Dans le cadre des opérations de démantèlement des centrales nucléaires UNGG (Uranium Naturel Graphite Gaz), l’occurrence de phénomènes indésirables, tels que l’inflammation et l’explosion de poudres, ne peut pas être systématiquement exclue. Plus particulièrement, le risque d’inflammation et d’explosion de poussières de graphite, pur ou mélangé avec des impuretés métalliques telles que des particules de magnésium ou de fer, nécessite d’être évalué de façon plus approfondie. Les travaux de cette thèse s’inscrivent donc dans ce contexte et ont deux objectifs principaux : l’évaluation expérimentale de l’explosivité et sa modélisation. 1. L’évaluation expérimentale de l’explosivité des poudres d'intérêt a été réalisée tant en termes de sensibilité à l’inflammation, en couche et en nuage, que de sévérité à l’explosion. En effet, les caractéristiques explosives d’une poussière ou d’un mélange sont fortement influencées par plusieurs paramètres. Ils dépendent d’une part des conditions opératoires, tels que la turbulence, la température et l'énergie d’inflammation, et d’autre part, des propriétés physico-chimiques et de la composition des matériaux. Cette étude s’est focalisée sur des poudres pures de graphite, de magnésium et de fer de taille micrométrique et sur leurs mélanges, dans un éventail de concentrations d’intérêt industriel. Nous avons constaté que l’introduction de métaux peut changer en premier lieu l’étape limitant la vitesse de combustion du graphite. Tout d’abord, les phénomènes cinétiques limitant de l’oxydation du graphite ont été distingués de ceux des métaux (respectivement, réaction hétérogène ou flamme de diffusion gazeuse). En deuxième lieu, il est apparu que la flamme peut être épaissie par la présence du rayonnement lors de la combustion du métal, alors que ce phénomène est négligeable pour le graphite pur. Enfin, la turbulence initiale du nuage de poussière peut être elle aussi modifiée par l'ajout d'une deuxième poudre en vue des caractéristiques granulométriques et de densité différentes. Une étude paramétrique a donc été réalisée afin d'évaluer l'explosibilité des mélanges considérés en prenant en compte les effets de l'humidité relative des poudres, de leur distribution granulométrique, de la puissance de la source d'ignition, de la turbulence initiale du milieu et de la composition. Pour ce faire, nous avons utilisé à la fois des appareils et des technologies conventionnelles, tels que la sphère de 20 litres, la vélocimétrie par images de particules et la thermogravimétrie, mais également des nouvelles installations dédiées à la caractérisation des écoulements turbulents transitoires lors de la dispersion des poudres dans la sphère d'explosion et à l’étude de la propagation d’une flamme en milieu semi-confiné. Il a été clairement démontré que l'ajout de poudres métalliques influence l'aptitude à enflammer le nuage de poussière. L'énergie et la température minimale d'inflammation diminuent fortement lorsque le magnésium est ajouté au graphite ; ce phénomène est moins sensible pour les particules de fer. De plus, la sévérité de l'explosion augmente avec une telle addition. Cet effet de promotion est particulièrement visible sur la cinétique de combustion. 2. La modélisation du phénomène explosif a été réalisée à l’aide de la simulation numérique afin d’estimer une vitesse de propagation de flamme laminaire et d’étudier les effets induits par des facteurs spécifiques d’intérêt industriel, tels que le diamètre des particules ou la concentration en poudre. L’intérêt d’estimer une vitesse de flamme laminaire réside dans son caractère pseudo-intrinsèque. En connaissant les caractéristiques turbulentes d’un milieu industriel complexe, ce paramètre donne la possibilité d’obtenir une vitesse de propagation de flamme turbulente propre au milieu réel et donc d’estimer les effets d’une explosion potentielle. Les résultats expérimentaux ont été utilisés afin de valider le modèle numérique développé / During the decommissioning operations of the UNGG (Natural Uranium Graphite Gas) nuclear plants, the occurrence of undesirable phenomena, such as dust ignition and explosion, cannot be systematically neglected. In particular, graphite powders, pure or mixed with metals impurities present on the sites, such as magnesium or iron, can represent a potential risk that needs to be further evaluated. This work falls within this context and has two main objectives: the experimental evaluation of the explosion severity and its modeling. 1. The experimental evaluation of the explosivity of such a powders has been carried out both in terms of ignition sensitivity, of dust layer and cloud, and explosion severity. Actually, explosive characteristics of a dust or of a mixture are strongly influenced by several parameters. They depend on the one side on the operating conditions, such as turbulence, temperature and energy of the ignition source, and on the other side, of course, on the materials physicochemical properties and composition. This study focuses on pure micronized powders of graphite, magnesium, and iron and on their mixtures, in a concentration range of industrial interest. It has been demonstrated that the introduction of metals can change, first of all, the rate limiting step of the graphite combustion. Therefore, the kinetic phenomena controlling the graphite oxidation have been distinguished from those of metals (oxygen diffusion or metal vaporization). Secondly, the flame can be thickened by the presence of the radiation during the metal combustion, while this phenomenon is negligible for pure graphite. Finally, the initial turbulence of the dust cloud can be modified by adding a second powder because of the different granulometric characteristics and density. A parametric study was conducted to evaluate the mixtures explosivity taking into account the effects of the relative humidity, the particle size distribution of the powders, the power of the ignition source, the initial turbulence and the composition of the mixture. In order to do this, we used both conventional devices and technologies, such as 20-liters explosion sphere, the particles image velocimetry and the thermogravimetry, but also new facilities dedicated to the characterization of the transient turbulent flow during the dispersion of the powders in the explosion sphere and to study the propagation of a semi-confined flame. It was clearly demonstrated that the addition of metals influences the ability to ignite the dust cloud. The minimum ignition energy and temperature greatly decrease when magnesium powder is added to graphite dust; this phenomenon is less remarkable for iron particles. In addition, the severity of the explosion increases with such an addition. This promotion effect is particularly significant on the combustion kinetics. 2. The modeling of the explosive phenomenon has been performed using numerical simulations in order to estimate a laminar flame propagation velocity and to study the effects induced by specific factors of industrial interest, such as the particle size or the powder concentration. The interest in determining a laminar flame velocity is its pseudo-intrinsic character. Once known the turbulent characteristics of a complex industrial environment, this parameter gives the opportunity to obtain a turbulent flame propagation velocity in a real environment and, therefore, to estimate the effects of a potential explosion. Experimental results were used to validate the numerical model developed during this work

This diploma thesis deals with the concentration of dust particles during harvesting of forage, namely hay, straw and fed forage. The measurements were always carried out on another land in the Vysočina Region. DUST TRAK II 8530 instrument was used to measure dust concentration. Each measurement was performed for ten minutes.

abstract: ABSTRACT The Spirit landing site in Gusev Crater has been imaged by the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) camera more than thirty times since 2006. The breadth of this image set allowed a study of changes to surface features, covering four Mars years. Small fields of bedforms comprised of dark material, and dark dust devil tracks are among the features revealed in the images. The bedforms are constrained within craters on the plains, and unconstrained in depressions less than 200m wide within the topography of the Columbia Hills, a ~120m-high structure in center of Gusev. Dust devil tracks appear in many images of the bedforms. Within the Columbia Hills, three bedform fields approximately 180m2 and composed of fine dark basaltic sand were studied, using five HiRISE images taken from 2006 to 2014. Both bedform crests and the dust devil tracks superimposed on them were evaluated for change to azimuth and length, and for correlation between the features. The linear to slightly sinuous transverse crests ranging from less than 1m to 113m in length and two to three meters in wavelength, are primary bedforms. During the study they shifted as much as 33 degrees in azimuth, and individual crests moved on the surface as much as 0.75m. The greatest changes corresponded to a global dust storm in 2007. Average crest movement was documented at the rate of 0.25m per year. Rather than moving progressively, the crests eventually returned to near their original orientation after the storm. The dust devil tracks, reflecting a more complex wind regime, including vortex development during diurnal heating, maintained predominantly NW-SE orientations but also reflected the effects of the storm. The observed modifications were neither progressive, nor strictly seasonal. The apparent stability of the bedform geometry over four seasons supports the predictions of the Mars Regional Atmospheric Modeling System (MRAMS): low speed (1-7.5 ms-1), daily alternating winds of relatively equal force. Crest profiles were found to be nearly symmetrical, without slipfaces to indicate a preferential wind direction; this finding also is supported by the MRAMS model. / Dissertation/Thesis / Masters Thesis Geological Sciences 2016

Orientador: Erivaldo Antônio da Silva / Coorientador: Pedro Miguel Berardo Duarte Pina / Banca: Ana Lucia Bezerra Candeias / Banca: João Rodrigues Tavares Júnior / Banca: José Roberto Nogueira / Banca: Maurício Araújo Dias / Resumo: Dust Devils são vórtices convectivos formados por correntes de ar quente instáveis, próximas à superfície planetária. Inúmeros pesquisadores têm estudado dust devils marcianos na tentativa de melhor entender o fenômeno. Em geral, as áreas de pesquisa compreendem a simulação numérica e mecânica de dust devils em laboratório, metodologias para reconhecimento de vórtices por robôs pousados na superfície de Marte e a detecção de vórtices e rastros em imagens orbitais. A despeito do grande número de artigos relacionados ao assunto, nenhum deles aborda a detecção automática de rastros de dust devils, tarefa que ganha especial importância quando a quantidade de imagens da superfície de Marte cresce a uma taxa maior que a capacidade humana de analisá-las em um curto período de tempo. Esta Tese descreve um método inédito para detecção automática de rastros de dust devils. O banco de imagens utilizado contém 200 imagens (90 MOC e 110 HiRISE), distribuídas pelas regiões Aeolis, Noachis, Argyre, Eridania e Hellas. O método é fortemente baseado na Morfologia Matemática e usa transformações como abertura e fechamento por área morfológicos, fechamento por caminho morfológico, método de Otsu... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Dust devils are vortices caused by unstable wind convection processes near the planetary surfaces, due to solar heat. Many researchers have being studying Martian dust devils in an attempt to better understand the phenomena. Generally, the research fields comprise mechanic and numerical simulation of dust devils in laboratories, methodologies for recognition of dust devils plumes from rovers on Mars surface, detection of plumes and tracks from orbital images. Despite the number of papers regarding the subject, none of them addresses the automatic detection of dust devil tracks which is an important issue as the amount of images taken grows at a rate greater than the human capability to analyze them. This Thesis describes a novel method to detect Martian dust devil tracks automatically. The dataset comprises 200 images (90 MOC and 110 HiRISE), distributed over the regions of Aeolis, Noachis, Argyre, Eridania and Hellas. The method is strongly based on Mathematical Morphology and uses transformations such as morphological surface area closing and opening, morphological path closing and Otsu's method for automatic image binarization, among others. The method was applied to the dataset and results were compared... (Complete abstract click electronic access below) / Doutor

A poeira doméstica tem sido identificada como um importante vetor de exposição por substâncias inorgânicas e orgânicas, potencialmente tóxicas, em crianças e adultos. A composição da poeira tem uma forte influência de contaminantes provenientes de ambientes internos e externos. Durante o uso normal ou por intempéries, de uma variedade de artefatos e materiais, as substâncias químicas são desincorporadas para o meio ambiente. Uma vez liberadas, elas tendem a se acumular e enriquecer na poeira doméstica; e por meio de exposição contínua (mecanismos de inalação, ingestão e contato direto com a pele) afeta a saúde humana. Neste trabalho, foi realizada uma avaliação da contaminação por constituintes inorgânicos e ésteres ftálicos em poeira doméstica; e a correlação com as prováveis fontes antropogênicas. As amostras de poeira foram coletadas de 69 residências, nos bairros Pirituba, Freguesia do Ó, Jaraguá e Perus, da região metropolitana de São Paulo, entre 2006 e 2008. As amostras foram separadas nas frações: 850, 850-300, 300-150, 150-75, 75- 63 e <63 &mu;m. A análise por fluorescência de raios X (WDXRF) mostrou a presença de Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr e Pb. A análise por cromatografia de fase gasosa acoplada o espectrômetro de massa (GCMS) a presença de ésteres ftálicos (DEHP, DnBP, DEP, DEHA, BBP e DMP). A partir do fator de enriquecimento (FE), os elementos P, S, Cr, Ni, Cu, Zn e Pb foram classificados como sendo significantemente e extremamente enriquecidos na poeira. As contribuições naturais e antropogênicas foram identificadas por meio de ferramentas estatísticas como análise de fatores (AF) e cluster (AC). Os elementos Cr, Ni, Cu, Zn e Pb foram encontrados em concentrações significativamente elevadas com relação aos valores de exposição total (ingestão, inalação e contato dérmico) e de risco. / Household dust has been identified as an important vector of exposure by inorganic and organic substances potentially toxic in children and adults. The dust composition has a strong influence of contaminants provided from internal and external environments. During the natural process of wearing or weather incidents of artifacts and materials variety, the chemical substances are released into the environment in the steam form or by leaching from final products. Once released, they can be accumulated and enriched in the dust; and by continuous exposure (inhalation, ingestion and dermal contact mechanisms), these substances are harmful to human health. In this work, a study to determine the inorganic constituents and phthalate esters concentrations in residential indoor environment dust samples, correlating them with the probable anthropogenic sources was proposed. Dust samples were collected from 69 residences in neighborhoods Pirituba, Freguesia do Ó, Jaraguá and Perus of the São Paulo metropolitan region, using a domestic vacuum cleaner, between 2006 and 2008. The samples were sieved in the fractions of 850, 850-300, 300-150, 150-75, 75-63 and <63 &mu;m. The analysis by X-ray fluorescence (WDXRF) showed the presence of Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr and Pb. The presence of phthalate esters (DEHP, DnBP, DEP, DEHA, DMP and BBP) was detected, by GCMS analyses. From the enrichment factor (EF), the elements P, S, Cr, Ni, Cu, Zn and Pb were classified as being significant and extremely enriched in the dust. The natural and anthropogenic contributions by statistical tools as factor analysis (AF) and cluster were identified. The elements Cr, Ni, Cu, Zn and Pb were present significantly elevated concentrations in relation to the total exposure values (ingestion, inhalation and skin contact) and to risk.

The Mars Science Laboratory Curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active Bagnold dune field. The Bagnold sands are rounded to subrounded, very fine to medium sized (similar to 45-500m) with 6 distinct grain colors. In contrast to sands examined by Curiosity in a dust-covered, inactive bedform called Rocknest and soils at other landing sites, Bagnold sands are darker, less red, better sorted, have fewer silt-sized or smaller grains, and show no evidence for cohesion. Nevertheless, Bagnold mineralogy and Rocknest mineralogy are similar with plagioclase, olivine, and pyroxenes in similar proportions comprising >90% of crystalline phases, along with a substantial amorphous component (35%15%). Yet Bagnold and Rocknest bulk chemistry differ. Bagnold sands are Si enriched relative to other soils at Gale crater, and H2O, S, and Cl are lower relative to all previously measured Martian soils and most Gale crater rocks. Mg, Ni, Fe, and Mn are enriched in the coarse-sieved fraction of Bagnold sands, corroborated by visible/near-infrared spectra that suggest enrichment of olivine. Collectively, patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in Martian soils: (1) amorphous components in the sand-sized fraction (represented by Bagnold) that are Si-enriched, hydroxylated alteration products and/or H2O- or OH-bearing impact or volcanic glasses and (2) amorphous components in the fine fraction (<40m; represented by Rocknest and other bright soils) that are Fe, S, and Cl enriched with low Si and adsorbed and structural H2O. Plain Language Summary The Bagnold dune field is an active sand field with moving dunes and sits between the landing site of the Curiosity rover and rocks of interest higher up on Mount Sharp. When passing through the dune field, we used all of Curiosity's instruments to measure the chemistry, mineralogy, and grain size of sands in the Bagnold dune field in order to figure out where they came from, how the sands are transported, and what volatile materials (like water) lie within Martian soils. We found that the Bagnold sand dunes are very well sorted; no dusty materials are found within them, in stark contrast to soils seen previously with Curiosity and with rovers at other landing sites. We found that the coarser sand grains are enriched in the volcanic minerals olivine and pyroxene, confirming a prediction from orbit that wind-related activity seems to concentrate these phases. We also found that the dunes were much lower in water and other volatile elements like sulfur and chlorine versus all previous Mars soils. Using a combination of the rover's sieving system and chemical measurement tools, we figured out that two types of materials host water. In the first type of material, common in these sands, water is low in abundance (similar to 1%), very tightly bound to the grains, and is not released until temperatures >200 degrees C. In the second type of material, water is higher in abundance (2%) and more easily released by heating. Sieved water-bearing fine materials may be a useful resource for human explorers.

Mine tailings pose a health risk for populations and ecosystems in the Southwest; this is why effective, and low-cost solutions for the long term are needed. This work is groundbreaking since little information is available with regards to applying greenhouse studies of phytostabilization to the field for mine tailing remediation. Mine tailings from Iron King Mine and Humboldt Smelter Superfund (IKMHSS) site can be considered one of the worst scenarios due to the extreme conditions which prevent the growth of a vegetation cap. The high concentration of metals, such as arsenic and lead, highly acidic, lack of the nutrients carbon and nitrogen in the soil structure, and low microbial communities are factors that negatively affect plant growth. This project provides practical field-scale applications for the use of phytostabilization, which uses plants to create a vegetation cap that stabilizes metals in the root zone while preventing wind and water erosion in mine tailings. The project is divided into three main studies: (1) the assessment of the translation of successful greenhouse results to the field of phytostabilization using compost-assisted direct planting. This includes the use of different rates of compost as an amendment and different desert native plant species in addition to some potential parameters that could be used as indicators of a successful modification of biochemical and physical environment from a disturbed soil towards a more healthy soil when compost assisted direct planting phytostabilization is used; (2) the second study aims to evaluate the effect of the phytostabilization strategy on reducing windborne transport of particle and metal(loids) following the establishment of the vegetation cap. The results indicate that the vegetation resulted from direct planting decreases dust emissions from IKMHSS mine tailings; and (3) the third study focuses on one of the most important requirements for phytostabilization application in the field, the performance of the different plant species selected from the greenhouse studies. This performance was evaluated as the metal accumulation in aerial plant tissue based on metal concentration guidelines from the National Research Council as well as changes in the composition of plant species and canopy cover with time. The results derived from the translation of compost–assisted direct plating based on successful greenhouse results are showing the capacity of this technology on a field scale by maintaining a canopy cover over time that decreases mobilization by not hyper-accumulating metals in the aerial tissue and by preventing windborne particle dispersion with the potential of disrupting contamination pathways.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Ronaldo G. Maghirang / This research was conducted to investigate the potential of charged-water spray in controlling dust in livestock buildings. Specific objectives were to: (1) develop a method to measure the electrostatic charge of airborne particles; (2) characterize the size distribution and charge of airborne particles in a livestock building; (3) evaluate the effectiveness of charged-water spray in controlling dust concentration in enclosed spaces under laboratory conditions; (4) model the effectiveness of charged-water spray in controlling dust in an enclosed building; and (5) develop and evaluate an electrostatically-assisted particulate wet scrubber (EAPWS). A dynamic Faraday-cage sampler was developed for measuring the net charge-to-mass ratio of particles. The device involves collecting particles on a filter and measuring the charge induced. The sampler was calibrated and then used to measure the charge of dispersed particles (i.e., corn starch, NaHCO3, positively charged water spray, negatively charged water spray, and uncharged water spray). The corresponding net charge-to-mass ratios were -0.11 (SD=0.07), +0.20 (0.001), +7.24 (1.6), -6.47 (0.9), and -0.30 (0.12) mC/kg. Characterization of dust in a swine building showed mean dust concentration of 0.89 (SD=0.45) mg/m3, geometric mean diameter of particles of 9.34 μm, and geometric standard deviation of 2.11. The Faraday-cage sampler was also used in the swine building; the net charge-to-mass ratio of particles was +0.68 mC/kg (SD=0.31 mC/kg). The effectiveness of charged-water spray in reducing dust concentration was investigated in an experimental chamber. Test particles (i.e., corn starch, NaHCO3) were dispersed into the chamber and then charged water was sprayed into the chamber. The charged-water spray was significantly more effective than either the uncharged-water spray or no water spray. The removal efficiency of the charged water spray (4 min spray duration, 120 mL/min), based on mass, ranged from 88% to 92% for particles ≤ 10 µm equivalent aerodynamic diameter (EAD) and from 34% to 70% for particles ≤ 2.5 µm EAD. A model based on coagulation was used to predict the particle concentration after spraying of charged water. Predicted values of concentration and removal efficiency agreed well with measured values. A prototype EAPWS was also developed. Laboratory and field evaluations of the EAPWS indicated that it had significantly higher particle removal efficiency than either the control (i.e., no water spray) or the uncharged wet scrubber.

Purpose. Exposures to paper dust, classified as Particulates Not Otherwise Regulated (PNOR), in an industrial setting can cause irritation to the eyes, skin, throat and upper respiratory tract. An exposure assessment was conducted to evaluate the paper dust exposures in the coupon manufacturing facility during a normal production working period. Methods. Total and respirable personal dust sampling was performed according to NIOSH 0500 and 0600 methods. Six total dust samples and seven respirable dust samples were taken within the sampling areas where airborne paper dust was produced to evaluate the Time Weighted Average (TWA) of the exposed employees. Results. Results showed that the TWAs for total dust within the three sampling areas ranged from 0.4% to 4.7% of the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and 0.5% to 7.1% of the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV), except sample RD-4 in the Baler Room. TWAs for respirable dust within the Press Room and Collation Area ranged from 0.8% to 0.9% of the OSHA PEL for all samples and 1.4% to 1.5% of the ACGIH TLV. Descriptive statistics showed the sample standard deviation for both total and respirable dust to be below 1.0. The coefficient of variation for TWAs of total dust in the Press Room was 32.7% while all other total dust and respirable dust coefficient of variations for TWA ranged from 1.3% to 3.4%. Conclusion. Exposures to paper dust ranged from 0.4% to 7.1% of either the OSHA PEL or ACGIH TLV with an exception of sample RD-4 in the Baler Room which was 34% of the OSHA PEL and 56.7% of the ACGIH TLV. Identical respirable dust data and variable total dust data in the Press Room and Collation Area suggest that the dust being generated is of a larger particle size and therefore affects the nose, throat, and upper lungs. The engineering and administrative controls present appeared to be adequate based on the sampling data. Respiratory Personal Protective Equipment (PPE) was not considered a requirement but should be permitted if requested. Present workplace practices also appeared adequate based on the sampling data.

Atmospheric aerosols are suspensions of solid and/or liquid particles in the air from natural and anthropogenic sources. Aerosols are ubiquitous in the air and are often observable as dust, smoke and haze. Dust is considered to be one of the major components of tropospheric aerosols over the globe. Natural and human processes contribute to aerosol emissions. Each year, several billion tons of soil-dust is entrained into the atmosphere playing a vital role in solar irradiance attenuation, and affects marine environments, atmospheric dynamics and weather. Air pollution has recently become a serious environmental problem. Over recent years in the public health domain particulate matter (PM) concentration has become a topic of considerable importance, since epidemiological studies have shown that exposure to particulates with aerodynamic diameters of < 10 ìm (PM10) and especially < 2.5 ìm (PM2.5) induces an increase of lung cancer, morbidity and cardiopulmonary mortality. Mineral dust plays an important role in the optical, physical and chemical processes in the atmosphere, while dust deposition adds exogenous mineral and organic material to terrestrial surfaces, having a significant impact on the Earth’s ecosystems and biogeochemical cycles. The role of dust aerosols in atmospheric processes, i.e. Earth’s radiation balance, cloud microphysics, etc, strongly depends on a variety of physico-chemical parameters, size distribution, dust sources, atmospheric lifetime and mixing processes in the atmosphere. Analysis of the physical properties and chemical composition of dust aerosols is important to determine aerosol sources, mixing processes, transport pathways and their effects on human health. Atmospheric aerosols affect the global climatic system in many ways, i.e. by attenuating the solar radiation reaching the ground, modifying the solar spectrum, re-distributing the earth-atmosphere energy budget and influencing cloud microphysics and the hydrological cycle. Satellite remote for sensing provides an important observational means for monitoring dust production and for improving the understanding of the effects of regional-scale atmospheric processes on dust emission and transport. The Sistan region is located in southeastern Iran, close to the Iranian borders with Pakistan and Afghanistan. The climate is arid, with low annual average precipitation of ~55 mm occurring mainly in the winter (December to February) and evaporation exceeding ~4000 mm.year-1. During summer (June – September), the area is under the influence of a low pressure system attributed to the Indian thermal low that extends further to the west as a consequence of the south Asian monsoon system. These low pressure conditions are the trigger for the development of the Levar northerly wind, commonly known as the “120-day wind”, causing frequent dust and sand storms and contributing to the deterioration of air quality. Therefore, one of the main factors affecting the weather conditions over the region is the strong winds rendering Sistan as one of the windiest deserts in the world. Severe droughts during the past decades, especially after 1999, have caused desiccation of the Hamoun lakes which is located in the northern part of Sistan, leaving a fine layer of sediment that is easily lifted by the wind, thus modifying the basin to one of the most active sources of dust in southwest Asia. The strong winds blow fine sand off the exposed Hamoun lake beds and deposit it to form huge dunes that may cover a hundred or more villages along the former lakeshore. Hamoun dry lake beds are mainly composed of quaternary lacustrine silt and clay material as well as Holocene fluvial sand, silt and clay. These materials have been carried to the basin by the rivers, while along their courses neogene fluvial sand, eolian sand, silt and clay are the main constituents. This thesis analyses the aerosol characteristics, dust loading and air quality over the Sistan region based on first time measurements conducted. The dust loading was measured using dust traps near the Hamoun basin during the period August 2009 to July 2010. Dust loading from the Hamoun basin appears to have a significant contributing influence on the development of extreme dust storms, especially during the summer days. This influence firstly seems to depend on the intensity and duration of dust storms, and secondarily, on the distance from the source region, the wind speed and altitude. The grain-size distribution of the dust loading is strongly influenced by the distance from the dust source. Furthermore, the particle size distribution exhibited a shift towards lower values as the altitude increases, with this feature found to be more obvious amongst larger sized particles, while the frequency of particles below 2.5 ìm seemed not to be affected by altitude. In general, the analysis revealed significant spatio-temporal variability of regional dust loading and characteristics. This finding necessitates more systematic observations at as many locations as possible around the Hamoun basin in order to improve the understanding of force dynamics, transport mechanisms as well as to quantify the dust amounts emitted from the Hamoun basin. To assess air quality characteristics in two cities of Zabol and Zahedan affected by the Sistan dust storms, systematic airborne PM concentrations were measured during the period September 2010 to September 2011 and July 2008 to March 2010, respectively. The results showed that the PM10 concentrations were considerably higher than the corresponding European Union air quality annual standard and the mean PM2.5 concentration (32 ìgm-3) also overcame the Air Quality Index (AQI) annual PM2.5 standards. This poor air quality is affected by dust storms from the Sistan desert. The drainage of the Hamoun wetlands, in association with the intense Levar winds in summer, is the main factor responsible for the frequent and massive dust storms over the Sistan region. Hamoun, as an intense dust source region, caused a dramatic increase in PM10 concentrations and a deterioration of air quality (65% of the days were considered unhealthy for sensitive people and 34.9% as hazardous) in Zabol city. The maximum PM10 concentrations occurred between 8:00 to 11:00 Local Sidereal Time (LST) in Zabol and between 12:00 and 20:00 LST in Zahedan, indicating that Sistan dust storms reach Zahedan after six to nine hours. The strong correlation between daily PM2.5 and PM10 concentrations indicated that they have similar sources and an increase of PM10 significantly affects PM2.5. Considering the air pollution standards defined by the United state Environmental Protection Agency (USEPA), determining that only on one day per year may the AQI be higher than 100 ìg.m-3, it was found that the values of AQI in Zahedan overcame this level for 86 days out of 399, expressing a fraction of 21.5%. It should be noted that on 25 days (6.3%) the atmospheric conditions were very unhealthy or hazardous for the whole population and this requires more attention by officials, managers and urban planners. Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. To mitigate the impact of these phenomena, this thesis examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol and soil samples. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. Dust aerosol characterization included chemical analysis of major and trace elements by X-Ray Fluorescence (XRF) and mineral analysis by X-Ray Diffraction (XRD). The results showed that quartz, calcite, muscovite, plagioclase and chlorite are the main mineralogical components of the dust, in descending order, over Sistan, and were present in all the selected airborne dust samples. In contrast, significantly lower percentages for enstatite, halite, dolomite, microcline, gypsum, diopside, orthoclase and hornblende were found, since these elements occurred only in some of the samples. On the other hand, silicone dioxide (SiO2), Calcium oxide (CaO), Aluminum oxide (Al2O3), Sodium oxide (Na2O), Magnesium Oxide (MgO) and Iron (III) Oxide (Fe2O3) were the major elements characterising the dust, while large amounts of Fluorine (F), Chlorine (Cl) and Sulfur (S) were also found as trace elements. The mineralogy and chemical composition of airborne dust at both stations were nearly the same and quite similar to the soil samples collected at several locations downwind. This suggests that the dust over Sistan is locally emitted, i.e. from the Hamoun basin, and in a few cases can also be long-range transported to distant regions. On the other hand, individual dust storms showed significant differences between either evaporite-dominated aerosols or those characterized by deflation from alluvial silts. These possibly reflect either localized climatic cyclicity or desiccation cycles. However, in some cases the soil samples showed poor comparisons with aerosol compositions, suggesting that dynamic sorting, soil-forming processes and climatic influences, such as rainfall, altered the mineralogy and chemistry in these partially eolian deposits. Estimates of Enrichment Factors (EF) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes. Scanning Electronic Microscope (SEM) analyses of the samples indicated that airborne dust has rounded irregular, prismatic and rhombic shapes, with only the finer particles and a few cases of the coarser dust being spherical. This thesis analyses the aerosol patterns over the arid environment of Sistan region by means of multiple satellite platforms aiming to reveal the spatio-temporal and vertical distribution of dust aerosols. The dataset used includes records of Aerosol Index (AI) from the Total Ozone Mapping Spectrometer (TOMS) on board the Nimbus-7 (1979–92) and the Earth Probe (mid-1996 to 2001) satellites and six-year AI records from OMI aboard Aura. Moreover, the Aerosol Optical Depth (AOD) is analyzed through 11-year records from Multi-angle Imaging Spectro Radiometer (MISR) aboard Terra (2000-2010) and from seven-year Deep Blue records from MODIS aboard Aqua (2002-2011). The main focus is to determine similarities and differences in dust climatology provided by these sensors over the Sistan region and surroundings. The results showed a marked seasonal cycle with high aerosol loading during summer and lower in winter, while MISR, MODIS Deep Blue and OMI climatologies agree in both terms of monthly and seasonally mean spatial and temporal aerosol patterns revealing similar seasonal behavior over the region. After prolonged drought conditions in 1999 at Hamoun lakes (northern of Sistan) the dust-aerosol load over the area has increased. The higher aerosol concentrations during summer are interpreted as a result of the Levar northerly winds and the drying of Hamoun lakes. The satellite monitoring highlights Sistan and Hamoun basin as major dust source regions in south Asia, spreading dust aerosols over Afghanistan, Pakistan and Arabian Sea. / Thesis (PhD)--University of Pretoria, 2012. / Geography, Geoinformatics and Meteorology / Unrestricted