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 CHARACTERIZATION OF LEACHABLE DISSOLVED ORGANIC MATTER FROM BIOSOLIDS AND IMPLICATIONS FOR NUTRIENT RELEASES, MODELING, AND EMERGING CONTAMINANTS(2019) Fischer, Sarah Jane; Torrents, Alba; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Treated wastewater residuals are utilized as a soil amendment to recycle nutrients to agricultural soils. Due to international application, biosolids are also a significant source of anthropogenic dissolved organic matter (DOM) to the environment. The first contribution of this dissertation characterized DOM and nitrogen mineralization rates of anaerobically digested (AnD) biosolids with variable pre-treatments, such as the thermal hydrolysis pretreatment coupled to anaerobic digestion (THP-AnD). There was not strong evidence that differently pretreated-AnD material had largely different aerobic inorganic nitrogen releases when incubated in a sandy loam soil. Variable pools of DOM decayed in soil treatments over time. Biosolids-DOM was then characterized from a greater representation of full-scale stabilization processes including (i) limed stabilization (LT), (ii) aerobic digestion (AeD), and (iii) anaerobic digestion (AnD). These different final stabilization processes produced substantially different leachates characterized by organic carbon content, size-exclusion chromatography, and fluorescence spectroscopy. Traditional optical metrics previously defined for aquatic DOM did not consistently capture fluorescence maxima of the anthropogenic material. Therefore, boundary-based excitation emission matrix (EEM) analyses were re-defined based on local fluorescence maxima. Novel parallel factor analysis (PARAFAC) and spectral database comparisons confirmed that biosolids-DOM contain both common high energy stimulated components and low energy stimulated components that are unique to digested leachates. The third research contribution applied fluorescence suppression experiments to measure interactions of halogenated ECs with contrasting biosolids-DOM types. Despite digested biosolids-DOM containing different humic acid-like or fulvic acid-like signatures than limed leachates, antimicrobial triclocarban and industrial compound 2-4 dichlorophenol suppressed similar high energy fluorescent signatures in all biosolids-DOM. This suggests TCC and 2-4 DCP electronically interacts with smaller aromatic compounds, such as amino acids, and this interaction is not unique to DOM from different waste stabilizations. This study contributes to future bioavailability assays modeling complex effects of leachate quality on halogenated contaminants. This thesis also confirmed the presence of dehalogenating microbes in the anaerobic microbial community structure of a THP-AD system. These results contribute to on-going work assessing solids treatments, where halogenated emerging contaminants can be dehalogenated before land application. This work advances understanding of biosolids DOM leachates, modeling EEM data, and fate of ECs during full-scale solids treatment processes.Item SITE-SPECIFIC INTERACTION OF DOXORUBICIN IN THE IRON RESPONSIVE ELEMENT RNA: IMPLICATIONS IN CELLULAR IRON HOMEOSTASIS AND NON-IRON DEFICIENCY ANEMIA(2014) Alvarado, Luigi Jhon; Dayie, Theodore K; Biochemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A widely utilized chemotherapy drug, doxorubicin, has recently been shown to bind to a mammalian 5′ untranslated region Iron Responsive Element (IRE) RNA. In conjunction with the Iron Regulatory Protein (IRP), IRE RNA is involved in cellular iron homeostasis at the translational level. This tight RNA/protein complex prevents ribosomal assembly, hindering translation initiation of iron storage proteins, e.g. ferritin, under low cellular iron conditions. Conversely, iron overload is conducive to complex dissociation, allowing for up-regulation of the same proteins. However, this system is not entirely efficient. Some anemic patients receive adjuvant chelation therapies upon chronic blood transfusions to sequester excess labile iron. The use of doxorubicin to promote RNA/protein dissociation could potentially allow for downstream up-regulation of ferritin. In this work, I show how doxorubicin interacts with IRE RNA using multidimensional nuclear magnetic resonance, fluorescence spectroscopy, and electrophoretic mobility shift assays. All three approaches converge on the observation that the IRE/IRP complex formation is disrupted by doxorubicin. Obtaining further data on the RNA/protein/drug interactions may lead to unveiling a validated RNA target as a complementary treatment of iron overload disease, e.g. sickle cell anemia.Item MODELING THE PH DEPENDENT OPTICAL PROPERTIES OF AQUATIC, TERRESTRIAL AND MICROBIAL HUMIC SUBSTANCES(2013) Heighton, Lynne Page; Mignerey, Alice C; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Humic substances (HS) and chromophoric dissolved organic matter (CDOM) are ubiquitous, widely impacting environmental processes, yet despite decades of study the link between structure and the unique optical properties evident in HS/CDOM remains elusive. Model compounds derived from a solely microbial source, as well as terrestrial sources from both aquatic environments and soil systems, exhibit many of the same optical properties despite their disparate methods of generation and sources. All show a pH dependent absorbance, exhibit increasing absorbance as wavelength decreases and a loss of absorbance upon borohydride reduction. The link between colored humic substances is their ability to form electronic interactions that extend long wavelength absorbance. The underlying processes by which charge transfer bands or electronic interactions in HS/CDOM are generated are investigated by optical and potentiometic titrations of untreated and borohydride reduced material. Borohydride reduction targets carbonyl functional groups such as aromatic ketones and quinones. The reduction of these groups affects the optical properties by reducing long wavelength absorbance and causing a blue shift in the fluorescence emission spectra. A direct comparison of divergent sources of fulvic and humic acids including an aquatic fulvic acid, Suwannee River Fulvic Acid (SRFA) and a microbial source of fulvic acid, Pony Lake Fulvic Acid (PLFA), the soil derived humic acids, Elliott (EHA) and Leonardite Humic Acids (LHA), an aquatic humic acid Suwannee River Humic Acid (SRHA) as well as Lignin Alkali Carboxylate (LAC) highlights differences between sources of humic material as exemplified by borohydride induced optical changes such as absorbance intensity in the UV and visible range, difference (DA), fractional difference, spectral slope (S), fluorescence excitation-emission matrix spectra (EEMS), and differential emission spectra (DF) as well as quantum yield. Traditional Raman spectroscopy, although capable of providing relevant chemical functional group information, cannot be applied to untreated CDOM because of high fluorescence background. Surface enhanced Raman scattering (SERS) provides the capability of overcoming the florescence background, thus providing useful Raman spectral data. SERS spectra of model compounds and CDOM were collected using roughened silver electrodes. Functional groups were identified from selected borohydride reduced CDOM SERS spectra.