Theses and Dissertations at Montana State University (MSU)
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Item The effect of permafrost thaw and geologic substrate on dissolved organic carbon mobilization and transformation in northern streams(Montana State University - Bozeman, College of Agriculture, 2019) Wologo, Ethan Andrew; Chairperson, Graduate Committee: Stephanie A. Ewing; Sarah Shakil, Scott Zolkos, Sadie Textor, Stephanie Ewing, Jane Klassen, Robert G.M. Spencer, David C. Podgorski, Suzanne E. Tank, Michelle A. Baker, Jonathan A. O'Donnell, Kimberly P. Wickland, Sydney S.W. Foks, Jay P. Zarnetske, Joseph Lee-Cullin, Futing Liu, Yuanhe Yang, Pirkko Kortelainen, Jaana Kolehmainen, Joshua F. Dean, Jorien E. Vonk, Robert M. Holmes, Gilles Pinay, Michaela M. Powell, Jansen Howe, Rebecca Frei and Benjamin W. Abbott were co-authors of the article, 'No evience of dissolved organic matter priming in permafrost stream networks: a circumpolar assessment' submitted to the journal 'Global biogeochemical cycles' which is contained within this thesis.; Stephanie Ewing, Jonathan A. O'Donnell, Jim Paces, Rob Striegl, Duane Froese and Joshua Koch were co-authors of the article, 'Groundwater connection and doc transport in the Yukon River Basin: uranium and strontium isotopes in permafrost catchments' submitted to the journal 'Global biogeochemical cycles' which is contained within this thesis.Permafrost landscapes exhibit unique hydrology that is linked both chemically and physically to nutrient cycling and geochemical processes. Permafrost thaw is expected to result in a positive feedback to Earth's climate system through carbon release to the atmosphere; this potential demands better understanding of hydrologic pathways in permafrost landscapes in the face of global change. The work that follows is divided into two main bodies of research that explore both carbon dynamics and isotope geochemistry of river waters draining permafrost catchments in the Yukon River Basin (YRB). The first study uses in-vitro incubations of stream water from seven permafrost regions to investigate how biolabile carbon additions (acetate) and inorganic nutrients (nitrogen and phosphorus) 'prime' water-column dissolved organic carbon (DOC) decomposition. No priming effect from biolabile carbon addition was evident through changes in DOC concentrations or compositional transformations, but consumption of added acetate was correlated with ambient nutrient concentrations. Sites with fine-textured, ice-rich substrate and proximal thermokarst features had higher ambient DOC and nutrient concentrations, and consequently the fastest rates of acetate consumption. We conclude that the fate of biolabile DOC released from degrading permafrost will depend largely on inorganic nutrient availability in receiving waterbodies. The second part of this thesis focuses on hydrology of intermediate-sized catchments in the YRB. We evaluate uranium isotope activity ratios ([234U/238U]) as tracers of groundwater-surface water connection in thawing permafrost landscapes. Streams draining loess-mantled areas had [234U/238U] values moderately increased relative to meteoric values. Streams draining low-order catchments with rocky substrate and surface disturbance exhibit dramatically increased [234U/238U] values, consistent with groundwater connection. In addition, we observed higher DOC concentrations both in areas influenced by recent thaw and where flow is restricted by ice-rich silt. The transformation of northern stream chemistry will likely continue as northern permafrost environents warm, with greatest resilience of ground ice in loess-blanketed areas not subject to thermal erosion by groundwater. As subsurface storage expands and groundwater exchange intensifies, ecosystems within and connected to northern streams will also be transformed, with implications for resource managers concerned with fish and wildlife management in these systems.Item Structural controls and chemical characterization of brecciation and uranium vanadium mineralization in the northern Bighorn Basin(Montana State University - Bozeman, College of Letters & Science, 2016) Moore-Nall, Anita Louise; Chairperson, Graduate Committee: David R. Lageson; Margaret Eggers, John Doyle, Myra Lefthand, Sara Young, Ada Bends, Anne Camper and CEHSC were co-authors of the article, 'Potential health risks from uranium in home well water: an investigation by the Apsaalooke (Crow) Tribal Research Group' in the journal 'GeoSciences' which is contained within this thesis.; Ranalda Tsosie was a co-author of the article, 'Ree data support oil with a Permian phosphoria formation source as a source of metals for U and V mineralization in the northern Bighorn Basin' submitted to the journal 'Minerals' which is contained within this thesis.The goals of this research were to determine if the mode of mineralization and the geology of two abandoned uranium and vanadium mining districts that border the Crow Reservation might be a source for contaminants in the Bighorn River and a source of elevated uranium in home water wells on the Reservation. Surface and spring waters of the Crow Reservation have always been greatly respected by the Crow people, valued as a source of life and health and relied upon for drinking water. Upon learning that the Bighorn River has an EPA 303d impaired water listing due to elevated lead and mercury and that mercury has been detected in the fish from rivers of the Crow Reservation this study was implemented. Watersheds from both mining districts contribute to the Bighorn River that flows through the Crow Reservation. Initial research used the National Uranium Resource Evaluation database to analyze available geochemistry for the study areas using GIS. The data showed elevated concentrations of lead in drainages related to the mining areas. The data also showed elevated uranium in many of the surface waters and wells that were tested as a part of the study on the Crow Reservation. The author attended meetings and presented results of the National Uranium Resource Evaluation data analyses to the Crow Environmental Health Steering Committee. Thus, both uranium and lead were added to the list of elements that were being tested in home water wells as part of a community based participatory research project addressing many issues of water quality on the Crow Reservation. Results from home wells tested on the reservation did show elevated uranium. Rock samples were collected in the study areas and geochemically analyzed. The results of the analyses support a Permian Phosphoria Formation oil source of metals in the two mining districts. Structural data support fracturing accompanied by tectonic hydrothermal brecciation as a process that introduced oil and brines from the Bighorn Basin into the deposits where the uranium vanadium deposits later formed.Item A molecular basis for uranium toxicity(Montana State University - Bozeman, College of Letters & Science, 2014) Burbank, Katherine Ann; Chairperson, Graduate Committee: Brent M. Peyton; Robert K. Szilagyi was a co-author of the article, 'Development of a computational model to describe U(VI) and Pyrroloquinoline quinone interactions' which is contained within this thesis.; Robert K. Szilagyi and Brent M. Peyton were co-authors of the article, 'The effect of CA 2+ displacement by UO 2 2+ on the biological funtion of methanol dehydrogenase' which is contained within this thesis.; Robert A. Walker and Brent M. Peyton were co-authors of the article, 'A molecular basis of metal toxicity by U(VI) in PQQ dependent bacterial dehydrogenase' which is contained within this thesis.Environmental and health problems associated with uranium extend well beyond its radioactive properties. Hexavelent uranium is a common environmental contaminant that reacts with water to form the dioxo-uranium cation, UO 2 2+. Environmental uranium contamination is the result of a number of activities including uranium mining, production and use of depleted uranium for military purposes, storage and disposal of nuclear weaponry, and fuel for nuclear power plants. Despite the potential importance of the interaction of UO 2 2+ with biologically relevant molecules, only limited molecular insight is available. In a recent publication, the presence of UO 2 2+ in submicromolar concentrations was shown to affect ethanol metabolism in Pseudomonas spp. by displacing the Ca 2+ of the pyrroloquinoline quinone (PQQ) cofactor. Accordingly, the interaction of UO 2 2+ with PQQ is used here as a starting point to carry out both an in vitro and in silico analysis of UO 2 2+ and its interactions with biologically relevant cofactors and metabolites. This work represents a proposed molecular mechanism of uranium toxicity in bacteria, and has relevance for uranium toxicity in many living systems. The structural insights from modeling allow us to expand the scope of potential uranium toxicity to other systems by considering the favorable coordination mode to pyridine nitrogen adjacent to carboxylic and/or carbonyl groups. Consequently, the recent discovery of uranium toxicity at submicromolar levels in bacteria provides relevance to serious environmental and public health issues in the light of current EPA regulation of 0.13 micron uranium limit in drinking water.Item Molecular aspects of uranium toxicity : speciation and physiological targeting(Montana State University - Bozeman, College of Engineering, 2009) VanEngelen, Michael Robert; Chairperson, Graduate Committee: Brent M. Peyton; Robin Gerlach (co-chair)Uranium (U), as the uranyl ion (UO 2 ²+), is a widely distributed contaminant at several Department of Energy (DOE) sites, former war zones, and across the globe. Although many U remediation efforts depend on U-bacterial interactions, little information regarding U-bacterial interactions resolved at the molecular level exist. In this study, experiments were performed aimed at understanding the effect of molecular UO 2 ²+ speciation on bacterial bioaccumulation and toxicity using an environmental Pseudomonas sp. isolate. Results showed that the charge and stability of UO 2 ²+ species largely controlled the extent of UO 2 ²+ bioaccumulation and UO 2 ²+ toxicity, respectively. Further experimentation, including a combination of in vivo, in vitro, and in silico studies, revealed a specific mechanism of UO 2 ²+ toxicity, the first to be reported. This mechanism involves the binding of UO 2 ²+ to pyrroloquinoline quinone (PQQ), a cofactor present in a number of bacterial dehydrogenase enzymes. Based on the specific binding mode of UO 2 ²+ to PQQ, it is hypothesized that the present work has direct implications for UO 2 ²+ inhibition of flavoproteins, potentially extending the application of the findings of this work to eukaryotic systems. Recent trends suggest that U-related activity will increase in the near future, and therefore understanding fundamental interactions between UO 2 ²+ and living systems is both an environmental and human health imperative.Item UO 2 reoxidation in the presence of chelators and Fe(III) (hydr)oxides(Montana State University - Bozeman, College of Engineering, 2010) Girardot, Crystal Lee; Chairperson, Graduate Committee: Brent M. PeytonA proposed method of limiting uranium (U) migration is the reduction of soluble U(VI) to U(IV) with subsequent precipitation of uraninite, UO 2(S). However, microbially reduced UO 2 may be susceptible to reoxidation by environmental factors, with Fe(III) (hydr)oxides playing a significant role. Little is known about the role that organic compounds such as Fe(III) chelators play in the stability of reduced U. Here we investigate the impact of DFB (desferrioxamine B), citrate, EDTA (ethylenediaminetetraacetic acid), and NTA (nitrilotriacetic acid) on biogenic UO 2 reoxidation with ferrihydrite, goethite, or hematite. Experiments were run in anaerobic batch systems in PIPES buffer (pH 7) with bicarbonate for approximately 80 days. U(VI) concentrations were measured using a kinetic phosphorescence analyzer. Results showed EDTA accelerated UO 2 reoxidation the most at an initial rate of 9.5 micron day -¹ according to the non-zero-order rate equation R = k 1 [chelator], with a rate constant k 1 of 0.049, 0.044, and 0.046 day -¹ for ferrihydrite, goethite, and hematite, respectively. NTA accelerated UO 2 reoxidation with ferrihydrite at a rate of 4.8 micron day -¹ with k 1 = 0.026 day -¹; rates were less with goethite and hematite (0.66 and 0.71 micron day -¹ with k 1 = 0.0038 and 0.0004 day -¹, respectively). Citrate increased UO 2 reoxidation with ferrihydrite at a rate of 1.8 micron day -¹ with k 1 = 0.009 day -¹, but did not increase the extent of reaction, and no reoxidation occurred with goethite or hematite. DFB inhibited UO 2 reoxidation with ferrihydrite, and no reoxidation occurred with goethite or hematite. In all cases, bicarbonate increased the rate and extent of UO 2 reoxidation with ferrihydrite in the presence and absence of chelators. The highest rate of UO 2 reoxidation occurred when the chelator promoted UO 2 and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO 2 dissolution did not occur, UO 2 reoxidation likely proceeded through an aqueous Fe(III) intermediate. The rate of UO 2 reoxidation was dependent on the stability constant between chelator and Fe(III), with DFB likely inhibiting reoxidation due to a very high stability constant (log K = 30.6). These results indicate that common chelators found in U contaminated sites can play a significant role in mobilizing U affecting efforts for bioremediation.