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Ozone is a heavily monitored pollutant. Ozone is not directly emitted into the atmosphere, but rather the product of chemical reactions. Ground level ozone occurs when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react with each other in the presence of sunlight. The primary precursors of ozone are anthropogenically emitted, and as a result, tropospheric ozone has cost millions of dollars in damages and has hurt the health of countless people. This dissertation is a collection of work that aims to provide insight into atmospheric reactions that result in tropospheric ozone and the instrumentation to study such reactions. While these reactions are well studied, this research is novel in its attempt to understand water vapor's influence in tropospheric ozone reactions. As the troposphere continues to get warmer and wetter from global climate change, water vapor will play a larger role in tropospheric reactions, which in turn may perturb the global reactions. Work is presented on the self-reaction of β-hydroxyethyl peroxy radical (β-HEP), an ozone precursor, and the increase in reaction rate catalyzed by water vapor. β-HEP serves as a model system for understanding the roles of water vapor in perturbing the kinetics and product branching ratio of ozone forming reactions. The self-reaction rate coefficient of β-HEP was investigated between 274-296 K with 1.0 × 1015 to 2.5 × 1017 molecules cm-3 of water vapor at 200 Torr total pressure by slow-flow laser flash photolysis coupled with UV time-resolved spectroscopy and long-path, wavelength-modulated, diode-laser spectroscopy. The overall rate constant is expressed as the product of temperature-dependent and water vapor-dependent terms giving k(T,H2O) = 7.8 × 10-14(e8.2 (±2.5) kJ/RT )(1 + 1.4 × 10-34 × e92 (±11) kJ/RT [H2O]). The results suggest that formation of a β-HEP-H2O complex is responsible for the observed water vapor enhancement of the self-reaction rate coefficient. A new discharge flow mass-spectrometer was engineered in collaboration with the California Institute of Technology and NASA's Jet Propulsion Laboratory. This instrument allows for rapid study of water vapor influence on the kinetics of atmospheric reactions. This instrument will be used in further studying the β-HEP + NO reaction as a function of water vapor concentration.

The objective of this study was to evaluate the practical limits of EPA's NONROAD 2005 to accurately simulate Central Florida conditions, especially with regard to lawn and garden equipment. In particular we investigated a NONROAD emission inventory using default inputs and then created a locally specific emission inventory. These emission inventories were prepared for Orange, Osceola, and Seminole county and focused only on the VOC and NOx emissions caused by lawn and garden equipment. The model was manipulated to assess its ability to represent this specific category of nonroad equipment for a given airshed first by running a base case scenario using default data and then by developing a locally-specific scenario through administration of a survey. The primary purpose of the survey was to evaluate local values for equipment population, equipment characteristics, activity estimates, and other relevant information. To develop these local input estimates, data were collected concerning population and usage statistics in the Central Florida area and were combined with emission factors, load factors, allocation factors, and other needed values that have been previously established by the U.S. EPA. The results of the NONROAD model were compared with the resulting emission estimates calculated from locally derived inputs, and as a result of the analysis an accurate emission estimate was calculated. In addition, several possible air quality action steps were further assessed according to feasibility, cost, and predicted emission benefit. These potential management projects were further investigated by assessing the success of other similar projects in other cities in an effort to establish specific costs and emission benefits as they relate to the tri-county area.

This study explores the efficacy of two advanced oxidation processes for generation of hydroxyl radicals to promote degradation of emerging contaminants. Drought and water shortage have become pressing issues caused by our world’s changing climate. Water reclamation and reuse are increasingly important options for relieving this water stress. Water reuse runs the risk of reintroducing recalcitrant compounds that can accumulate in our bodies and environment. Advanced treatment methods that degrade these compounds are vital to protect our health and the health of the environment while providing necessary water resources. Advanced oxidation processes (AOPs) have shown great promise for removing recalcitrant compounds through the production of highly reactive hydroxyl radicals (·OH). This study investigated two AOPs for their production of ·OH as indicated by the probe compound pCBA. One of the AOPs examined was a proprietary device that utilizes ambient air and UV to generate singlet oxygen, which subsequently produces ·OH in water. The other is a more common method that combines UV and ozone (O3) to produce ·OH. The proprietary method was not found to produce notable hydroxyl radicals compared to the UV/O3 AOP. The UV dose of the UV/O3 AOP was also altered to analyze the impact on hydroxyl radical production and removal of a representative emerging contaminant, diclofenac (DCF). The sleeves made to alter the UV dose were not found to change the UV dose enough to show a consequential difference in degradation for the fluence indicator atrazine (ATZ) or the emerging contaminant DCF. Further testing with thicker sleeves would be important to determine the necessary amounts of UV and reasonably scale this technology for a water treatment facility.

Water scarcity is a growing concern at the global scale. Large scale water reuse is growing both in necessity and popularity. Before water reuse can be performed efficiently on a large scale or be used for potable supply, even indirectly, contaminants of emerging concern (CECs) will need to be treated at the full scale. Advanced oxidation processes (AOPs) are a form of advanced water treatment capable of treating a wide range of CECs. This study contributes to the growing field of AOPs and more specifically AOPs using ozone combined with functionalized multi-walled carbon nanotubes (MWCNTs). Ozonation of MWCNTs has been found to increase hydroxyl radical production and improve AOP treatment. Novel MWCNT-enabled membranes were used as catalysts for ozonation to degrade the CEC Atrazine. Atrazine is an ozone recalcitrant CEC that is commonly found in herbicides. Atrazine removal results, found using a high-performance liquid chromatograph (HPLC), were inconsistent between membranes constructed using identical procedures. Further analysis using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopes (SEM), and UV-Vis spectrophotometry was conducted to explore inconsistencies in construction of the membranes which might explain removal inconsistencies and predict membrane longevity. Removal was found to be influenced by filtration time and ozone exposure. Ozone exposure and filtration time influence percent removal because they both affect hydroxyl formation. The membrane test filtration duration, for equal filtered volumes, ranged from under 5 minutes to nearly an hour. It is believed that filtration time inconsistency was due to inconsistent MWCNT loading on the surface of the membranes. Extended exposure to ozone might change the surface chemistry of the MWCNTs on the membrane surface, affecting hydroxyl radical production. Additionally, repeated use of the membrane created surface defects that might reduce the membrane strength. This study found that the lifetime of the membrane is far past what was simulated in lab and further testing must be performed.

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This work was concerned with the determination of mass transfer and kinetic parameters of ozone reactions with four organic compounds from different families, namely reactive dye RO16, triclocarban, naphthalene and methanol. In order to understand the mechanisms of ozone reactions with the organic pollutants, a radical scavenger (t-butanol) was used and the pH was varied from 2 to 9. Ozone solubility (CAL*) is an important parameter that affects both mass transfer rates and chemical reaction kinetics. In order to determine accurate values of the CAL* in the current work, a set of experiments were devised and a correlation between CAL* and the gas phase ozone concentration of the form CAL*(mol/L) = 0.0456 CO3 (g/m3 NTP) was obtained at 20°C. This work has also revealed that t-butanol did not only inhibit hydroxyl radical reactions but also increased mass transfer due to it increasing the specific surface area (aL). Values of the aL were determined to be 2.7 and 3.5 m2/m3 in the absence and presence of t-butanol respectively. It was noticed that the volumetric mass transfer coefficient (kLa) has increased following the addition of t-butanol. Ozone decomposition was studied at pH values of 2 to 9 in a 500 mL reactor initially saturated with ozone. Ozone decomposition was found to follow a second order reaction at pH values less than 7 whilst it was first order at pH 9. When the t-butanol was added, the decomposition of ozone progressed at a lower reaction order of 1.5 for pH values less than 7 and at the same order without t-butanol at pH 9. Ozone decomposition was found significant at high pHs due to high hydroxide ion concentration, which promotes ozone decomposition at high pHs. The reaction rate constant (k) of RO16 ozonation in the absence of t-butanol was determined. The result suggests that RO16 degradation occurs solely by molecular ozone and indirect reactions by radicals are insignificant. The chemical reaction of triclocarban with ozone was found to follow second order reaction kinetics. The degradation of naphthalene using the liquid/gas-ozone (LGO) system was studied. This result showed that hydroxyl radicals seemed to have limited effect on naphthalene degradation which was also observed when a radical scavenger (t-butanol) was used. Reaction rate constants were calculated and were found around 100 times higher than values reported in the literature due to differences in experimental conditions. From the results of the experimental investigation on the degradation of methanol by ozone it was found that the rate constant (k) of the degradation reaction increased at pH 9. The reaction stoichiometry was found to have a value of 1 mol/mol. The two steps of the liquid/solid-ozone (LSO) system were studied on beds of silica gel and a zeolitic material (D915) and the ozone adsorption process was modeled and found that particle rate controls ozone adsorption step but liquid rate controls the water treatment step. Ozone desorption with pure deionised water was studied. The water flow rate was found to accelerate the desorption rates but pH was found to decrease the desorption rates. In contrast, the effect of pH was insignificant in the presence of t-butanol. Determination of the adsorption isotherms for RO16, naphthalene and methanol revealed that RO16 did not exhibit adsorption on silica gel, but both naphthalene and methanol showed adsorption on D915 described by Langmuir model. / Education Service Department of the Libyan Government

Tomatoes are widely produced and consumed due to their nutritional content and versatility. However, the tomato is a soft fruit liable to damage and flavour deterioration. Hence, the main challenge for the tomato producing industry is to prevent the high loss incurred during harvest, handling and transportation of the crops. The objective of this study was to investigate the overall nutritional implication of controlled storage of tomatoes using ozone on the ripening process and the basic nutritional components of tomatoes. This investigation was also designed to focus on the effect of different ozone doses on the basic components and properties (carotenoids, ascorbic acid, total antioxidant activity and soluble sugars content) of the quality and dynamic maturity of tomatoes. Green tomatoes (Rio Grande) were treated in glass chambers with ozone enriched air [(air + 2, 7 and 21 mg O3/g tomato) and control (air only)] under humidity and temperature of 90-95% and 14-17 oC respectively. Tomatoes were sampled after 14 days of ozone treatment in the storage chamber and analyzed for different quality parameters (appearance, weight loss, Total Soluble Solids (TSS), titratable acidity, total ascorbic acid and carotene) of the ripening. The variety Elegance tomatoes were selected and the fruits were graded by colour and subjected to treatment with ozone (in doses 0 (clean air), 0.25, 0.50, and1.00 mg O3/g tomatoes) during storage for 6 days under the same humidity and temperature conditions. The fruits were analysed for carotenoids, ascorbic acid content, total antioxidant activity and soluble sugars.Analysis of the fruits clearly showed that ozone significantly delayed the development of colour on the surface, particularly in the low doses, and caused black spots on the surface of the tomatoes, particularly in higher ozone doses. Ozone did not affect the ascorbic acid and titratable acidity content. However ozone did reduce the Total Soluble Solids (TSS) by about 10% at the lowest ozone dose. A high inhibition of accumulation of carotenoids, particularly at low dose, of the tomatoes (Rio Grande) was also observed. Tomatoes (Elegance) under ozone treatments contained higher ß-carotene than those under the control treatment and lycopene content increased during storage in the red stage of tomato fruits. Ascorbic acid (AsA), dehydroascorbic acid (DHA) and the total of AsA and DHA concentrations, and ratios of redox (ASA/ (ASA + DHA) and DHA/AsA in pericarp and pulp of tomatoes tissue, did not show clear differences between the different treatments. The concentrations of the glucose and fructose increased in the tomatoes which were subjected to ozone treatments. Results from this study show that controlled atmosphere storage of tomatoes using ozone is a viable technique which warrants further study. / Libyan government

The landfill leachate is commonly treated for non-biodegradable organic matters, ammonia and colour. Experimental investigations using polyaluminium chlorite (PAC) and UV/O3 have been conducted for the determination of optimal pH value, reaction time and PAC concentration for the removal of chemical oxygen demand (COD) and colour. In pre-treatment coagulation stages, the highest COD and colour removal efficiencies were observed at the concentration of PAC ≥ 3,000 mglG1 and pH values between 7 and 8. However, these experiments also indicated significant removal efficiency for PAC starting with concentrations of 1,500 mglG1. The efficiency of COD and colour removal were approximately 30% and 70%, respectively. Similar efficiencies have been observed also during the second treatment stage where UV/O3 processes were used to treat coagulated leachate. After UV/O3 application, the pH of leachate reached the optimum value of 7.5 whereas the highest COD and colour removal efficiency was 55% and 72%, respectively, and the optimal reaction time was achieved after 80 min. / Nước rỉ rác sinh ra từ bãi chôn lấp chất thải rắn cần được xử lý các thành phần chất hữu cơ khó phân hủy sinh học, xử lí amoni và độ màu. Một số kết quả thử nghiệm về xử lý COD và màu của nước rỉ rác bằng việc sử dụng phương pháp keo tụ với PAC và quá trình UV/O3 đã được thực hiện cùng với việc xác định các giá trị pH tối ưu, thời gian phản ứng và nồng độ PAC tối ưu. Hiệu suất xử lý cao nhất đạt được khi nồng độ của PAC ≥ 3.000 mg/l, pH trong khoảng từ 7 đển 8 trong giai đoạn tiền xử lý. Tuy nhiên, hiệu quả loại bỏ COD và màu bắt đầu tăng rõ khi nồng độ PAC từ 1.500 mg/l trở lên. Hiệu quả loại bỏ COD và màu tương ứng là khoảng 30% và 70%. Các giá trị pH này phù hợp cho quá trình phản ứng UV/O3 được sử dụng sau giai đoạn keo tụ. Sau quá trình xử lý bằng hệ UV/O3, pH của nước rỉ rác tối ưu được xác định là 7,5 (hiệu suất xử lý COD và màu cao nhất tương ứng là 55% và 72%), thời gian phản ứng tối ưu là 80 phút.

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