Browsing by Subject "Ozone"
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Item Applications of satellite remote sensing data for regional air quality modeling(2010-05) Feldman, Michael S., 1979-; McDonald-Buller, Elena; Allen, David T.; Bonnecaze, Roger T.; Mullins, C. B.; Tapley, Byron D.; Wiedinmyer, ChristinePhotochemical grid models are used to evaluate air pollution control strategies by simulating the physical and chemical processes that influence pollutant concentrations. Their accuracy depends on the accuracy of input data used for anthropogenic and biogenic emissions, land surface characteristics, initial and boundary conditions and meteorological conditions. Evaluation of model performance requires sufficient ambient data. This work develops approaches for applying satellite data to allow more frequent and timely estimates of parameters required to estimate emissions and pollutant removal processes for regional air quality modeling. Land use and land cover (LULC) data prepared from remote sensing satellite data were evaluated for use as inputs to photochemical grid models for estimating dry deposition velocities and biogenic emissions. The results indicated that satellite-based data derived from the Moderate Resolution Imaging Spectroradiometer instrument can be used to provide periodic updates to LULC information used in photochemical models. The sensitivity of predicted ozone concentrations to LULC data used for biogenic emission estimates was examined by comparing the database currently used for modeling in southeastern Texas with a new database prepared from Landsat satellite imagery and field data. The satellite data and image classification techniques provide useful tools for mapping and monitoring changes in LULC. However, field validation is necessary to link species and biomass densities to the classification system needed for accurate biogenic emissions estimates, especially in areas that have dense concentrations of species that emit high levels of biogenic hydrocarbons. The application of NO2 measurements from the Ozone Monitoring Instrument (OMI) to validation of NOx emission estimates and identification of emission sources for regional air quality modeling for Texas was examined. OMI observations can be used to identify regions with changes in emissions over time or where estimates have large uncertainties and to evaluate the effectiveness of emission reduction strategies. For example, in the Dallas-Fort Worth area, observed NO2 column densities from OMI indicate that emission controls are less effective than anticipated due to increased area source emissions. The techniques developed in this work have broad applicability in the advancement of methods for including satellite remote sensing data in regional air quality modeling.Item Aqueous phase oxidation with activated oxygen species for wastewater treatment(Texas Tech University, 1979-08) Lin, Richard Chia-HuiNot availableItem Assessing the sustainability of transportation fuels : the air quality impacts of petroleum, bio and electrically powered vehicles(2010-05) Alhajeri, Nawaf Salem; Allen, David T.; McDonald-Buller, ElenaTransportation fleet emissions have a dominant role in air quality because of their significant contribution to ozone precursor and greenhouse gas emissions. Regulatory policies have emphasized improvements in vehicle fuel economy, alternative fuel use, and engine and vehicle technologies as approaches for obtaining transportation systems that support sustainable development. This study examined the air quality impacts of the partial electrification of the transportation fleet and the use of biofuels for the Austin Metropolitan Statistical Area under a 2030 vision of regional population growth and urban development using the Comprehensive Air Quality Model with extensions (CAMx). Different strategies were considered including the use of Plug-in Hybrid Electric Vehicles (PHEVs) with nighttime charging using excess capacity from electricity generation units and the replacement of conventional petroleum fuels with different percentages of the biofuels E85 and B100 along or in combination. Comparisons between a 2030 regional vision of growth assuming a continuation of current development trends (denoted as Envision Central Texas A or ECT A) in the Austin MSA and the electrification and biofuels scenarios were evaluated using different metrics, including changes in daily maximum 1-hour and 8-hour ozone concentrations, total area, time integrated area and total daily population exposure exceeding different 1-hour ozone concentration thresholds. Changes in ozone precursor emissions and predicted carbon monoxide and aldehyde concentrations were also determined for each scenario. Maximum changes in hourly ozone concentration from the use of PHEVs ranged from -8.5 to 2.2 ppb relative to ECT A. Replacement of petroleum based fuels with E85 had a lesser effect than PHEVs on maximum daily ozone concentrations. The maximum reduction due to replacement of 100% of gasoline fuel in light and heavy duty gasoline vehicles by E85 ranged from -2.1 to 2.8 ppb. The magnitude of the effect was sensitive to the biofuel penetration level. Unlike E85, B100 negatively impacted hourly ozone concentrations relative to the 2030 ECT A case. As the replacement level of petroleum-diesel fuel with B100 in diesel vehicles increased, hourly ozone concentrations increased as well. However, changes due to the penetration of B100 were relatively smaller than those due to E85 since the gasoline fraction of the fleet is larger than the diesel fraction. Because of the reductions in NOx emissions associated with E85, the results for the biofuels combination scenario were similar to those for the E85 scenario. Also, the results showed that as the threshold ozone concentration increased, so too did the percentage reductions in total daily population exposure for the PHEV, E85, and biofuel combination scenarios relative to ECT A. The greatest reductions in population exposure under higher threshold ozone concentrations were achieved with the E85 100% and 17% PHEV with EGU controls scenarios, while the B100 scenarios resulted in greater population exposure under higher threshold ozone concentrations.Item The characterization of regional ozone transport(2010-05) Dionisio, Mariana Costa; Allen, David T.; McDonald-Buller, Elena C.; Bonnecaze, Roger T.; Webber, Michael E.; Edgar, Thomas F.Among the most ubiquitous and persistent air quality problems facing urban areas are high concentrations of gas phase oxidants and fine particulate matter. Ozone and particulate matter concentrations in urban areas are significantly influenced by other factors in addition to local emissions, such as regional transport spanning distances as large as 1000 kilometers. Despite the importance of regional transport in meeting air quality standards, to date most analyses of regional transport have focused only on short duration episodes, or semi-quantitative assessments. The development and evaluation of seasonal, quantitative assessments of regional pollutant transport, based on modeling calculations and observational data is the topic of this dissertation. The observational data available through the Texas Air Quality Studies in 2000 and 2006 provide a unique opportunity to develop, evaluate, and improve methods for characterizing regional air pollutant transport. Measurements collected during these studies are used as the primary observational basis for characterizing regional ozone transport and to evaluate the performance of photochemical models. Results suggest that measurements (from aircraft and surface monitors) and the photochemical model provide consistent estimates of the magnitude of ozone transport. On this basis, photochemical modeling is used to determine potential impacts of regional ozone transport in Texas, under varying meteorological and photochemical conditions, as well as to characterize the dominant chemical and physical processes within urban plumes. While qualitative studies and limited quantitative analyses have been performed to assess regional ozone transport, this work includes the first detailed quantitative characterization of the importance of ozone transport over the course of an entire ozone season using both photochemical modeling and ambient data. Results demonstrate that urban plumes in Texas are capable of transporting significant amounts of ozone over distances spanning hundreds of kilometers. Furthermore, on a seasonal basis, there are a number of days characterized by high contributions from inter-city transport coinciding with high total ozone concentrations, suggesting that the role of inter-city transport will remain significant for many areas to demonstrate attainment of the NAAQS for ozone. Results also indicate that reductions in the impacts of inter-city transport are possible by decreases in emissions from source regions.Item Classical and quasiclassical trajectory calculations of ozone isotopomer formation in atomic oxygen and molecular oxygen collisions(Texas Tech University, 2002-08) Baker, Thomas A.In the present study, the ozone formation rate is determined using the calculated O3 survival time (ST) distribution explicitly rather than an average lifetime. This approach has the advantage of not constraining the PM dependence of ke6 by any assumptions about the nature of the ST distribution. The present chapter will be confined principally to modeling the absolute rate of ozone formation over the broad range of temperature (T = 130 - 370 K) and density (PM = 10^18 - 10^22 cm^-1 for which experimental information is available[10, 22, 23, 29, 32, 1].Item Evaluating the design of emissions trading programs using air quality models(2008-12) Thompson, Tammy Marie; Allen, David T.; McDonald-Buller, ElenaIn order to meet the US EPA's National Ambient Air Quality Standards as set under the provisions of the Clean Air Act, states and regions throughout the United States are designing cap and trade programs aimed at reducing the emissions of the two dominant precursors for ozone, nitrogen oxides (NOx) and Volatile Organic Compounds (VOCs). While emission cap and trade programs are becoming more common, relatively few analyses have examined the air quality implications of moving emissions from one location to another (due to trading of emissions between facilities), from one sector to another (due to the use of technologies such as Plug-in Electric Hybrid Vehicles - PHEVs), and changing the temporal distribution of emissions (through emissions trading among facilities with different temporal profiles). This thesis will examine, in detail, the air quality implications of two emission cap and trade programs. The first program is a NOx trading program that covers Electricity Generating Units (EGUs) in the Northeastern United States. Results show that refining the temporal limits on this cap and trade program, by charging facilities more to emit NOx on days when ozone is most likely to form, has the potential to significantly reduce NOx emissions and ozone concentrations. Additionally, this research also shows that, for this region, the spatial redistribution of NOx emissions due to trading leads to greater ozone reductions than similar amounts of NOx emission reductions applied evenly across all facilities. Analyses also indicate that displacing emissions from the on-road mobile sector (vehicles) to the EGU sector through the use of PHEVs decreases ozone in most areas, but some highly localized areas show increases in ozone concentration. The second trading program examined in this thesis is limited to Houston, Texas, where a VOC trading program is focused on a sub-set of four Highly Reactive Volatile Organic Compounds (HRVOCs), which have been identified as having substantial ozone formation potential. Work presented in this thesis examined whether this trading program, in its current form or in an expanded form, could lead to air pollution hot spots, due to spatial reallocation of emissions. Results show that the program as currently designed is unlikely to lead to ozone hot spots, so no further spatial limitations are required for this program. Expanding the trading to include Other VOCs, fugitive emissions and chlorine emissions, based on reactivity weighted trading, is also unlikely to lead to the formation of ozone hot spots, and could create more flexibility in a trading market that is currently not very active. Based on these air quality modeling results, policy suggestions are provided that may increase participation in the trading market. These case studies demonstrate that use of detailed air analyses can provide improved designs for increasingly popular emission cap and trade programs, with improved understanding of the impacts of modifying spatial and temporal distributions of emissions.Item An exploratory analysis of textile fabric soil content through ozone reaction(2013-05) Rajaganesh, Shamini; Krifa, MouradCleanliness is one of the most essential virtues needed for a healthy lifestyle. While there have been several attempts made to characterize the cleanness of food, water and air by quality monitoring, there has been very little attention given to the cleanness characterization of clothing. Clothing worn next to the skin is easily contaminated by solid particles and fluid substances picked up from the surrounding environment and the skin surface. The fluid contamination could be either aqueous or oily in nature. Human sweat and sebum are one of the major constituents of oily organic soils found in worn clothing. Studies show that oily organic contaminations tend to remain in the clothing even after laundering, thereby creating malodors. While there are several industry established standards to evaluate visible solid contamination such as dust, dirt and colored stains, measuring the amount of invisible oily contaminations has been difficult. Moreover, many of the cleanness evaluation methods are subjective. This exploratory research aimed at measuring the level of sweat and sebum soiling in textile fabrics. Due to the affinity of ozone towards the unsaturated components of sebum, the feasibility of using the reaction rates of ozone as a metric to quantify the level of organic soiling in clothing was tested. The fabrics selected for this study were representative of the commonly used fiber composition in activewear and innerwear. The sweat and sebum used for fabric soiling were synthetic in nature. The fabric swatches were soiled with synthetic sebum at two extreme levels of soiling (0.3% and 1% of the fabric weight). A lab built four-chamber ozonation equipment was used for the experimentation with ozone. The reactivity of ozone with the soiled fabrics was measured in terms of ozone concentrations in ppb. The data obtained was plotted against time and the slopes were recorded. The plots showed a significant difference in the slopes indicating that the rate of ozone reactivity varied with the level of soiling. The slopes were steeper for higher levels of soils, particularly in the cotton samples. There was also a marked difference in the reaction rates between the cotton and polyester fabrics at the same level of soiling. The results obtained from the study fulfilled the hypothesis and looks promising for developing an objective method of measuring cleanness of clothing. Moreover, an adjunct qualitative study was conducted to assess the sensitivity of the human odor sensor to acknowledge the difference in the level of soiling through sensory analysis. The results from the study substantiated the need for an objective method of cleanness measurement.Item Gas phase oxidation of onion dehydration odors with ozone(Texas Tech University, 1977-12) Purkaple, Jerry DixonThe kinetics of the reaction between ozone and three identified components associated with onion dehydration odor were studied in a flow reactor. Temperatures in the range of 95-150°F were used in an attempt to estimate the temperature dependence of the reaction rate constant. However, this temperature range was not great enough to establish a meaningful relationship. A homogeneous gas phase model and a heterogeneous model were found to fit the experimental data reasonably well. Due to the mathematical similarities between the two models, no real distinction could be made between them. Initial rate data indicated that the initial reaction was first order with respect to the odor components and of fractional order with respect to ozone.Item Impact of flare destruction efficiencies on ozone concentrations: a case study for Houston, Texas(2010-05) Alfadhli, Fahad Mohammed; Allen, David T.; Edgar, Thomas F.Industrial flaring can result in atmospheric emissions that have significant impact on regional air quality. This study investigates the impact on one-hour average ozone concentrations due to industrial flaring, using the region around Houston, Texas as a case study. Specifically, this study examined the impact on ozone formation of different flare destruction efficiencies. There are some concerns about whether flare destruction efficiency is reduced from design conditions (98 to 99% destruction) at low flare flow rates. Some studies have reported very low flares destruction efficiencies under low flow, so it is possible that ozone precursor emissions may be underestimated by an order of magnitude or more at low flow conditions. In this thesis, 100 different destruction efficiency scenarios have been constructed where destruction efficiency depends on the ratio of flare flow rate to the maximum flow rate (turndown ratio). The scenarios differ in the assumed destruction efficiency at near zero flow and the turndown ratio at which destruction efficiency returns to the design value. These destruction scenarios are applied to hourly mass flow data for twenty-five flares in Houston, Texas. The scenarios have very different impacts on air quality. The air quality implications of these results for possible modifications to flare operation are explored.Item Impact of variable emissions on ozone formation in the Houston area(2009-12) Pavlovic, Radovan Thomas, 1971-; Allen, David T.; McDonald-Buller, ElenaGround level ozone is one of the most ubiquitous air pollutants in urban areas, and is generated by photochemical reactions of oxides of nitrogen (NOx) and volatile organic compounds (VOCs). The effectiveness of emission reduction strategies for ozone precursors is typically evaluated using gridded, photochemical air quality models. One of the underlying assumptions in these models is that industrial emissions are nearly constant, since many industrial facilities operate continuously at a constant rate of output. However, recent studies performed in the Houston-Galveston-Brazoria area indicate that some industrial emission sources exhibit high temporal emission variability that can lead to very rapid ozone formation, especially when emissions are composed of highly reactive volatile organic compounds. This work evaluates the impact of variable emissions from industrial sources on ground-level ozone formation in Houston area, utilizing a unique hourly emission inventory, known as the 2006 Special Inventory, created as a part of the second Texas Air Quality Study. Comparison of the hourly emissions inventory data with ambient measurements indicated that the impact of the variability of industrial source emissions on ozone can be significant. Photochemical modeling predictions showed that the variability in industrial emissions can lead to differences in local ozone concentrations of as much as 27 ppb at individual ozone monitor locations. The hourly emissions inventory revealed that industrial source emissions are highly variable in nature with diverse temporal patterns and stochastic behavior. Petrochemical and chemical manufacturing flares, which represent the majority of emissions in the 2006 Special Inventory, were grouped into categories based on industrial process, chemical composition of the flared gas, and the temporal patterns of their emissions. Stochastic models were developed for each categorization of flare emissions with the goal of simulating the characterized temporal emission variability. The stochastic models provide representative temporal profiles for flares in the petrochemical manufacturing and chemical manufacturing sectors, and as such serve as more comprehensive input for photochemical air quality modeling.Item Increasing the in vitro digestibility of mesquite with inorganic catalysts and ozone(Texas Tech University, 1982-08) Fish, Steven JeffreyNot availableItem Indoor secondary organic aerosol formation : influence of particle controls, mixtures, and surfaces(2009-08) Waring, Michael Shannon; Siegel, Jeffrey A.; Corsi, Richard L.Ozone (O₃) and terpenoids react to produce secondary organic aerosol (SOA). This work explored novel ways that these reactions form SOA indoors, with five investigations, in two categories: investigations of (i) the impacts of particle controls on indoor SOA formation, and (ii) two fundamental aspects of indoor SOA formation. For category (i), two investigations examined the particle control devices of ion generators, which are air purifiers that are ineffective at removing particles and emit ozone during operation. With a terpenoid source present (an air freshener), ion generators acted as steady-state SOA generators, both in a 15 m³ chamber and 27 m³ room. The final investigation in category (i) modeled how heating, ventilating, and air-conditioning (HVAC) systems influence SOA formation. Influential HVAC parameters were flow rates, particle filtration, and indoor temperature for residential and commercial models, as well as ozone removal by particle-laden filters for the commercial model. For category (ii), the first investigation measured SOA formation from ozone reactions with single terpenoids and terpenoid mixtures in a 90 L Teflon-film chamber, at low and high ozone concentrations. For low ozone, experiments with only d-limonene yielded the largest SOA number formation, relative to other mixtures, some of which had three times the effective amount of reactive terpenoids. This trend was not observed for high ozone experiments, and these results imply that ozone-limited reactions with d-limonene form byproducts with high nucleation potential. The second investigation in category (ii) explored SOA formation from ozone reactions with surface-adsorbed terpenoids. A model framework was developed to describe SOA formation due to ozone/terpenoid surface reactions, and experiments in a 283 L chamber determined the SOA yield for ozone/d-limonene surface reactions. The observed molar yields were 0.14–0.16 over a range of relative humidities, and lower relative humidity led to higher SOA number formation from surface reactions. Building materials on which ozone/d-limonene surface reactions are predicted to lead to substantial SOA formation are those with initially low surface reactivity, such as glass, sealed materials, or metals. The results from category (ii) suggest significant, previously unexplored mechanisms of SOA number formation indoors.Item The nexus of energy and health : a systems analysis of costs and benefits of ozone control by activated carbon filtration in buildings(2015-08) Aldred, Josh Ryan; Corsi, Richard L.; Novoselac, Atila; Kinney, Kerry; Liljestrand, Howard; Siegel, JeffreyAmericans spend nearly 90% of their lifetimes indoors, where they receive 50-70% of their exposure to ozone. The US EPA has designated ozone as a hazardous air pollutant and ozone exposure has been linked to respiratory mortality, hospital admissions, restricted activity days, and school loss days. In addition, the most susceptible populations to ozone exposure are children and the elderly, especially if they suffer from an existing respiratory health condition. One possible solution to reduce indoor ozone exposure is to use activated carbon filtration in a building's heating, ventilation, and air conditioning (HVAC) system. In many cases, using commercially available activated carbon filters will have minimal additional capital and energy costs in comparison to standard particle filters. A complex systems model for evaluating the potential costs and benefits of ozone control by activated carbon filtration in buildings was developed as part of this dissertation. The modeling effort included the prediction of indoor ozone concentrations and exposure with and without activated carbon filtration. As example applications, the model was used to predict benefit-to-cost ratios for commercial office buildings, long-term healthcare facilities, K-12 schools, and single-family homes in 12 American cities in five different climate zones. Health outcomes due to reduced indoor ozone exposure were determined using the USEPA methodology for outdoor ozone exposure, which includes city-specific age demographics and disease prevalence. Health benefits were evaluated using disability-adjusted life-years, which were then converted to a monetary value to compare with activated carbon filtration costs. Modeling results indicate that activated carbon filtration during the summer ozone season should be beneficial and economically feasible in commercial office buildings, long-term healthcare facilities, and K-12 schools. The benefits of activated carbon filtration in single-family homes are predicted to be marginal, except for sensitive populations or in cities with high seasonal ozone and high air conditioning usage. Field experiments of activated carbon filters in an operational university laboratory resulted in an average ozone single-pass removal efficiency of 70%. An additional benefit-cost analysis of activated carbon filtration in the laboratory showed that ozone-related health costs were reduced by 62% and fan energy costs were reduced by 21% compared to a baseline condition. Finally, the field study demonstrated that activated carbon filtration for ozone removal could be economically beneficial in buildings with very high ventilation due to reductions in health, energy, and filter replacement and installation costs.Item Oxidation of pharmaceuticals : impacts of natural organic matter and elimination of residual pharmacological activity(2011-08) Blaney, Lee Michael; Lawler, Desmond F.; Katz, Lynn Ellen; Liljestrand, Howard M.; Richburg, John H.; Speitel Jr., Gerald E.; Kirisits, Mary JoAnthropogenically-derived substances, including pharmaceuticals and personal care products, endocrine-disrupting chemicals, and pesticides, are increasingly being detected in drinking water supplies and wastewater effluents. Concerns over the presence of these compounds in water supplies include their ability to impart toxicological activity, their capacity to spread antibiotic resistance, and their potential to affect cell-signaling processes. For these reasons, water treatment processes geared towards removal of these trace organic contaminants are vital. In this work, ozone was used to treat four pharmaceutical contaminants: ciprofloxacin, cyclophosphamide, erythromycin, and ifosfamide. Ciprofloxacin and erythromycin are antibiotic/antimicrobial compounds, and cyclophosphamide and ifosfamide are chemotherapy agents. Ozone effectively transformed all four pharmaceuticals, even in the presence of background natural organic matter, which exerts a considerable ozone demand. The apparent rate constants for the reaction of the pharmaceuticals with ozone at pH 7 were determined: 3.03 M-1s-1 for cyclophosphamide; 7.38 M-1s-1 for ifosfamide; 1.57×104 M-1s-1 for ciprofloxacin; and 7.18×104 M-1s-1 for erythromycin. Cyclophosphamide and ifosfamide, which do not react quickly with ozone, exhibited high rate constants (2.7×109 M-1s-1) for transformation by hydroxyl radicals, which are formed through ozone decomposition. Nevertheless, complete removal of cyclophosphamide and ifosfamide was achievable using a novel continuous aqueous ozone addition reactor and an ozone-based advanced oxidation process (peroxone). In ozone-based processes, pharmaceuticals are systematically transformed via complex oxidative pathways towards CO2, H2O, and the oxidized forms of other elements. Intermediate oxidation products containing oxygen atoms or hydroxyl groups substituted into the chemical structure of the parent pharmaceutical were identified using liquid chromatography-mass spectrometry (LC-MS). Given the structural similarity of intermediate oxidation products to the parent pharmaceuticals, an antimicrobial activity assay was employed to monitor the removal of pharmacological activity associated with ciprofloxacin, erythromycin, and their respective intermediate oxidation products throughout treatment. For solutions containing ciprofloxacin or erythromycin, ozone was able to completely eliminate the corresponding antimicrobial activity. Ciprofloxacin intermediate oxidation products were pharmacologically active; however, erythromycin’s intermediate products did not contribute to the residual antimicrobial activity. These results suggest that the design of conventional and advanced ozone-based processes must incorporate ozone demand from background organic matter and account for destruction of pharmacologically active intermediates.Item Ozonation of erythromycin and the effects of pH, carbonate and phosphate buffers, and initial ozone dose(2011-08) Huang, Ling, Ph. D.; Katz, Lynn Ellen; Lawler, Desmond F.The ubiquitous presence and chronic effect of pharmaceuticals is one of the emerging issues in environmental field. As a result of incomplete removal by sewage treatment plants, pharmaceuticals are released into the environment and drinking water sources. On the other hand, conventional drinking water treatment processes such as coagulation, filtration and sedimentation are reported to be ineffective at removing pharmaceuticals. Therefore, the potential presence of pharmaceuticals in finished drinking water poses a threat on public health. Antibiotics, as an important group of pharmaceuticals, are given special concerns because the potential development of bacteria-resistance. Ozonation and advanced oxidation processes are demonstrated to be quite effective at removing pharmaceuticals. The oxidation of pharmaceuticals is caused by ozone itself and hydroxyl radicals that are generated from ozone decomposition. Whether ozone or hydroxyl radicals are the primary oxidant depends on the specific pharmaceutical of interest and the background water matrix. In this research, erythromycin, a macrolide antibiotic, was chosen as the target compound because of its high detection frequency in the environment and its regulation status. The objective of this research was to investigate the removal performance of erythromycin by ozonation from the standpoint of kinetics. The effects of pH, carbonate and phosphate buffers, and initial ozone dose on ozonation of erythromycin were also studied. The second-order rate constant for the reaction between deprotonated erythromycin and ozone was determined to be 4.44x10⁹ M⁻¹·s⁻¹ while protonated erythromycin did not react with ozone. Ozone was determined to be the primary oxidant for erythromycin removal by ozonation. pH was found to have great positive impact on the degradation of erythromycin by ozonation due to the deprotonation of erythromycin at high pH. Carbonate and phosphate buffers were found to have negligible effects on the degradation of erythromycin by ozonation. Initial ozone dose showed a positive impact on the total erythromycin removal rate by ozonation.Item Ozone (o3) efficacy on reduction of phytophthora capsici in recirculated horticultural irrigation water(2009-05-15) McDonald, Garry VernonMicroorganisms that cause plant disease have been isolated in recirculated irrigation water and increase the risks of disease incidence in horticultural operations. Ozone is an effective oxidizer used to disinfect drinking water supplies and treat industrial wastewater. The objective of this research was to investigate using ozone gas as part of a strategy to reduce the incidence of Phytophthora deBary in recirculated irrigation water. An isolate of Phytophthora capsici Leonian was cultured to induce sporulation. Spore dilutions were placed in aliquots of reverse osmosis water and bubbled with ozone gas (O3) to concentrations of 0 to 1.5 mg?L-1. Ozonated samples were plated and observed for colony forming units. Increasing ozone concentrations reduced the number of colony forming units to 0 at 1.5 mg? L-1 03. Turbidity effects on efficacy on Phytophthora capsici were tested using bentonite clay at 0 to 2.0 nephelometric turbidity units and ozone concentrations of 0 to 1.5 mg? L-1. Increasing bentonite did not affect the efficacy of increasing ozone concentrations on reducing colony formation to 0 at 1.5 mg?L-1 O3. Bioassays using Phytophthora capsici on Capsicum annuum L. seedlings confirmed apparent pathogenicity. Reverse osmosis water, containing a soluble fertilizer at 0 to 300 mg? L-1 N, was ozonated to concentrations of 0 to 1.5 mg?L-1 O3 and used to irrigate Chrysanthemum x morifolium T. de Romatuelle. Increasing ozone concentrations did not interact with increasing fertilizer levels to affect the final growth parameters. Chrysanthemum exposed to ozone gas concentrations of 0.5 to 1.5 mg?L-1 showed symptomatic ozone damage. Complete soluble fertilizer solutions with micronutrients were ozonated from 0 to 1.5 mg?L-1 O3 and analysed for nutrient content. Increasing ozone levels did not interact with fertilizers to affect macronutrients. Increasing ozone interacted with iron at a high fertilizer level. Ozone did not affect the efficacy of paclobutralzol in controlling growth in Viola x wittrockiana. Ozone was effective in controlling Phytophthora capsici in recirculated irrigation water with minimum impact on plant growth. Adjustments in fertility regiemes may be needed to counteract the oxidizing affect of ozone on micronutrients.Item Ozone interactions with HVAC filters(2006) Zhao, Ping; Siegel, Jeffrey A.,Corsi, Richard L.,Item Ozone treated sorghum stover for ruminants(Texas Tech University, 1982-12) Bunting, Lawrence DwainNot availableItem Particulate reactive oxygen species in indoor and outdoor environments : prevalence and health effects(2015-05) Khurshid, Shahana Sarfraz; Kinney, Kerry A.; Siegel, Jeffrey A; Corsi, Richard; Novoselac, Atila; Wells, J. RaymondReactive Oxygen Species (ROS) are an important class of air pollutants generated from photochemical and ozone-initiated reactions in indoor and outdoor environments. Despite the fact that Americans spend nearly 90% of their time inside buildings and extended exposures to ROS can occur in indoor environments, ROS has received very little attention as an indoor pollutant. This is one of the first research studies to measure the concentration of particulate ROS (on PM [subscript 2.5] and TSP) in indoor environments. A significant fraction of indoor particulate ROS was found to exist on PM [subscript 2.5] (58±10%) which is important from a health perspective since PM [subscript 2.5] can carry ROS deep into the lungs. The indoor concentrations of ROS on PM [subscript 2.5] sampled in residential and commercial buildings were not significantly different from the outdoor concentrations. This result is intriguing because it implies that generation of ROS inside buildings and/or transport of outdoor ROS and precursors of ROS into buildings are important processes and can be as significant as ROS generation in outdoor environments. Controlled studies show that when outdoor ozone concentrations are relatively low, indoor concentrations of ROS are dominated by indoor sources of ROS rather than outdoor sources of ROS. However, when outdoor ozone concentrations are relatively high, indoor and outdoor sources of ROS contribute almost equally to the indoor concentration of ROS. This study is also one of the first to assess seasonal variations in outdoor particulate ROS concentrations. Ambient sampling conducted over an 11-month period indicates that outdoor particulate ROS concentrations are influenced by the ozone concentration, solar radiation intensity and temperature. In order to understand the potential health effects of exposure to ROS, an in vitro exposure system of lung epithelial cells and differentiated lung tissue was also utilized. Results from these experiments indicate that exposure to products of limonene ozonolysis (which include ROS) can lead to a greater inflammatory response than exposure to either ozone or limonene. This highlights the need to include biologically relevant pollutants, such as ROS, in indoor air quality studies. Further work is warranted to better understand the parameters that drive indoor particulate ROS concentrations.Item Regional-scale land--climate interactions and their impacts on air quality in a changing climate(2010-12) Jiang, Xiaoyan, doctor of geological sciences; Yang, Zong-liang; Dickinson, Robert E.; Guenther, Alex; Jackson, Charles; Sharp, Jr., John M.; Wilson, Clark R.Land surface areas, which represent approximately 30% of the Earth’s surface, contribute largely to the complexity of the climate system by exchanging water, energy, momentum, and chemical materials with the overlying atmosphere. Because of the highly heterogeneous nature of the land surface and its rapid transformation due to human activities, future climate projections are less certain on regional scales than for the globe as a whole. The work presented in this dissertation is focused on a better understanding of regional-scale land–atmosphere interactions and their impacts on climate and air quality. Specifically, I concentrate my research on three typical regions in the United States (U.S.): 1) the Central U.S. (representing transition zones between arid and wet climates); 2) the Houston metropolitan region (representing a major urban area); and 3) the eastern U.S. (representing temperate forested regions). These regions are also chosen owing to the consideration of data availability. The first study concerns the roles of vegetation phenology and groundwater dynamics in regulating evapotranspiration and precipitation over the transition zones in summer months. It is found that the warm-season precipitation in the Central U.S. is sensitive to latent heat fluxes controlled by vegetation dynamics. Groundwater enhances the persistence of soil moisture memory from rainy periods to dry periods by transferring water to upper soil layers through capillary forces. Enhancement in soil moisture facilitates vegetation persistence in dry periods, producing more evaporation to the atmosphere and resulting in enhanced precipitation, which then increases soil moisture. The second study compares the impacts of future urbanization and climate change on regional air quality. The results show that the effect of land use change on surface ozone (O3) is comparable to that of climate change, but the details differ across the domain. The third study deals with the formation and distributions of secondary organic aerosols (SOA) — a largely overlooked but potentially important component in the climate system. Under future different climate scenarios, I found that biogenic emissions — an important precursor of SOA — are expected to increase everywhere over the U.S., with the largest increase found in the southeastern U.S. and the northwestern U.S., while changes in SOA do not necessarily follow those in biogenic emissions. Other factors such as partitioning coefficients, atmospheric oxidative capability, primary organic carbon, and anthropogenic emissions also play a role in SOA formation. Direct and indirect impacts from climate change complicate the future SOA formation.