Lake Victoria (LV), is the largest tropical fresh water lake. It is however facing a myriad of challenges like eutrophication, introducing species, mass extinction and climate change. Eutrophication has mostly been seen as a result of non-point pollution from upstream agricultural areas. However, studies have found that atmospheric deposition could perhaps be the greatest cause of nutrient loading in the lake. Our study looked at black carbon as one of the factors favoring eutrophication in LV. Black carbon is a product of incomplete combustion of biomass or fossil fuel. Biomass burning is prevalent in many areas of Africa and our results have shown a great spatial and temporal variability in its concentration in sediments. The sedimentation rates calculated after analyzing 210Pb activity were 0.87, 0.53 and 0.35 g cm-2 yr-1 while the average black carbon concentrations were 4.6, 2.1 and 6.9 mg g-1 for Siaya, Kisumu and Busia, respectively. These results provided valuable information when compared to past historical events in the Lake region especially eutrophication. The study also found that soot BC has been increasing in the past 100 years suggesting the input from fossil fuels. This study elucidates the complexity of drivers of eutrophication in Lake Victoria. Nitrogen and Phosphorous from the upstream agricultural sites has long been seen as the main cause of eutrophication. Through this study we find that soot deposition in the lake coincides with the period of increased primary productivity. The Total Organic Carbon and Total Nitrogen were also analyzed and have shown increased remarkable increase with time. All these geochemical variables are a testament to the increased role of human activities on the lake’s productivity. While other studies on soot in marine environments have associated bacterial growth to nutrients attached to soot black carbon. We correlate the concentration of soot in Lake Victoria basin to blooming of cyanobacteria.

Doctor of Philosophy / Department of Chemistry / Ryszard J. Jankowiak / This dissertation reports the low temperature frequency domain spectroscopic study of three different natural pigment protein complexes and one artificial antenna system. The main focus of this work is to better understand electronic structure, excitation energy transfer (EET), and electron transfer (ET) dynamics in these systems that could have impact on achieving higher efficiency in future artificial solar cells. In the first part of this dissertation, electronic structure and EET pathways in isolated intact CP43 prime protein complex, which is isolated from Cyanobacterium synechocystis PCC 6803 grown under iron stressed conditions, are investigated using low-temperature absorption, fluorescence, fluorescence excitation, and hole-burning (HB) spectroscopies. This work suggests that, in analogy to the CP43 complex of PSII core, CP43 prime possesses two quasi-degenerate low energy states, A prime and B prime. The various low-temperature optical spectra are fitted considering an uncorrelated EET model. This work suggests that for optimal energy transfer from CP43 prime to PSI, the A prime and B prime state chlorophylls belonging to each CP43 prime should face towards the PSI core. The second part of dissertation reports the photochemical HB study on novel Zinc bacterial reaction center (Zn-RC) from Rhodobacter sphaeroides and its β-mutant (Zn-β-RC). This study shows that ET in the two samples is similar; however, the quantum efficiency of charge separation in the mutant decreases by 60 %. This finding suggests that the coordination state of the HA site zinc bacteriochlorophyll does not tune the active branch ET. Simultaneous fits of various optical spectra using experimentally determined inhomogeneity provides more reliable electron phonon coupling parameters for the P870 state of both RC samples. In the last part of this dissertation, EET in a novel artificial antenna system (ethynyl linked chlorophyll trefoil, ChlT1) is investigated. EET time in ChlT1 is ~2 ps. ChlT1 in MTHF/ethanol glass forms four different types of aggregates, A1-A4. The EET time in A1 and A2 type aggregates slows down only by a factor of 5 and 7, respectively. This study suggests that ChlT1 and its aggregates can be used as efficient antenna systems in designing organic solar cells.

"The hazard associated with dust deflagrations has increased over the last decade industries that manufacture, transport, process, or use combustible dusts. Identification of the controlling parameters of dust deflagration mechanisms is crucial to our understanding of the problem. The objective of this study is to develop an experimental platform, called the Hybrid Flame Analyzer (HFA), capable of measuring the laminar and turbulent burning velocity of gas, dust, and hybrid (gas and dust) air premixed flames as a function of properties specific to the reactants such as dust-particle size and concentration. In this work the HFA is used to analyze a particle-gas-air premixed system composed of coal dust particles (75-90 µm and 106-120 µm) in a premixed CH4-air ( = 0.8, 1.0 and 1.2) flame. This work ultimately aims to improve the knowledge on fundamental aspects of dust flames which is essential for the development of mathematical models. This study is the first of its kind where multiple different parameters that govern flame propagation (initial particle radius, particle concentration, gas phase equivalence ratio, turbulent intensity, and integral length scale) are systematically analyzed in a spatially uniform cloud of volatile particles forming a stationary flame. The experiments show that the turbulent burning velocity is more than two-times larger than the laminar counter-part for each and every case studied. It is observed that smaller particles and larger concentrations (> 50 g/m3) tend to enhance the turbulent burning velocity significantly compared to larger particle sizes and lower concentration ranges. The experimental data is used to develop a correlation similar to turbulent gas flames to facilitate modeling of the complex behavior. "

"This study investigates the interaction of micron- sized coal particles entrained into lean methane €“ air premixed flames. In a typical axisymmetric burner, coal particles are made to naturally entrain into a stream of the premixed reactants using an orifice plate setup. Pittsburgh seam coal dust, with three particle sizes in the range of 0 to 25 µm, 53 to 63 µm, and 75 to 90 µm is used. The effects of different coal dust concentrations (10 €“ 300 g/m3) at three lean equivalence ratios, ϕ (methane-air) of 0.75, 0.80 and 0.85 on the laminar burning velocity are determined experimentally. The laminar burning velocity of the coal dust-methane-air mixture is determined by taking a shadowgraph of the resulting flame and using the cone-angle method. The results show that the addition of coal dust in methane-air premixed flame reduces the laminar burning velocity at particle size of 53 to 63 µm and 75 to 90 µm. However, burning velocity promotion is observed for 0 to 25 µm particles at ϕ = 0.80. Two competing effects are assumed involved in the process. The first is burning velocity promotion effect that the released volatile increases the gaseous mixture equivalence ratio and thus the burning velocity. The second is the heat sink effect of the coal particles to reduce the flame temperature and accordingly the burning velocity. A mathematical model is developed based on such assumption and it can successfully predict the change of laminar burning velocity at various dust concentration. Furthermore, the implication of this study to coal mine safety is discussed."

Digitized by Kansas Correctional Industries

The Earth’s atmosphere consists of both gaseous and condensed-phase components, the condensed-phase material is called particulate matter (PM). The effects of atmospheric PM include adverse health impacts, as well as climate forcing. Both qualitative and quantitative knowledge about PM is necessary to assess these effects, and to devise best mitigation strategies. Understanding the distribution of atmospheric particulate matter is complex because much of it is of secondary origin rather than from primary emissions. Furthermore, there are multiple anthropogenic and natural sources of the contributing precursors, and all these processes are influenced by atmospheric conditions and transport. In this work, one of the major constituents of atmospheric PM - carbonaceous aerosol - is studied. A regional application of the EMEP MSC-W atmospheric chemical transport model - EMEP4UK - was used to model air pollution over the British Isles with a horizontal resolution of 5 km x 5 km. One-way nesting was used from the European computational domain of 50 km x 50 km to the finer spatial grid of EMEP4UK. Several model experiments were devised in order to investigate the well-known deficiency that models currently underestimate organic aerosol (OA) concentrations compared with observations. The model experiments were evaluated with comprehensive year-long novel measurements from the Clear Air for London (ClearfLo) campaign in 2012. Several sources of organic aerosol that are either missing, greatly underestimated, or may be spatially misplaced in official emissions inventories were re-evaluated. Firstly, missing diesel-related intermediate volatility organic compound (IVOC) emissions from diesel vehicles derived directly from field measurements at the urban background site during the 2012 ClearfLo campaign were added into the model. According to the model simulations, these diesel-IVOCs can explain on average ~30% of the annual secondary organic aerosol (SOA) in and around London. Furthermore, the 90- th percentile of modelled daily SOA concentrations for the whole year was 3.8 μgm-3, constituting a notable addition to total particulate matter. More measurements of these precursors (currently not included in official emissions inventories) is recommended. Secondly, spatially and temporally resolved emissions of cooking OA (COA; emissions from meat charbroiling, or frying and deep-frying) were developed. These emissions are currently neglected in European emissions inventories, yet measurements point to significant COA contribution to ambient PM concentrations (up to 2.0 μgm-3 on annual average for central London). The final COA emission source strength derived here (320 mg person-1 day-1) was spatially distributed to workday population density (as opposed to residential population density). The impact of COA on surface concentrations is spatially very limited, however, as the modelled concentrations dropped markedly outside of urban areas. For example, annual average modelled concentration for the Harwell location was just 0.1 μgm-3. Thirdly, redistributing 50% of non-industrial wood and coal burning emissions to residential population density (thus over-writing, in part, the assumption made by the national emissions inventory that only smokeless fuels are burned in smoke control areas) increased the modelled solid fuel OA (SFOA) concentration at the London North Kensington site to 0.8 μgm-3, from the Base run value (using the emissions’ spatial distribution and total as officially reported) of just 0.3 μgm-3. For comparison, the measured annual mean concentration of SFOA at this site was 1.0 μgm-3. Based on the model evaluation presented, redistribution of SFOA emissions into smoke control areas is justified, but further refinement of the amount, as well as the temporal emission profile of this component is necessary. The total effect of the three refinements undertaken in this work increased the model estimate of the annual mean OA concentration at the London North Kensington site from 1.8 μgm-3 to 3.8 μgm-3, which is much closer to the observed value of 4.2 μgm-3. Thus, this work has provided relevant insight into the nature and magnitude of missing, under-represented, and spatially inappropriately-distributed emissions of primary OA and OA precursors. Although the study area was focused on pollutant concentrations over the British Isles, all of the components examined here are of great relevance to the air quality in other countries as well — in Europe and globally. Therefore, the inclusion of these improvements into other air quality models and official emissions’ inventories is advised.

Aerosol particles are ubiquitous in the atmosphere and their properties impact on the atmospheric energy balance. They scatter and absorb incoming sunlight and can perturb cloud microphysical properties, which affects cloud lifetimes and albedo. Africa is one of the world’s largest sources of aerosol due to both its large deserts and prolific biomass burning during the dry seasons. Nevertheless, the continent's atmosphere has, to date, been among the least studied in the world. The southern coast of West Africa is developing rapidly, with both population and anthropogenic emissions being predicted to increase substantially in coming years. It is therefore becoming ever more important to understand the characteristics of aerosols in this region, which will have consequences for issues as diverse as local health and global climate change. This project addresses this problem in two ways: first, laboratory experiments were carried out to characterise biomass burning aerosol at source. Biomass burning is one of the most poorly understood aerosol sources, but one of the most prevalent in tropical regions. Second, aircraft observations were made in southern West Africa during the Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA) field campaign in summer 2016, to observe the broad-scale distribution of chemical and physical aerosol properties. Results were collected in-situ with Aerodyne Aerosol Mass Spectrometers (AMS) and other online aerosol instrumentation; they were considered alongside observations from DACCIWA ground sites and model results. Distinguishable chemical signatures were reliably observed during three phases of combustion events in the laboratory study. This gave insight into the mechanisms linking combustion phases and emissions. Airborne observations in southern West Africa revealed a remarkably consistent background of aged, accumulation mode aerosol present across the region in the boundary layer, including in the region upwind of the cities on the south coast. It was demonstrated that this likely originated from large-scale biomass burning in central and southern Africa, which had become entrained into the boundary layer above the Atlantic and transported north. A second result from the DACCIWA campaign showed that the hygroscopic growth of these particles, due to the high humidity in the region during June and July, more than doubled the mean dry aerosol optical depth. Taken together, these findings shed light on the substantial impacts that biomass burning aerosol, in particular, has on the atmosphere above southern West Africa.

Graduation date: 1970

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 153-168).

Composite propellants are composed of a solid oxidizer that is mixed into a hydrocarbon binder that when polymerized results in a solid mass capable of selfsustained combustion after ignition. Plateau propellants exhibit burning rate curves that do not follow the typical linear relationship between burning rate and pressure when plotted on a log-log scale, and because of this deviation their burning behavior is classified as anomalous burning. It is not unusual for solid-particle additives to be added to propellants in order to enhance burning rate or other properties. However, the effect of nano-size solid additives in these propellants is not fully understood or agreed upon within the research community. The current project set out to explore what possible variables were creating this result and to explore new additives. This thesis contains a literature review chronicling the last half-century of research to better understand the mechanisms that govern anomalous burning and to shed light on current research into plateau and related propellants. In addition to the review, a series of experiments investigating the use of nanoscale TiO2-based additives in AP-HTPB composite propellants was performed. The baseline propellant consisted of either 70% or 80% monomodal AP (223 μm) and 30% or 20% binder composed of IPDI-cured HTPB with Tepanol. Propellants’ burning rates were tested using a strand bomb between 500 and 2500 psi (34.0-170.1 atm). Analysis of the burning rate data shows that the crystal phase and synthesis method of the TiO2 additive are influential to plateau tailoring and to the apparent effectiveness of the additive in altering the burning rate of the composite propellant. Some of the discrepancy in the literature regarding the effectiveness of TiO2 as a tailoring additive may be due to differences in how the additive was produced. Doping the TiO2 with small amounts of metallic elements (Al, Fe, or Gd) showed additional effects on the burning rate that depend on the doping material and the amount of the dopant.