). However, associations between indoor submicrometer particle number concentration and some house characteristics (stove type, water heater type, number of cars and condition of paintwork) were significant at the 5% level. Associations between indoor NO2 and some house characteristics (house age, stove type, heating system, water heater type and floor type) were also significant (p < 0.05). The results of these analyses thus strongly suggest that the gas stove, gas heating system and gas water heater system are main indoor sources of indoor submicrometer particle and NO2 concentrations in the studied residential houses. The significant contributions of this PhD project to the knowledge of indoor particle included: 1) improving an understanding of indoor particles behaviour in residential houses, especially for submicrometer particle; 2) improving an understanding of indoor particle source and indoor particle sink characteristics, as well as their effects on indoor particle concentration levels in residential houses; 3) improving an understanding of the relationship between indoor and outdoor particles, the relationship between particle mass and particle number, correlation between indoor NO2 and indoor particles, as well as association between indoor particle, NO2 and house characteristics.

The understanding of human exposure to indoor particles of all sizes is important to enable exposure control and reduction, but especially for smaller particles since the smaller particles have a higher probability of penetration into the deeper parts of the respiratory tract and also contain higher levels of trace elements and toxins. Due to the limited understanding of the relationship between particle size and the health effects they cause, as well as instrument limitations, the available information on submicrometer (d < 1.0 µm) particles indoors, both in terms of mass and number concentrations, is still relatively limited. This PhD project was conducted as part of the South-East Queensland Air Quality program and Queensland Housing Study aimed at providing a better understanding of ambient particle concentrations within the indoor environment with a focus on exposure assessment and control. This PhD project was designed to investigate comprehensively the sources and sinks of indoor aerosol particles and the relationship between indoor and outdoor aerosol particles, particle and gaseous pollutant, as well as the association between indoor air pollutants and house characteristics by using, analysing and interpreting existing experimental data which were collected before this project commenced, as well as data from additional experiments which were designed and conducted for the purpose of this project. The focus of this research was on submicrometer particles with a diameter between 0.007 - 0.808 µm. The main outcome of this project may be summarised as following: * A comprehensive review of particle concentration levels and size distributions characteristics in the residential and non-industrial workplace environments was conducted. This review included only those studies in which more general trends were investigated, or could be concluded based on information provided in the papers. This review included four parts: 1) outdoor particles and their effect on indoor environments; 2) the relationship between indoor and outdoor concentration levels in the absence of indoor sources for naturally ventilated buildings; 3) indoor sources of particles: contribution to indoor concentration levels and the effect on I/O ratios for naturally ventilated buildings; and 4) indoor/outdoor relationship in mechanically ventilated buildings. * The relationship between indoor and outdoor airborne particles was investigated for sixteen residential houses in Brisbane, Australia, in the absence of operating indoor sources. Comparison of the ratios of indoor to outdoor particle concentrations revealed that while temporary values of the ratio vary in a broad range from 0.2 to 2.5 for both lower and higher ventilation conditions, average values of the ratios were very close to one regardless of ventilation conditions and of particle size range. The ratios were in the range from 0.78 to 1.07 for submicrometer particles, from 0.95 to 1.0 for supermicrometer particles and from 1.01 to 1.08 for PM2.5 fraction. Comparison of the time series of indoor to outdoor particle concentrations showed a clear positive relationship existing for many houses under normal ventilation conditions (estimated to be about and above 2 h-1), but not under minimum ventilation conditions (estimated to be about and below 1 h-1). These results suggest that for normal ventilation conditions and in the absence of operating indoor sources, outdoor particle concentrations could be used to predict instantaneous indoor particle concentrations but not for minium ventilation, unless air exchange rate is known, thus allowing for estimation of the "delay constant". * Diurnal variation of indoor submicrometer particle number and particle mass (approximation of PM2.5) concentrations was investigated in fifteen of the houses. The results show that there were clear diurnal variations in both particle number and approximation of PM2.5 concentrations, for all the investigated houses. The pattern of diurnal variations varied from house to house, however, there was always a close relationship between the concentration and human indoor activities. The average number and mass concentrations during indoor activities were (18.2±3.9)×10³ particles cm-³ and (15.5±7.9) µg m-³ respectively, and under non-activity conditions, (12.4±2.7)x10³ particles cm-³ (11.1±2.6) µg m-³, respectively. In general, there was a poor correlation between mass and number concentrations and the correlation coefficients were highly variable from day to day and from house to house. This implies that conclusions cannot be drawn about either one of the number or mass concentration characteristics of indoor particles, based on measurement of the other. The study also showed that it is unlikely that particle concentrations indoors could be represented by measurements conducted at a fixed monitoring station due to the large impact of indoor and local sources. * Emission characteristics of indoor particle sources in fourteen residential houses were quantified. In addition, characterizations of particles resulting from cooking conducted in an identical way in all the houses were measured. All the events of elevated particle concentrations were linked to indoor activities using house occupants diary entries, and catalogued into 21 different types of indoor activities. This enabled quantification of the effect of indoor sources on indoor particle concentrations as well as quantification of emission rates from the sources. For example, the study found that frying, grilling, stove use, toasting, cooking pizza, smoking, candle vaporizing eucalyptus oil and fan heater use, could elevate the indoor submicrometer particle number concentration levels by more than 5 times, while PM2.5 concentrations could be up to 3, 30 and 90 times higher than the background levels during smoking, frying and grilling, respectively. * Indoor particle deposition rates of size classified particles in the size range from 0.015 to 6 µm were quantified. Particle size distribution resulting from cooking, repeated under two different ventilation conditions in 14 houses, as well as changes to particle size distribution as a function of time, were measured using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS), and a DustTrak. Deposition rates were determined by regression fitting of the measured size-resolved particle number and PM2.5 concentration decay curves, and accounting for air exchange rate. The measured deposition rates were shown to be particle size dependent and they varied from house to house. The lowest deposition rates were found for particles in the size range from 0.2 to 0.3 µm for both minimum (air exchange rate: 0.61±0.45 h-1) and normal (air exchange rate: 3.00±1.23 h-1) ventilation conditions. The results of statistical analysis indicated that ventilation condition (measured in terms of air exchange rate) was an important factor affecting deposition rates for particles in the size range from 0.08 to 1.0 µm, but not for particles smaller than 0.08 µm or larger than 1.0 µm. Particle coagulation was assessed to be negligible compared to the two other processes of removal: ventilation and deposition. This study of particle deposition rates, the largest conducted so far in terms of the number of residential houses investigated, demonstrated trends in deposition rates comparable with studies previously reported, usually for significantly smaller samples of houses (often only one). However, the results compare better with studies which, similarly to this study, investigated cooking as a source of particles (particle sources investigated in other studies included general activity, cleaning, artificial particles, etc). * Residential indoor and outdoor 48 h average levels of nitrogen dioxide (NO2), 48h indoor submicrometer particle number concentration and the approximation of PM2.5 concentrations were measured simultaneously for fourteen houses. Statistical analyses of the correlation between indoor and outdoor pollutants (NO2 and particles) and the association between house characteristics and indoor pollutants were conducted. The average indoor and outdoor NO2 levels were 13.8 ± 6.3 ppb and 16.7 ± 4.2 ppb, respectively. The indoor/outdoor NO2 concentration ratio ranged from 0.4 to 2.3, with a median value of 0.82. Despite statistically significant correlations between outdoor and fixed site NO2 monitoring station concentrations (p = 0.014, p = 0.008), there was no significant correlation between either indoor and outdoor NO2 concentrations (p = 0.428), or between indoor and fixed site NO2 monitoring station concentrations (p = 0.252, p = 0.465,). However, there was a significant correlation between indoor NO2 concentration and indoor submicrometer aerosol particle number concentrations (p = 0.001), as well as between indoor PM2.5 and outdoor NO2 (p = 0.004). These results imply that the outdoor or fixed site monitoring concentration alone is a poor predictor of indoor NO2 concentration. * Analysis of variance indicated that there was no significant association between indoor PM2.5 and any of the house characteristics investigated (p > 0.05). However, associations between indoor submicrometer particle number concentration and some house characteristics (stove type, water heater type, number of cars and condition of paintwork) were significant at the 5% level. Associations between indoor NO2 and some house characteristics (house age, stove type, heating system, water heater type and floor type) were also significant (p < 0.05). The results of these analyses thus strongly suggest that the gas stove, gas heating system and gas water heater system are main indoor sources of indoor submicrometer particle and NO2 concentrations in the studied residential houses. The significant contributions of this PhD project to the knowledge of indoor particle included: 1) improving an understanding of indoor particles behaviour in residential houses, especially for submicrometer particle; 2) improving an understanding of indoor particle source and indoor particle sink characteristics, as well as their effects on indoor particle concentration levels in residential houses; 3) improving an understanding of the relationship between indoor and outdoor particles, the relationship between particle mass and particle number, correlation between indoor NO2 and indoor particles, as well as association between indoor particle, NO2 and house characteristics.

Incident ions, from a Van de Graaff accelerator, in the MeV energy range, deposit their energy into the near surface of a sample. This, in turn, causes atomic, molecular, cluster and fragment ion species to be desorbed and ionized, while simultaneously emitting characteristic elemental X-rays. The multielemental X-rays provide qualitative elemental information, which may be deconvoluted and fit to a theoretical X-ray spectrum, generated by a quantitative analysis program, GUPIX, while the atomic, molecular, cluster, and fragment ion species are identified using a quadrupole mass spectrometer. This methodology directly links elemental determinations with chemical speciation.The development of this particle desorption ionization particle induced X-ray emission mass spectrometer, the PDI-PIXE-MS (or PIXE-MS) instrument, which has the ability to collect both qualitative multielemental X-rays and mass spectral data is described. This multiplexed instrument has been designed to use millimeter-sized MeV particle beams as a desorption ionization (PDI) and X-ray emission (PIXE) source. Two general methods have been employed, one simultaneous and the other sequential. Both methods make use of a novel X-ray/ion source developed for use with the quadrupole mass spectrometer used in these experiments. The first method uses a MeV heavy ion particle beam, typically oxygen, to desorb and ionize the sample, while simultaneously producing characteristic multielemental X-rays. The resulting molecular, cluster, and fragment ions are collected by the mass spectrometer, and the X-rays are collected using a Si-PIN photodiode detector in conjunction with a multichannel analyzer (MCA). Heavy ions of N+, O+, O+2, Ar+, and Kr+ have been investigated, although heavy ion X-ray and mass spectra have focused on the use of oxygen particle beams. The second method is performed by first collecting the X-ray data with a MeV ion beam of He+ ions, then desorbing and ionizing the sample species with a MeV particle beam of heavy ions, producing good ion yields, for mass spectral data collection. The potential development of a scanning microprobe instrument, that would provide micron-scale, imaged, multielemental, and molecular and fragment ion chemical information is being investigated through the development of this prototype PIXE-MS instrument.

Automotive brake systems are source of particulate matter (PM) emissions, particularly in the urban areas. Several human ill-health are related with this kind of pollution. Along tire wear, road wear and dust from resuspension, the brake wear comprises the most relevant non-exhaust source of road traffic related emissions. Aiming at studying the PM brake emissions, this thesis is composed of an introductory part containing the main concepts and the state of art of the main subjects; and the experimental part, which comprehends three investigations. Chapters 2, 3, 4 and 5 are dedicated to the introduction part. Chapter 2 provides a brief description of the friction and wear, as well as the fundamental principles of braking by contact. Chapter 3 discuss the disc braking system, with particular attention to the pad friction materials. Chapter 4 is dedicated to friction layer: the layer usually developing at the disc/pad interface, affecting the performances of the tribological system. Finally, Chapter 5 provides an extensive discussion of the issues related to the particulate matter originated from disc brake systems. The experimental part is presented in the Chapters 6, 7, 8 and 9. Chapter 6 describes the methodology applied in all the investigations. Chapter 7 investigates the PM emissions behavior and its interaction with the friction and wear, aiming to identify the mechanism of generation the PM emissions. A copper-containing and a copper-free commercial friction materials were used, with particular emphasis on the effect of the scorching treatment. The Chapter 8 is dedicated at investigating the tribological behavior and the corresponding PM emissions in two Cu-free commercial friction materials, aiming to a better understanding the effect of abrasive ingredients on the emissions generation. Finally, the Chapter 9 investigated the addition of natural ingredient rice husk in a new eco-friendly Cu-free brake friction material composition, focusing the attention on the tribological and emissions behavior. All tests were carried out using a pin-on-disc tribometer equipped with an enclosure, especially designed for investigating the tribological properties, as well as the airborne particles generated by contact. Low-metallic friction materials, both commercial and laboratory-produced, were tested against cast iron discs. The tests parameters used correspond to mild sliding conditions resembling those faced in real braking. Such conditions are characteristic of driving in urban areas, where the expose to traffic PM is concentrated. A specific methodology of analysis was developed, based on SEM/EDXS techniques. Using this methodology, comparative investigations between the elemental composition of the virgin friction materials, the worn surfaces of the friction materials and the airborne particles collected during the tribological tests were carried out. The results point out the triboxidative wear as the main mechanism of the PM brake emissions generation. Moreover, particles produced by abrasive wear can be also directly emitted to the environment.

Motor vehicles are a major source of gaseous and particulate matter pollution in urban areas, particularly of ultrafine sized particles (diameters < 0.1 µm). Exposure to particulate matter has been found to be associated with serious health effects, including respiratory and cardiovascular disease, and mortality. Particle emissions generated by motor vehicles span a very broad size range (from around 0.003-10 µm) and are measured as different subsets of particle mass concentrations or particle number count. However, there exist scientific challenges in analysing and interpreting the large data sets on motor vehicle emission factors, and no understanding is available of the application of different particle metrics as a basis for air quality regulation. To date a comprehensive inventory covering the broad size range of particles emitted by motor vehicles, and which includes particle number, does not exist anywhere in the world. This thesis covers research related to four important and interrelated aspects pertaining to particulate matter generated by motor vehicle fleets. These include the derivation of suitable particle emission factors for use in transport modelling and health impact assessments; quantification of motor vehicle particle emission inventories; investigation of the particle characteristic modality within particle size distributions as a potential for developing air quality regulation; and review and synthesis of current knowledge on ultrafine particles as it relates to motor vehicles; and the application of these aspects to the quantification, control and management of motor vehicle particle emissions. In order to quantify emissions in terms of a comprehensive inventory, which covers the full size range of particles emitted by motor vehicle fleets, it was necessary to derive a suitable set of particle emission factors for different vehicle and road type combinations for particle number, particle volume, PM1, PM2.5 and PM1 (mass concentration of particles with aerodynamic diameters < 1 µm, < 2.5 µm and < 10 µm respectively). The very large data set of emission factors analysed in this study were sourced from measurement studies conducted in developed countries, and hence the derived set of emission factors are suitable for preparing inventories in other urban regions of the developed world. These emission factors are particularly useful for regions with a lack of measurement data to derive emission factors, or where experimental data are available but are of insufficient scope. The comprehensive particle emissions inventory presented in this thesis is the first published inventory of tailpipe particle emissions prepared for a motor vehicle fleet, and included the quantification of particle emissions covering the full size range of particles emitted by vehicles, based on measurement data. The inventory quantified particle emissions measured in terms of particle number and different particle mass size fractions. It was developed for the urban South-East Queensland fleet in Australia, and included testing the particle emission implications of future scenarios for different passenger and freight travel demand. The thesis also presents evidence of the usefulness of examining modality within particle size distributions as a basis for developing air quality regulations; and finds evidence to support the relevance of introducing a new PM1 mass ambient air quality standard for the majority of environments worldwide. The study found that a combination of PM1 and PM10 standards are likely to be a more discerning and suitable set of ambient air quality standards for controlling particles emitted from combustion and mechanically-generated sources, such as motor vehicles, than the current mass standards of PM2.5 and PM10. The study also reviewed and synthesized existing knowledge on ultrafine particles, with a specific focus on those originating from motor vehicles. It found that motor vehicles are significant contributors to both air pollution and ultrafine particles in urban areas, and that a standardized measurement procedure is not currently available for ultrafine particles. The review found discrepancies exist between outcomes of instrumentation used to measure ultrafine particles; that few data is available on ultrafine particle chemistry and composition, long term monitoring; characterization of their spatial and temporal distribution in urban areas; and that no inventories for particle number are available for motor vehicle fleets. This knowledge is critical for epidemiological studies and exposure-response assessment. Conclusions from this review included the recommendation that ultrafine particles in populated urban areas be considered a likely target for future air quality regulation based on particle number, due to their potential impacts on the environment. The research in this PhD thesis successfully integrated the elements needed to quantify and manage motor vehicle fleet emissions, and its novelty relates to the combining of expertise from two distinctly separate disciplines - from aerosol science and transport modelling. The new knowledge and concepts developed in this PhD research provide never before available data and methods which can be used to develop comprehensive, size-resolved inventories of motor vehicle particle emissions, and air quality regulations to control particle emissions to protect the health and well-being of current and future generations.

Motor vehicles are a major source of gaseous and particulate matter pollution in urban areas, particularly of ultrafine sized particles (diameters < 0.1 µm). Exposure to particulate matter has been found to be associated with serious health effects, including respiratory and cardiovascular disease, and mortality. Particle emissions generated by motor vehicles span a very broad size range (from around 0.003-10 µm) and are measured as different subsets of particle mass concentrations or particle number count. However, there exist scientific challenges in analysing and interpreting the large data sets on motor vehicle emission factors, and no understanding is available of the application of different particle metrics as a basis for air quality regulation. To date a comprehensive inventory covering the broad size range of particles emitted by motor vehicles, and which includes particle number, does not exist anywhere in the world. This thesis covers research related to four important and interrelated aspects pertaining to particulate matter generated by motor vehicle fleets. These include the derivation of suitable particle emission factors for use in transport modelling and health impact assessments; quantification of motor vehicle particle emission inventories; investigation of the particle characteristic modality within particle size distributions as a potential for developing air quality regulation; and review and synthesis of current knowledge on ultrafine particles as it relates to motor vehicles; and the application of these aspects to the quantification, control and management of motor vehicle particle emissions. In order to quantify emissions in terms of a comprehensive inventory, which covers the full size range of particles emitted by motor vehicle fleets, it was necessary to derive a suitable set of particle emission factors for different vehicle and road type combinations for particle number, particle volume, PM1, PM2.5 and PM1 (mass concentration of particles with aerodynamic diameters < 1 µm, < 2.5 µm and < 10 µm respectively). The very large data set of emission factors analysed in this study were sourced from measurement studies conducted in developed countries, and hence the derived set of emission factors are suitable for preparing inventories in other urban regions of the developed world. These emission factors are particularly useful for regions with a lack of measurement data to derive emission factors, or where experimental data are available but are of insufficient scope. The comprehensive particle emissions inventory presented in this thesis is the first published inventory of tailpipe particle emissions prepared for a motor vehicle fleet, and included the quantification of particle emissions covering the full size range of particles emitted by vehicles, based on measurement data. The inventory quantified particle emissions measured in terms of particle number and different particle mass size fractions. It was developed for the urban South-East Queensland fleet in Australia, and included testing the particle emission implications of future scenarios for different passenger and freight travel demand. The thesis also presents evidence of the usefulness of examining modality within particle size distributions as a basis for developing air quality regulations; and finds evidence to support the relevance of introducing a new PM1 mass ambient air quality standard for the majority of environments worldwide. The study found that a combination of PM1 and PM10 standards are likely to be a more discerning and suitable set of ambient air quality standards for controlling particles emitted from combustion and mechanically-generated sources, such as motor vehicles, than the current mass standards of PM2.5 and PM10. The study also reviewed and synthesized existing knowledge on ultrafine particles, with a specific focus on those originating from motor vehicles. It found that motor vehicles are significant contributors to both air pollution and ultrafine particles in urban areas, and that a standardized measurement procedure is not currently available for ultrafine particles. The review found discrepancies exist between outcomes of instrumentation used to measure ultrafine particles; that few data is available on ultrafine particle chemistry and composition, long term monitoring; characterization of their spatial and temporal distribution in urban areas; and that no inventories for particle number are available for motor vehicle fleets. This knowledge is critical for epidemiological studies and exposure-response assessment. Conclusions from this review included the recommendation that ultrafine particles in populated urban areas be considered a likely target for future air quality regulation based on particle number, due to their potential impacts on the environment. The research in this PhD thesis successfully integrated the elements needed to quantify and manage motor vehicle fleet emissions, and its novelty relates to the combining of expertise from two distinctly separate disciplines - from aerosol science and transport modelling. The new knowledge and concepts developed in this PhD research provide never before available data and methods which can be used to develop comprehensive, size-resolved inventories of motor vehicle particle emissions, and air quality regulations to control particle emissions to protect the health and well-being of current and future generations.

Air borne or liquid-laden solid particle transport is a common phenomenon in various industrial applications. Solid particles, transported at severe operating conditions such as high flow velocity, can cause concerns for structural integrity through wear originated from particle impacts with structure. To apply Acoustic Emission (AE) in particle impact monitoring, previous researchers focused primarily on dry particle impacts on dry target plate and/or wet particle impacts on wet or dry target plate. For dry particle impacts on dry target plate, AE events energy, calculated from the recorded free falling or air borne particle impact AE signals, were correlated with particle size, concentration, height, target material and thickness. For a given system, once calibrated for a specific particle type and operating condition, this technique might be sufficient to serve the purpose. However, if more than one particle type present in the system, particularly with similar size, density and impact velocity, calculated AE event energy is not unique for a specific particle type. For wet particle impacts on dry or wet target plate (either submerged or in a flow loop), AE event energy was related to the particle size, concentration, target material, impact velocity and angle between the nozzle and the target plate. In these studies, the experimental arrangements and the operating conditions considered either did not allow any bubble formation in the system or even if there is any at least an order of magnitude lower in amplitude than the sand particle impact and so easily identifiable. In reality, bubble formation can be comparable with particle impacts in terms of AE amplitude in process industries, for example, sand production during oil and gas transportation from reservoir. Current practice is to calibrate an installed AE monitoring system against a range of sand free flow conditions. In real time monitoring, for a specific calibrated flow, the flow generated AE amplitude/energy is deducted from the recorded AE amplitude/energy and the difference is attributed to the sand particle impacts. However, if the flow condition changes, which often does in the process industry, the calibration is not valid anymore and AE events from bubble can be misinterpreted as sand particle impacts and vice versa. In this research, sand particles and glass beads with similar size, density and impact velocity have been studied dropping from 200 mm on a small cylindrical stepped mild steel coupon as a target plate. For signal recording purposes, two identical broadband AE sensors are installed, one at the centre and one 30 mm off centred, on the opposite of the impacting surface. Signal analysis have been carried out by evaluating 7 standard AE parameters (amplitude, energy, rise time, duration, power spectral density(PSD), peak frequency at PSD and spectral centroid) in the time and frequency domain and time-frequency domain analysis have been performed applying Gabor Wavelet Transform. The signal interpretation becomes difficult due to reflections, dispersions and mode conversions caused by close proximity of the boundaries. So, a new signal analysis parameter - frequency band energy ratio - has been proposed. This technique is able to distinguish between population of two very similar groups (in terms of size and mass and energy) of sand particles and glass beads, impacting on mild steel based on the coefficient of variation (Cv) of the frequency band AE energy ratios. To facilitate individual particle impact identification, further analysis has been performed using Support Vector Machine (SVM) based classification algorithm using 7 standard AE parameters, evaluated in both the time and frequency domain. Available data set has been segmented into two parts of training set (80%) and test set (20%). The developed model has been applied on the test data for model performance evaluation purpose. The overall success rate of individually identifying each category (PLB, Glass bead and Sand particle impacts) at S1 has been found as 86% and at S2 as 92%. To study wet particle impacts on wet target surface, in presence of bubbles, the target plate has been sealed to a cylindrical perspex tube. Single and multiple sand particles have been introduced in the system using a constant speed blower to impact the target surface under water loading. Two sensor locations, used in the previous sets of experiments, have been monitored. From frequency domain analysis it has been observed that characteristic frequency for particle impacts are centred at 300-350 kHz and for bubble formations are centred at 135 – 150 kHz. Based upon this, two frequency bands 100 – 200 kHz (E1) and 300 – 400 kHz (E3) and the frequency band energy ratio (E3E1,) have been identified as optimal for identification particle impacts for the given system. E3E1, > 1 has been associated with particle impacts and E3E1, < 1 has been associated with bubble formations. Applying these frequency band energy ratios and setting an amplitude threshold, an automatic event identification technique has been developed for identification of sand particle impacts in presence of bubbles. The method developed can be used to optimize the identification of sand particle impacts. The optimal setting of an amplitude threshold is sensitive to number of particles and noise levels. A high threshold of say 10% will clearly identify sand particle impacts but for multiparticle tests is likely to not detect about 20% of lower (impact) energy particles. A threshold lower than 3% is likely to result in detection of AE events with poor frequency content and wrong classification of the weakest events. Optimal setting of the parameters used in the framework such as thresholds, frequency bands and ratios of AE energy is likely to make identification of sand particle impacts in the laboratory environment within 10% possible. For this technique, once the optimal frequency bands and ratios have been identified, then an added advantage is that calibration of the signal levels is not required.

Birmingham Positron Imaging Centre has the only known Positron Camera dedicated solely for industrial processes. It has been successfully applied to numerous industrial processes as a non-invasive imaging method such as oil flow in engines, flow in rocks and extrusion processes. A novel technique of particle tracking has been developed at the University of Birmingham using a single radio nuclide labelled particle as a tracer. This technique allowed non-invasive monitoring of industrial processes such as mixing, gas fluidised beds and rotating drums. It provided important information about the effects that govern physical behaviour of the particle inside an industrial machine during its natural working cycle. This information can be used in designing and building more efficient, full scale industrial plants. However, if more than one particle could be traced simultaneously, more information such as interaction between the particles could be gathered and this could be used to identify the physical processes that are taking place. This study is about tracking multiple particles-particularly two particles. A number of methods such as positron emission holography, cluster analysis and tomography have been considered and related computer codes have been developed. The principals of Positron Emission Tomography (PET) and Positron Emission Particle Tracking Method (PEPT) have been explained in Chapter 2. The PEPT algorithm is discussed with some of the applications. Chapter 3 gives an overview of zone plate coded imaging technique that makes it possible to image incoherent radiation that would not be possible with reflective and refractive methods. It reviews some of the important zone plate designs and makes use of an ideal zone plate. Furthermore, a description of a reconstruction computer code that simulates diffraction is given. Chapter 4 gives the application of the zone plate encoded holography, Positron Emission Holography (PEH) technique, to the PET trajectories obtained experimentally for two particle tracking for the first time. The limitations of this technique have been evaluated for a different number of trajectories and resolution of the system was investigated. The trajectories obtained should ideally cross at the location of the particle. Since there are two particles, it is sometimes possible to group these trajectories into two groups of particles. The techniques of grouping are mainly found in the literature under the title of cluster analysis. It is for this reason, that Chapters gives a review of the principles and comparison of the different clustering techniques available in the literature. Chapter 6 describes a unique way of representing the trajectories. It is the midpoint of the closest distance between the trajectories. It also describes a clustering method that will cluster these midpoints into two clusters, rather than trajectories themselves,in order to locate the two particles. The advantages of this algorithm in comparison to the techniques given in Chapter 5 are illustrated with examples. Some of the difficult questions such as how well the objects are clustered or how many natural clusters can be formed by these objects that arise in cluster analysis are also investigated. The application of the clustering algorithm described in the above chapter is given for two stationary positron particles in Chapter 7. The application is repeated for different particle distances, for different particle orientations and a different number of trajectories. Chapter 8 describes another clustering method known as Multiple Location-Allocation method that is mainly used in economics or resource management. This technique is applied to the voxel reconstruction of the trajectories. A computer code for this technique was developed and wide range of techniques were considered from Digital Image Processing for thresholding. The application of the above technique to the experimental data for two stationary particles is given in Chapter 9. The initial allocation techniques were tested and a simple but very effective way of thresholding was described. In Chapter l0, all the above techniques were employed in tracking moving particles. One of the particles was placed on a rotating table which can be rotated at a constant angular speed. The other particle was fixed to a stationary position. The PEH algorithm does need a high number of trajectories but this puts limitations on the accuracy of the particle locations since during the time it takes to collect that number of trajectories, the particle might have moved to another position. However, the clustering algorithm developed in Chapter 6 provided very accurate results making it possible to track the particles for very short time periods. The algorithm developed in Chapter 8 also provides very accurate results but the PAM algorithm can work with a smaller number of trajectories. Finally Chapter l0 gives a summary of the conclusions and makes suggestions for possible future work.

The movement of particles inside a jig ultimately determines the efficiency of the jig. The movement of these particles is a function of the particle properties (size, density and shape) and the jigging parameters (pulse shape, water flow, etc.). The purpose of this study was to investigate how particle properties affect the movement of particles inside a jig. Positron Emission Particle Tracking (PEPT) is one of the few techniques that can trace the movement of particles inside an enclosed system without interfering with the particle flow and has successfully been used to study mills, hydrocyclones and flotation. In this study, PEPT was evaluated as a possible technique to study the flow of iron ore particles inside a laboratory scale jig. The results showed that very accurate three dimensional trajectories could be obtained, with a temporal resolution high enough to see the movement of a particle during a single pulse. The vertical component from the trajectories showed the rate at which particles moved through the jig bed (stratification rate). The particle property that affected the stratification rate the most was density, followed by size. Shape didn't have a large influence on the stratification rate. However, it was evident that the flat particles have a slightly higher rate, compared to cubic and elongated particles. The PEPT testwork showed the existence of a circular flow pattern (secondary flow) that emerged inside the batch jig. Throughout the test results, the effects of the secondary flow pattern on the movement of the tracer particles was observed. It was seen that particles with densities close to that of the jigging bed were affected the most and that some of these particles showed no degree of stratification .A possible origin of this secondary flow can be the uneven water velocity under the jig bed. The uneven velocity profile was confirmed by looking at the difference in pulse height at different position in the jig bed, with the help of PEPT. None of the existing jigging models in literature take into account this back mixing caused by the secondary flow. An attempt was made to add this effect to King's potential energy model to improve its accuracy with regards to iron ore jigging. From the PEPT observations, the assumption was made that the back mixing experienced by a particle is related to the difference between the mass of the tracer particle and the average particle mass inside the jig. Simulated stratification profiles generated with the modified stratification model were compared to published data of batch iron ore jigging and showed better correlation compared to the standard model.
Dissertation (MEng)--University of Pretoria, 2017.
Materials Science and Metallurgical Engineering
MEng
Unrestricted

Even at low concentrations, the criteria air pollutant particulate matter (PM) is an environmental and public health hazard. Emissions levels legislated for modern diesel vehicles are so low (~90% lower than 2003) that it has become difficult to accurately measure PM by the regulatory metric: the mass of particles collected on a filter (i.e., the gravimetric method). Additionally, gravimetric analysis cannot measure real-time emission rates, and therefore is unable to characterize high-emitting transient events (e.g., engine starts, stop-and-go driving). By an alternate method, PM can be estimated by measuring the number-weighted particle size distribution (PSD) and calculating mass with a combination of theoretical and empirical constants (e.g., particle effective density). This integrated particle size distribution (IPSD) method is capable of high measurement sensitivity and real-time resolution. Real-time measurements by the IPSD method require fast-sizing spectrometers, such as the TSI Engine Exhaust Particle Sizer (EEPS), which sizes (between 5.6-560 nm) and counts particles based on their electrical mobility. The EEPS utilizes a unipolar charger to quickly charge particles for sizing and counting, however this mechanism has been shown to produce a less predictable charge distribution than bipolar chargers used in Scanning Mobility Particle Sizer (SMPS) systems – the gold standard 'slow-sizing' spectrometer. Several evaluations have shown deficiencies in EEPS PSD measurements due to charging differences (associated with particle morphology) unaccounted for in the transfer function matrix used to calibrate the EEPS. Specifically, the unipolar charger multiply charges a higher percentage of soot agglomerates (fractal-like particles common in diesel engine exhaust) than bipolar chargers. Because inaccurate PSDs are a primary reason for reported discrepancies between IPSD calculated mass and the gravimetric method, it is important to correct this deficiency in EEPS measurements. Recently, TSI has released additional EEPS calibration matrices ('soot' and 'Compact') which have shown better agreement with SMPS measurements under preliminary test conditions. This study further evaluates the performance of these new matrices relative to the original 'Default' matrix for diesel and biodiesel exhaust particles. Steady-state (75% engine load) emissions were generated by a light-duty diesel engine operating on (1) ultra-low sulfur diesel (ULSD) and (2) 100% soybean biodiesel. Raw EEPS data processed with each matrix were compared to simultaneously collected reference measurements from an SMPS. PSDs were evaluated based on their shape – i.e., multimodal fits of geometric mean diameter (GMD) and geometric standard deviation (GSD) – and concentration at peak particle diameter. For both fuels, all measurements agreed well in terms of the shape of the PSD: primary mode (accumulation) GMD ± 10nm, GSD ± 0.3. For ULSD, EEPS Default, Soot, and Compact concentrations were higher than the SMPS by factors of 1.9, 1.3, and 2.5, respectively. For biodiesel, EEPS Default, Soot, and Compact concentrations were higher than the SMPS by factors of 2.1, 1.7, and 2.4, respectively. Based on these results, the Soot matrix produced acceptable agreement between EEPS and SMPS measurements of ULSD exhaust particles. However, based on the factor of ~2 difference observed here, an additional calibration matrix may be necessary for the EEPS to accurately measure biodiesel exhaust particles. The IPSD method for estimating PM mass was applied to available data sets with corresponding gravimetric measurements (one ULSD transient cycle test and the same biodiesel steady-state test used for PSD evaluation). Real-time PSDs from each of the three EEPS matrices were used in combination with three sets of values assumed for size-dependent particle effective density (representing a range of potential conditions), resulting in nine IPSD estimates of PM mass corresponding to each gravimetric sample (one ULSD, one biodiesel). For the transient ULSD test, a widely used effective density distribution for fractal-like soot agglomerates resulted in good agreement between IPSD estimated mass and the gravimetric measurement (within 9% and 6% for Soot and Compact matrices, respectively). For the steady-state biodiesel test, assuming unit density (1g/cm³ for all particles) resulted in good agreement between IPSD estimated mass and the gravimetric measurement (within 7% and 2% for Soot and Compact matrices, respectively). These results support previous findings that the Soot matrix is currently the best available option for measurement of ULSD exhaust particles by the EEPS and that particle effective density distributions similar to the "fractal-like" one used here are an accurate estimate for ULSD exhaust particles under many conditions. However, based on the discrepancies between the EEPS and SMPS measured biodiesel exhaust PSDs observed here, as well as a current lack of information on the effective density of biodiesel exhaust particles, it is clear that additional research is necessary in order to understand the properties of biodiesel exhaust particles, especially as they relate to electrical mobility measurements and IPSD estimation of PM mass.

Direct fuel injection technology is increasingly being applied to the spark ignition internal combustion engine as one of the many actions required to reduce the CO2 emissions from road transport. Whilst the potential for CO2 reductions is compelling, the technology is not without disadvantages. Early examples typically emitted over an order of magnitude more Particulate Matter (PM) than vehicles with conventional spark ignition engines. Consequently, future revisions to European and North American exhaust emissions legislation are likely to regulate the particulate emissions from vehicles with direct injection gasoline engines. This thesis undertakes to investigate a) instrumentation capable of simultaneously resolving the number concentration and size distribution of particles in the 5-1000 nm size range and b) the factors affecting the PM emissions from spark ignition engines with direct fuel injection. The first objective is achieved by evaluation and comparison of a differential mobility spectrometer; photo-acoustic soot sensor; condensation particle counter and electrical low pressure impactor. To address the second question, a differential mobility spectrometer is applied to quantify the PM emissions from a number of direct injection gasoline engines, together with investigation of their dependence on various calibratable parameters, operating temperature and fuel composition. The differential mobility spectrometer showed good agreement with the other more established instruments tested. Moreover, it exhibited a faster time response and finer resolution in particle size. The number weighted size distribution of the PM emitted was typically lognormal with either one or two modes located between 20 and 100 nm. Chemical analysis of PM samples showed the presence of elemental carbon, volatile organic material and sulphates. Transient PM measurements enabled short time-scale events such as mode switching between homogeneous and stratified mixture preparation to be identified. PM number concentrations in stratified mode exceeded those in homogeneous mode by a factor of 10-100. Dynamometer based experiments showed that PM emissions increase for rich air fuel ratios, retarded fuel injection and advanced ignition events. They also demonstrated a strong dependence on fuel composition: the highest PM emissions were measured with an aromatic fuel, whereas blending alcohols such as methanol or ethanol tended to suppress PM emissions, particularly in the accumulation mode size range. These measurements are amongst the first of their kind and demonstrate the applicability of the differential mobility spectrometer to the measurement of ultra-fine particulate emissions from engines with direct fuel injection systems. Numerous explanations are put forward to describe the data obtained, together with suggestions for future work on PM control and abatement.

Non-thermal plasma (NTP) is a promising candidate for controlling engine exhaust emissions. Plasma is known as the fourth state of matter, where both electrons and positive ions co-exist. Both gaseous and particle emissions of diesel exhaust undergo chemical changes when they are exposed to plasma. In this project diesel particulate matter (DPM) mitigation from the actual diesel exhaust by using NTP technology has been studied. The effect of plasma, not only on PM mass but also on PM size distribution, physico-chemical structure of PM and PM removal mechanisms, has been investigated. It was found that NTP technology can significantly reduce both PM mass and number. However, under some circumstances particles can be formed by nucleation. Energy required to create the plasma with the current technology is higher than the benchmark set by the commonly used by the automotive industry. Further research will enable the mechanism of particle creation and energy consumption to be optimised.

Ultrasonic humidifier use is a potential source of human exposure to inhalable particulates. This paper focused on the behavior of insoluble iron oxides particles, and aluminum oxide particles in ultrasonic humidifiers. 10 mg/L Fe oxide particles and 5 mg/L Al oxide suspension solutions were added into tap water, as fill water for ultrasonic humidifiers operated for 14 hours. Denser, heavier particles of approximate 1.5 um diameter of iron or aluminum oxides accumulated in the humidifier reservoir. Smaller, suspended metal oxide particles of 0.22-0.57 um diameter were emitted as aerosols from humidifiers. Soluble anions and cations in tap water were present in the aerosols emitted from humidifiers. The results indicate that if suspended particles and dissolved minerals are present in source water, they will be transported in aerosolized waters.
M. S.

Due to their large surface area, complex chemical composition and high alveolar deposition rate, ultrafine particles (UFPs) (< 0.1 ìm) pose a significant risk to human health and their toxicological effects have been acknowledged by the World Health Organisation. Since people spend most of their time indoors, there is a growing concern about the UFPs present in some indoor environments. Recent studies have shown that office machines, in particular laser printers, are a significant indoor source of UFPs. The majority of printer-generated UFPs are organic carbon and it is unlikely that these particles are emitted directly from the printer or its supplies (such as paper and toner powder). Thus, it was hypothesised that these UFPs are secondary organic aerosols (SOA). Considering the widespread use of printers and human exposure to these particles, understanding the processes involved in particle formation is of critical importance. However, few studies have investigated the nature (e.g. volatility, hygroscopicity, composition, size distribution and mixing state) and formation mechanisms of these particles. In order to address this gap in scientific knowledge, a comprehensive study including state-of-art instrumental methods was conducted to characterise the real-time emissions from modern commercial laser printers, including particles, volatile organic compounds (VOCs) and ozone (O3). The morphology, elemental composition, volatility and hygroscopicity of generated particles were also examined. The large set of experimental results was analysed and interpreted to provide insight into: (1) Emissions profiles of laser printers: The results showed that UFPs dominated the number concentrations of generated particles, with a quasi unimodal size distribution observed for all tests. These particles were volatile, non-hygroscopic and mixed both externally and internally. Particle microanalysis indicated that semi-volatile organic compounds occupied the dominant fraction of these particles, with only trace quantities of particles containing Ca and Fe. Furthermore, almost all laser printers tested in this study emitted measurable concentrations of VOCs and O3. A positive correlation between submicron particles and O3 concentrations, as well as a contrasting negative correlation between submicron particles and total VOC concentrations were observed during printing for all tests. These results proved that UFPs generated from laser printers are mainly SOAs. (2) Sources and precursors of generated particles: In order to identify the possible particle sources, particle formation potentials of both the printer components (e.g. fuser roller and lubricant oil) and supplies (e.g. paper and toner powder) were investigated using furnace tests. The VOCs emitted during the experiments were sampled and identified to provide information about particle precursors. The results suggested that all of the tested materials had the potential to generate particles upon heating. Nine unsaturated VOCs were identified from the emissions produced by paper and toner, which may contribute to the formation of UFPs through oxidation reactions with ozone. (3) Factors influencing the particle emission: The factors influencing particle emissions were also investigated by comparing two popular laser printers, one showing particle emissions three orders of magnitude higher than the other. The effects of toner coverage, printing history, type of paper and toner, and working temperature of the fuser roller on particle number emissions were examined. The results showed that the temperature of the fuser roller was a key factor driving the emission of particles. Based on the results for 30 different types of laser printers, a systematic positive correlation was observed between temperature and particle number emissions for printers that used the same heating technology and had a similar structure and fuser material. It was also found that temperature fluctuations were associated with intense bursts of particles and therefore, they may have impact on the particle emissions. Furthermore, the results indicated that the type of paper and toner powder contributed to particle emissions, while no apparent relationship was observed between toner coverage and levels of submicron particles. (4) Mechanisms of SOA formation, growth and ageing: The overall hypothesis that UFPs are formed by reactions with the VOCs and O3 emitted from laser printers was examined. The results proved this hypothesis and suggested that O3 may also play a role in particle ageing. In addition, knowledge about the mixing state of generated particles was utilised to explore the detailed processes of particle formation for different printing scenarios, including warm-up, normal printing, and printing without toner. The results indicated that polymerisation may have occurred on the surface of the generated particles to produce thermoplastic polymers, which may account for the expandable characteristics of some particles. Furthermore, toner and other particle residues on the idling belt from previous print jobs were a very clear contributing factor in the formation of laser printer-emitted particles. In summary, this study not only improves scientific understanding of the nature of printer-generated particles, but also provides significant insight into the formation and ageing mechanisms of SOAs in the indoor environment. The outcomes will also be beneficial to governments, industry and individuals.

L’émission cyclotronique ionique (ice) présente un grand potentiel comme diagnostic des ions rapides, en particulier des particules alpha de fusion, dans les tokamaks. Nous présentons les résultats expérimentaux pendant l'expérience préliminaire tritium de jet. Les spectres de l'ice présentent jusqu'a 11 pics étroits et régulièrement espaces. Les fréquences de ces pics sont aux harmoniques cyclotroniques de l'ion majoritaire (deuterium) au bord extérieur du plasma (grand rayon 4. 0m), près de la dernière surface fermée. Ceci représente un paradoxe majeur parce que l'ice est fortement corrélée aux ions rapides et cette densité d'ions rapides au bord extérieur du plasma est très faible. Les formes des spectres dans des plasmas d-d ou d-t sont similaires et un continuum d'émission apparait pour des fréquences supérieures a 120 mhz. Une corrélation presque linéaire entre l'intensité de l'ice et le flux de neutrons est observée sur 6 ordres de grandeur. Cela confirme que ce sont les ions de fusion rapides qui fournissent l'énergie nécessaire a l'excitation de l'ice. Nous observons aussi de fortes correlations temporelles entre l'intensite de l'ice et les instabilités mhd, particulièrement celles se produisant au bord extérieur du plasma. En particulier, le signal s'effondre pendant chaque instabilité elm de grande amplitude. Dans les decharges d-t, l'intensité de l'ice est corrélée avec des oscillations cohérentes observées dans differents signaux. Nous développons un calcul de l'émission spontanée dans le mode d'alfven rapide (fw). Le point de depart est le courant electrique cree par un ion test en rotation autour d'une ligne de champ magnetique, considere comme un courant externe. Nous exprimons les champs électriques et magnétique crees dans le mode fw en utilisant le tenseur dielectrique de plasma chaud. Nous obtenons alors les champs electrique et magnetique totaux de l'onde par sommations statistiques sur les ions majoritaires et les ions rapides de fusion en utilisant leurs distributions de vitesse specifiques. Nous prenons une distribution maxwellienne pour le deuterium majoritaire et une distribution de freinage pour les particules alphas au centre du plasma. Parallèlement, nous résolvons la relation de dispersion du mode fw dans le domaine de fréquences et de vecteurs d'onde ou il est couple avec le mode de bernstein, et donc avec les ions rapides. Nous calculons alors la densite d'energie du plasma et la puissance rayonnee dans le mode fw par integration sur les solutions de la relation de dispersion. Les spectres numériques de puissance emise presentent de grandes similarites avec les spectres experimentaux. Cette théorie est donc satisfaisante et doit être étendue pour l'interprétation des expériences

Doctor of Philosophy
Department of Biological and Agricultural Engineering
Ronaldo G. Maghirang
Emission of particulate matter (PM) and various gases from open-lot beef cattle feedlots is becoming a concern because of the adverse effects on human health and the environment; however, scientific information on feedlot emissions is limited. This research was conducted to estimate emission rates of PM[subscript]10 from large cattle feedlots. Specific objectives were to: (1) determine feedlot PM[subscript]10 emission rates by reverse dispersion modeling using AERMOD; (2) compare AERMOD and WindTrax in terms of their predicted concentrations and back-calculated PM[subscript]10 emission rates; (3) examine the sensitivity of both AERMOD and WindTrax to changes in meteorological parameters, source location, and receptor location; (4) determine feedlot PM[subscript]10 emission rates using the flux-gradient technique; and (5) compare AERMOD and computational fluid dynamics (CFD) in simulating particulate dispersion from an area source. PM[subscript]10 emission rates from two cattle feedlots in Kansas were determined by reverse dispersion modeling with AERMOD using PM[subscript]10 concentration and meteorological measurements over a 2-yr period. PM[subscript]10 emission rates for these feedlots varied seasonally, with overall medians of 1.60 and 1.10 g /m[superscript]2 -day. Warm and prolonged dry periods had significantly higher PM emissions compared to cold periods. Results also showed that the PM[subscript]10 emissions had a diurnal trend; highest PM[subscript]10 emission rates were observed during the afternoon and early evening periods. Using particulate concentration and meteorological measurements from a third cattle feedlot, PM[subscript]10 emission rates were back-calculated with AERMOD and WindTrax. Higher PM[subscript]10 emission rates were calculated by AERMOD, but their resulting PM[subscript]10 emission rates were highly linear (R[superscript]2 > 0.88). As such, development of conversion factors between these two models is feasible. AERMOD and WindTrax were also compared based on their sensitivity to changes in meteorological parameters and source locations. In general, AERMOD calculated lower concentrations than WindTrax; however, the two models responded similarly to changes in wind speed, surface roughness, atmospheric stability, and source and receptor locations. The flux-gradient technique also estimated PM[subscript]10 emission rates at the third cattle feedlot. Analyses of PM[subscript]10 emission rates and meteorological parameters indicated that PM[subscript]10 emissions at the feedlot were influenced by friction velocity, sensible heat flux, temperature, and surface roughness. Based on pen surface water content measurements, a water content of at least 20% (wet basis) significantly lowered PM[subscript]10 emissions at the feedlot. The dispersion of particulate from a simulated feedlot pen was predicted using CFD turbulence model ([kappa]-[epsilon] model) and AERMOD. Compared to CFD, AERMOD responded differently to wind speed setting, and was not able to provide detailed vertical concentration profiles such that the vertical concentration gradients at the first few meters from the ground were negligible. This demonstrates some limitations of AERMOD in simulating dispersion for area sources such as cattle feedlots and suggests the need to further evaluate its performance for area source modeling.