abstract: Understanding and predicting climate changes at the urban scale have been an important yet challenging problem in environmental engineering. The lack of reliable long-term observations at the urban scale makes it difficult to even assess past climate changes. Numerical modeling plays an important role in filling the gap of observation and predicting future changes. Numerical studies on the climatic effect of desert urbanization have focused on basic meteorological fields such as temperature and wind. For desert cities, urban expansion can lead to substantial changes in the local production of wind-blown dust, which have implications for air quality and public health. This study expands the existing framework of numerical simulation for desert urbanization to include the computation of dust generation related to urban land-use changes. This is accomplished by connecting a suite of numerical models, including a meso-scale meteorological model, a land-surface model, an urban canopy model, and a turbulence model, to produce the key parameters that control the surface fluxes of wind-blown dust. Those models generate the near-surface turbulence intensity, soil moisture, and land-surface properties, which are used to determine the dust fluxes from a set of laboratory-based empirical formulas. This framework is applied to a series of simulations for the desert city of Erbil across a period of rapid urbanization. The changes in surface dust fluxes associated with urbanization are quantified. An analysis of the model output further reveals the dependence of surface dust fluxes on local meteorological conditions. Future applications of the models to environmental prediction are discussed. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2019

Mineral dust aerosol plays an important role in determining the physical and chemical equilibrium of the atmosphere. The radiative balance of the Earth's atmosphere can be affected by mineral dust through both direct and indirect means. Mineral dust can directly scatter or absorb incoming visible solar radiation and outgoing terrestrial IR radiation. Dust particles can also serve as cloud condensation nuclei, thereby increasing albedo, or provide sites for heterogeneous reactions with trace gas species, which are indirect effects. Unfortunately, many of these processes are poorly understood due to incomplete knowledge of the physical and chemical characteristics of the particles including dust concentration and global distribution, as well as aerosol composition, mixing state, and size and shape distributions. Much of the information about mineral dust aerosol loading and spatial distribution is obtained from remote sensing measurements which often rely on measuring the scattering or absorption of light from these particles and are thus subject to errors arising from an incomplete understanding of the scattering processes. The light scattering properties of several key mineral components of atmospheric dust have been measured at three different wavelengths in the visible. In addition, measurements of the scattering were performed for several authentic mineral dust aerosols, including Saharan sand, diatomaceous earth, Iowa loess soil, and palagonite. These samples include particles that are highly irregular in shape. Using known optical constants along with measured size distributions, simulations of the light scattering process were performed using both Mie and T-Matrix theories. Particle shapes were approximated as a distribution of spheroids for the T-Matrix calculations. It was found that the theoretical model simulations differed markedly from experimental measurements of the light scattering, particularly near the mid-range and near backscattering angles. In many cases, in the near backward direction, theoretical models predicted scattering intensities for near spherical particles that were up to 3 times higher than the experimentally measured values. It was found that better agreement between simulations and experiments could be obtained for the visible scattering by using a much wider range of more eccentric particle shapes.

Indoor air contaminants such as dust and gases are present in concentrations that may be hazardous to worker health in poultry production. Poultry dust may contain inflammatory agents (e.g., endotoxin) and inhalation exposure has been associated with pulmonary symptoms. The current control practice to reduce worker exposure to poultry dust is the use of respiratory protection (e.g., filtering face-piece respirators). Limited research has been conducted to evaluate engineering controls to reduce dust concentrations in broiler chicken production. Therefore, the purpose of this research was to evaluate the effectiveness of a water sprinkling system to reduce inhalable dust and ammonia concentrations in a broiler chicken house. Inhalable dust and ammonia concentrations were measured daily for the production cycle of a flock of broiler chickens (63 days). Inhalable dust was measured gravimetrically using an inhalable sampler and ammonia was measured by a direct reading sensor. Sampling was performed on a stationary mannequin inside two broiler chicken houses. One house used a sprinkler cooling system to deliver a water mist throughout the house and the second house was an untreated control. The sprinkler system activated 5 days after chicken placement and continued through day 63 of the broiler chicken production cycle. The following sprinkler activation program was used each hour from 6am to 10pm: days 5 – 9 five seconds, days 10 – 14 ten seconds, and days 15-63 for fifteen seconds. Geometric mean (GM) inhalable dust concentrations collected in the treatment house (5.2 mg/m3) were lower than those found in the control house (6.0 mg/m3). The GM ammonia concentration within the treatment house was higher at 10.6 ppm (GSD: 1.80), compared to the control house (GM 9.51 ppm; GSD: 1.77). However, the observed differences were not statistically significant (p = 0.33 and p = 0.34, respectively). Concentrations of inhalable dust were reduced by 11β when using the water sprinkling system, however the reduction was not statistically significant. The observed reduction in dust concentration was not sufficient to eliminate the need for respiratory protection.

Dust generation at an underground coal mine working face continues to be a health and safety issue. Prolonged exposure to high concentrations of airborne respirable dust can cause a debilitating and often fatal respiratory disease called Black Lung. In addition, the deposition of float dust in mine return airways poses a serious safety hazard if not sufficiently diluted with inert rock dust. A localized methane explosion can transition into a self-propagating dust explosion. Since dust is a byproduct of various mining activities, such as cutting and loading, crushing, and transportation, the dust-related issues cannot be totally eliminated. However, the adverse health effects and safety concerns can be minimized if a significant amount of the generated dust is removed from the ventilation air by a mechanical device, such as a dust scrubber. Over the last three decades, flooded-bed dust scrubbers integrated into continuous miners have been successfully applied for capturing and removing airborne dust generated at the working face. According to the National Institute for Occupational Safety and Health (NIOSH), a flooded-bed scrubber can achieve more than 90% capture and cleaning efficiencies under optimum conditions. Although flooded-bed scrubbers have proven useful in the vast majority of cases, they have not yet been successfully applied to a longwall face. In the United States, numerous attempts have been made to reduce dust concentration at a longwall face through the application of a scrubber; but, none were successfully implemented. Encouraged by the successful use of a flooded-bed scrubber system at continuous miner faces, this research revisits the flooded-bed scrubber concept for a longwall shearer. For this investigation, a full-scale physical model of a Joy 7LS longwall shearer, modified with an integrated flooded-bed dust scrubber, was designed and fabricated at the University of Kentucky. The scope of work for this research was limited to capturing and cleaning dust generated near the shearer headgate drum only. The mock-up was transported to, and assembled in, the full-scale longwall dust gallery at the NIOSH Pittsburgh Research Laboratory (PRL). Tests were conducted to examine: (1) the effect of the scrubber on headgate-drum dust reduction and (2) the combined effect of the scrubber and splitter sprays on headgate drum dust reduction. Analysis of test results for the scrubber-alone condition indicates a significant dust reduction of up to 57% in the return airway and 85% in the test gallery walkway, whereas the combination of scrubber and splitter-arm sprays shows dust reduction of up to 61% and 96% in the return and walkway, respectively. These results indicate that a flooded-bed scrubber integrated into a longwall shearer can be used as a viable technique to reduce a large portion of airborne dust at a longwall face. Subsequently, a Computational Fluid Dynamics (CFD) model of the longwall gallery and shearer was developed and validated using the results of the experimental study. The CFD simulation results are in good agreement with the experimental results with a maximum of 9.7% variation. This validated CFD model can be used in future research to predict the effects of modifications to the scrubber system, including modifications to the scrubber inlet, to optimize the scrubber design, and to evaluate the effectiveness of adding a tailgate drum dust scrubber.

Utilizing data collected by the University of Kentucky Lung Cancer Research Initiative (LCRI), this study investigated potential mining-related sources for the elevated levels of cadmium in Harlan and Letcher counties. Statistical analyses for this study were conducted utilizing SAS. A number of linear regression models and logarithmic models were used to evaluate the significance of the data. The linear regression models consisted of both simple and multivariate types, with the simple models seeking to establish significance between the potential sources and urine cadmium levels and the multivariate models seeking both to identify any statistically significant linear relationships between source types as well as establish a relationship between the potential source and the urine cadmium levels. The analysis began by investigating which ingestion method caused the increased levels of cadmium exposure. The analysis included ingestion through water sources and inhalation of dust. Of these two, dust showed the higher level of correlation. The second step was to analyze a number of sources of dust, particularly those related to mining practices in the area. These included the proximity to the Extended Haul Road System, secondary haul roads, rail roads, and processing plants. Of the variables in the analysis, Extended Haul Roads, secondary haul roads, and rail roads showed no correlation, and only the proximity to processing plants showed statistical significance.

Dust creates health and safety issues in mining and there are several different ways to reduce the amount of respirable dust created. Dust particles also affect the operation and efficiency of mining equipment. One device currently used to reduce dust in a coal mine is a flooded-bed dust scrubber. These type of scrubbers are found on continuous miners and are designed to capture dust particles close to the cutting head. However, the fibrous screens on the flooded-bed dust scrubber clog easily reducing both production and the quality and quantity of air miners are exposed too. The flooded-bed dust scrubber was designed in the 1980s and has not seen any significant changes since. A Vortecone is a wet scrubber system designed to capture small particles in the air and can easily replace the flooded-bed dust scrubber system on a continuous miner. The Vortecone was initially developed to capture over-sprayed paint particles and due to the capture ability was converted over into the mining industry. The first design of the Vortecone had two outlets and a large pressure drop across the system. The Vortecone was redesigned to have one outlet in order to increase confinement time of particles and thus increase the capture abilities. Using CFD analysis and laboratory testing, the redesigned Vortecone has been proven to have a lower resistance than the original design as well as the currently used convention screens. The Vortecone also proved to have a high capture efficiency at high airflows. This maintenance-free wet scrubber device requires much less maintenance than a conventional screen and thus can be used continually without interrupting production. The Vortecone has been designed so it can easily be mounted onto a continuous miner in place of the currently used scrubbers.

Dust is ubiquitous in underground mine activities. Continuous inhalation of dust could lead to irreversible occupational diseases. Dust particles of size lower than 75.0 µm, also known as float coal dust, can trigger a coal dust explosion following a methane ignition. Ventilation air carries the float coal dust from the point of production to some distance before it’s deposited on the surfaces of underground coal mine. Sources of dust are widely studied, but study of dust transportation has been mainly based on experimental data and simplified models. An understanding of dust transportation in the mine airways is instrumental in the implementation of local dust control strategies. This thesis presents techniques for sampling float coal dust, computational fluid dynamics (CFD) analysis, and mathematical modeling to estimate average dust deposition in an underground coal mine. Dust samples were taken from roof, ribs, and floor at multiple areas along single air splits from longwall and room and pillar mines. Thermogravimetric analysis of these samples showed no conclusive trends in float coal dust deposition rate with location and origin of dust source within the mine network. CFD models were developed using the Lagrangian particle tracking approach to model dust transportation in reduced scale model of mine. Three dimensional CFD analysis showed random deposition pattern of particle on the mine model floor. A pseudo 2D model was generated to approximate the distance dust particles travel when released from a 7 ft. high coal seam. The models showed that lighter particles released in a high airflow field travel farthest. NIOSH developed MFIRE software was adopted to simulate dust transportation in a mine airway analogous to fume migration. The simulations from MFIRE can be calibrated using the dust sampling results to estimate dust transportation in the ventilation network.

Metal oxides in the atmosphere emitted from various natural and anthropogenic processes alter the chemical balance of the Earth's atmosphere due to heterogeneous and photochemical processes with atmospheric trace gases. Therefore, understanding the heterogeneous chemistry and heterogeneous photochemistry of atmospheric trace gases on these oxide surfaces has become vital to precisely predict the effect of mineral dust loading on the Earth's atmosphere. Among the various components of mineral dust, light absorbing oxides play a significantly important role during the daytime. The work reported herein has focused mainly on TiO2 and Α-Fe2O3. These are light adsorbing components found in atmospheric mineral dust. Apart from being a component of mineral dust, TiO2 is heavily used in a number of industrial applications ranging from uses in self-cleaning, water purification to cosmetics. These applications have led to their presence in the atmosphere as anthropogenic dust particles and in contact with the atmosphere as a stationary phase. Iron-containing particles are transferred to the atmosphere mainly from wind and volcanic activities in the form of iron-containing mineral dust and volcanic ash aerosols. Α-Fe2O3 is the most stable iron containing compound found in the Earths' crust which constitutes in significant amounts in mineral dust. The presence of these oxide surfaces in the atmosphere can play a major role in heterogeneous chemistry and photochemistry. In this dissertation research, transmission FTIR spectroscopy and X-ray photoelectron spectroscopy are used to probe the details of heterogeneous chemistry and photochemistry of CO2, SO2, NO2, HCOOH, and HNO3 on titanium dioxide and hematite surfaces. Adsorption sites, surface speciation and surface species stability have been determined from analysis of FTIR and XPS spectra. Isotope labeling experiments were also carried out in order to obtain mechanistic information about the details of surface hydroxyl group reactivity on these oxide particle surfaces. Furthermore, heterogeneous photochemical reactions of adsorbates from atmospheric trace gas adsorption on TiO2 and Α-Fe2O3 were investigated under the conditions pertinent to troposphere. The role of adsorbed water on the stability of adsorbed species that form as a result of heterogeneous reactions and the effect of relative humidity on photochemistry on these oxide particles surfaces has also been investigated due to its important implications in the atmospheric chemistry of oxide surfaces. The research adds to our overall scientific understanding of the molecular level details of heterogeneous chemistry and photochemistry of light absorbing components in the atmosphere.

Particulate matter in the atmosphere emitted from various natural and anthropogenic sources is important due to their effects on the chemical balance of the atmosphere, the Earth's climate, human health and biogeochemical cycles. Although there have been many studies performed to understand the above effects, there still remains substantial uncertainty associated with processes involved and thus it is difficult for current atmospheric chemistry and climate models to reconcile model results with field measurements. Therefore, it is important to have better agreement between models and observations as the accuracy of future atmospheric chemistry and climate predictions depends on it. In this research, a greater understanding of the role of mineral dust chemistry was pursued through focused laboratory studies in order to better understand fundamental processes involved. In particular, studies to further understand the photochemistry of adsorbed nitrate, an important inorganic ion associated with particulate matter exposed to gas-phase nitrogen oxides, were conducted using Al2O3, TiO2 and NaY zeolite to represent non-photoactive components, photoactive components and aluminosilicate respectively, present in mineral dust. These studies reveal that photochemistry of nitrate adsorbed on mineral dust is governed by wavelength of light, physicochemical properties of dust particles and adsorption mode of nitrate. Gas phase NO2, NO and N2O are the photolysis products of nitrate on oxide particles under dry conditions. In contrast, nitrate adsorbed on zeolite is converted mainly to adsorbed nitrite upon irradiation. This nitrite yield is decreased with increasing relative humidity. Gas phase N2O is the main photolysis product of nitrate adsorbed in zeolite in the presence of co-adsorbed ammonia. Water adsorbed on semiconducting TiO2 can be photochemically converted to hydroxyl radicals. These hydroxyl radicals can be involved in surface mediated as well as gas phase oxidation reactions in the presence of cyclohexane. Another focus of this dissertation was to investigate the oxidation of sulfur dioxide oxidation in the presence of mineral aerosol, particularly, coal fly ash (FA), γ-Fe2O3 and Arizona test dust (AZTD), a model for mineral dust aerosol. Depending on the temporal evolution of Fe(II), we proposed that S(IV) oxidation in the presence of FA and γ-Fe2O3 initially occurs through a heterogeneous pathway and a homogeneous pathway is also possible over later time scales. S(IV) oxidation in the presence of AZTD appears to be mostly heterogeneous and does not lead to iron dissolution. Overall, these studies suggest that the rate, extent and products of atmospheric S(IV) oxidation can be highly variable and heavily dependent upon the nature of aerosol sources, thereby precluding simple generalizations about this reaction when modeling atmospheric processes involving diverse mineral dust aerosols. With the recent development in nanotechnology, nanoparticles are becoming a major fraction of atmospheric particulate matter. These particles can undergo aging under ambient conditions at any stage of their life cycle. This impacts the fundamental properties of these materials and therefore the behavior in the environment and interactions with biomolecules and biological systems. ZnO and CuO nanoparticles form adsorbed carbonate phases upon exposure to CO2 and water vapor. These carbonates become more solvated as the relative humidity is increased. Presence of carbonate phases on ZnO particles increases their water solubility. Thus, overall the work reported in this dissertation provides insights into heterogeneous and multiphase atmospheric chemical reactions in the presence of mineral aerosol and atmospheric aging of nanoparticles.

Particulate nitrates play important roles in the atmosphere. They consist mainly of NH4NO3 and NaNO3, products from the reactions of gaseous HNO3 with gaseous NH3 and sea salt, respectively. The gas-to-particle phase conversion of nitrate changes its deposition characteristics and ultimately changes the transport and deposition rates of the locally produced species. Studies were conducted to develop background information on the particle concentrations and size distributions and the chemistry and kinetics behind the interactions. The predominant nitrate species in the Tampa Bay area was identified as coarse mode NaNO3. NH4NO3 was not detected as it has high volatility at ambient temperatures. Spatial distribution sampling determined a gradient of NaCl and NaNO3 with increased distance from the coastal shore and an increase in the gas-to-particle conversion of nitric acid along a predominant air mass trajectory. The EQUISOLV II thermodynamic equilibrium model was evaluated. It was determined that the model can be used to predict gas and size-distributed particulate matter concentrations. The model was also used to examine the gas-to-particle partitioning of nitric acid to nitrate by NaCl and CaCO3. Both sodium and calcium partitioned nitrate to the particle phase. The magnitude of the partitioning was directly dependent on the equilibrium coefficients. The fine mode percentage of the total nitrate was determined using two methods. The results were used to expand the current data set to account for the coarse mode nitrate, and they indicated that particle nitrate accounted for 9% of the total nitrogen deposition flux to Tampa Bay. The formation of particle nitrate was examined using a nitrate accumulation model. Results indicated that the equilibrium time for particles less than 10 um in diameter was significantly less than their atmospheric residence time, with fastest conversion occurring under the highest relative humidity conditions. This information is vital in the development of atmospheric nitrogen dry deposition estimates, which are used to assess water quality and nutrient loading. These data can be used to determine air-monitoring strategies and to develop models that account for the coarse particle nitrogen species.