Recent Submissions

  • Microbes and sulfur in a cave and karst system

    Robinson, Sasha R.; Slayback, Paul
    Shoshone Canyon Conduit Cave lies five miles west of Cody, Wyoming, and was found during the building of an irrigation tunnel through Cedar Mountain by the Bureau of Reclamation (BoR). As the cave lies within the tunnel, it can only be accessed with permission during the non-irrigation time of year. What makes this cave special is the high number of sulfides and sulfur deposits, alongside the many unique speleothems. To get a better understanding of the ecosystem and development of this karst system, a geobiological survey was completed of the microbiology and mineralogy of this sulfur cave on its speleothems, mineral deposits, and water. An analysis of the microbial population was done through small subunit ribosomal 16S rRNA gene analysis, prepared using a polymerase chain reaction (PCR) to amplify Bacteria and Archea. Within the low biomass we found more Bacteria over Archea, with a prevalence of sulfur metabolizers. Three especially interesting taxa present were Acidithiobacillus, Anaerolinacaea, and Ferroplasma. Petrography done on the mineral and speleothem samples showed diverse crystal growth, while X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) showed a variety of mineral morphotypes. With the amount of elemental sulfur in the cave, the taxa present, and the speleothems present, it is likely that this cave contains a semi-isolated complete sulfur cycle. Findings from this research can help to develop a greater understanding of the geobiology of sulfur karst systems, not just in the Rocky Mountains and the Greater Yellowstone Ecosystem.
  • Ray tracing ocean surface waves with rust

    Irving, Bryce A.; Castelão, Guilherme; Bôas, Bia Villas
    Ray-tracing is a powerful technique used in computer graphics and scientific simulations to model the propagation of waves. When it comes to ocean surface gravity waves, ray-tracing can provide valuable insights into wave propagation, including their interaction with ocean currents and the seafloor. Such insights are crucial for better understanding ocean wave physics and their role in climate, as waves are a major player in heat transfer and the exchange of gases between the ocean and the atmosphere. In the present work, we introduce a novel package to calculate the path of a wave propagating through the ocean. We developed the code in Rust for memory safety, high performance, robustness, and simple testing. The ray tracing uses the Runge-Kutta 4th order and bilinear interpolation methods to reduce integration error. The package includes supporting Python files to visualize the results. The components are tested individually, and the overall output is checked against known idealized cases. With these methods, our Rust crate can trace the propagation of a wave through a variable depth represented in cartesian coordinates and plot the results. These results are significant because accurately tracing the propagation of ocean waves with an efficient language will increase performance making it seamless to run large simulation ensembles. There are many reasonable opportunities for improvement in the future. The accuracy and realism of the program will improve by tracing bundles of multiple rays and accounting for the interactions with ocean currents. Additionally, the computational performance will improve by parallelizing the ray tracing.
  • Nucleophilic substitution reactions in hydrothermal degradation of per- and polyfluoroalkyl substances

    Brooks, Sean E.; Hao, Shilai; Strathmann, Timothy J.
    Per- and polyfluoroalkyl substances (PFAS) are a class of fluorinated surfactants used in aqueous film forming foam, plastics production, and semiconductor manufacturing, among other industrial applications. PFAS are highly recalcitrant and have been demonstrated to toxicologically affect wild organisms and humans. Hydrothermal alkaline treatment (HALT), which involves the rection of PFAS in a subcritical aqueous environment with the addition of a strong base, has been demonstrated to destroy two major categories of PFAS, perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), in highly-concentrated aqueous matrices. This research investigates the reaction mechanisms underpinning HALT by comparing the reactivity of different nucleophiles. Solutions (1M) of four nucleophiles – sodium bromide (nucleophilicity [n] =3.89), sodium hydroxide (n=4.20), potassium iodide (n=5.04), and sodium hydrosulfide (n=5.10 ) – were combined with a concentrated sample of ultrashort chain PFAS trifluoromethane sulfonate (TFMS) and reacted at 350°C for times ranging from 30 minutes to 180 minutes. Defluorination rates were determined by measuring fluoride in the post-treatment samples with a fluoride ion selective electrode (FISE). For each reaction time, sodium hydroxide promoted the greatest defluorination, which was nearly an order of magnitude higher than the next-best performing nucleophile, sodium hydrosulfide, for the 180 minute reaction. The findings from this study extend prior research into long chain PFSAs by experimentally determining the hydroxide amendment as the most effective nucleophile for defluorination of ultrashort chain PFSAs. This study provides further evidence to support the hypothesis that nucleophilic substitution reactions form the mechanism through which defluorination of PFAS occurs in HALT.
  • Quantifying flow regimes in pipelines using rock-flow cell

    Carmosino, Catherine J.
    For multiphase system under flow, as in oil and gas production, flow regime in flow lines are of great importance to efficiently and safely transport fluids. In this research, the flow regime and mixing of the phases that occur in these flow lines are experimentally studied by using a novel device called rock-flow cell, which is a benchtop tool that simulates multiphase flow conditions by controlling temperate, pressure, liquid volume, and rocking conditions (rate and tilt angle). Through the manipulation of these conditions, every type of flow regime can be replicated and analyzed. This research aims to quantify and correlate the flow conditions in the rock-flow cell to those in flow lines by using video images with image analysis, coded in Python, to quantify the flow elements, which will later be used to match with other experiments and simulations of actual flow lines.