A year-long study was conducted in Pinal County, Arizona to characterize fine and coarse particulate matter as a means of furthering our understanding of ambient concentrations and composition in rural, arid environments. Detailed measurement of ambient fine and coarse mass, ion, metal, and carbon concentrations at one-in-six day resolution was conducted at three sites from February 2009 to February 2010. Detailed organic carbon speciation was collected at 5-week resolution. A series of samples representing native soil, agricultural soil, road dust, and cattle feed lot material was collected, resuspended in the laboratory, and analyzed to provide a chemical source profile for each soil type yielding insights into unique source signatures. Observations within the chemical speciation data and subsequent modeling analysis show a strong impact from local sources at the Cowtown site where mass concentrations are highest. Source apportionment results confirm the significant impact from the cattle feedlot adjacent to the site. Chemical analysis of ambient particles and local feedlot material shows the presence of chemical marker species including phosphate which is unique to this source. Fugitive dust is a significant contributor to ambient particulate matter concentrations at all monitoring locations. Seasonal observations show higher concentrations during tilling and harvesting indicating the large role agricultural sources play on particle concentrations in this area. Chemical characterization and modeling show that re-entrained road dust is a significant factor. Fine particle modeling results indicate that concentrations are influenced significantly by motor vehicles including impacts from direct emissions including brake wear and indirect emissions including resuspended road dust. A significant fraction is also associated with crustal sources while about 5 g/m3 appears to be transported into the region from beyond the air shed. Detailed analysis of the local monsoon season indicates that monsoon rains serve to clean the atmosphere resulting in a marked decrease in ambient coarse mass and resulted in a period where local coarse PM concentrations measured at all sites became more uniform. The monsoon season also featured localized high wind events which severely increased coarse PM concentrations and often caused exceedences of the PM National Ambient Air Quality Standard.

A year-long study was conducted in Pinal County, Arizona to characterize fine and coarse particulate matter as a means of furthering our understanding of ambient concentrations and composition in rural, arid environments. Detailed measurement of ambient fine and coarse mass, ion, metal, and carbon concentrations at one-in-six day resolution was conducted at three sites from February 2009 to February 2010. Detailed organic carbon speciation was collected at 5-week resolution. A series of samples representing native soil, agricultural soil, road dust, and cattle feed lot material was collected, resuspended in the laboratory, and analyzed to provide a chemical source profile for each soil type yielding insights into unique source signatures. Observations within the chemical speciation data and subsequent modeling analysis show a strong impact from local sources at the Cowtown site where mass concentrations are highest. Source apportionment results confirm the significant impact from the cattle feedlot adjacent to the site. Chemical analysis of ambient particles and local feedlot material shows the presence of chemical marker species including phosphate which is unique to this source. Fugitive dust is a significant contributor to ambient particulate matter concentrations at all monitoring locations. Seasonal observations show higher concentrations during tilling and harvesting indicating the large role agricultural sources play on particle concentrations in this area. Chemical characterization and modeling show that re-entrained road dust is a significant factor. Fine particle modeling results indicate that concentrations are influenced significantly by motor vehicles including impacts from direct emissions including brake wear and indirect emissions including resuspended road dust. A significant fraction is also associated with crustal sources while about 5 g/m3 appears to be transported into the region from beyond the air shed. Detailed analysis of the local monsoon season indicates that monsoon rains serve to clean the atmosphere resulting in a marked decrease in ambient coarse mass and resulted in a period where local coarse PM concentrations measured at all sites became more uniform. The monsoon season also featured localized high wind events which severely increased coarse PM concentrations and often caused exceedences of the PM National Ambient Air Quality Standard.

No description available.

O dimensionamento de sistemas de transporte hidráulico de polpas minerais exige especial atenção à medida que partículas grossas apresentam um comportamento de sedimentação no interior dos tubos. Dentro desta situação, a velocidade de transporte da polpa mineral deve ter magnitude suficiente para suspender e transportar os sólidos, evitando que os mesmos se depositem na base da tubulação. O bombeamento de polpas minerais em tubos horizontais contendo partículas grossas constituiu o objeto desta tese. Um levantamento sobre a literatura corrente foi realizado e, através de procedimentos experimentais, obteve-se um banco de dados para o modelamento da velocidade crítica (VC), isto é, a velocidade mínima em que ocorre a formação de um leito móvel na base do tubo, apresentando magnitude ligeiramente superior à velocidade de deposição VD, caracterizada pelo início da deposição das partículas na base dos dutos. Para a realização dos ensaios, foram construídas duas unidades experimentais de bombeamento de polpa mineral, onde foram estudadas as seguintes variáveis: i) gradiente de pressão por metro de tubo horizontal (\'delta\'P/L), ii) velocidade média do fluxo (V), iii) perfil de concentração de sólidos ao longo da seção transversal, iv) fator de forma através da função de esfericidade das partículas (\'psi\'), v) densidade do sólido e do líquido, vi) concentração volumétrica dapolpa mineral, vii) granulometria dos sólidos e viii) diâmetro da tubulação. A primeira unidade experimental foi montada com tubulação em PVC transparente de diâmetro interno de 25,4mm e a segunda unidade foi construída em PVC branco com um trecho de 2m em acrílico transparente, apresentando diâmetro interno de 50,8mm. A velocidade critica (VC) para cada condição estudada foi determinada visualmente, através das seções transparentes da tubulação. As amostras utilizadas neste trabalho foram: concentrados de apatita e hematita e o mineral quartzo. As frações granulométricas estudadas foram inseridas em duas classes de tamanho, sendo a primeira classe passante em 297µm e retida em 249µm e a segunda classe passante em 149µm e retida em 105µm. Os resultados permitiram determinar um novo modelo semiempírico para VC, alcançando desvios menores que 10% para as velocidades preditas em relação aos valores de velocidades observadas experimentalmente. / The design of hydraulic systems of slurry transport demands a special attention due to coarse particles present a settling behavior inside the pipes. In this situation, the transport velocity should have order of magnitude sufficient to promote the suspension and the transport of particles, avoiding the solids deposition at the bottom of pipe. The transport of mineral slurries containing coarse particles was the primary goal of the thesis. A survey of the available literature was done and through the experimental tests could be possible to raise a data bank in order to develop a new best fit correlation for the critical velocity (VC) which included the particle shape effect, through the sphericity function. VC could be defined as the minimum velocity where a moving bed of particles takes place at the bottom of the horizontal pipe and it is slightly above the deposition velocity VD, which could be characterized by a bed of stationary particles at the bottom of pipe. The research was conducted using two recirculating pipe test rigs with transparent PVC pipe of 25.4mm and 50.8mm internal diameter with slurry concentrations from 8% up to 27% by volume. The material used was apatite and hematite concentrates and quartz mineral, clustered in two classes of size range (-0.297+0.210mm; -0.149+0.105mm), where the variables were: i) Head losses per meter of horizontal pipe (\'delta\'P/L), ii) Mean transport velocity (V), iii) solids distribution profile, iv) particle shape effect, through the sphericity function (\'psi\'), v) density of particles and liquid, vi) Volumetric concentration of slurries, vii) particles size and viii) pipe diameter. The critical velocity (VC), for each studied condition, was visually determined through the transparent sections of the pipes. The results have yielded a new semi empirical model to predict the critical velocity, yielding a deviation of less than 10% from the observed values of experimental data for VC.

The overall goals of this dissertation are: 1) to better quantify the spatial heterogeneity of coarse particulate matter (PM10-2.5) and its chemical composition; and 2) to evaluate the performance (accuracy and precision) of passive samplers analyzed by computer-controlled scanning electron microscopy with energy-dispersive X-ray spectroscopy (CCSEM-EDS) for PM10-2.5. For these goals, field studies were conducted over multiple seasons in Cleveland, OH and were the source of data for this dissertation. To achieve the first goal, we characterized spatial variability in the mass and composition of PM10-2.5 in Cleveland, OH with the aid of inexpensive passive samplers. Passive samplers were deployed at 25 optimized sites for three week-long intervals in summer 2008 to characterize spatial variability in components of PM10-2.5. The size and composition of individual particles were determined using CCSEM-EDS. For each sample, this information was used to estimate PM10-2.5 mass and aerosol composition by particle class. The highest PM10-2.5 means were observed at three central industrial urban sites (35.4 Μg m-3, 43.4 Μg m-3, and 47.6 Μg m-3), whereas lower means were observed to the west and east of this area with the lowest means observed at outskirt suburban background sites (12.9 Μg m-3 and 14.7 Μg m-3). Concentration maps for PM10-2.5 and some compositional components of PM10-2.5 (Fe oxide and Ca rich) show an elongated shape of high values stretching from Lake Erie south through the central industrial area, whereas those for other compositional components (e.g., Si/Al rich) are considerably less heterogeneous. The findings from the spatial variability of coarse particles by compositional class analysis, presented in Chapter II of this dissertation, show that the concentrations of some particle classes were substantially more spatially heterogeneous than others. The data suggest that industrial sources located in The Flats district in particular may contribute to the observed concentration variability and heterogeneity. Lastly, percent relative spatial heterogeneity (SH%) is more consistent with spatial heterogeneity as visualized in the concentration surface maps compared to the coefficient of divergence (COD). The second goal was achieved by assessing the performance of passive samplers analyzed by CCSEM-EDS to measure PM10-2.5 (Chapter III) and investigating potential sources of variability in the measurement of PM10-2.5 with passive samplers analyzed by CCSEM-EDS (Chapter IV). Data for these analyses were obtained in studies conducted in summer 2009 and winter 2010. The precision of PM10-2.5 measured with the passive samplers was highly variable and ranged from a low coefficient of variation (CV) of 2.1% to a high CV of 90.8%. Eighty percent of the CVs were less than 40%. This assessment showed the CV for passive samplers was greater than that recommended by the United States Environmental Protection Agency (EPA) guidelines for the Federal Reference Method (FRM). Several CV values were high, exceeding 40% indicating substantially dissimilar results between co-located passive samplers. The overall CV for the passive samplers was 41.2% in 2009 and 33.8% in 2010. The precision when high CVs > 40% (n = 5 of 25) were excluded from the analysis was 24.1% in 2009 and 18.2% for 2010. Despite issues with precision, PM10-2.5 measured with passive samplers agreed well with that measured with FRM samplers with accuracy approaching EPA Federal Equivalent Method (FEM) criteria. The intercept was 1.21 and not statistically significant (p = 3.88). The passive to FRM sampler comparison (1:1) line fell within the 95% confidence interval (CI) for the best-fit linear regression and was statistically significant (p < 0.05). However, several data points had large standard deviations resulting in high variability between co-located passive samplers (n = 3), which extend outside of the 95% CI's. The passive sampler limit of detection (LOD) for the CCSEM method was 2.8 Μg m-3. This study also showed certain samples had higher CVs and that further investigation was needed to better understand the sources of variability in the measurement of PM10-2.5 with passive samplers. Sources of variability observed in the measurement of PM10-2.5 with passive samplers analyzed by CCSEM were explored in Chapter IV of this dissertation. This research suggests mass concentrations greater than 20 Μg m-3 for week long samples are needed on the passive sampler substrate to obtain overall CVs by mass less than 15%. It also suggests that greater than 55 particle counts within a compositional class are needed to reduce analytical CVs to less than 15%. Another finding from this study was increasing the concentration from 6.2 to 10.6 Μg m-3 increases the CCSEM analytical precision by mass 38% and by number 75% for random orientation. Also certain compositional classes appeared problematical for precision of passive sampler measurements. For example, the presence of salt plus moisture introduces challenges for CCSEM analysis through the wetting of salt crystalline particles which dissolve creating a displaced dry deposition pattern of particles upon subsequent evaporation. This process can falsely elevate or reduce the particle count and alter its distribution on the sampling media.

In this study the incipient motion of coarse solitary particles on channel beds having different roughness heights was experimentally investigated. The experiments were conducted in a tilting flume of a rectangular cross-section having a working length of 12 m and a rough bed composed of at least 2 layers of coarse gravel of almost constant size. The roughness material of the channel bed was changed three times. The slope of the channel bed and the discharge are two main parameters that determine the initiation of motion of a given particle. The artificial particles tested in the experiments were obtained by mixing cement and iron dust at certain ratios. Dimensionless hydraulic parameters determined from theoretical analysis were related to each other. Flow depths, velocity profiles were measured and flow conditions that represent the critical conditions of initiation of motion were expressed in terms of critical velocities and shear velocities. The results were compared with the previous studies&rsquo / results.

O dimensionamento de sistemas de transporte hidráulico de polpas minerais exige especial atenção à medida que partículas grossas apresentam um comportamento de sedimentação no interior dos tubos. Dentro desta situação, a velocidade de transporte da polpa mineral deve ter magnitude suficiente para suspender e transportar os sólidos, evitando que os mesmos se depositem na base da tubulação. O bombeamento de polpas minerais em tubos horizontais contendo partículas grossas constituiu o objeto desta tese. Um levantamento sobre a literatura corrente foi realizado e, através de procedimentos experimentais, obteve-se um banco de dados para o modelamento da velocidade crítica (VC), isto é, a velocidade mínima em que ocorre a formação de um leito móvel na base do tubo, apresentando magnitude ligeiramente superior à velocidade de deposição VD, caracterizada pelo início da deposição das partículas na base dos dutos. Para a realização dos ensaios, foram construídas duas unidades experimentais de bombeamento de polpa mineral, onde foram estudadas as seguintes variáveis: i) gradiente de pressão por metro de tubo horizontal (\'delta\'P/L), ii) velocidade média do fluxo (V), iii) perfil de concentração de sólidos ao longo da seção transversal, iv) fator de forma através da função de esfericidade das partículas (\'psi\'), v) densidade do sólido e do líquido, vi) concentração volumétrica dapolpa mineral, vii) granulometria dos sólidos e viii) diâmetro da tubulação. A primeira unidade experimental foi montada com tubulação em PVC transparente de diâmetro interno de 25,4mm e a segunda unidade foi construída em PVC branco com um trecho de 2m em acrílico transparente, apresentando diâmetro interno de 50,8mm. A velocidade critica (VC) para cada condição estudada foi determinada visualmente, através das seções transparentes da tubulação. As amostras utilizadas neste trabalho foram: concentrados de apatita e hematita e o mineral quartzo. As frações granulométricas estudadas foram inseridas em duas classes de tamanho, sendo a primeira classe passante em 297µm e retida em 249µm e a segunda classe passante em 149µm e retida em 105µm. Os resultados permitiram determinar um novo modelo semiempírico para VC, alcançando desvios menores que 10% para as velocidades preditas em relação aos valores de velocidades observadas experimentalmente. / The design of hydraulic systems of slurry transport demands a special attention due to coarse particles present a settling behavior inside the pipes. In this situation, the transport velocity should have order of magnitude sufficient to promote the suspension and the transport of particles, avoiding the solids deposition at the bottom of pipe. The transport of mineral slurries containing coarse particles was the primary goal of the thesis. A survey of the available literature was done and through the experimental tests could be possible to raise a data bank in order to develop a new best fit correlation for the critical velocity (VC) which included the particle shape effect, through the sphericity function. VC could be defined as the minimum velocity where a moving bed of particles takes place at the bottom of the horizontal pipe and it is slightly above the deposition velocity VD, which could be characterized by a bed of stationary particles at the bottom of pipe. The research was conducted using two recirculating pipe test rigs with transparent PVC pipe of 25.4mm and 50.8mm internal diameter with slurry concentrations from 8% up to 27% by volume. The material used was apatite and hematite concentrates and quartz mineral, clustered in two classes of size range (-0.297+0.210mm; -0.149+0.105mm), where the variables were: i) Head losses per meter of horizontal pipe (\'delta\'P/L), ii) Mean transport velocity (V), iii) solids distribution profile, iv) particle shape effect, through the sphericity function (\'psi\'), v) density of particles and liquid, vi) Volumetric concentration of slurries, vii) particles size and viii) pipe diameter. The critical velocity (VC), for each studied condition, was visually determined through the transparent sections of the pipes. The results have yielded a new semi empirical model to predict the critical velocity, yielding a deviation of less than 10% from the observed values of experimental data for VC.

Flotation is regarded as the best available separation method for the recovery of valuable minerals such as chalcopyrite (CuFeS2), sphalerite (ZnS), etc., from mined ores. Practically all metals humans use today are produced by flotation. The process relies on controlling the stability of the thin liquid films (TLFs) of water formed between minerals and air bubbles (wetting film), air bubbles (foam film), and mineral particles (colloid films). In flotation, a desired mineral is rendered hydrophobic by surfactant coating as a means to destabilize the TLFs, so that they can be attached to the hydrophobic air bubbles. A TLF ruptures when the disjoining pressure (or surface forces per unit area) of the film becomes negative, i.e., Π < 0. Thermodynamically, a wetting film can rupture when the contact angle (θ) of a mineral surface is larger than zero. It would, therefore, be reasonable to consider the roles of the surface forces to better understand the fundamental mechanisms involved in flotation. The surface forces considered in the present work included the electric double layer (EDL), van der Waals (vdW), and attractive hydrophobic (HP) forces. A flotation model has been developed by using the hydrophobic force as a kinetic parameter, which made it possible to track the fates of mineral particles of different of size, surface liberation, and contact angle to predict both recovery and grades for the first time. The model has been validated against the plant survey data obtained from an operating copper flotation plant. The simulation results obtained using the first principles model have been utilized to address the limitations of current flotation practices. One such limitation is the presence of slow-floating target minerals present in the cleaner-scavenger tails (CST) that are routinely recycled back to the rougher flotation bank as circulating loads (CLs) to allow longer retention times for the slow-floating particles for additional recovery. The simulation results show also that opening a flotation circuit by treating the CST streams separately in an advanced circuit can substantially improve the plant performance. One of the major limitations of flotation is that the coarse particles in a feed stream are difficult to recover due to the low hydrophobicity associated with poor surface liberation. A new flotation model developed in the present work suggests various ways to address the problem. One is to increase the hydrophobicity of the composite (poorly liberated) particles using the Super Collectors that can increase the contact angles to 150 -170o. Simulation results obtained using the model developed in the present work show significant financial benefits of using Super Collectors. Flotation is controlled by surface forces as noted above. As particle size becomes larger than 150 µm, however, the gravitational force comes into the picture and can override the surface forces. A new flotation cell has been developed to mitigate the effects of the extraneous force by decreasing the effective specific gravity (SG) by attaching air bubbles to facilitate levitation and by creating a pulsation to allow particles to move according to SGs independent of particle size, which should help increase the upper particle size limit of flotation. Surface forces in foam and oil-in-water emulsion films have been measured at different temperatures to determine the changes in thermodynamic properties of the thin liquid films (TLFs) of water confined between two bubbles and two oil drops. The results show that the films are destabilized by the attractive hydrophobic forces created during the course of building H-bonded structures in confined spaces, which entails decreases in enthalpy (H < 0) and entropy (TS < 0), the second term representing the thermodynamic cost of building the structures. / Doctor of Philosophy / Flotation is a kinetic process designed to separate valuable minerals from mined ores. This process depends on several hydrodynamic and surface chemistry parameters making it hard to model. A U.S. patent was awarded to Sulman and Picard in 1905 for using air bubbles to selectively collect hydrophobic particles from the aqueous phase, leaving hydrophilic particles behind. Since then, the separation process known as flotation has been used to produce practically all metals humans use. Many investigators developed flotation models using hydrodynamic parameters, e.g., particle size, bubble size, energy dissipation rate, etc., but without a reference to particle hydrophobicity. Therefore, the models were successful in predicting recoveries but not product grades. Derjaguin and Dukhin (1961) were the first to model flotation using surface forces but without due consideration of the role of hydrophobic force in flotation. Therefore, it also failed to predict product grades. In the current work, a new flotation model has been developed using the hydrophobic force as a kinetic parameter. This approach made it possible to predict both recoveries and grades for the first time. The model has been reduced to a simple form mimicking the Arrhenius equation so that it can be used to delineate the different conditions required for optimizing coarse and fine particle flotation. The model has been derived by considering the surface forces in the thin liquid films (TLFs) of water confined between bubbles, and bubbles and particles. It has been found that the hydrophobic force plays a decisive role in destabilizing a wetting film and inducing bubble-particle attachment. The surface forces measured in the present work show that the hydrophobic interactions in macroscopic scales are controlled by enthalpy rather than entropy, which is contrary to the nanoscale hydrophobic interactions. The model has been validated against a full-scale plant operation and demonstrated predictive capabilities. The simulation results have been analyzed to determine the limitations of the current flotation practices. It was found that coarse particle flotation is difficult either due to the presence of composite particles reducing the particle contact angle or due to their poor hydrodynamic properties. Utilizing the insights from the model, various methods of alleviating these limitations have been developed and presented in the current work. References Derjaguin, B.V., Dukhin, S.S., 1961. Theory of flotation of small and medium-size particles. Inst. Min. Metall. 241–267. Sulman, H.L., and Kirkpatrick-Picard (1905). U.S. Patent No. 793,808.

In this study the incipient motion of coarse solitary particles having different specific weights and shapes was investigated. A tilting flume of rectangular cross-section having a net working length of 12 m was used through the experiments. The slope of the channel and the discharge in the channel are the two basic variable parameters that determine the initiation of motion. Particles made of cement and mixture of cement and iron dust in certain ratios were used in the experiments with an obstructing element of various heights right behind the particles. Dimensionless hydraulic parameters determined from theoretical analysis were related to each other. Velocity profiles over the flow depths were measured and flow conditions corresponding to critical conditions were evaluated in terms of critical velocities and shear velocities. The findings of this study were compared with the results of similar studies given in the literature.

Aerosols are small, micrometer-sized particles, whose optical effects coupled with their impact on cloud properties is a source of large uncertainty in climate models. While their radiative forcing impact is largely of a cooling nature, there can be significant variations in the degree of their impact, depending on the size and the nature of the aerosols. The radiative and optical impact of aerosols are, first and foremost, dependent on their concentration or number density (an extensive parameter) and secondly on the size and nature of the aerosols (intensive, per particle, parameters). We employed passive (sunphotmetry) and active (backscatter lidar) measurements to retrieve extensive optical signals (aerosol optical depth or AOD and backscatter coefficient respectively) and semi-intensive optical signals (fine and coarse mode OD and fine and coarse mode backscatter coefficient respectively) and compared the optical coherency of these retrievals over a variety of aerosol and thin cloud events (pollution, dust, volcanic, smoke, thin cloud dominated). The retrievals were performed using an existing spectral deconvolution method applied to the sunphotometry data (SDA) and a new retrieval technique for the lidar based on a colour ratio thresholding technique. The validation of the lidar retrieval was accomplished by comparing the vertical integrations of the fine mode, coarse mode and total backscatter coefficients of the lidar with their sunphotometry analogues where lidar ratios (the intensive parameter required to transform backscatter coefficients into extinction coefficients) were (a) computed independently using the SDA retrievals for fine mode aerosols or prescribed for coarse mode aerosols and clouds or (b) computed by forcing the computed (fine, coarse and total) lidar ODs to be equal to their analog sunphotometry ODs. Comparisons between cases (a) and (b) as well as the semi-qualitative verification of the derived fine and coarse mode vertical profiles with the expected backscatter coefficient behavior of fine and coarse mode aerosols yielded satisfactory agreement (notably that the fine, coarse and total OD errors were <~ sunphotometry instrument errors). Comparisons between cases (a) and (b) also showed a degree of optical coherency between the fine mode lidar ratios.