Master of Science (M.S.), University of Dayton, 2025, Interdisciplinary Studies

This study assesses groundwater recharge dynamics in the Gilgel Gibe, Gombora, and Neri watersheds of the Omo Gibe River Basin (OGRB), Ethiopia, using a comparative approach that integrates stable isotope mass balance and the WetSpass-M hydrological models. The research aims to analyze isotopic compositions of precipitation and groundwater, estimate seasonal and spatial groundwater recharge rates, and evaluate the performance of both models across diverse hydro-climatic zones. The stable isotope approach involved analyzing δ18O and δ2H compositions to establish Local Meteoric Water Lines (LMWLs), seasonal distribution of isotopes, and quantifying seasonal recharge contributions using the oxygen-18 mass balance method. Concurrently, using meteorological and physical data, the WetSpass-M model simulated monthly water balance components, including recharge, surface runoff, and evapotranspiration. Model calibration, validation, and sensitivity analysis were performed using observed streamflow data. Key findings indicate that groundwater recharge is primarily driven by wet-season precipitation, with minimal contributions from the dry season. An isotope analysis revealed that 88.1% and 83.7% of recharge in the Gilgel Gibe and Gombora watersheds, respectively, occur during the wet season. In contrast, the Neri watershed exhibits a more balanced distribution due to its bimodal rainfall pattern. The WetSpass-M model confirmed these results, showing peak recharge during the wettest months and emphasizing the influence of land cover, soil properties, and precipitation. Both methods agreed strongly on seasonal recharge patterns, with isotopes providing direct field-based estimates and WetSpass-M offering high-resolution spatial insights. The study concludes that combining stable isotope techniques with hydrological modeling improves the accuracy and reliability of recharge assessments. It highlights the critical role of wet-season precipitation in sustaining groundwater a (open full item for complete abstract)

MS, Kent State University, 2025, College of Arts and Sciences / Department of Biological Sciences

Eutrophication in lakes is often the result of human activity and land-use changes, particularly the loss of or modification to wetlands, at a watershed-scale. Many state and federal governments are turning to wetland protection, restoration, and construction to meet water quality goals. Better characterization of biogeochemical characteristics related to P-sorption across spatial and temporal scales is needed to inform wetland management decisions and design, set realistic expectations for P storage, and anticipate potential P export events. Here we investigated whether the integrated biogeochemical effects of hydrology and the associated wetland plant community assemblages lead to macro-scale differences in several parameters related to Fe-driven P retention in wetland sediments during the growing season in an intact, freshwater, lacustrine wetland on the coast of Lake Erie (Old Woman Creek Estuary, Huron OH). Additionally, we assessed the magnitude of iron's role in sediment P dynamics, among distinct hydro-eco patches. As hypothesized, we did find significant differences in some parameters related to sediment P biogeochemistry and the Fe to P relationship between hydro-eco patches. Typha-dominated patches showed distinct biogeochemical characteristics, including higher concentrations of porewater Fe, soil P, and P sorption capacity.

Master of Science, The Ohio State University, 2025, Earth Sciences

Megabeds, also known as "megaturbidites," are exceptionally large submarine sediment deposits formed by catastrophic geohazard events. These deposits provide valuable insights into deep marine sedimentation processes and geohazard dynamics, yet their origins and characteristics remain debated. Recently, subbottom profiler data revealed at least four megabeds within the upper 70 meters of sediment in the Marsili Basin of the Tyrrhenian Sea. These deposits are hypothesized to have been triggered by explosive volcanic eruptions of the Campanian Volcanic Province, including the ~39.8 ka Campanian Ignimbrite (CI) super-eruption, which is among the largest known eruptions (VEI = 7). These megabeds were intersected by Ocean Drilling Program (ODP) Leg 107 Site 650, where sediment cores were collected in the late 1980s. However, their presence was not recognized at the time due to lack of geophysical data. To better understand the properties and origins of the Marsili Megabeds, I identified the megabeds within the ODP cores and conducted detailed sedimentological and elemental analyses, along with age dating, to determine their possible sediment provenance, depositional mechanisms, and potential triggering events. The findings reveal that the megabeds are more internally complex than previously thought, with variations in their depositional processes. Elemental analysis and age dating suggest a potential link between these megabeds and known eruptions from the Campanian Volcanic Province, including the Neapolitan Yellow Tuffs eruption (14.9 ka), the Masseria del Monte Tuff eruption (29.3 ka), and the Campanian Ignimbrite super-eruption (39.8 ka). A new megabed discovered below the Y-7 tephra is older than 60,300 years but its triggering event is unknown.

Doctor of Philosophy, University of Akron, 2024, Integrated Bioscience

Corrosion in natural gas transmission pipelines poses significant risks to infrastructure integrity, leading to environmental damage and economic loss. This dissertation investigates microbiologically influenced corrosion (MIC) mechanisms and develops detection methods using split-chamber zero-resistance ammetry (SC-ZRA). Microbial cultures were enriched from natural gas pipeline samples, focusing on fermentative and sulfur-metabolizing bacteria, and their corrosion activities were evaluated using SC-ZRA. Chapter I reviewed the threat corrosion posed to carbon steel pipelines transporting oil and natural gas, emphasizing MIC's role. It described the electrochemical nature of corrosion and explained how microorganisms like sulfate-reducing and fermentative bacteria accelerated the process through biofilm formation, production of corrosive metabolites, and disruption of electrochemical balance. The chapter also highlighted electrochemical techniques, particularly SC-ZRA, used to detect and monitor MIC. ZRA allowed real-time observation of corrosion currents and distinguished between biotic and abiotic corrosion activities. Chapter II demonstrated that organic acid production by fermentative bacteria lowered pH, accelerating corrosion through cathodic hydrogen reduction on carbon steel. When buffered with sodium bicarbonate, acidity was reduced, effectively mitigating corrosion. Chapter III explored sulfur-metabolizing bacteria's role in corrosion. Experiments with thiosulfate and thiols showed that these bacteria, particularly Desulfovibrio alaskensis, produced sulfide, promoting corrosion. SC-ZRA measurements highlighted how cysteine degradation and thiosulfate reduction drove electron transfer, leading to metal oxidation. Metagenomic analysis confirmed the presence of genes responsible for sulfate and thiosulfate reduction and hydrogenase activity, indicating that diverse metabolic pathways contributed to corrosion. Chapter IV discussed the integration of microbiol (open full item for complete abstract)

Doctor of Philosophy, University of Akron, 2024, Integrated Bioscience

Over 3,000 iron formation caves (IFCs) have formed in erosion-resistant Fe(III)- rich rocks throughout Brazil. These rocks include banded iron formation (BIF) and canga (BIF/goethite breccia), and serve as some of the leading global iron mining sources. Microbial Fe(III) reduction occurs in IFCs, where a microbe-rich paste (sub muros) is found behind an Fe(III)-(hydr)oxide crust in the ceilings and walls. This microbial Fe(III) reduction is thought to transform insoluble Fe(III) to soluble Fe(II), driving cave formation. Fe(III) reduction is controlled by O2 and organic carbon availability, which are linked to seasonal changes. However, it was unknown how the geochemistry in situ may affect microbial Fe(III) reduction and therefore cave formation. To address this, I conducted a series of microbial incubations and analyzed the chemical and microbial changes. This showed sub muros-associated microorganisms can reduce Fe(III) in BIF, with Acidobacteria, Alphaproteobacteria, and Firmicutes implicated as possible Fe(III) reducers. Fe(III)- and sulfate- reduction genes were detected in several Metagenome Assembled Genomes, indicating a role for sulfate reduction, which may occur concurrently with fermentation, enhancing Fe(III) reduction. Upon aeration, partial Fe(II) oxidation occurred, indicating complete oxidation may have been prevented by a chemical process that stabilized Fe(II). I analyzed the Fe(III) reducing abilities of the sub muros microbial community with a variety of substrates and the subsequent microbial community composition and found that Fe(III) reduction was enhanced with sulfate amendment, corresponding to greater relative abundance of Desulfosporosinus and Clostridium. This study also showed the sub muros microbial community reduced Fe(III) without an exogenous organic carbon source, suggesting organic carbon that percolates into IFCs from the overlying soil can support microbial Fe(III) reduction of the host rocks. These results indicate members (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

The development of commercially available single particle inductively coupled plasma time of flight mass spectrometers (spICP-TOFMS) has made it possible to measure the elemental compositions, mass equivalent diameters, and number concentrations (number of particles detected per volume of analyzed sample) of thousands of individual multi-element nanoparticles and microparticles using a small volume (<10 mL) of sample suspension in minutes. Effective particle analysis by spICP-TOFMS requires a deep understanding of the technical challenges and limitations of the technique. Solution-NP and NP# transport efficiency methods can vary up to a factor of two, resulting in a 20% difference in particle mass equivalent diameters and a factor of two difference in particle number concentrations. Particle transport efficiency depends on the uptake rate. Nanoparticles transport efficiency is ~30% and ~20% at 20 and 60 µL/minute, respectively. Particle transport efficiency decreases for particles larger than ~500 nm. Element- and sample-dependent quasi-continuous backgrounds limit the smallest particle mass equivalent diameter that can be determined in samples. Diluting a sample can reduce element thresholds by a factor of ~2. The smallest detectable amount of each element is sample and isotope dependent. The linear dynamic required to measure nanoparticles and fine microparticles is over seven orders of magnitude. Particles as large as 3170 nm are vaporized, atomized, and ionized in the ICP but produce signals outside the linear dynamic range the instrument using optimized sensitivity. Four ice core samples from the Alto Dell'Ortles glacier, Italy, from pre-Roman (780 BCE) to modern (1955 CE) times with a focus on lead (Pb)-bearing particles were measured by spICP-TOFMS. The number concentration and mass equivalent diameter distributions of all detected insoluble mineral particles were similar in the four samples. However, the number concentration and the mass fraction of Pb i (open full item for complete abstract)

Doctor of Philosophy, Case Western Reserve University, 2024, Geological Sciences

Little is understood about the chemical evolution of banded iron formations (BIFs) subducted into the mantle during the Precambrian era. In general, the mantle becomes more reducing with increasing depth, with much of the deep mantle thought to be below the iron-wustite (IW) buffer. At equilibrium, under shallower mantle conditions, the hematite and magnetite in subducted BIFs would reduce wustite. In more deeply subducted BIFs, where the oxygen fugacity buffer is below IW, the wustite would reduce to iron metal. A key question is how rapidly iron oxide reduction reactions proceed at mantle pressures and temperatures. Fast reaction rate would imply that large amounts of wustite and/or metal may have precipitated in the deep mantle. BIFs that reduced to wustite and resisted further reduction could exist in the form of ULVZs (ulta-low velocity zones), as suggested by Dobson and Brodholt (2005). BIFs that fully reduced to iron metal could have produced large volume iron diapirs which would have been capable of sinking into the core and providing an inner core nucleation substrate, as suggested by Huguet et al. (2018). The studies reported here seek to answer these questions by determining the high-pressure, high-temperature reduction rates of iron oxides under mantle conditions. Chapter one describes the various approaches used to recreate banded iron formation subduction at high-pressures and high temperatures. Experiments explore temperatures from 600-1200 oC and pressures from 1.5-15 GPa. Chapter two addresses the first step of BIF reduction—the reduction of hematite and magnetite to wustite in the upper mantle. Experiments explore 14 temperatures from 600-1400 oC and pressures between 2-14 GPa. Chapter three addresses the final step in BIF reduction—the reduction of wustite to iron metal in the lower mantle.

Master of Science (MS), Ohio University, 2024, Geological Sciences

This study investigates the extent, nature, and formation processes of Paleo Lake Buckeye during the Late Pleistocene, located in the Buckeye Creek watershed in the central Appalachian Mountains. This thesis integrates GIS mapping, field methods utilizing sediment coring and trenching, radiocarbon dating and grain size analysis to reconstruct the margins and depositional environments of Paleo Lake Buckeye and its surrounding landscape. Radiocarbon and optically stimulated luminescence (OSL) dating indicate that the lake formed between 20,000 and 40,000 years ago, coinciding with the peak of the last glacial epoch. The stratigraphic analysis shows fine-grained lacustrine deposits, organic rich layers, and episodic coarse-grained beds, which reflects periods of quiet water deposition interrupted by high-energy events. Paleo Lake Buckeye's formation is linked to periglacial conditions, where freeze thaw cycles mobilized sediments and permafrost dynamics influenced hydrological processes. This research not only interpret the paleoenvironmental conditions of the Buckeye Creek watershed during the Late Pleistocene, but also contributes to broader discussions on glacial and periglacial processes, climate variability, and landscape evolution in the central Appalachian Mountains.

Master of Science (MS), Ohio University, 2024, Geological Sciences

Blueschists are an important petrogenetic indicator of subduction and the first appearance of blueschists in the geologic record is commonly taken as evidence for the start of modern-style plate tectonics on Earth. The oldest known blueschists are Neoproterozoic in age, so studies of these blueschists may provide information about the processes and conditions associated with the initiation of plate tectonics on Earth. Of the known Neoproterozoic blueschist localities, the Anglesey (Wales, UK) blueschists are of particular importance because they contain the mineral lawsonite and are thought to be the oldest known lawsonite-bearing rocks in the geologic record. Petrographic, bulk-rock geochemical, and mineral composition and zoning data were acquired to better understand the protolith of the Anglesey blueschists, the conditions (P-T) under which they formed, and their metamorphic evolution. The bulk-rock major and trace element compositions of the metamafic rocks in the Anglesey blueschist belt are generally consistent with a mid-ocean ridge basalt (MORB) protolith, although some samples display variable enrichments in the large ion lithophile elements (LILEs; Cs, Ba, Rb), as well as Sr, Pb, and U. Incompatible trace element systematics suggest most samples underwent seafloor alteration prior to subduction. The most common amphiboles in the Anglesey blueschist belt are glaucophane, winchite, actinolite, riebeckite, and magnesio-riebeckite. Amphiboles in the blueschist facies rocks have core-to-rim zoning and record a transition from calcic/sodic-calcic amphiboles (winchite and/or actinolite cores) to sodic amphiboles (glaucophane rims). Riebeckite and magnesio-riebeckite are most common in greenschist and transitional greenschist-blueschist facies rocks, where they display patchy zoning and compositional variations in Fe3+ and Al. Differences between the amphiboles developed in the greenschist and blueschist facies rocks likely reflect variations in the pressure- (open full item for complete abstract)

Master of Science, The Ohio State University, 2024, Evolution, Ecology and Organismal Biology

Eutrophication of freshwater ecosystems is a global environmental problem often caused by excess bioavailable phosphorus (P). Thus, it is important to understand the sources and sinks of bioavailable P in a watershed. Previous work suggests that during high flow events, which dominate annual P and sediment loads, exchange of P between dissolved and particulate forms impacts the bioavailability of P exports to recipient ecosystems. Yet, suspended sediment is derived from many sources on the landscape, which can differ in chemical composition and likely, affinity for P sorption. Human activities can impact sediment source so, it is important to understand the connection of composition to sediment source, and how source influences sediment-P (sedP)-dissolved reactive P (DRP) interactions during high flow. To address this, I collected seven distinct sources (four streambank soils, two cropland soils, and streambed sediment) from a Maumee River tributary; the Maumee watershed is the main source of P fueling Lake Erie cyanobacteria blooms. Using source material collected in May, June, and December, I conducted three experiments which examined sedP-DRP interactions in a simulated high flow environment for 120 hours. I also measured aspects of sediment composition including size, P content, and P saturation (Mehlich-III P:Mehlich-III Fe). Cropland, streambank, and streambed sources were distinct in chemical composition and P sorption rate capacity; streambed and streambank sources had low P saturation and high P sorption during the first day of the experiment. In contrast, cropland sources had high P saturation and low P sorption. My results indicate that sediment source influences sedP-DRP interactions during high flow events, suggesting that changes in land management that alter the relative balances of sediment sources, or P saturation, may influence in stream P transformations and bioavailability of P exports to recipient ecosystems.

MS, Kent State University, 2024, College of Arts and Sciences / Department of Earth Sciences

Understanding how paleoenvironments and biogeochemical cycles operate in response to local sea-level fluctuations at a time when climatic conditions were warmer, and CO2 was higher than today can help contextualize how the Earth will respond to future warming and sea-level rise. The Cretaceous Straight Cliffs Formation of Utah is an ideal study site to investigate the relationship between sea-level, carbon, and nutrient cycling, as it provides an opportunity to observe the transport and delivery of organic matter (OM) and nutrients across a terrestrial-marine margin. Samples were collected from two cores that span the paleoshoreline of the Western Interior Seaway (WIS) and record locations that oscillate between terrestrial (floodplain, fluvial, peat mires), and transitional (estuarine), and marine (near-shore and offshore) depositional environments. Most of these sediments contain high levels of organic carbon, and as local sea level fluctuated, the two cores experienced variable amounts of marine influence during deposition. Marine influence was greater in the older Calico Sequence as indicated by higher sulfur content. The presence of sulfur during the Calico Sequence led to enhanced pyrite formation and enabled phosphorus to be lost from the system, presumably to the open seaway. During the younger A Sequence, a lack of sulfur and abundant reactive iron in the sediments meant that these marginal environments became effective traps for phosphorus during the younger A Sequence, retaining this critical nutrient in marginal terrestrial environments. These indicate how change in the relative abundance of sulfur in reactive iron rich coastal environments can cause a cascading effect of phosphorus cycling and delivery into the open ocean.

Master of Science (MS), Bowling Green State University, 2024, Geology

Soil is at the center of two linked global environmental problems: climate change due to anthropogenic carbon emissions and soil degradation caused by anthropogenic landscape alteration, with 37% of global land and 52% of land in the United States used for agriculture. A robust understanding of soil dynamics can aid in making sustainable management decisions to maximize soil potential for both fertility and carbon sequestration needs. Soil organic matter (SOM) is often used as a proxy for soil health, with humic substances (HS) comprising most of SOM and driving reactivity and recalcitrance in the soil, depending on composition. HS have historically been challenging to analyze due to low solubility and widely varying molecular size, leading to the use of operational definitions and unclear models. Recent advances in spectroscopic techniques, however, have led to the development of sequential fractionation techniques, like the humeomics methodology, that progressively break bonds within the HS structure, allowing for greater characterization and understanding of composition. In this study, SOM from an organically managed farm soil was qualitatively and quantitatively characterized using the humeomics sequential methodology, extracting six primary fractions and two residual fractions. All fractions were characterized for nutrient (TOC, TN, and TP) content, FTIR was used to assess functional groups present, and EEM-PARAFAC analyzed fluorophore groups to calculate descriptive indices and model components. Analysis indicates the SOM within the farm soil is weakly humified, labile, and biologically available, with most OC and N present in the weakly-bound fractions of the SOM structure. Future research could focus on characterizing and comparing soils from conventionally managed agricultural soils, different BMP regimes (including amendment with dredged material), as these are factors known to contribute to variations in SOM quality and nutrient cycling.

Master of Science (MS), Wright State University, 2024, Chemistry

Previously, mineral nucleation was described by Classical Nucleation Theory (CNT), a theory based on the thermodynamic properties of bulk materials. However, an alternative model, known as the Prenucleation Cluster Pathway, has been increasingly used to describe nucleation of minerals. This model considers the presence of thermodynamically stable ion clusters known as “prenucleation clusters” (PNCs). In the present research, the nucleation mechanism of calcium fluoride was investigated to identify evidence of PNCs by means of the ion-selective electrode (ISE) method, where a CaCl2 solution was titrated into a NaF solution while investigating the effects of saturation level and the aqueous ratio of [Ca2+] to [F-]. It was concluded that the nucleation of fluorite is better supported by the Prenucleation Cluster Pathway rather than CNT. However further analysis of the accuracy of ion-pair formation constants is necessary in order to confirm.

Doctor of Philosophy, The Ohio State University, 2024, Earth Sciences

Knowledge of the distribution of Fe2+ and Mg between olivine and melt (the distribution coefficient, KD) is crucial to understand the origin and evolution of magmas. However, there is disagreement regarding which variables (temperature, melt composition, and oxygen fugacity – fO2) influence the value of KD, as well as the magnitude of their effects. To evaluate the dependence of KD on these variables, data were compiled from literature consisting of equilibrium olivine-melt pairs in experiments at controlled temperature, fO2, and 1 atm pressure. The results confirm that KD is essentially independent of temperature and fO2. However, it is strongly dependent on melt composition (particularly the concentration of silica and alkalis). An evaluation of different published formulations for KD using these data demonstrates that the expression of Gee and Sack (1988) is the most accurate and precise. Furthermore, a new and simpler model based on variation of KD with silica and alkalis has been fit to the olivine-melt database. This reproduces KD with the same accuracy and precision as the Gee and Sack (1988) formulation. The olivine-melt database also illustrates that KD can be used to calculate the proportion of the different valence states of iron in the melt (the Fe3+/ΣFe ratio), which cannot be measured using routine analytical techniques. The melt Fe3+/ΣFe can then be related to fO2 using empirical relationships. This method, referred to as the Olivine-Melt Equilibrium (OME) method, reproduces the fO2 imposed on the experiments within ±0.3 log units. This method was applied to compiled data for natural samples from literature from mid-ocean ridges, ocean islands, back-arc basin spreading centers, and volcanic arcs. Olivine-melt calculated values of fO2 for each location investigated agree with the results of independent techniques. These include compiled measurements of Fe3+/ΣFe ratios using Fe K-edge μ-X-ray Absorption Near Edge Structure (XANES) spectroscopy, as we (open full item for complete abstract)

Master of Science, Miami University, 2024, Geology and Environmental Earth Science

Tonopah NV has a long history of mining operations. Between 1900 - 1947 gold and silver were mined from a multitude of districts with a total value of >$1 billion in today's market value. The mine tailings at Tonopah are poorly understood and have the potential for mineral recovery, critical metal recycling, and the potential for ceramics. Bulk samples are composed of quartz, illite, feldspar, and other minor phases. The clay size fraction is primarily quartz, illite, and kaolinite, with occasional expandable clays. TGA results agree with the XRD composition of the samples and highlights the complexity of heterogeneous clay-rich mine tailings. Overall physical characteristics are promising for use in ceramics as anthropogenic ball clay, expected to be effective in ceramic tiles. There is significant potential for Au and Ag recovery, with samples containing low-grade ore concentrations (Ag~11 ppm, Au~0.20 ppm), equating to ~181 kg of gold (6,400 oz) and ~9,980 kg (352,000 oz) of silver resources. There are also elevated levels of Ba, Pb, As, and Ag that are toxic to human health, and proper care should be taken to ensure no additional harm to the environment or human health results from the reprocessing of the mine tailings.

Master of Science, The Ohio State University, 2024, Civil Engineering

Reclamation of abandoned surface mine lands (AML) with coal combustion residuals (CCRs) may reduce AML hazards and beneficially reuse the waste product of coal combustion, CCRs. CCRs pose a risk of leaching harmful trace elements into the environment, endangering human and ecological receptors. Quantification of risk should be site and material specific, to capture the leaching mechanisms and the concentrations of trace elements. This study analyzed two types of Leaching Environmental Assessment Framework (LEAF) leaching experiment data, as well as over 7 years of site water quality analysis from an AML reclaimed with CCRs. In this work, we applied statistical methods and developed geochemical models to evaluate the expected leachate composition and predict future risk of arsenic (As), selenium (Se), and boron (B) from CCR leachate. The expectation of As, Se, and B to leach from a type of CCR, stabilized flue gas desulfurization (SFGD), was calculated with interval censored parametric bootstrapping for mean. The geochemical model was calibrated with Bayesian Inversion methods, allowing highly uncertain mobilization mechanisms of the proposed calcium mineral host phases to be uncovered. Our results indicate the potential for Se and B to leach from SFGD above the chronic aquatic health criteria in a lab setting and As to pose increased cancer risk. However, in a field application, we do not observe elevated risk of As and Se to human or ecological systems. At the site in Conesville, OH, B poses risk to ecological systems and may be sourced from the CCRs placed in the AML, alterations in groundwater flow, or other site minerals. This work contributes an integrated approach to risk analysis. We include both a statistical analysis and geochemical model to predict the expected leachate composition from SFGD. The statistical analysis may be applied to any LEAF experiments conducted for evaluation of beneficial reuse of CCR. The geochemical model, calibrated with Bayesian I (open full item for complete abstract)

Master of Science, University of Akron, 2024, Geology

Partial melting of hydrous phases such as amphibole, biotite, and muscovite occurs in orogens where distributed ductile thinning is causing exhumation of mid- to lower-crustal rocks. The partial melting of these hydrous phases contributes significantly to the physical and chemical evolution of the crust, as well as affecting the crust's strength. The Si-rich melts generated from partial melting reactions of mid- to lower-crustal assemblages migrate toward the upper crust leaving a more mafic restite. Previous laboratory experiments conducted on amphibole-, biotite-, or muscovite-bearing rocks performed at rapid strain rates (10-4/s to 10-5/s) result in brittle deformation due to high local pore pressures. These rapid experiments suggest this brittle behavior is the likely mechanism causing melt segregation in the crust. However, field evidence and slower strain rate experiments (10-6/s to 10-7/s) suggest that crystal plastic processes may be dominant during syndeformational partial melting. To investigate grain-scale melt segregation mechanisms in a common lower crustal protolith, I performed a suite of axial compression and general shear experiments on an amphibole-bearing source rock during syndeformational partial melting at T = 800-975°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s. I also performed axial compression experiments on a biotite-bearing gneiss and a muscovite-bearing quartzite at T = 950°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s to compare the differences in melt development depending on which hydrous phase is partially melting. The Nemo Amphibolite (d = 140 ± 85 μm) is composed of 62 vol% amphibole (Fe-hornblende), 27 vol% plagioclase (andesine; An30Ab69Or1), 8 vol% quartz, and 3 vol% titanite. The biotite-bearing gneiss (d = 80 +/- 40 microns) consists of quartz (43 vol%), plagioclase (andesine (An22Ab77Or1); 40 vol%), biotite (16 vol%), and ~1 vol% muscovite/Fe-Ti oxides. The muscovite-bearing quartzite is composed of 90 vol% q (open full item for complete abstract)

Master of Science (MS), Bowling Green State University, 2024, Geology

Yearly, millions of tons of sediments are dredged from USA lakes and federal navigation channels to maintain the economic activity of ports and harbors. About 1.5 million cubic yards of dredged sediment are excavated yearly from the Western Lake Erie Basin, Ohio. Following the prohibition on dumping dredged material into open water, the State of Ohio recommends finding several beneficial uses for this material, including using the sediment as farm soil amendment. My research examined the health risk assessment of potential heavy metal contamination in specialty crops grown in soils amended with dredged material. The research objectives were to (1) determine the potential bioaccumulation of organic (PAHs) and inorganic (heavy metals) contaminants in specialty crops, (2) determine the expected daily intake of metals, ecological risk coefficient, health risk index, transfer factor, and their implications in soil and human health, and (3) provide insights on ecological and agricultural implications when dredged sediments are used as farm soil amendment. Our soil blends consisted of 100% farm soil, 90% farm soil/10% dredged sediment, and 100% dredged sediment. The ecological risk assessment index (taking into consideration the metal toxicity) indicated that Pb, As, Zn, Cr, Ni, Co, and Cu were below the threshold value of 40 (unitless). Values below 40 represent lower sensitive toxicity to organisms when exposed to the specific metal. Our results indicated a small translocation of Al, Co, Cr, Fe, Mn, Pb, Ni, and Zn into the edible biomass from the mixture soil as reported by the translocation factor. Only arsenic showed enrichment in the edible biomass across all treatments and crops; however, the enrichment decreased as the dredged sediment ratio increased, except for lettuce in the mixture treatment. We also calculated the health risk index that takes into consideration the reference oral dose (maximum exposure with likely no detrimental effects on human health). The a (open full item for complete abstract)

PHD, Kent State University, 2023, College of Arts and Sciences / Department of Biological Sciences

Climate change is exerting profound and far-reaching impacts on ecosystems worldwide, encompassing both aquatic and terrestrial environments. The evolving precipitation patterns and shifting temperature regimes impact fluctuations in hydrology, resulting in shifts in redox conditions which can impact the availability of nutrients like phosphorus (P). Phosphate, the bioavailable form of P, is only present in small amounts within soils, making the biological demand greater than soil phosphate availability. The majority of soil P is present in non-labile forms including organic P and phosphate sorbed to metal oxides like iron (Fe). Microorganisms must content with geochemical and other abiotic factors to access phosphate from these non-labile sources through the use of various strategies including the secretion of enzymes, the production of phosphate solubilizing acids, as well as indirect mechanisms associated with the reduction of Fe oxides. The primary goal of this dissertation was to advance our understanding of how microorganisms access both labile and non-labile forms of P in the presence of changing hydrologic and redox conditions which impact the speciation of Fe that is present, altering phosphate availability. Specifically, I investigated 1) how phosphate availability changes across a permafrost thaw gradient (palsa, bog, and fen) in the presence of iron oxides, 2) how microorganisms access and mobilize chemically diverse phosphorus sources under contrasting redox conditions, and 3) how changes in hydrology, redox, iron mineralogy, and phosphate availability drive shifts in microbial community composition, specifically iron oxidizers, reducers, and phosphate solubilizers. In our first study assessing microbial phosphate accessibility across a permafrost thaw gradient, we found that near surface redox conditions changed as a function of permafrost thaw which impacted phosphate availability. Reducing conditions in the bog promoted the dissolution of Fe oxides, (open full item for complete abstract)

Master of Science, The Ohio State University, 2023, Earth Sciences

Water tables in coastal aquifers respond to a variety of hydrologic forcings, including precipitation, coastal flooding, and tides. Water table fluctuations induce the flow of water and air across shallow organic-rich soils, which affects the supply of nitrogen (N), dissolved organic carbon (DOC), oxygen, and other reactive solutes, and leads to changes in water quality. My goal was to investigate reactive N transport near a fluctuating water table using a meter-long column containing reconstructed coastal soil and aquifer material from a Mediterranean site (Mataro, Spain). I continuously monitored in-situ redox potential, soil moisture, and matric potential and collected frequent pore water samples for analysis of dissolved inorganic N species and DOC over 16 days. Local groundwater containing high concentrations of nitrate-N (16.5 mg/L) was supplied to the column base. As the water table rose and fell, redox potential fluctuated widely from -600 to 600 mV within the zone of variable saturation. Redox potential typically increased upon saturation and declined again as soils drained, with more subtle changes occurring during the first wetting and drying cycle and greater changes occurring during repeated cycles. Pore water analysis shows that nitrate was depleted near the zone of fluctuation, while ammonium, nitrite, and DOC were elevated, relative to groundwater entering the base of the column. When the water table rose, nitrate was transported up into soils from the groundwater, and concentrations fell as denitrification occurred in the presence of DOC. At the end of the experiment, the column was flooded with seawater at the top of the column. Seawater mobilized ammonium, nitrate, and DOC in the vadose zone, but nitrate did not accumulate beneath the water table, presumably due to enhanced denitrification. Seawater flooding therefore has the potential to mobilize accumulations of N in soils if an ample supply of DOC is not present. In the absence of seawater inun (open full item for complete abstract)