Theses
Permanent URI for this collectionhttps://hdl.handle.net/1969.6/1140
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Browsing Theses by Department "Environmental Science"
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Item Characterization of green surfactants with Dicarboxylate Polar Head(2023-08) Fritz, Shayden; Billiot, Fereshteh; Xu, Wei; Billiot, Eugene; Olson, MarkThere has been a growing emphasis on developing biodegradable and environmentally friendly surfactants. One such relatively new class of surfactants that fall into this category are amino acid-based surfactants. This research focused on studying the physical properties (critical micelle concentration [CMC] and hydrodynamic radius) of aspartic and glutamic amino acid-based surfactants with two different types of hydrophobic tails (saturated hydrophobic chain with 13 carbons and an unsaturated hydrophobic tail containing 11 carbons). In addition to the varying types of hydrophobic tails and polar headgroups, this study also examined what effect different types of diamine counterions had on the physical properties examined. It is interesting to note that the type of diamine counterion or the amino acid head group, for the most part, had little effect on the physical properties examined. The major factor affecting significant changes in the physical properties was the type of hydrophobic tail. The CMC value obtained for saturated 13 carbon surfactants was significantly lower compared to the surfactant with an unsaturated hydrophobic tail containing 11 carbon chains. The range for the CMC values of saturated 13 carbon surfactant was 6 to 12 mM, while the range of the CMC values of unsaturated 11 carbon surfactant was found to have a value of 33 to 52 mM. The surfactant with the unsaturated 11 carbon chain had a significantly smaller hydrodynamic radius in comparison to the saturated 13 carbon surfactant. The range of the hydrodynamic radius for the unsaturated 11 carbon surfactant had a hydrodynamic range from 1 to 5 nm and the saturated 13 carbon surfactant was between 5 to 8 nm. However, there was one exception to this trend and that was the saturated 13 carbon glutamic surfactant in the presence of 1,2 diaminoethane counterion. It had a significantly larger size than all other surfactants measured. The hydrodynamic radius that was measured from saturated 13 carbon surfactant in the presence of 1,2 diaminoethane had a value of 106.47 nmItem Development and verification of a computational model for the prediction of critical micelle concentrations (CMCs) for monoanionic amino acid-based surfactants(2023-08) Black, Nathan D.; Billiot, Eugene; Billiot, Fereshteh; Olson, MarkIn this research, the critical micelle concentrations (CMCs) of nine novel monoanionic amino acid-based surfactants (AABSs) were experimentally determined and used to validate a CMC prediction model based upon molecular dynamics (MD) simulations. The AABSs were synthesized, purified, and had their CMCs determined via the electrical conductivity method. After parametrizing the AABSs with a hybrid gaff2/ff14SB force field, MD simulations were performed in which they were solvated with various explicit and implicit solvents at concentrations ranging from 0.1 – 100 mM. This produced several parameters which are believed to be representative of the thermodynamics of AABS solutions. A battery of polynomial regression and statistical uncertainty analyses were performed on the concentration-dependent values of each parameter for the AABSs. It was found that using the implicit solvent model IGB8 results in distinct measurement uncertainties before and after specific concentrations that strongly agreed with the experimental CMCs. Utilizing an algorithm based upon the t-test in which these values were identified, the total potential and van der Waal energies were found to be the best predictors of AABS CMCs. This was supplemented by a quantitative structure-property relationship (QSPR) study in which ionization potentials and van der Waal energies were identified as strong predictors for experimental CMCs. It was jointly concluded from the results of MD simulation analysis and QSPR regressions that electrostatic energies restrict the CMCs of this family of AABSs to a particular order of magnitude, while the van der Waal energies distinguish each AABs from one another. This research represents the first documented (and successful) attempt to theoretically predict CMCs for AABSs, as well as a pioneering unification between MD simulation- and QSPR-based theoretical studies.Item Development of bis-bipyridinium and anthracene carboxyimide-based stimuli-responsive soft matter(2023-08) Jakharia, Vandan Paresh; Olson, Mark; Billiot, Fereshteh; Billiot, EugeneThis thesis focuses on the design and synthesis of an array of novel amphiphilic and polymeric molecules as precursors for developing dynamic stimuli-responsive supramolecular materials by harnessing the competency of non-covalent interactions. Over the past decades, bipyridinium-based derivatives have gained tremendous attention due to their applicability as functional units in tunable supramolecular complexes. The innate propensity of functionalized bipyridinium salts to serve as a ?-electron deficient acceptor allows them to undergo ?-? stacking donor-acceptor CT interactions in the presence of ?-electron rich organic molecules. This characteristic feature was employed to develop novel bipyridinium-functionalized amphiphiles and bio-polymeric materials that are capable of engaging in molecular recognition with and facilitating the extraction of melatonin, a neurotransmitter from water. The first project reports the design and development of heptyl and glycol-bridged bis-bipyridinium-based gemini amphiphiles that can undergo template-directed self-assembly. Previous studies indicated that the electrophilic aromatic nature of tetra-cationic bis-bipyridinium gemini amphiphiles can be exploited to form ?-? stacking charge-transfer interactions with ?-electron rich molecules. Thus, in an effort to establish structure-property relationships and understand the effect of the bridging unit, varied bridged bis-bipyridinium gemini amphiphiles were synthesized. They were investigated for their use of melatonin as a template for directed self-assembly processes. The charge-transfer interactions between the units lead to absorption band formation in the visible region of the electromagnetic radiation that can be exploited for various material applications. Upon comparing, the two derivatives in detail, their micellization behavior, surface properties, thermodynamic parameters, UV-Vis absorption, and micellar size exhibited similar characteristics. However, the heptyl-bridged gemini amphiphile responded to templation much more strongly, while the glycol-bridged gemini amphiphile exhibited higher solubility, they both portrayed excellent amphiphile and surface-active characteristics. The second part of this work focuses on employing ?-electron deficient bipyridinium units to design and process functional lipoic ester-based polymeric materials for the indole-base molecular targets from water. A series of lipoic-ester based-bipyridinium functionalized polymers with varying alkyl tail lengths were developed and studied to determine structure-property correlations and analyze their material characteristics. Out of the eight-novel functionalized polymeric materials, bipyridinium-bridged lipoic ester polymer (BLEP) formed polymeric sheets while nonyl-bipyridinium-functionalized lipoic ester polymer (9C-BFLEP) formed coacervates in water. Both materials showed comparable and acceptable efficiency in adsorbing melatonin out of solution by harnessing ?-? stacking charge-transfer interactions in conjugation with the hydrophobic effect. This approach provided a quick and promising method for the remediation of indole-cored molecules from water. Lastly, an anthracene carboxyimide derivative was synthesized with the ability to undergo a photo-induced [4+4] cycloaddition dimerization process. The dimerization can easily be reversed upon heating. The compound was found to be able to have a special feature that allows them to undergo single crystal-to-single crystal photo-dimerization upon exposure to UV light. This controlled switchable characteristic property of anthracene carboxyimide are unique and can be utilized for developing tunable molecular switches with applications where stimuli-responsive materials are required.Item Exploration of relationships between the hail report sizes and the radar-derived convective features and atmospheric environments from ERA5 reanalysis: A study over the contiguous United States(2023-05) Vasquez, Edward Raven; Liu, Chuntao; Shinoda, Toshiaki; Xie, FeiqinHail is a type of frozen precipitation that originates from cumulonimbus clouds with updraft velocities sufficient to suspend hailstones until the terminal velocity of the hail overcomes the updraft velocity. While larger hailstones have been studied extensively due to their significant economic impacts, small hail is also known to cause comparable impacts yet remain understudied due to report biases towards recording larger hail sizes. Consequently, the full spectrum of hail size properties, encompassing both the radar observations and the environmental conditions that produced hail reported at various sizes, is still to be assembled as a unified dataset. To fill this gap, we paired ground hail reports from National Centers for Environmental Information Storm Data, Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) and Meteorological Phenomena Identification Near the Ground (mPING) databases with the attributes of radar-derived convective features and the European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA5) atmospheric vertical profiles to construct a rich dataset. Our study investigates how characteristics of radar reflectivity and atmospheric profiles are related to the size of hail reported over the Contiguous United States, where report density is the greatest and radar network coverage is robust. Convective features extracted from the Multi-Radar/Multi-sensor System (MRMS) allow comparable remote sensing observations of hailstorms. We evaluate the single-polarization radar reflectivity derived Maximum Expected Size of Hail (MESH) performance against reported hail sizes. ERA5 vertical atmospheric profiles are explored to form relationships between the thermodynamic environment including the derived convective indices, hodographs, and the hail sizes. The properties of convective systems and their dynamic and thermodynamic variables in three hail size categories are summarized. Major findings include: • Supplemental datasets, obtained through crowdsourcing and volunteer observers, provide small hail report sizes that align with the broader spectrum of hail properties. • MRMS MESH has some biases toward the reported hail size, as it tends to overestimate small hail and underestimate significant hail sizes. • Hodographs constructed from ERA5 reanalysis vertical wind profiles, composited by region, reveal an apparent increase in low-level streamwise vorticity with increasing hail size. Additionally, regional variations of thermodynamic properties for reported hail events are found in the Contiguous United States. These results provide insights into the relationships between radar observations and atmospheric environments and the sizes of hail, including small hailstones that are often overlooked in previous studies.Item Nitrogen and phosphorus budgets in estuaries of the Texas Coast(2023-05) Marshall, Danielle; Montagna, Paul; Hu, Xinping; Wetz, MichaelEstuaries are highly valuable ecosystems that depend on nutrients for their productivity. On-going urbanization and socio-economic activities are constantly affecting nutrient dynamics and estuarine organisms. The purpose of this study was to determine how hydrology affects nutrient budgets in Texas estuaries through biogeochemical budget modeling under the land-ocean interaction in the coastal zone (LOICZ) guidelines. LOICZ budgets were applied to the seven major estuaries in Texas to address the long-term water, salt, and nutrient budgets to calculate daily averages using various datasets from multiple agencies. The Laguna Madre Estuary was further separated into two budgets: the Lower Laguna Madre Estuary and the Upper Laguna Madre Estuary. The results revealed that the climate gradient plays a crucial role in the water budgets indicating that precipitation is a main driving factor to inflow balance. In addition, inflow balance is a main driving factor to salinity and nutrient concentrations among these estuaries. However, external factors such as urbanization, return flows, and agricultural runoff have elevated the nutrient levels in two estuaries. The Trinity-San Jacinto Estuary had higher daily average dissolved inorganic phosphorus (DIP) and total phosphorus (TP) levels compared to the other estuaries due to the large population density of Houston, TX, and the frequent use of detergents and possible fecal and urine waste in wastewater return flows. In contrast, the Upper Laguna Madre Estuary higher total Kjeldahl nitrogen (TKN) compared to the other estuaries due to its unique geographical features and inflow primarily dominated by sewage and agricultural runoff. The implications of these results are that altered hydrology can alter the nutrient dynamics of these estuaries and can affect biological productivity and water quality in an estuary.Item PH effects on solid phase extractable dissolved organic matter: Expanding the analytical window(2023-08) Elliott, Justin Yoshida; Abdulla, Hussain; Felix, Joseph; Hu, XinpingMarine dissolved organic matter (DOM) is the largest exchangeable organic carbon pool, holding comparable amounts of carbon as CO2 in the atmosphere and exceeding all biomass. DOM constituents are made up of thousands of unique organic compounds with astounding molecular diversity, featuring a wide range of hydrophobicity, size, and acidic or basic properties. Modern high resolution, high accuracy, and fast cycle time mass spectrometers can provide deep molecular insights into complex mixtures but require compatible samples. The inorganic matrix and low DOM concentrations have required organic biogeochemists to rely on Agilent Bond Elut Priority PoLutant (PPL) Solid Phase Extraction (SPE) to isolate and concentrate DOM through hydrophobic interactions. Currently, the standard SPE method has been optimized to maximize recovery? of dissolved organic carbon (DOC) through sample acidification and methanol elution. However, there is a lack of full understanding of the effect of adjusting the sample pH on the extraction efficiency of different DOM compounds. This study investigated the effects of pH modification on the SPE recoveries and the effects of various procedures on the isolated DOM. This study collected water samples from three sites to represent different marine systems (Lavaca River, Baffin Bay and Gulf of Mexico) with unique sources and signatures of DOM. Samples were acidified to pH 2, kept at natural pH, basified to pH 10 or run sequentially where the permeate was further isolated. Various modified methanol elution solvents were tested, comparing methanol, acidic methanol, basic methanol, and combinations of both. The isolated DOM was chemically characterized in positive mode separated with reverse-phase high performance liquid chromatography (RP-HPLC) and in negative mode with Anion Exchange Ion Chromatography (AEX-IC) on an Orbitrap Fusion Tribrid mass spectrometer (OT-FTMS) using data dependent acquisition (DDA). The standard SPE procedure with acidification yielded the highest recoveries but showed bias against dissolved organic nitrogen (DON). The samples that were not acidified, including natural pH or pH 10, yielded a different fraction of enigmatic DOM with a higher nitrogen percentage than the DOM isolates using the standard procedure. We found that through isolating DOM from a water sample at natural pH and pH 2, two fractions of DOM can be isolated, including hydrophobic DOM, acidic DOM, and basic DOM. These results suggest in order to better represent DOM from marine systems, collecting both fractions and analyzing in both positive and negative modes provide a more comprehensive and representative isolate of DOM.Item Socio-Economic drivers of surface water quality impairment(2023-05) Kramer, Mary Louise; Wetz, Michael; Wowk, Katya; Yoskowitz, DavidWater quality is a key factor in ecosystem health. While physical and ecological models of pollution have been widely used to determine water quality, there is a significant gap in the use of socioeconomic metrics in these models. The purpose of this study was to identify and visualize social, cultural, behavioral, and economic drivers of surface water quality impairment. Standardized socio-economic data with links to water quality data were mapped across two study sites: San Antonio Bay and Baffin Bay. A binomial logistic regression model was utilized to identify connections between socio-economic metrics and water quality impairment status. In the San Antonio Bay study site, important predictors of surface water quality impairment were housing type and transportation vulnerability, percentage of 5% or more impervious land cover within 30m if shoreline, amount of developed area, and forest and woody wetland cover. In the Baffin Bay study site, important predictors were minority status and language vulnerability, percentage of 5% or more impervious land cover within 30m of shoreline, forest and woody wetland cover, and amount of cropland. Understanding the interactions between communities and local water quality will allow for more thorough and effective management of water resources.