Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item HEALTH IMPACTS OF THERMAL RUNAWAY EVENTS IN OUTDOOR LITHIUM-ION BATTERY ENERGY STORAGE SYSTEM INSTALLATIONS(2024) Zhao, Zelda Qijing; McAllister, Jamie; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study aimed to develop a methodology for characterizing health impacts of large-scale, outdoor, lithium-ion battery energy storage systems (BESS) thermal runaway events. A literature review was conducted to identify toxic gas yields produced during flaming and non-flaming thermal runaway, as well as mass loss rates, gas temperature, typical BESS unit capacity and dimensions, and event durations. Lithium-iron-phosphate and nickel-manganese-cobalt cell chemistries were assessed. The BESS unit thermal runaway events were modeled in Fire Dynamics Simulator with a bounding analysis for wind and ambient temperature. Concentrations were evaluated using Immediately Dangerous to Life or Health values for occupational exposure and the Protective Action Criteria for Chemicals hierarchy values (Acute Exposure Guideline Levels- Level 1, Emergency Response Planning Guidelines- Level 1, Temporary Emergency Exposure Limits- Level 1) for community exposure. Through application of the methodology, a relationship between exposure limit distance and wind speed, ambient temperature, event duration, cell chemistry, and toxic gas species can be assessed. Under the conditions modeled in this project, exposure limits were exceeded at longer distances in the non-flaming scenarios when compared to the flaming scenarios. Wind speed, ambient temperature, event duration, cell chemistry, and toxic gas species were the controlling factors for non-flaming exposure limit distances. Wind speed was the primary controlling factor for flaming exposure limit distances; however, event duration had some influence.Item Sperm Quality Characterization of Male Mummichog (Fundulus heteroclitus) in Response to Legacy Contaminants(2024) Malik, Sabine; Yonkos, Lance; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Historically contaminated rivers persist as hazards to ecosystem and human health despite remediation attempts, impacting the species found in these ecosystems. These rivers contain complex mixtures of legacy contaminants, including dioxins, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons, many of which are classified as endocrine disrupting compounds. Due to this level of contamination, few fish species are pervasive in these systems, an exception being the mummichog (Fundulus heteroclitus), known for its acquired tolerance of contaminated environmental conditions. While female and offspring reproductive success have been well-documented in the literature, few studies have investigated the use of sperm quality as a tool for assessing reproductive harm from contaminant exposure. Therefore, this study aims to demonstrate the usefulness of sperm quality characterization through the use of three assays: computer-assisted sperm analysis (CASA), a bioluminescent adenosine triphosphate (ATP) assay, and a modified Comet assay. This novel method was developed through field-collection of F. heteroclitus in three historically-contaminated tidal rivers in the United States: the Passaic River, NJ, the Christina River, DE, and the Anacostia River, MD. The results of this study not only present a novel method for investigating fish health in contaminated aquatic environments, but also a comparison of differential outcomes that can occur in rivers with varied contaminants and histories of pollution.Item Impact of Plant-Derived Allelochemicals on Harmful Algal Blooms(2023) Armstrong, Christen Taylor; Place, Allen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Harmful algal blooms (HABs) are a global concern in both freshwater and coastal systems; creating dire consequences for public health, water resources, and local economies. Thus, there is a focus among scientists and environmental managers on HAB prediction, prevention, and mitigation. Current chemical mitigation methods include algicides such as copper sulphate, chlorination, and hydrogen peroxide, which can have high financial costs and secondary pollution associated with them. The use of natural allelochemicals produced by plants and bacteria has received considerable attention as an alternative to synthetic algicides, as they can have negligible toxins, be highly selective, and easily degraded in the environment. This dissertation is a coalition of research looking into new sources of plant allelochemicals and whether natural levels of allelochemicals in the water column, can impact phytoplankton communities and the presence of toxin-producing algal species. The first objective focused on the use of the waste product: brewer’s spent grain (BSG), as a new control mechanism to inhibit the growth of toxic algae. BSG extract of doses higher than 250mg/L inhibited the growth of freshwater and marine toxin-producing cyanobacteria and dinoflagellate species (Microcystis aeruginosa and Karenia brevis), while not impacting the diatom and chlorophyte tested (Scenedesmus obliquus and Prorocentrum tricornutum). This same dosage of BSG caused cyanobacteria abundance in lake water to decline by 90% within 4 days and chlorophytes to dominate the community by day 6 during a microcosm study. However, an experiment controlling bacteria levels demonstrated that the decline of K. brevis growth was likely due to the increase in abundance or presence of certain types of bacteria growing with exposure to BSG extract rather than due to chemicals released from the BSG. The second and third objectives shifted focus to the New Jersey Pinelands and whether the chemicals released into the water from terrestrial and marine plants in these waters, like phenolic compounds, impact the phytoplankton community and toxin-producing species. The second objective focused on the spatial and temporal distribution of phycotoxins along two New Jersey estuaries using passive samplers and whether the utility of passive samplers was impacted by the excess phenolic compounds in the water. By utilizing passive samplers in New Jersey, phycotoxins not previously reported in the area were described, such as azaspiracids, goniodomin-A and yessotoxins. However, this objective also showed some of the caveats of passive samplers, especially at sites with high phenolic compounds. The third objective focused on identifying the primary environmental drivers of chlorophyll a concentration and phytoplankton community along the freshwater – marine continuum of two New Jersey Estuaries with varying levels of disturbance. This dissertation explored BSG as a novel control method of HABs, and provided new information for monitoring, managing, and modeling HABs based on phenolic content measured in the water.Item EXAMINATION OF THE ASSOCIATIONS BETWEEN SELECTED PERFLUOROALKYL SUBSTANCES AND THEIR ISOMERS WITH BODY WEIGHT IN ADOLESCENTS USING NHANES 2013-2018(2023) Snyder, Jessica A; Payne-Sturges, Devon; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)0ABSTRACT Title of thesis: EXAMINATION OF THE ASSOCIATIONS BETWEEN SELECTED PERFLUOROALKYL SUBSTANCES AND THEIR ISOMERS WITH BODY WEIGHT IN ADOLESCENTS USING NHANES 2013-2018 Jessica Snyder, Master of Science, 2023 Thesis Directed by: Professor Devon Payne-Sturges Maryland Institute for Applied Environmental Health Perfluoroalkyl substances (PFAS), a class of environmentally persistent chemicals, are suspected of having obesogenic properties, with studies thus far being inconclusive. Few past studies of PFAS toxicity have distinguished between isomer types of each PFAS group during analysis, however. In this thesis, data for non-smoking 14-19 year-olds from three cycles of the National Health and Nutrition Examination Survey was analyzed to identify potential associations in adolescents between bodyweight and two major families of PFAS: perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) and to additionally determine if differentiating between linear and branched isomeric groups of two major PFAS families could better elucidate any associations found. In unadjusted models, weighted linear regression of body mass index (BMI) and serum concentrations of branched, linear, and total PFAS isomer groups, all returned positive associations ranging from β (95% confidence interval) of 4.06 (3.44, 4.68) for total PFOS to 12.33 (10.39,14.28) for linear PFOA. When models were adjusted for sex, age, race/ethnic origin and income level, however, only a negative association between BMI and branched PFOS (bPFOS) was found, with β= -1.24 (-2.10, -0.39). Unadjusted weighted logistic regression models of both overweight and obese status resulted in positive associations between obesity and both branched PFOS and total PFOS with odds ratios (95% confidence intervals) of 0.45 (0.27, 0.74) and 0.86 (0.75, 0.99) respectively. After adjusting for potential confounders, the only statistically significant relationship was between branched bPFOS and obesity, with a 56% decrease in the odds of obesity for every unit increase in serum concentration of bPFOS [β =-1.06, adjusted odds ratio= 0.44 (0.26,0.76)]. There was no significant difference between the sexes in any results. The apparent protective effect that bPFOS has against obesity and elevated BMI, notable as a health outcome association in itself, also illustrates that isomeric differentiation is important in studying PFAS, as nPFOS had no statistically significant 1 association by itself while ΣPFOS, used by many studies, did. Thus, the lack of differentiation could mask which PFAS type contributes to any associations discovered.Item COUPLING DNA LABELING AND NEXT-GENERATION SEQUENCING TECHNIQUES TO CHARACTERIZE METABOLICALLY-ACTIVE BACTERIA IN NONTRADITIONAL IRRIGATION WATER(2019) Malayil, Leena; Sapkota, Amy R; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bacteria are ubiquitous in irrigation water resources and can include pathogens that may compromise food safety and public health. However, only a small fraction of total bacterial community members in water can be identified through standard culture-based laboratory methods. 16S rRNA and shotgun sequencing techniques have improved the identification of non-culturable bacteria in water resources. Nevertheless, because sequencing approaches are nucleic-acid based, they are unable to differentiate between the proportion of bacterial communities identified that are live and metabolically-active versus those that are represented by free, relic DNA, not present in viable cells. To bridge this knowledge gap, my dissertation research coupled DNA-labeling (using 5-bromo-2’- deoxyuridine (BrdU) and propidium monazide (PMA)) with next-generation sequencing approaches to identify and comprehensively characterize metabolically-active bacteria in multiple nontraditional irrigation water sources in the Mid-Atlantic region. My aims were as follows: 1) To characterize the metabolically-active fraction of bacterial communities, as well as antibiotic resistance genes and virulence gene profiles in nontraditional irrigation water sources; 2) To evaluate culture-dependent and -independent methods in the detection of metabolically-active pathogenic and non-pathogenic Vibrio species in four nontraditional irrigational water sources; and 3) To track metabolically-active bacterial communities from rooftop-harvested rainwater to irrigated produce in Maryland. Overall, we identified diverse metabolically-active bacterial communities in all nontraditional water sources. Notably, we observed the presence of viable bacteria of importance to both human and/or animal health (Actinobacterium spp., Flavobacterium spp., Aeromonas spp. Pseudomonas spp. and Vibrio spp.). Interestingly, diverse antimicrobial resistance and virulence genes were predominantly found in non-BrdU-treated samples, indicating that these genes can persist in relic DNA and could be transferred to other environmental bacteria through transformation events. We also source-tracked viable bacteria, including Sphingomonas spp., Enterobacter spp., Enterococcus spp, and Citrobacter spp. from rooftop-harvested irrigation water to produce. In summary, this work provides the first description of total, viable, and metabolically-active bacterial communities in different nontraditional irrigation water sources. These data can be used to improve risk characterization of these water sources, and ultimately inform the selection of appropriate cost-effective remediation methods to treat these waters prior to irrigation activities in order to prevent foodborne outbreaks.Item Effect Of Nrf2 Inducers On Honey Bee Gene Expression And Pesticide-Related Mortality(2019) Brandt, Elizabeth A.; Hawthorne, David; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Honey bees are vitally important as pollinators to ecosystems and agricultural economy, yet they are threatened by the presence of pesticides and the wide array of xenobiotics they encounter while foraging. To better understand their metabolic detoxification of these compounds, it is important to elucidate the gene expression pathways involved in their response to toxin exposure. I investigated the potential detoxification role in honey bees of the Nrf2/Keap1 regulatory pathway, one of the most well-researched cellular toxin response mechanisms in vertebrates. I analyzed the effect of inducers on the toxicity of three different pesticides when exposed to bees, and the effects of Sulforaphane on select detoxification gene expression. Inducer consumption effects on pesticide toxicity ranged from synergistic to abrogative depending on the pesticide tested. PCR analysis of gene expression did not reveal significant effects of inducer consumption on expression of detoxification genes. This study and its results lay important groundwork for future research of this regulatory pathway in honey bees.Item A TISSUE-ENGINEERED PLACENTAL BARRIER MODEL FOR TOXICOLOGY AND PHARMACOLOGY APPLICATIONS(2019) Arumugasaamy, Navein; Fisher, John P; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Throughout history, there have been two major instances where a substance caused thousands of birth defects, yet it took a few years for the causation to be noted: thalidomide, in the late 1950s and early 1960s, and Zika Virus, just recently in 2014 to 2016. In both instances, the developing fetus was indirectly exposed to the substance through the placental barrier. Pregnant women took thalidomide as a medication or were stung by mosquitos and exposed to Zika Virus. These examples clearly show why models of the placental barrier and downstream fetal tissues are critically needed. Herein, I present our work on the development and utilization of a biomimetic placenta-fetus model. The three objectives in this work were to: (1) develop and validate the tissue-engineered BPB model through study of biologically relevant substances; (2) assess the effects of SSRIs on the BPB’s cells and evaluate the drugs’ transport profile across the barrier; and, (3) assess how SSRIs influence cardiomyocyte signaling and injury biomarker release following passage through the BPB. We suggest that this work provides a critically needed and biologically relevant placenta-fetus model, useful as a method to assess pharmacology and toxicology properties of medications and other substances. Moreover, the knowledge gained through the studies performed may hopefully improve clinical care of pregnant women through enhanced understanding of how a medication impacts both the pregnant mother-to-be and her developing fetus.Item Diversity, dynamics, and dissemination of microbial communities in reclaimed and untreated surface waters used for agricultural irrigation(2019) Chopyk, Jessica; Sapkota, Amy R; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)High quality freshwater is a vital resource for sustaining agriculture and feeding a growing global population. Yet, due to increasing declines in groundwater, key food production regions across the world face uncertainty with regard to water availability. Nontraditional irrigation water sources, such as reclaimed water (advanced treated municipal wastewater) and untreated surface water (e.g. creeks, ponds, and brackish rivers), may contribute to sustainable solutions to conserve groundwater supplies. However, the microbial community composition and dynamics within these water sources are typically poorly characterized and comparative analysis of their microbial communities are rare. Using high-throughput, cultivation-independent sequencing methodologies, this dissertation research focused on three aims: 1) exploring the functional and taxonomic features of bacteria in nontraditional irrigation water sources; 2) assessing the bacterial and viral communities of agricultural pond water in relation to seasonality; and 3) describing the dynamics, composition, and potential dissemination of irrigation water microbiota from a freshwater creek to an irrigated field. The first aim was addressed through a broad investigation of bacteria within agricultural ponds, freshwater creeks, brackish rivers, and reclamation facilities. Through metagenomic-based analyses, features of the bacterial community, such as antimicrobial resistance genes (ARGs) and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) arrays, were found to vary by sampling date and specific site. For the second aim, agricultural pond water was sampled over two time periods and found to harbor diverse bacteria and bacteriophage species, the abundance and composition of which were influenced by factors characteristic of the pond’s topography and seasonality. For the final aim, samples from a creek used actively for agricultural irrigation, as well as samples of pre- and post-irrigated soil, were analyzed. ARGs and virulence factors were identified in the water and soil samples, with the majority being specific to their respective environment. Moreover, analyses of CRISPR arrays from the creek samples indicated the persistence of certain bacterial lineages, as well as specific interactions between creek bacteriophage and their hosts. Overall, this research improves scientific knowledge of bacterial and viral composition, dynamics, and interactions that can be utilized to assess the suitability and safety of nontraditional irrigation water sources.Item The Impact of Private Drinking Water Wells and Animal Feeding Operations on the Incidence of Acute Gastroenteritis in Maryland: A Mixed Methods Approach(2019) Murray, Rianna Teresa Frederika; Wilson, Sacoby M; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)More than 44.5 million people in the United States (approximately 14% of the population) rely on private domestic wells as their primary source of drinking water. The water quality of private wells is not regulated at the state or federal level, leaving homeowners with wells responsible for the safety of their water. Meanwhile, each year, an estimated 48 million people in the U.S. are sickened, 128,000 are hospitalized, and 3,000 die of gastrointestinal (GI) illnesses caused by microorganisms that are typically transmitted through contaminated food. Given that the potential of private wells as a non-foodborne transmission pathway for these microorganisms is not well understood, my dissertation evaluated these relationships, as well as characterized the quality of private well water in Maryland. My objectives were to: 1.) Investigate the water quality of private wells in Maryland and the effect of animal feeding operations on this water quality using fecal indicator bacteria; 2.) Investigate associations between the prevalence of private wells and the incidence of campylobacteriosis in Maryland at the zip code level using data from the FoodNet active surveillance System; and 3.) Investigate associations between the prevalence of private wells and the incidence of salmonellosis in Maryland at the zip code level using FoodNet data. My findings demonstrated that 43.2% of private wells tested in Maryland did not meet at least one federal health-based drinking water standard. Additionally, my data showed that the prevalence of private wells in Maryland is a risk factor for the incidence of campylobacteriosis and salmonellosis in the coastal counties of the state. The presence of broiler chicken operations in a zip code is also a risk factor for campylobacteriosis and salmonellosis in coastal counties. These findings provide evidence for the strengthening of private well water regulations and for improving education and outreach to private well owners on proper maintenance and testing for their wells.Item Biomonitoring organochlorine compounds using bald eagles (Haliaeetus leucocephalus) in Voyageur's National Park 2011-2017 and developing new biomonitoring techniques(2018) Eberius, Rachel Ann; Bowerman, William W; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wildlife are used to monitor the presence and persistence of legacy organochlorine contaminants in the environment. In this study, bald eagles (Haliaeetus leucocephalus) were utilized as an indicator of exposure to organochlorine compounds at Voyageur’s National Park, Minnesota from 2011-2017. This demonstrated decreasing concentration trends and a lack of recent inputs of organochlorine compounds. However, the use of organochlorine compounds continues in other parts of the world. Therefore, a technique for using solid phase extraction to quantify organochlorine analytes in avian plasma was developed in order to facilitate international biomonitoring of these compounds. Using this method, organochlorine compounds are extracted from plasma and stored within extraction cartridges during transport from collection site to analysis site. This has important implications for international wildlife biomonitoring. If organochlorine analytes are separated from their matrix at the site of collection, sensitive or hazardous biological materials do not need to be transported or stored.
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