Madison Callan
Madison is a senior at the University of Texas at Austin double majoring in Environmental Science, Geological Sciences and Environmental Engineering. For the last year, she has been conducting research for her honors thesis in the Jackson School Undergraduate Honors Research Program under the supervision of Dr. Toti Larson at the Bureau of Economic Geology. Her research focuses on how hydrogen gas is consumed by microbes during storage in porous reservoirs. After graduation in May, Madison plans to attend the University of California, Berkeley for a Masters in Geosystems Engineering.
Abstract:
Renewable hydrogen energy is made possible through the storage of large quantities of hydrogen gas in salt caves and potentially in porous subsurface media. Hydrogen is injected into subsurface reservoirs where it displaces existing fluids, typically brine, oil, or natural gas, and spreads under an impermeable caprock to prevent leakage. Due to hydrogen being such a novel energy resource, there are several concerns and possible limitations associated with large-scale storage. Hydrogen is unstable as a liquid, so it must be stored as a gas; however, natural porous media such as aquifers, salt caverns, and oil or gas reservoirs host diverse microbial communities as deep as several kilometers into the subsurface. While previous studies have been conducted on the future of hydrogen energy, few analyses have been done on the behavior of hydrogen gas in the subsurface, and even fewer investigate the interaction between hydrogen and microbes. This research project focuses on examining the microbial consumption of hydrogen gas in a system able to store excess energy in a porous reservoir (HSPR). Ultimately, this work aims to monitor hydrogen consumption over time and determine the driving biogeochemical reaction pathways that occur in the presence of microbes.
By monitoring hydrogen consumption using Wilcox core, it was concluded that iron-reducing bacteria are the most prevalent microorganism in the system, which produce ferrous iron while depleting hydrogen. The iron-stained sandstone resulted in more hydrogen being consumed than quartz sandstone; however, hydrogen consumption occurs at relatively slow rates on the scale of 105 nM/hr. Abiotic samples proved that in the absence of microbes, little to no hydrogen is lost in comparison to biotic samples. These novel data will contribute to quantifying the difference in hydrogen depletion between quartz sandstone and iron sandstone reservoirs as well as provide a deeper understanding of the reactivity of hydrogen gas in fluids containing abundant microbial communities.
James Sun
James is a 4th year undergraduate student studying geology at the University of Texas at Austin. James has enjoyed working as an undergraduate research assistant over the past couple of years on various projects. For his honors thesis, James is working under Dr. James Gardner (Supervisor) and Wade Aubin (Graduate Supervisor) studying the kinetics of heterogeneous bubble nucleations. After graduation, James plans to attend Colorado School of Mines to pursue studies in economic geology.
Abstract:
The exsolution of dissolved gasses from magmas drives volcanic eruptions. These gasses exsolve by forming gas bubbles in response to decreasing magmatic pressure. Bubbles nucleate from silicate melt either homogeneously or on preexisting surfaces, such as crystals. Heterogenous nucleation is considered favorable because it has a much lower energy barrier than homogenous nucleation, and natural magmas are rarely free of crystals. Despite the importance of heterogeneous nucleation, little is known about how it varies with differing numbers and sizes of crystals in silicic melts. We are conducting an experimental campaign designed to constrain the factors that influence heterogeneous nucleation of bubbles in silicic magmas. We are conducting temperature, pressure, and time-controlled experiments using samples prepared with known numbers and sizes of crystals. Samples with different number densities of crystals of a given size will enable us to determine how bubble number densities relate to crystal abundances.
Samples with varying sizes of crystals will allow us to recognize how nucleation sites (crystal faces, tips, corners) become important with changing decompression conditions. Samples with known crystal concentrations but different melt compositions (rhyolite-trachyte-phonolite) will enable us to discern whether heterogeneous nucleation behavior differs across the spectrum of silicic magma types. When combined with our understanding of homogeneous nucleation, this study will help to construct a more complete model for bubble formation that will elucidate the interplay between heterogenous and homogenous nucleation in erupting silicic magmas.
David Keith
David is a senior in the Jackson School of Geosciences Undergraduate Honors Research Program double majoring in Geosystems Engineering and Hydrogeology and Environmental Science, Geology. David was born in Austin and grew up a lifelong Longhorn but spent most of
his life living in Boerne, outside San Antonio. David is working with Professor M. Bayani Cardenas within the Jackson School and their research focuses on measuring the thermochemical properties of Lake Travis and assessing the impact that recent drought and climate change may have had on the behavior and magnitude of lake stratification typically experienced there. David has recently accepted a full-time position within Occidental Petroleum’s Engineering Development Program as a Production Engineer and looks forward to working on projects modernizing the energy industry. Outside of work and education, David is a passionate outdoorsman, reader, and cinephile and is going to particularly enjoy watching Texas beat A&M in the SEC next year.
Abstract:
Lake stratification is an important process affecting the biogeochemical characteristics of inland lakes throughout the year. Lakes play a critical role in supporting inland life across the globe, providing a source of food, drinking water, biodiversity, and shelter to untold organisms and supporting millions of distinct ecosystems across the Earth. Consequently, understanding the stratification patterns of inland lakes is pivotal to understanding the health of nearby ecosystems and communities. Lake Travis, located outside Austin, Texas, is one of seven freshwater reservoirs in Central Texas collectively known as the Highland Lakes and is the sole source of drinking water for the city of Austin. In the face of anthropogenic climate change and worsening drought, a clear understanding of Lake Travis’ seasonal stratification pattern and its reaction to climatic change is needed to protect and preserve the surrounding communities. Vertical profiling of Lake Travis’ temperature, pH, dissolved oxygen, dissolved carbon dioxide, and specific conductivity, and turbidity—achieved via regular scuba dives over a 12-month period from October 2020 to October 2021—revealed that Lake Travis is a monomictic lake, meaning that it experiences a complete turnover only once a year. During stratification, a lake separates into an upper and lower layer, known as the epilimnion and hypolimnion, respectively. Thermal stratification of Lake Travis appears to occur during summer months, from April to November, while a separate chemical stratification appears to occur during the winter turnover period, from December to March. Time series of each chemical data set data show that during stratification, the rate of carbon cycling increases within the hypolimnion, accompanied by an acidification and accumulation of CO 2 . Vertical profiling dives of Lake Travis resumed in February 2023 in order to characterize the lake stratification pattern under severe drought conditions and draw comparisons to the 2020/2021, pre-drought pattern.
Mercedes Jordan
Mercedes Jordan is a first-generation geophysics (B.S.) honors student at the University of Texas at Austin’s Department of Earth and Planetary Sciences and an undergraduate research assistant at the University of Texas Institute for Geophysics. Mercedes’ research involves radar reflectometry, with current work focused on calibrating surface reflectivity from Kaguya’s Lunar Radar Sounder data using laboratory measurements of permittivity. During her time at UT, Mercedes has been recognized as a college scholar at the top of her class and has participated in the Undergraduate Honors Research Program. Mercedes hopes to pursue a doctoral degree in geophysics with a focus on planetary research following the completion of her undergraduate degree.
Abstract:
The Lunar Radar Sounder (LRS) instrument aboard the Kaguya spacecraft collected extensive radar data during its mission, yet its utility for geologic interpretation was limited by its relative power scaling. Laboratory measurements of permittivity from recently collected Chang’E-5 samples allow for an estimation of the reflection coefficient at the landing site, allowing for an absolute calibration of Kaguya's LRS surface reflectivity. Focused on the Procellarum KREEP Terrane (PKT) region, this study aims to revitalize the LRS dataset, providing a more robust understanding of lunar surface materials within the first 50-75 meters of depth. Given PKT’s lack of rough and sloped terrain, it provides the perfect location for conducting absolute calibration of the signal through radar statistical reconnaissance (RSR) as most of the signal is coherent and specular. The methodology involved extracting surface reflectivity, fitting a distribution of amplitudes near the CE-5 landing site to a Rice probability density model, computing a gain correction factor, and applying this correction factor to the entire dataset. Preliminary results depict three distinct facies in the PKT region, associated with varying degrees of reflectance power. However, these heterogeneities in reflectance cannot be solely explained by surface geology as we see facies transition within the bounds of both mare basalt units. Mapping TiO2 abundance, FeO abundance, and roughness reveals dependencies on ilmenite content, with TiO2 showing a significant correlation with radar surface reflectivity.