Factors that may govern diesel particulate matter (DPM) oxidation at low temperatures (~200°C) were studied using reactivity and TP-ToFSIMS analysis. Best-case scenarios that give maximum gasification rates were determined for DPM impregnated with KOH and non-catalyzed DPM using temperature programmed oxidation and isothermal experiments. Conditions of intimate catalyst-carbon contact (K/C molar ratio=1/50) and high NO2 concentrations (1%) to improve the reactivity of the carbon reactive sites were unable to meet the steady state gasification rate needed for particulate filter regeneration for a modern diesel engine at 200°C. Oxygen-free thermal annealing (>500°C) caused reactivity losses of a maximum of 40% that correspond to changes to surface morphology and/or concentration of oxygen-containing functional groups. TP-ToFSIMS identified surface functional group changes with temperature on non-dosed and NOX pre-dosed (1.5%NO, 1%NO2, 4.5%O2, balance helium) diesel soot and sucrose char. Detailed analysis of the NOX dosed sucrose char spectra using both inspection and principal component analysis techniques revealed that the 1200 ion fragments created could be reduced to five sets of ions that are chemically and kinetically distinct. These sets presumably represent surface functional groups on the carbon. For example, Set IV may represent carboxylic acid, lactone, or carboxylic anhydride functional groups. Based on these results a mechanism for the surface reaction of NO2 with carbon under vacuum conditions was postulated. At temperatures less than 200°C the ion fragments contain primarily carbon-NO2 type ions. As temperature increases between 200 and 400°C the ion fragments are primarily carbon-NO and carbon-N type fragments. At higher temperatures (>500°C) the surface is enriched with nitrogen containing functional groups. A surface reaction mechanism is proposed where NO2 is bonded to an armchair site and with increasing temperatures and molecular rearrangements the N is incorporated into the carbon ring. The initial surface composition of NOx containing functional groups changes within the area of relevance of low temperature soot regeneration (i.e. between 25° and 200°C). Further studies are needed to understand the effect of N-incorporation on carbon reactivity. No rate processes either in reactor studies or based on surface functional groups met the rate criteria for low temperature DPM oxidation.

To design a cyclone abatement system for particulate control, it is necessary to accurately estimate cyclone performance. In this cyclone study, new theoretical methods for computing travel distance, numbers of turns and cyclone pressure drop have been developed. The flow pattern and cyclone dimensions determine the travel distance in a cyclone. The number of turns was calculated based on this travel distance. The new theoretical analysis of cyclone pressure drop was tested against measured data at different inlet velocities and gave excellent agreement. The results show that cyclone pressure drop varies with the inlet velocity, but not with cyclone diameter. Particle motion in the cyclone outer vortex was analyzed to establish a force balance differential equation. Barth??s "static particle" theory, particle (with diameter of d50) collection probability is 50% when the forces acting on it are balanced, combined with the force balance equation was applied in the theoretical analyses for the models of cyclone cut-point and collection probability distribution in the cyclone outer vortex. Cyclone cut-points for different dusts were traced from measured cyclone overall collection efficiencies and the theoretical model for calculating cyclone overall efficiency. The cut-point correction models (K) for 1D3D and 2D2D cyclones were developed through regression fit from traced and theoretical cut-points. The regression results indicate that cut-points are more sensitive to mass median diameter (MMD) than to geometric standard deviation (GSD) of PSD. The theoretical overall efficiency model developed in this research can be used for cyclone total efficiency calculation with the corrected d50 and PSD. 1D3D and 2D2D cyclones were tested at Amarillo, Texas (an altitude of 1128 m / 3700 ft), to evaluate the effect of air density on cyclone performance. Two sets of inlet design velocities determined by the different air densities were used for the tests. Experimental results indicate that optimal cyclone design velocities, which are 16 m/s (3200 ft/min) for 1D3D cyclones and 15 m/s (3000 ft/min) for 2D2D cyclones, should be determined based on standard air density. It is important to consider the air density effect on cyclone performance in the design of cyclone abatement systems.

Cyclone separators are widely used in agricultural processing industries as air pollution abatement devices. The performance of cyclones is a function of the geometry of the cyclone, operating parameters, and the particle size distribution (PSD) of the entrained aerosol. Multiple models have been proposed to predict the performance of cyclones given different geometric proportions, but many of these models do not quantify changes in performance with changes in inlet velocity or cyclone diameter given fixed geometric proportions. The Texas A&M Cyclone Design (TCD) method is a simple method for designing cyclones based on an inlet design velocity. The TCD method specifies “ideal” inlet velocities of 975 ± 120 m/min (3200 ± 400 fpm) and 914 ± 120 m/min (3000 ± 400 fpm) for 1D3D and 2D2D cyclones, respectively. However, there is evidence that higher dust collection efficiencies may be obtained from cyclones using different inlet velocities than those specified as the “ideal” velocity. Furthermore, the TCD method assumes that cyclone performance is independent of cyclone diameter. The present research demonstrates that, for large particles, the collection efficiency of 15.24 cm (six inch) diameter 1D3D and 2D2D cyclones is similar for inlet velocities from 10.16 standard m/s (2000 fpm) up to the design velocity, with significantly lower pressure drop at lower inlet velocities, resulting in lower energy requirements. However, the performance of cyclones is a function of cyclone diameter. Using similar operating parameters, the collection efficiency of a 60.96 cm (24 inch) diameter 1D3D cyclone was significantly lower (α = 0.05) than that of a 15.24 and a 30.48 cm (6 and 12 inch) diameter cyclone, and the collection efficiency of a 91.44 cm (36 inch) cyclone was significantly lower (α = 0.05) than that of a 60.96 cm (24 inch) diameter cyclone. The results of this research suggests the need for a new mathematical model to predict the performance of cyclones.

Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-06-07Bitstream added on 2014-06-13T19:38:00Z : No. of bitstreams: 1 azevedo_rc_me_araiq.pdf: 304556 bytes, checksum: ded49f14a2e14cead8af1a701b99e4ec (MD5) / Os hidrocarbonetos policíclicos aromáticos nitrados (NHPAs) constituem a classe de compostos aromáticos que têm pelo menos um grupo nitro (-NO2) ligado à cadeia aromática de um hidrocarboneto policíclico aromático (HPA). Nos anos 70 a descoberta das propriedades mutagênicas destes compostos, presentes em material particulado atmosférico e na exaustão de motores a diesel, aumentaram o interesse científico sobre a ocorrência dos mesmos no ambiente. Estes compostos, como os HPAs, estão associados a fontes de combustão como automóveis, sistemas de aquecimento (baseados na queima de biomassa ou de combustíveis fósseis); queima de biomassa (cigarro, florestas, culturas agrícolas, etc), por causa disso pode-se prever que tenham uma distribuição abrangente no ambiente. Os NHPAs são produtos da reação dos HPAs com óxidos de nitrogênio na atmosfera, apresentando-se em concentrações muito baixas neste compartimento ambiental. A análise de NHPAs é muito difícil, principalmente pelos artefactos de amostragem e pela interferência analítica causada por HPAs e outros compostos. Assim sendo, a investigação de métodos alternativos que sejam sensíveis e seletivos são de extrema importância na determinação de NHPAs em amostras atmosféricas. Neste trabalho estudou-se um método para determinação de 1-nitropireno em material particulado proveniente da queima de cana-de-açúcar. O método inclui a redução do grupo nitro a amino, com posterior determinação por HPLC/fluorescência. O método proposto tem limite de detecção de 0,930ng mL-1 e limite de determinação de 1,250ng mL-1, apresentando recuperação entre 77,00 e 86,34%, para 5,00 e 50,00ng mL-1 respectivamente. / Nitrated Polycyclic Aromatic Hydrocarbons (NPAHs) are the class of aromatic compounds with at least one nitro group (-NO2) enhanced to aromatic chain of a Polycyclic Aromatic Hydrocarbon (PAH). In 70’s the discovery of mutagenic properties of these compounds present in atmospheric particulate matter and in gas exhaust of diesel motors are increased the scientific interess on occurrence of NPAHs into environment. These compounds, as PAHs, are associated with combustion sources as automobiles; harming systems (biomass and combustible based); burning of biomass (cigarette, florest, agricultural cultures, etc), because this they have a ubicous dissemination on environment. NPAHs are product of reaction of PAHs with nitrogen oxides on atmosphere, and they are present there at very low concentrations. The analysis of NPAHs in atmospheric samples is very difficult, because of artefacts of sampling process and PAH and other compounds interference on analytical determination. Because this, investigation of alternative methods sensitive and selective is necessary for NPAHs determination in atmospheric samples. In this work is studied a method for determination of 1-nitropyrene from particulate matter of sugar cane burning. The method include reduction of nitro group to amino, and analysis by HPLC/ Fluorescence. The proposed method has detection limit of 0, 930ng mL-1 and quantification limit of .1,250ng mL-1 showing recovery ranged between 77,00 and 86,34% for concentrations of 5,00 and 50,00ng mL-1, respectively.

Texas is the second largest state in U.S.A. based on geographical area, population and the economy. It is home to several large coastal urban areas with major industries and infrastructure supporting the fossil-fuel based energy sector. Most of the major cities on the state have been impacted by significant air pollution events over the past decade. Studies conducted in the southern coastal region of TX have identified long range transport as a major contributor of particulate matter (PM) pollution along with local emissions. Biomass burns, secondary sulfates and diesel emissions sources are comprise as the dominant mass of PM2.5 have been noted to be formed by the long range transport biomass from Central America. Thus, the primary objective of this study was to identify and quantify local as well as regional sources contributing to the PM pollution in the coastal area of Brownsville located along the Gulf of Mexico. Source apportionment techniques such as principal component analysis (PCA) and positive matrix factorization (PMF) were employed on the air quality monitoring data to identify and quantify local and regional sources affecting this coastal region. As a supplement to the PMF and PCA, conditional probability function (CPF) analysis and potential source contribution function (PSCF) analysis were employed to characterize the meteorological influences for PM events. PCA identified an optimal solution of 6 sources affecting the coastal area of Brownsville, while PMF resolved 8 sources for the same area. Biomass comingled with sea salt was identified to be the dominant contributor from the PCA analysis with 30.2% of the apportioned PM mass in Brownsville, meanwhile PMF account secondary sulfates I & II with 27.6%. the other common sources identified included, biomass burning, crustal dust, secondary sulfate, oil combustion, mobile sources and miscellaneous traffic sources.

Air pollution is highly variable in both space and time, which presents many challenges to researchers when they wish to model concentrations. The modelling of air pollution is necessary for a number of reasons, which include the determination of human health effects, providing warning of health risks, and to understand general ecosystem health. In this thesis, modelling of air pollution through both space and time has been explored, with a focus on improving models that can be used to assign air pollution exposure. The techniques presented in this thesis have leveraged the ability of mobile monitoring units to collect air pollution concentration data multiple locations throughout a study period. First, we explore the use of combining mobile air pollution monitoring data with traditional fixed location monitoring. We find that the mobile data is able to provide insight into changes in spatial pattern between two temporal periods that could not be identified solely with the fixed location monitors, which demonstrates value in this monitoring approach that can be built upon with refinement of techniques. Second, we present a method to determine the amount of classical error that will be introduced when a long-term mean concentration is calculated from a discontinuous time-series dataset, which are the type of datasets collected by mobile air pollution monitoring. Third, we merge mobile and stationary air pollution monitoring data, along with meteorological, transportation, and land use information to model the hourly air pollution field using neural network models. The models developed allowed for the assignment of air pollution exposure incorporating human activity patterns. Also, they can be used to provide a spatially refined air quality health index. Lastly, we demonstrate exposure assignment that incorporates human activity patterns to calculate the dose exposure for students during their trips to school. This work commences with a demonstration of the basic utility of mobile air pollution monitoring data, which is to increase the number of monitored locations. Building on that utility of mobile technology, a technique was developed to estimate the error when mobile units are used for long-term estimates, similar to stationary monitoring units; and we were able to provide guiding principles for mobile monitoring data collection. Furthering our objective, to better understand the value of mobile data in a fully integrated monitoring network, we utilized both mobile and stationary data collection techniques together, in a single model, to produce accurate estimates of an air pollution field on an hourly basis. Finally, the research culminates with the demonstration of how mobile monitoring can be used for activity based air pollution exposure estimates, which was shown with a case-study of students’ trips between home and school. Overall, the chapters in this thesis work toward a better understanding of how to incorporate mobile monitoring data into air pollution assessment studies. / Thesis / Doctor of Philosophy (PhD)

There are a number of inherent problems associated with the analysis of polycyclic aromatic compounds (PAC) in airborne particulate matter. The compounds of interest constitute a very small fraction of the total sample, but consist of hundreds of different components. Therefore, analytical techniques with very high resolving power are required. To try to address these problems, methods have been developed and improved to isolate, and subsequently profile, and identify the PAC present in typical airborne particulate samples. Since no single chromatographic technique can provide the desired resolution, a multi-stage clean-up scheme was required prior to analysis. Two methods were investigated in this study. Both methods used a Soxhlet extraction followed by fractionation using an adsorption chromatography step (silica or alumina) and Sephadex LH-20 to isolate the PAC fraction from the other organic constituents. Another problem associated with the analysis of PAC in airborne particulate matter was because of the method of sample collection. It was believed that there were changes in the chemical composition of the particulate and hence the PAC, during sample collection using a Hi-Vol sampler. Artifacts were being formed by reaction of gaseous pollutants with the particulate collected on the filter. An experiment was established to show that the addition of a denuder bundle to a Hi-Vol sampler could reduce this artifact formation during sampling by removing the reactive gases prior to the surface of the filter. The value of the denuder bundle was evaluated by comparison of the PAC from the denuder Hi-Vol with a standard Hi-Vol. Normal-phase HPLC coupled with mass spectrometry was shown to be a good method to compare the PAC in these samples. Some differences between standard and denuder Hi-Vol samples were observed in laboratory experiments, while the results from field sampling were inconclusive. The use of a parallel column gas chromatography-mass spectrometry (GC-MS) (also called third order chromatography) technique was investigated to determine its viability for the identification of the diverse range of PAC present in environmental samples. The PAC . in the NBS urban dust sample (SRM 1649) was analyzed to evaluate the method. To aid in data processing, a semi-automated peak detection routine has been developed. This routine used programs to aid in the data processing by simplifying peak detection and allow calculation of the retention indices of the components. Using the information supplied by the retention indices and the mass spectra, a data base was developed that was applied to a typical airborne particulate sample. / Thesis / Doctor of Philosophy (PhD)

No description available.

No description available.

Atmospheric ammonia (NH₃(g)) poses an environmental concern mainly due its ability to form fine particulate matter (PM2.5 with a diameter smaller than 2.5 micrometers) in the form of ammonium nitrate (NH₄NO₃) and ammonium sulfate ([NH₄]₂SO₄). These forms of PM2.5 may reduce visibility, contribute to eutrophication through deposition, and be detrimental to human health through inhalation. A more complete understanding of ammonia emissions may bring significant PM2.5 reductions within grasp. According to recent studies, one of the largest contributors to atmospheric ammonia is dairy cattle excreta. In this study, seven lactating Holstein cows were subjected to four feeding trials with diets containing 14.5, 15.5, 17, and 18% crude protein (CP). The first objective was to determine the effect of protein content/intake on ammonia fluxes to the atmosphere from each stage of manure handling at a flush dairy. The second objective was to examine the effect of manure handling itself on ammonia fluxes. We examined four different stages of manure handling: 1. Fresh mixture of urine and feces to represent what may be scraped from a barn floor 2. Diluted mixture of urine and feces to represent what is flushed from a barn floor 3. Solids portion of a diluted mixture of urine and feces to represent what is retained by a solids separator at a dairy 4. Liquid portion of a diluted mixture of urine and feces to represent the permeate from a solids separator at a dairy Ammonia fluxes from scraped manure began low and rose to higher fluxes and peaked at an average of 25 hours after mixing urine and feces. Fluxes from flushed manure showed the same behavior. The average pH values for the scraped and flushed manure were relatively low at 6.87±0.17 and 7.05±0.13, respectively, and unfavorable toward ammonia versus ammonium. Fluxes from the separated solids and liquid manure, whose pH values were higher at 8.70±0.30 and 8.55±0.19, respectively, peaked almost immediately. For a time period of 18 hours after beginning flux measurements from the separated liquid manure, fluxes stayed relatively constant. Compared to hours 0-9, fluxes from the separated solids manure decreased 11% in hours 9-18. These results indicate that ammonia fluxes from the scraped and flushed manure were initially limited by the relatively low pH of the slurries, until they aged and released carbon dioxide, after which fluxes became controlled by temperature. Fluxes from the separated solids and liquid manure, however, were temperature-controlled from the start, as this manure had already undergone some aging and the initial pH was more favorable to ammonia loss. Multivariable regressions predicting the mass of ammonia lost to the atmosphere as a function of total ammoniacal nitrogen (TAN) and temperature (T) show that fluxes from the scraped and flushed manure are very sensitive to temperature compared to the separated solids and liquid manure. The same regressions show that ammonia fluxes from the separated solids and liquid manure are predicted well by TAN and T (R² = 0.906 and 0.812, respectively), indicating that dietary protein manipulation, which affects TAN content of the manure, may have a greater effect in this stage of handling. Regressions predicting the mass of ammonia lost to the atmosphere as a function of crude protein intake show crude protein intake is a poor predictor of the overall ammonia flux from a flush dairy. Low correlation coefficients from these regressions are likely a result of cow-to-cow variability in the effect of crude protein intake on ammonia emissions. Significant reductions in ammonia fluxes are possible; however, they will require new regulations on manure handling at flush dairies or incentives for flush dairies to pursue alternate means of manure handling with low emissions. Dairies can begin attacking the problem of excessive emissions by lowering the dietary protein content for older cows to reduce the mass of TAN excreted in their manure, thereby reducing ammonia fluxes in accordance with Henry's law. Once manure is excreted on the barn floor, dairies must encourage mixing between urine and feces and use the natural acidity of the feces in delaying emissions by converting aqueous ammonia in the urine to ammonium. Dairies can achieve well-mixed slurries by manually mixing the manure or with a sloped floor, channeling urine and feces to a common area. Covering holding tanks containing flushed manure to minimize CO₂ stripping and a rise in pH is one measure that may reduce ammonia fluxes. Finally, requiring nitrification or nitrification and denitrification in on-site storage tanks will biologically convert ammonia to nitrate or nitrogen gas, respectively, reducing fluxes from the separated liquid manure. Although burdensome to dairies, these measures would drastically reduce ammonia emissions from flush dairies. Regulatory agencies may choose to ignore the separated solids manure when considering strategies to reduce ammonia emissions, since ammonia volatilization becomes limited by aqueous ammonia in the first 18 hours following separation. / Master of Science