No description available.

Mining activities generate aerosol in a wide range of sizes. Smelting activities produce mainly fine particles (<1 μm). On the other hand, milling, crushing and refining processes, as well tailings management, are significant sources of coarse particles (>1 μm). The adverse effects of aerosols on human health depend mainly on two key characteristics: size and chemical composition. One of the main objectives of this research is to analyze the size distribution of contaminants in aerosol produced by mining operations. For this purpose, a Micro-Orifice Uniform Deposit Impactor (MOUDI) was utilized. Results from the MOUDI samples show higher concentrations of the toxic elements like lead and arsenic in the fine fraction (<1 μm). Fine particles are more likely to be deposited in the deeper zones of the respiratory system; therefore, they are more dangerous than coarse particles that can be filtered out in the upper respiratory system. Unfortunately, knowing the total concentration of contaminants does not give us enough information to identify the source of contamination. For this reason, lead isotopes have been introduced as fingerprints for source apportionment. Each source of lead has specific isotopic ratios; by knowing these ratios sources can be identified. During this research, lead isotopic ratios were analyzed at different sites and for different aerosol sizes. From these analyses it can be concluded that lead isotopes are a powerful tool to identify sources of lead. Mitigation strategies could be developed if the source of contamination is well defined. Environmental conditions as wind speed, wind direction, relative humidity and precipitation have an important role in the concentration of atmospheric dust. Dry environments with low relative humidity are ideal for the transport of aerosols. Results obtained from this research show the relationship between dust concentrations and meteorological parameters. Dust concentrations are highly correlated with relative humidity and wind speed. With all the data collected on site and the analysis of the meteorological parameters, models can be develop to predict the transport of particles as well as the concentration of contaminants at a specific point. These models were developed and are part of the results shown in this dissertation.

Wind erosion, transport and deposition of particulate matter can have significant impacts on the environment. It is observed that about 40% of the global land area and 30% of the earth's population lives in semiarid environments which are especially susceptible to wind erosion and airborne transport of contaminants. With the increased desertification caused by land use changes, anthropogenic activities and projected climate change impacts windblown dust will likely become more significant. An important anthropogenic source of windblown dust in this region is associated with mining operations including tailings impoundments. Tailings are especially susceptible to erosion due to their fine grain composition, lack of vegetative coverage and high height compared to the surrounding topography. This study is focused on emissions, dispersion and deposition of windblown dust from the Iron King mine tailings in Dewey-Humboldt, Arizona, a Superfund site. The tailings impoundment is heavily contaminated with lead and arsenic and is located directly adjacent to the town of Dewey-Humboldt. The study includes in situ field measurements, computational fluid dynamic modeling and the development of a windblown dust deposition forecasting model that predicts deposition patterns of dust originating from the tailings impoundment. Two instrumented eddy flux towers were setup on the tailings impoundment to monitor the aeolian and meteorological conditions. The in situ observations were used in conjunction with a computational fluid dynamic (CFD) model to simulate the transport of windblown dust from the mine tailings to the surrounding region. The CFD model simulations include gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport was used to track the trajectories of larger particles and to monitor their deposition locations. The CFD simulations were used to estimate deposition of tailings dust and identify topographic mechanisms that influence deposition. Simulation results indicated that particles preferentially deposit in regions of topographic upslope. In addition, turbulent wind fields enhanced deposition in the wake region downwind of the tailings. This study also describes a deposition forecasting model (DFM) that can be used to forecast the transport and deposition of windblown dust originating from a mine tailings impoundment. The DFM uses in situ observations from the tailings and theoretical simulations of aerosol transport to parameterize the model. The model was verified through the use of inverted-disc deposition samplers. The deposition forecasting model was initialized using data from an operational Weather Research and Forecasting (WRF) model and the forecast deposition patterns were compared to the inverted-disc samples through gravimetric, chemical composition and lead isotopic analysis. The DFM was verified over several month-long observing periods by comparing transects of arsenic and lead tracers measured by the samplers to the DFM PM₂₇ forecast. Results from the sampling periods indicated that the DFM was able to accurately capture the regional deposition patterns of the tailings dust up to 1 km. Lead isotopes were used for source apportionment and showed spatial patterns consistent with the DFM and the observed weather conditions. By providing reasonably accurate estimates of contaminant deposition rates, the DFM can improve the assessment of human health impacts caused by windblown dust from the Iron King tailings impoundment.

Dense cluster environment influences the properties of galaxies and their evolution. In order to understand this environmental effect and how it evolves with time, we study the infrared (IR) properties of galaxies in three rich clusters. The IR luminosities provide us with extinction-free measurements of the star formation rates (SFRs) of these cluster galaxies. We find a strong evolution in the IR luminosity function (LF) of two z ∼ 0:8 clusters when compared to two local clusters. The evolution rate of the IR LF found in these clusters is consistent with the evolution in field IR LFs. The similar evolution rate found in very different environments favors some internal mechanism, e.g., the gradual consumption of the gas fuel in galaxies, as being responsible for much of the star formation evolution. The mass-normalized integrated SFRs within 0.5R₂₀₀ of these clusters also shows an evolution trend, ∝ (1 + z)5. But this evolution has large scatter and may be affected by the mass selection effect of the sample. In the dense cluster core regions (r < 0.3 Mpc), we find evidence for enhanced SFR suppression. A substantial fraction of members in MS 1054-03 (z ∼ 0.8) are still forming stars actively. This cannot be explained by the scenario where the cluster is only passively accreting star-forming galaxies from the surrounding field, after which their star formation is quenched quickly. We also study the extended IR emission from the intracluster dust (ICD) in A2029. We only find weak signals at 24 and 70 μm and obtain upper limits for the ICD emission.

Background: Polybrominated diphenyl ethers (PBDEs) are additive flame retardants which are found in household and commercial products. These chemicals have the potential to leach from the product into the environment. Human health effects include neurodevelopmental changes, low birth weight and thyroid hormone changes have also been reported, although continued research in this field is needed. Humans are exposed to PBDEs through various exposure pathways and recent studies have determined that exposure to household dust is also a significant route of exposure for humans. The purpose of this study was to access the risk for PBDE intake through an exposure assessment. Also, a laboratory protocol for the fractionation and determination of PBDEs in household dust was developed and evaluated. Methods: PBDE concentrations in indoor dust were measured and compared to previously published data on the topic. A laboratory protocol for fractionation of indoor dust and determination of PBDEs in indoor dust was developed. The new laboratory method was compared to a previously published lab procedure to determine its effectiveness. A p-value of <0.01 and 95% confidence intervals were used to determine statistical significance. Intake estimates were also determined for adults and children exposed at different rates. Results: PBDEs were detected in all the house dust samples with total concentrations (sum of 12 congeners) ranging from 2,870 to 50,642 ng/g dry mass. The averaged concentrations from the six replicate sieve fractions ranged from 106 to 5,697 ng/g dry weight. Daily dust intake rates, based on previously published estimates, range from 20 to 200 mg/day for children and 0.56 to 50 mg/day for adults. Low and high estimates of the daily intake of PBDEs in children and adults were calculated using the average concentration of total PBDEs found in house dust in this study. The exposure estimates for children were approximately 371 to 3,709 ng PBDEs daily based on a mean value of 18,546 ng/g dry weight. The estimate for adults was approximately 10.4 to 927 ng/g dry weight. Conclusions: The new laboratory protocol produces comparable results for QA/QC materials compared to a previously published protocol. Particulate size does not appear to be a significant factor in PBDE concentration and future analysis may only need dust particles to be sieved to one or two sizes (i.e. 500 um and 125 um). Based on the potential intake calculations for children and adults, dust appears to be a significant route of exposure for PBDEs and analysis of additional dust samples will broaden the scope of available data for this method.

Dust and hybrid mixture explosions continue to occur in industrial processes that handle fine powders and flammable gases. Considerable research is therefore conducted throughout the world with the objective of both preventing the occurrence and mitigating the consequences of such events. In the current work, research has been undertaken to help advance the field of dust explosion prevention and mitigation from an emphasis on hazards to a focus on risk. Employing the principles of quantitative risk assessment (QRA) of dust and hybrid mixture explosions, a methodological framework for the management of these risks has been developed. The Quantitative Risk Management Framework (QRMF) is based on hazard identification via credible accident scenarios for dust explosions, followed by probabilistic Fault Tree Analysis (using Relex – Reliability Excellence – software) and consequence severity analysis, represented by maximum explosion pressure, (using DESC – Dust Explosion Simulation Code – software). Identification of risk reduction measures in the framework is accomplished in a hierarchical manner by considering inherent safety measures, passive and active engineered devices, and procedural measures. Dust explosion tests to determine icing and granulated sugar dust explosibility characteristics have been achieved in a 20-L Siwek chamber, and, accordingly, DESC fuel files were built and DESC has validated. Three industrial case studies are presented to show how the QRMF could has been helpful in reducing dust and hybrid mixture explosion risk at the Imperial Sugar refinery, the Semabla grain storage silo, and a hypothetical 400-m3 polyethylene storage silo. DESC simulations and Probit equation for structural damage provide the destructive percentage of each pressure zone in the simulations, followed by probabilistic FTA that were achieved for the first two case studies, before and after applying the framework. Detailed individual and societal risks calculations were made and F-N curves plotted for the two processes. The polyethylene silo case study is presented to show how inherent safety measures can be helpful in reducing dust and hybrid mixture explosion risk. The framework showed significant risk reduction to the point where the residual risks are acceptable for both processes. Finally, assessment results are compared and improvements measured. / The research main objective is: to manage the risks of any expected dust or hybrid mixture explosion in industrial complexes (large-scale).

No description available.

No description available.

No description available.

This mini-dissertation aims to examine the way in which Breyten Breytenbach explores the concepts of home and exile in his novel Memory of Snow and of Dust. The author captures and conveys the experience of exile, and envisages through the exile’s double vision a more complicated conception of home. Through the novel one is able to observe the exilic condition and gain access to new insights. The narrative structure comprises of various discourses and illustrates the restless nature of an unsettling and unstable existence. In the Introduction the theoretical framework for this study is outlined: recent developments in postcolonial and postmodern theories, Breytenbach’s oeuvre and literary criticism devoted to his work are discussed. Chapter One examines the distressing journey into a new awareness of what constitutes home. Chapter Two inspects the restless, yet regenerative condition of exile. Chapter Three considers a more fluid response to spatiality and the concept of home through an exploration of fresh perspectives that may emerge from extreme mental suffering. This study concludes with an affirmation of the relevance of Memory of Snow and of Dust, in times in which the overlapping boundaries of home and exile are becoming a global condition. / Thesis (M.A.) - University of KwaZulu-Natal, Durban, 2010.