Geochemistry Commons^™

Differentiating Biotic Vs. Abiotic Co2 In The Formation Of Pedogenic Carbonate In Agriculture And Natural Dryland Soils, Valeria Isabel Molina

Open Access Theses & Dissertations

Drylands, characterized by low and sporadic precipitation, require irrigation for crop growth. However, irrigation practices can lead to salt accumulation in soil due to high evaporation rates and reduced leaching. In addition to loading salts to soil, irrigation promotes the accumulation of secondary calcite. In natural systems, the formation of pedogenic carbonate (secondary calcite, CaCO3) is critical, impacting the soil properties hydrologically and biogeochemically, and modifying the global carbon cycle over geological time, albeit at a lower rate. In agricultural sites, irrigation water supplies HCO3- and Ca2+, accelerating the rates of CaCO3 formation and releasing abiotic CO2. This study investigated …

Investigating The Petrogenesis Of The Naifeh And Plumeria Seamounts: Insights Into The Geochemical Diversity Of Seamounts Adjacent To The Hawaiian Seamount Chain, Geoffrey Montour

Boise State University Theses and Dissertations

The Naifeh and Plumeria seamount clusters, which consist of 10 submarine volcanoes located ~220km north of the Northwest Hawaiian Ridge, were mapped and sampled by the E/V Nautilus expedition NA101 in 2018. The origin of these seamounts is unknown, but their unique orientation and location imply several possible mechanisms of formation. Four possible mechanisms of formation include: 1) off-axis upwelling of the Hawaiian mantle plume, 2) ancient arch volcanism, 3) intraplate extension and deformation, 4) hotspot volcanism. Investigating the origin of these seamount clusters will better constrain the composition of the underlying mantle, as well as the depth and extent …

The Impact Of Glacial Proximity On The Elemental Composition Of Leachate Derived From Sediment Weathering, Karoline Ford

Theses/Capstones/Creative Projects

This study assesses chemical weathering trends as they relate to glacial retreat. The chemical environment of surfaces exposed to the atmosphere differs significantly from beneath a glacier. As a glacier melts, changes to the biogeochemical processes generate environmental gradients. This study analyzed chemical weathering signals at different distances from a glacial front by comparing the elemental composition of leachate derived from sediments in southeastern Greenland. Samples from proglacial, nonglacial, and moraine locations were weathered in a laboratory setting, and ion chromatography was used to determine the elemental composition of the products. Divergent trends in leachate composition were observed as distance …

Modeled Uranium Series Disequilibria In A Heterogeneous Mantle Underlying Iceland, Dana Andersen

Honors Program: Senior Projects (Public)

Regional lithologic heterogeneities in Earth’s mantle may significantly contribute to variations in magma productivity and crustal generation. Such heterogeneities may be a key factor in the anomalously high rates of magmatism and thickened crust of Iceland, which are not fully explained by the presence of a mantle plume. However, the exact lithologic composition of the mantle underlying Iceland is largely unknown. Recent trace element modeling has suggested a two-component melt source beneath Iceland, consisting of a typical upper mantle peridotite mixing with one of several compositions of pyroxenitic material. This study further investigates these potential melt sources by calculating U-series …

Isotopic Insights Into Water Of Condensation, Cross-Formation Water Flow, And Natural Hydrocarbon Migration In Sedimentary Basins, Lisa J. Molofsky

Open Access Theses & Dissertations

This dissertation applies geochemical tools to track the movement, transformation, and behavior of water and gases in hydrocarbon-bearing sedimentary basins. During petroleum exploration and production, hydrocarbons are generated at the surface along with other fluids naturally present in the formation, such as formation water. In addition, where hydraulic fracturing is used to stimulate shale gas and oil production, a percentage of the injected fracturing fluid also returns to the surface. Understanding the origin and movement of these water sources, as well as targeted and non-targeted hydrocarbon gases is critical to evaluating reservoir performance and properly managing fluids at the surface. …

Study Of Trace Elements In Southern Nevada Spring Waters And Lakes, Hyejeong Lee

UNLV Theses, Dissertations, Professional Papers, and Capstones

Comprehending the natural water resource is imperative for the entire state of Nevada and of particular significance for Southern Nevada, where rapid population growth and climate change are placing significant strain on supplies. This research underscores the significance of water chemistry in identifying potential water source areas through trace elements. For the first time, the study proposed measuring the compositions of the entire suite of metal elements, ranging from Li to U, in over 40 springs in the Moapa Valley and its upper gradient valleys, utilizing the iCAP Qc ICP-MS (Inductively Coupled Plasma Mass Spectrometer) at UNLV. The research evaluated …

Impacts Of Preferential Flow On Tc-99and Np-237 Vadose Transport In Soils At The Savannah River Site, Josh Parris

All Theses

Since the 1950s, the United States has produced approximately 90,000 metric tons of spent nuclear fuel (SNF) (Office of Nuclear Energy, 2022); however, no long-term storage solutions are available. Technecium-99 and neptunium-237, two fission products found in SNF, readily form highly mobile species in oxidizing conditions (Hu, 2008; Bondietti, 1979) and have respective half-lives of 2.13 x 10⁵ and 2.14 x10⁶ years (Hu, 2010). Considering these characteristics, ⁹⁹Tc and ²³⁷Np are two risk-driving isotopes found in SNF storage. The process of macropore-facilitated preferential flow, transport through cracks within a soil matrix, has been recognized to increase …

Quantifying Heterogeneity Along A Hillslope Using Seismic Refraction, Structure From Motion, And X-Ray Fluorescence In The Piedmont, South Carolina, Leah Topping

All Theses

The critical zone (CZ) is the life sustaining outer layer of the earth that spans from the top of unweathered bedrock to the tops of the trees. This dynamic zone is always evolving because a variety of chemical, physical, and biological processes transform bedrock into regolith, creating a spatially heterogeneous CZ architecture. This study aims to investigate the relationships between regolith thickness, seismic velocities, and chemical profiles as a function of slope position and it is hypothesized bedrock composition, fracture density, and foliation are the key factors controlling the physical heterogeneity in the top 1-2 meters of the CZ. To …

Comparing Igneous Geochemical Data From Hawaii And Southern California Via Machine Learning, Miro Manestar

MS in Computer Science Project Reports

Bi-plots are commonly used in geochemical analyses. However, their use can become cumbersome in the case of multi-variate analyses. Therefore, this thesis explores the application of unsupervised machine learning techniques, specifically PCA and K-Means, to analyze large geochemical data sets from two distinct regions, Hawaii and the \acrfull{prb} in Southern California. The IBM Foundational Methodology for Data Science was utilized to ensure proper data preparation and analysis. PCA provided dimensionality reduction, revealing which features correlated most strongly with variances within the data. K-Means clustering allowed for deeper interpretation of the data. The analysis yielded valuable insights into the composition and …

The Phosphorus Puzzle: Why Metal Phosphites Could Be The Missing Piece, Eleanor Boyle, Thomas J. Leyden Iii

Symposium of Student Scholars

It is well understood that phosphorylation of organic molecules is a keystone mechanism toward developing early cell function. However, the source of phosphorous in prebiotic chemistry is under debate. Phosphate minerals were abundant on the early Earth, but they are highly insoluble. In comparison, metal phosphites are significantly more soluble. While they may not have been preserved in the geological record, there are several plausible pathways for their formation under prebiotic conditions. We hypothesize that metal phosphites were a major source of phosphorus. To test our hypothesis, we synthesized and characterized metal phosphites, containing the most abundant cations on the …

Evaluating Fungal Population Response To The Miocene Climatic Optimum: High-Resolution Palynological Insights From The South China Sea And Mcmurdo Sound, Antarctica, Mallory Pilie

LSU Master's Theses

Fungi play key and specific roles in ecosystems, specifically as many have restricted geographic distributions, known host/substrate preferences, and are important local environmental indicators due to their short dispersal distances. This study of fossil fungi from a time interval of pronounced global warming, the Miocene Climatic Optimum (MCO), allows analysis of fungal response to an analogue for future climate change scenarios. The research presented herein is part of a larger project, Fungi in a Warmer World (FiaWW), which is using globally-distributed sediment samples to provide foundational information on fungal community distribution patterns and will provide the first fungi-based climatological reconstructions …

Concept Validation: Collecting Composite Samples To Understand The Presence Of Per- And Polyfluoroalkyl Substances (Pfas) In Michigan Forested Areas, Nicole Renee Sanabria

Masters Theses

This research discusses the results of a state-wide study conducted by The Michigan Department of Environment, Great Lakes, and Energy to assess the presence of PFAS in shallow soils of state-owned forested areas in Michigan utilizing a composite sampling method. One sample collected from each of Michigan’s 83 counties reveals the presence of PFAS in all but one sample, with total PFAS concentrations ranging from non-detect to 2.016 μg/kg (dry weight). PFOS is generally detected at the highest concentrations, ranging from non-detect to 0.88 μg/kg, followed by PFBA, with concentrations ranging from non-detect to 0.69 μg/kg, and PFOA, with concentrations …

Lithium And Lithium Isotope Behavior During High Temperature Solid/Fluid Exchanges: Examples From Iceland And The Izu-Bonin Forearc, Alex Maruszczak

USF Tampa Graduate Theses and Dissertations

The development of a method for lithium isotopic measurement was developed using a quadrupole, single-collector ICP-MS. Measured precision was ±1.00‰ 2σ over a 15-month period based on measurements of international rock standards. A 1-hour leach using cold, HCl was sufficient to remove alteration-related Li in minimally to moderately altered seafloor basalts. Measurements on the Holocene ages lavas from the neovolcanic zones of Iceland suggest no systematic Li isotopic variability among the differing Icelandic sources. Felsic samples from Hekla and Pumice contain elevated Li contents of >18ug/g while the tholeiitic and alkaline basalts are <8ug/g Li. Most of the island lies around MORB values of ~+3 to +5‰ with the exception of Western Volcanic Zone samples that show evidence for seawater inputs. The RN-17 drillcore, which penetrates >3000m through a hydrothermal system in the …

Extreme Differentiation Along Multiple Liquid Lines Of Descent In Strongly Peralkaline Magma Series At Pantelleria (Italy), John C. White, Ray Macdonald, Bogusław Bagiński, Katarzyna M. Liszewska

EKU Faculty and Staff Scholarship

The liquid line of descent from trachyte to pantellerite is controlled primarily by fractional crystallization of alkali feldspar, with whole rock compositions following a fractionation path along the ‘thermal valley’ in the peralkaline haplogranite system Qz-Ab-Or-Ac-Ns and terminating at a minimum on the feldspar-quartz cotectic. Although whole-rock compositions for different pantelleritic suites follow nearly identical paths in a Qz-Ab-Or projection that terminate near the experimental minimum (Qz40.5Or34.5Ab25 at 100 MPa, projected from Ac-Ns), matrix glass from samples with near-minimum compositions record extreme differentiation and form a ‘cotectic delta’ beyond the terminus of the ‘thermal valley’. Although each glass trend shows …

Assessing Ecosystem Health Through Contaminants In The Tijuana River National Estuarine Research Reserve, Nancy Torres

Theses

Although the Tijuana River Estuary (TRE) remains the largest, most-intact coastal wetland in Southern California, it has a history of major changes, much of this related to its location immediately north of the US / Mexico Border. One of the primary challenges is cross-border flows from the rapidly growing city of Tijuana, Baja California, Mexico, and the delivery of wastewater, debris, and sediment to sensitive coastal wetland ecosystems. There is a need to more fully investigate these environmental changes to assess the ecosystem health of the Tijuana River Estuary over time, especially related to pollution impacts. This can inform an …

Cementation And Groundwater Chemistry In Pleistocene Paleodune Deposits Of The Central Oregon Coast, Adrienne Lynn Stephens

Dissertations and Theses

Pleistocene paleodune deposits occur along the Oregon coast, underlying coastal towns, roadways, and associated power and water infrastructure(s). Secondary cementation within these deposits provides some stability, allowing for near-vertical sea cliffs and roadcut outcrops. Yet, slope instability is a prevalent hazard observed within the paleodune deposits. Weakening of cementing agents via changes to groundwater conditions due to altered vegetation, climate change, or contamination, for example, could promote slope instability, threatening lives and infrastructure. This study aims to investigate the variability in the type and degree of cementation and to determine how they are affected by changes in groundwater conditions.

To …

Cryogenic Ridges: A New Speleothem Type, Bogdan P. Onac, Daniel M. Cleary, Oana A. Dumitru, Victor J. Polyak, Ioan Povara, Jonathan G. Wynn, Yemane Asmerom

International Journal of Speleology

Cryogenic cave carbonates have been described from several formerly or presently glaciated karst caves. In most of these occurrences, they precipitated as loose grains or aggregates with various morphologies and sizes. Here, we report on a new speleothem type (cryogenic ridges) identified in Sohodoalele Mici Cave (SW Romania) within a large chamber near the entrance shaft. This study was motivated by the presence of a network of calcite ridges over the stalactites’ surface and by the observation that during winter, these speleothems are covered by a thin ice layer. The higher δ¹⁸O (−3.5 to –1‰) and …

Organic Matter Content And Grain Size Analysis In Seagrass Sediments, Adriana Amrhein, Rip Hale

College of Sciences Posters

Anthropogenic stresses including increased water temperatures, decreased water quality, sea level rise, ocean acidification and sediment biogeochemical processes have caused a significant loss in seagrass meadow acreage. Seagrass meadows provide coastal protection from storms and recently have been emphasized for their importance in sequestering and storing “Blue Carbon” from the atmosphere and ocean. Seagrass meadows can trap this blue carbon in their sediment as organic carbon, and it can be stored for hundreds to thousands of years. Restoration efforts of seagrass meadows in the Virginia coast started in the 1990s and effects of increasing seagrass density can be observed in …

Dust Deposition To The Bermuda Region: A Comparison Of Estimates Using Seasonally-Resolved Measurements Of Aluminum In Water-Column, Aerosol, And Rain Samples, Tara Williams, Peter Sedwick, Bettina Sohst, Joe Resing, Kristen Buck, Salvatore Caprara, Rod Johnson, Dan Ohnemus, Ben Twining, Alessandro Tagliabue

College of Sciences Posters

Dust deposition is a major source of bioactive trace elements to the surface ocean, yet this flux remains difficult to constrain. Previously, time-averaged dust flux has been estimated using surface ocean dissolved aluminum (DAl) concentrations, assumed values for aerosol aluminum solubility (%Al_S), and the residence time of DAl in the surface mixed layer (SML). We apply this method to estimate dust deposition in the Bermuda Atlantic Time-series Study (BATS) region using water-column DAl data from cruises in 2019, which is compared with direct flux estimates from contemporaneous measurements of aluminum in aerosols and rain collected on Bermuda. Seasonal …

Vanadium Partitioning Between Magnetite, Hematite, And A Hydrothermal Fluid: Implications For Iocg And Ioa Deposits, Jeremy Raymond Nederbo

Graduate Research Theses & Dissertations

Iron oxide-copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of iron contained within magnetite and/or hematite as well as copper contained within copper-iron sulfides and gold as a native metal. Their formations have been attributed to magmatic, hydrothermal, or a mixture of magmatic-hydrothermal processes. Vanadium can readily substitute into magnetite via ion exchange due to similar atomic radii and charges as iron and has thus been hypothesized to be an effective tracer of hydrothermal or magmatic inputs. To evaluate the mobility of vanadium in a magnetite-hematite-fluid system, experiments on the partitioning of vanadium between magnetite, hematite and a …