The study investigates the surface controls of major dust emissions and determines the patial distribution of major dust source in South Africa. This study follows a multi-disciplinary approach where primary and secondary data were used. The main objective of the study is to determine the spatial distribution of South Africa's Major Dust Sources. Meteosat Second Generation (MSG) satellite imagery, land use and land cover maps were used to achieve the first and the second objectives of the study. Primary data involved sampling 30 soil samples in the field in order to achieve the third objective of the study. The crust, soil moisture, soil texture and grain size are all controls of dust emission. This investigation is however focused predominantly on grain size characteristics. GIS methods were also used to determine soil type from the African soil map. Soil samples in both provinces were then collected to assess the Particle Size Distribution (PSD) of the soils. The particle size was determined based on a sieve analysis for grain sizes that were greater than 2mm and laser diffractometry, MasterSizer (Malvern) was used to achieve this. The results from the Malvern were later put to R Statistics where they were clustered into eight clusters to determine similarities and difference of the grain size. Because there is no uniqueness in the soil types found in the study area, there were no solid conclusions made based in them. The results show that the soil types are found across South Africa but not the same amount of dust activity was detected in the other parts of the country. Previous studies show that global significant dust sources are natural sources such as lakes, pans and depressions. However, results demonstrate that South African dust sources are anthropogenic sources resulting from commercial agriculture in semi-arid regions. This study has demonstrated that surface sediments suitable for dust production are a mixture of fine material, silt (50µm) and coarse material, sand (2000µm) and it appears that all clusters in this study all contained both mixtures and all have potential to emit dust.

No description available.

No description available.

In addition to ventilation practices, the application of water via sprays is the most economical and popular means of combating respirable dust in an underground coal mine. Due to a noticeable increase in black lung among coal miners and new dust regulations, surfactants or wetting agents have been used to aid in dust suppression. The surfactant facilitates the wetting process by lowering the surface tension and allowing the hydrophobic coal dust to come into contact with the water. One of the most straightforward and effective benchtop tests is a simple wetting test. Although there are variations of this type of test, principle and technique remain the same. A known amount of dust was placed on the surface of a solution and the time it takes for all the dust to fall through the interface would be the wetting rate. This investigation examined the specific density of the bulk dust and concentration of a surfactant in solution and their effects on the wetting rate. It was found that both factors were significant in determining the wetting rate. It was seen that the surfactant had a more significant effect on the dust which consisted mostly of coal particle when compared to a dust with a higher non-coal mineral content. Additionally, full-scale tests were conducted to determine the effect of the surfactant at a constant concentration. During the field implementation, the surfactant was pumped through the mines spray water to the cutter heads of the continuous miner. A large number of uncontrollable variables present during the implementation, made determining the effects difficult, and the resulting impact from the surfactant inconclusive. Further long-term testing would be needed while accounting for all of the identified variables. Significantly higher concentration was however found when using the continuous personal dust monitor as opposed to the older personal dust samples when left in the same environment. Additionally, a very significant drop in dust concentrations was observed when the miner operators were allowed to activate the scrubbers. / Master of Science / People who work in mines are exposed to many dangers and illnesses. One of the illnesses, which has in recent history resurged, is black lung. Black lung is a disease caused by coal dust entering the lungs. The body’s reaction to it is to build scar tissue around the piece of dust. If this happens enough times over the miner’s career, then it becomes nearly impossible to breath. Normally, to prevent this from happening, water is sprayed in the coal before it is chipped off by the machine. Since this appears to no longer be effective, soapy chemicals are added to the water, which helps to keep the dust from lifting into the air in the first place. One of the easiest ways to test whether the chemicals are working well or not is to conduct a wetting test. When conducting a wetting test, a known about of dust is placed on top of the water and chemical mixture, and the time it takes for all of the dust to be wet is call the wetting rate. To get better results in an actual mine, faster wetting rates were sought after. The wetting test showed that the two main factors which determine the wetting were how much coal is in the coal and rock dust mixture and how much chemical is used. It was seen that the chemical had a more significant effect on the dust which had mostly of coal particle when compared to dust with more rock dust. Another study was conducted at a mine with only one mixture of water and chemical. During the study, the chemical was pumped through the mine and to the cutter heads of the continuous miner. A continuous miner is the name of the equipment used to mine coal and other soft material. The cutter head is the piece of the equipment which actually makes contact with coal. Since the conditions at the mine were not ideal and not enough data was taken, the resulting effect of the chemical could not be certain. More long-term studies need to be done in the future to help account for the less than ideal conditions. There were, however, larger amounts of dust when using new sampling equipment as opposed to the older equipment given the same conditions. Also, smaller amounts of dust were seen when the miner operators were allowed to activate the air cleaning attachments on the continuous miner. These issues should be revisited in the future.

Atmospheric dust is the largest contributor to global aerosols from land. Dust emissions rate and properties are influenced by meteorological conditions, parent soil, and landscape, and in turn, it affects impacts on climate, ecosystems, and human societies through various pathways. This dissertation aims to explore the coupled dynamics of dust particle emissions and their essential properties in relation to topography, ecosystem, and atmospheric conditions by integrating information across multiple scales. Specifically, three research projects are pursued. First, the modulation of dust emissions by non-photosynthetic vegetation (NPV) is evaluated by implementing a satellite-based total vegetation dataset, which includes NPV, into a regional atmospheric chemistry model. Simulations of the entire year 2016 over the conterminous United States demonstrate that NPV reduces dust emissions by 10-70% from most dust sources in the southwest, particularly in spring. Second, the relationship between topographic wind conditions (i.e., speed and direction with respect to surface slope) and dust particle size distribution is investigated using a decade's worth of dust reanalysis data covering North Africa. Findings indicate that the fraction of coarse dust in emissions increases with wind speed and slope, particularly under uphill winds, the latter highlighting the role of topography in enhancing vertical transport for larger particles. These positive correlations weaken during the afternoon and summer events, suggesting that turbulence associated with haboob events suspends coarse particles. Finally, a series of air samples collected in Tenerife, Spain is revisited for a detailed study on the associated dust plume characteristics, which would facilitate the understanding of how environmental factors during transport influence airborne microbial assemblages. Using back trajectory analysis and dust optical depth reanalysis data, air samples impacted by African dust are identified. Seasonal variations in trajectories and associated environmental conditions reveal highly variable trans-Atlantic airflows. Elevated altitudes, higher temperatures, and lower relative humidity (RH) along summer trajectories implied the presence of Saharan Air Layer, whereas the frequent occurrence of higher RH (> 40%) and light precipitation in spring indicate more deposition of dust and associated microbes during transport. Overall, this work highlights the importance of accurately representing of various environmental elements that interact with the dust cycle, such as vegetation and topographic winds, which improves our ability to predict and manage the impacts of dust as well as other components of the Earth system. / Doctor of Philosophy / Dust particles can be lifted by strong winds from dry lands, and they are a major contributor to the amount of particles in the air. Suspended dust particles can alter temperatures and weather patterns, reduce visibility, and cause health problems. When settling back to land or oceans, they can carry nutrients and microbes that influence the growth of plants and animals. The movement and properties of dust are subject to various elements of the environment, spanning from microscopic scale to global scale. This dissertation aims to explore the interactions between dust and a few of these environmental elements that are not well understood. Specifically, we first provide information about brown vegetation, which was previously lacking, to a dust model, and find that the dust emissions in the southwestern United States is reduced by 10-70%, particularly in spring. Second, we examine how the changes of wind over slopes influence the size of dust particles in the air by analyzing data for 10 years that combine information from models and satellite observations. We find that faster winds and uphill slopes lead to more large dust particles in the atmosphere. The third study analyzes the pathways of air samples from Africa to Tenerife, Spain, to understand how the transport of dust might affect the types of bacteria that travel with it across the ocean. We find that the airflows from Africa to Tenerife vary greatly from case to case, and the environmental conditions, such as precipitation and relative humidity, varying significantly across seasons and during the dust travel. Overall, this dissertation provides a deeper understanding of the complex ways dust interacts with our world, offering insights that can help us manage its impacts on climate, ecosystems, and human society more effectively.

Yes / In this commentary, we focus on allergy as a facilitating factor in the pathogenesis of alopecia areata (AA). From previous studies on AA, it is well known that subsets of patients can have one or more of; seasonal relapse, comorbid atopic rhinitis, asthma and dermatitis, lesion infiltrating eosinophils and plasma cells, high levels of total IgE, specific IgE for house dust mites (HDMs), and/or disrupted skin barrier function by the evaluation of filaggrin. Allergy and AA share a similar genetic background; both contributing to an immune reaction imbalance. Furthermore, adjunctive treatment with antihistamines, or desensitization for HDM, can reduce the severity of alopecia in atopic AA patients. Therefore, allergies may contribute to the onset and relapse of AA. Identification of an allergic or atopic immune component in AA patient subsets may indicate adjunctive treatment intervention measures against allergies should be taken which may improve the success of conventional AA treatment.

In many arid regions, particle ingestion can occur within propulsive gas turbines. The ingested particles can severely impact performance and may damage many primary gas path components through erosion or deposition. Characterizing crystalline deposits on metallic substrates can allow for the prediction of deposition to improve component resilience and develop health monitoring algorithms. This work investigates the effect of temperature and angle on sand deposits and attempts to quantitatively characterize the deposition of Arizona Test Dust (ATD) onto Hastelloy X. The first study presented in this thesis describes a preliminary investigation of sand deposition at temperatures and velocities similar to those found in the turbine section of propulsive gas turbine engines and presents an equation for predicting deposition as a function of gas path temperature and impact angle. The sand and air mixture maintained a constant flow velocity of approximately 70 m/s, impact angle was varied from 30° to 90°, and the gas path temperature was varied from 1000 °C to 1100 °C. The number of deposits was found to linearly increase with temperature for all coupon angles tested. The model was able to explain approximately 67% of the deposition that occurs, with the remaining percentage due to other factors such as injection rates and surface temperature. The second study describes an improved investigation of sand deposition and presents an equation for predicting deposition as a function of surface temperature and impact angle. This study characterizes deposition using percent coverage in addition to deposits per square millimeter. Deposition is a quadratic function of both near surface coupon temperature and coupon angle. The model using deposits per mm2 was able to explain 96.3% of the deposition that occurred and the model using percent coverage was able to explain 98.9% of the deposition that occurred. / Master of Science / In desert regions, sand particles can be sucked into helicopter and airplane jet engines which can severely impact performance and may damage many engine components through erosion or hot deposits. By measuring the sticking properties of sand on materials used in jet engines, equations to predict sticking can be created and combined with previous erosion research to develop computational simulations of sand behavior in jet engines. This work investigates the effect of temperature and angle on sand deposits and numerically characterizes the deposition of sand particles onto jet engine materials. The first study presented in this thesis describes an initial investigation of sand deposition at temperatures and speeds similar to those found in the turbine section of jet engines and presents an equation for predicting deposition as a function of flow temperature and impact angle. The model was able to explain approximately 67% of the deposition that occurs, with the remaining percentage due to other factors such as injection rates and test coupon surface temperature. The second study describes an improved investigation of sand deposition and presents an equation for predicting deposition as a function of metal surface temperature and impact angle. The model is able to explain 98.9% of the deposition that occurred. The improved sand sticking model will allow designers to improve engine resilience and develop health monitoring algorithms. Improved resilience and health monitoring will increase airplane safety as well as reducing maintenance and operating costs when flying in sandy or arid regions.

Call number: LD2668 .T4 1985 S562 / Master of Science

Dust is a well-known occupational hygiene challenge and has been throughout the years, especially in the coal mining industry. The hazards arising from coal dust will differ between geographical areas due to the unique characteristics of dust from the coal mining environment. It is therefore of upmost importance to identify these qualities or characteristics of coal dust in order to understand the potential hazards it may pose. It is also important to consider the presence of nanoparticles which until recently remained neglected due to the absence of methods to study them. Aim: The aim of this study was to collect significant quantities of airborne dust through static sampling to characterise the physical, morphological as well as elemental properties of inhalable and respirable dust produced at two South African underground and two opencast coal mines. Personal exposure quantification was therefore not the primary concern in this study. Method: Static dust sampling was done at two mining areas of the two opencast and underground coal mines using four Institute of Occupational Medicine (IOM) and four cyclone samplers per area at each mine. A condensation particle counter (CPC) was also used at the opencast areas. The opencast areas included blast hole drilling, drag line and power shovel operations. The underground areas included the continuous miner and roof bolter operations. Gravimetric analyses of the cyclone and IOM samples were done as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. Results: Mine A (opencast and underground) produces higher grade coal in comparison to mine B (opencast and underground). Gravimetric analysis indicated higher average inhalable (55.35 mg/m3) and respirable (2.13 mg/m3) concentrations of dust in the underground areas when compared to the opencast areas (34.73 mg/m3 and 0.33 mg/m3). Blast hole drilling operations indicated higher average inhalable and respirable dust concentrations (39.02 mg/m3 and 0.41 mg/m3) when compared to the drag line and power shovel operations (30.44 mg/m3 and 0.246 mg/m3). CPC results showed higher average concentrations of sub-micron particles at the blast hole drilling areas per cubic metre (63132 x 106) compared to the drag line and power shovel operations (38877 x 106). EDS analysis from the opencast areas indicated much higher concentrations of impurities (with lower concentrations of carbon – 33.33%) when compared to samples taken from the underground mining activities (65.41%). The EDS results from the opencast areas differed substantially. The highest concentrations of silica were found at the blast hole drilling areas. EDS results from the underground areas indicated that mine A has slightly higher concentrations of carbon (66.2%) with less impurities when compared to mine B (64.62%). The continuous miner operations showed a higher concentration of impurities when compared to the dust from the roof bolter. SEM results from the opencast areas revealed that the majority of particles are irregularly shaped and the presence of quartz and agglomerations are evident. SEM results from the underground areas were similar except that the roof bolter produced smaller sized particles when compared to the continuous miner. It also seemed that the areas with higher levels of impurities produced more sub-micron particles. Conclusions: It is possible to identify the majority of physical and elemental characteristics of coal dust by means of gravimetric analysis, particle counting, SEM and EDS. There were differences found, regarding the morphological; chemical and physical characteristics, between the different opencast and underground areas at mine A and mine B due to the type of mining activity and amount of overburden present. Silicosis, Pneumoconiosis and Chronic obstructive pulmonary disease are some of the possible health concerns. It has been seen that dust from higher grade coal mines contributed to more developed stages of these diseases. / MSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2015

Dust is a well-known occupational hygiene challenge and has been throughout the years, especially in the coal mining industry. The hazards arising from coal dust will differ between geographical areas due to the unique characteristics of dust from the coal mining environment. It is therefore of upmost importance to identify these qualities or characteristics of coal dust in order to understand the potential hazards it may pose. It is also important to consider the presence of nanoparticles which until recently remained neglected due to the absence of methods to study them. Aim: The aim of this study was to collect significant quantities of airborne dust through static sampling to characterise the physical, morphological as well as elemental properties of inhalable and respirable dust produced at two South African underground and two opencast coal mines. Personal exposure quantification was therefore not the primary concern in this study. Method: Static dust sampling was done at two mining areas of the two opencast and underground coal mines using four Institute of Occupational Medicine (IOM) and four cyclone samplers per area at each mine. A condensation particle counter (CPC) was also used at the opencast areas. The opencast areas included blast hole drilling, drag line and power shovel operations. The underground areas included the continuous miner and roof bolter operations. Gravimetric analyses of the cyclone and IOM samples were done as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. Results: Mine A (opencast and underground) produces higher grade coal in comparison to mine B (opencast and underground). Gravimetric analysis indicated higher average inhalable (55.35 mg/m3) and respirable (2.13 mg/m3) concentrations of dust in the underground areas when compared to the opencast areas (34.73 mg/m3 and 0.33 mg/m3). Blast hole drilling operations indicated higher average inhalable and respirable dust concentrations (39.02 mg/m3 and 0.41 mg/m3) when compared to the drag line and power shovel operations (30.44 mg/m3 and 0.246 mg/m3). CPC results showed higher average concentrations of sub-micron particles at the blast hole drilling areas per cubic metre (63132 x 106) compared to the drag line and power shovel operations (38877 x 106). EDS analysis from the opencast areas indicated much higher concentrations of impurities (with lower concentrations of carbon – 33.33%) when compared to samples taken from the underground mining activities (65.41%). The EDS results from the opencast areas differed substantially. The highest concentrations of silica were found at the blast hole drilling areas. EDS results from the underground areas indicated that mine A has slightly higher concentrations of carbon (66.2%) with less impurities when compared to mine B (64.62%). The continuous miner operations showed a higher concentration of impurities when compared to the dust from the roof bolter. SEM results from the opencast areas revealed that the majority of particles are irregularly shaped and the presence of quartz and agglomerations are evident. SEM results from the underground areas were similar except that the roof bolter produced smaller sized particles when compared to the continuous miner. It also seemed that the areas with higher levels of impurities produced more sub-micron particles. Conclusions: It is possible to identify the majority of physical and elemental characteristics of coal dust by means of gravimetric analysis, particle counting, SEM and EDS. There were differences found, regarding the morphological; chemical and physical characteristics, between the different opencast and underground areas at mine A and mine B due to the type of mining activity and amount of overburden present. Silicosis, Pneumoconiosis and Chronic obstructive pulmonary disease are some of the possible health concerns. It has been seen that dust from higher grade coal mines contributed to more developed stages of these diseases. / MSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2015