A Hydrologic and Geochemical Investigation of Basin Infiltrated River Water in Alluvial, Basalt, and Combination Alluvial/Basalt Aquifers

Groundwater overdraft is a persistent problem in the western US including in the East Snake River Plain (ESRP) Aquifer (ESRPA), the largest in Idaho. Managed aquifer recharge (MAR) is a tool increasingly utilized for stabilizing aquifer storage volumes and is employed across the ESRP to infiltrate untreated river water through constructed recharge basins. Hydrologic and water quality data from monitoring well networks in the vicinity of three ESRP MAR basins – one each in an alluvial, basalt, and combination alluvial/basalt setting, together representative of the ESRPA – were examined. Processes investigated were hydrologic mixing between ambient groundwater and infiltrated water and whether cation exchange and calcite precipitation/dissolution reactions impacted MAR water. In addition, groundwater level increases and decreases in response to infiltration events were investigated as to whether they indicated the arrival and departure of MAR water at a pumping location. The results also provide suggestions regarding the location of hydrologic and chemical monitor well placement as MAR programs continue to evaluate new sites. A sample analysis provided results consistent with the stratification of infiltrated and ambient groundwater at all three sites. In the alluvial and basalt settings some sampling locations were entirely infiltrated water while at the combination alluvium/basalt setting vertical stratification in the aquifer was inferred. Hydrologic responses to basin inflow events in wells chemically unimpacted by MAR water indicated that water table responses did not necessarily evidence the arrival or departure of infiltrated water but could be the result of a “mound” of infiltrated water growing under the basins that displaced ambient groundwater away from it. At the alluvial site an analysis of samples indicated that reverse cation exchange impacted infiltrated water, but calcite precipitation (if it occurred) did not impact infiltrated water chemistry. Geochemical modeling predicted that the reverse cation exchange processes would continue with increased alluvium interaction, but that calcite precipitation would have a nondetectable impact on the chemistry of infiltrated water and in any case would not be discernable from an analysis of the samples because much of the calcium precipitated as calcite would have been derived from reverse cation exchange. All wells, located between 620 ft (190 m) downgradient and 100 ft (30 m) cross gradient, were chemically impacted by infiltrated water (primary infiltration event average of 24.8 AF [30,590 m3] per day for 54 days) suggesting that these are appropriate distances for chemical monitor wells. However, local heterogeneities in the flow field played a larger role in the movement of infiltrated water than simple distance from the basin. At the basalt site, fracture flow governed hydrologic and chemical impacts. Two distant (greater than 5,280 ft [1,609 m]) locations showed no chemical interactions between the aquifer matrix and infiltrated water. At a third location cation exchange processes may have impacted the samples. The three wells chemically impacted by infiltrated water were within 600 ft (183 m) of the basin while the other locations, 5,280 ft (1,609 m) or greater, were hydrologically impacted but showed no evidence of infiltrated water possibly because preferential flow paths routed the high volumes (primary infiltration event average of 730 AF [900,440 m3] per day for 133 days) away from the wells. Together these results suggest a range in which chemical monitor wells might be located but also demonstrate the significance of flow field heterogeneity. At the combination alluvium/basalt site, wells were located 1,250 ft (380 m) cross gradient and 6,750 ft (2,060 m) downgradient and were not chemically impacted by the basin (infiltration event average of 88.3 AF [180,900 m3] per day for 136 days) suggesting that these locations are too distant to be appropriate for chemical monitoring. Hydrologic responses to infiltration events were observed only in the closer location.masters, M.S., Geography & Geological Science -- University of Idaho - College of Graduate Studies, 2023-0

Differentiating Science Motivational Factors of Adolescent College Students by Career Orientation with a Self-Determination Theory Lens on Variables and Voices – an Explanatory Sequential Mixed Methods Study Utilizing the Academic Motivation Scale in Survey and Interviews

This study investigated how undergraduate college students with different STEM career orientations differ in their motivation toward science education. The purpose of this study was to surface differences in the quality of motivations between groups of students with different orientations toward STEM careers to support them in science education classrooms better. A more in-depth understanding of motivational quality would allow science course instructors to design learning more specific to the types of student motivational profiles. Specifically, five motivational sub-dimensions of the Self-Determination Theory were investigated using the Academic Motivation Scale: amotivation, external, introjected, identified, and intrinsic motivation. This explanatory sequential mixed methods study investigated the the between-groups differences in each motivational sub-dimension quantitatively with a survey and qualitatively with interviews. The researcher conceptualized this study with a critical realist epistemology, applying self-determination theory as theoretical lens of the study. Results show significant differences in intrinsic motivation between all three STEM career orientation groups investigated, those interested in STEM careers, those interested in STEM-related careers, including technical careers and health professions, and those not interested in STEM careers. For all other motivational sub-dimensions, students not interested in STEM careers were significantly different in their motivation from the other two groups. Interviews surfaced the following theme trends for motivational qualities. Students oriented toward STEM careers discussed the challenges of pulling apart dense science concepts to learn as part of their cognitive process to become competent. In contrast, students oriented toward STEM-related careers tended to view the science courses as an externally imposed hurdle toward a career that required learning of knowledge comprised of facts, often not seen as relevant to their career. Overall, the narratives were in line with the empirical results. These outcomes constitute tools for science educators to assess students’ motivational profiles for science alongside authentic perspectives, allowing tangible insight into student views on education and their motivation to learn.doctoral, Ph.D., Education -- University of Idaho - College of Graduate Studies, 2023-0

Characterization of Fusarium Dry Rot Pathogens of Potato and Fusarium Dry Rot Disease Management in the Pacific Northwest of the United States

Fusarium dry rot is a worldwide fungal disease of potato causing seed decay at planting and postharvest tuber decay in storage with lesions appearing as sunken, wrinkled, darkened areas on the periderm and dry, crumbly decayed tissue internally. With average yield losses of 6 to 25%, Fusarium dry rot is one of the most important postharvest potato diseases worldwide. The disease is managed through cultural practices such as wound management and crop rotation, chemical fungicides and use of less susceptible potato varieties. Recently, an increase of Fusarium dry rot has been observed by growers in the Pacific Northwest (PNW) of the United States, a major potato production region of the world where the states of Idaho, Oregon and Washington collectively produce around 11.3 million metric tons of potatoes annually. The reported increase in the disease justified an investigation of potential contributing factors. This study characterized Fusarium diversity associated with Fusarium dry rot of potato in the PNW using molecular and phylogenetic techniques, confirmed pathogenicity of PNW Fusarium isolates to potato, assessed relative aggressiveness of prevalent PNW Fusarium dry rot pathogens to selected potato varieties, screened Fusarium species in vitro for sensitivity to fungicides typically used for dry rot management and investigated fungicide efficacy in both seed treatment application and a field trial.Fusarium isolates were recovered from tuber samples from seed and commercial storages using standard isolation and culturing techniques and single-spored to obtain pure cultures. Isolates were identified to species or species complex by sequencing portions of the translation elongation factor 1-alpha (TEF) and/or phosphate permease (PHO) genes, and identification was confirmed by phylogenetic analysis of selected isolates. For Fusarium species not previously reported as dry rot pathogens in the PNW or worldwide, whole asymptomatic tubers were wounded, inoculated, and incubated, with lesion presence or absence used to determine pathogenicity. The relative aggressiveness of four prevalent PNW Fusarium species on seven potato varieties important to the PNW was determined by wounding, inoculating and incubating whole asymptomatic tubers and then comparing lesion size among both species and varieties. The sensitivity of PNW Fusarium isolates to difenoconazole, fludioxonil and thiabendazole was assessed via three different methods: laboratory sensitivity screening tests using on fungicide-amended agar plates, laboratory tests of fungicide effectiveness as a seed treatment and a field trial testing effectiveness of fludioxonil against Idaho F. sambucinum isolates. Twenty Fusarium species were recovered in this survey of PNW tubers, with F. sambucinum the most prevalent species in Idaho and F. oxysporum the most prevalent in Washington. Both species combined accounted for approximately 50% of isolates recovered from each state. Pathogenicity to potato tuber was confirmed for 14 Fusarium species (F. acuminatum, F. avenaceum, F. cerealis, F. culmorum, F. equiseti, F. flocciferum, F. graminearum, F. oxysporum, F. redolens, F. sambucinum, F. solani, F. sporotrichioides, F. stercicola and F. venenatum) including eight species not previously reported as Fusarium dry rot pathogens in the PNW. More severe Fusarium dry rot was observed with certain combinations of Fusarium species and potato variety, e.g., Umatilla Russet infected with F. sambucinum and Dark Red Norland infected with F. oxysporum. For main effects, F. sambucinum was determined to be the most aggressive of all tested species, followed by F. avenaceum and F. oxysporum. Fusarium redolens and F. culmorum were least aggressive. Results of the fungicide sensitivity experiments indicate that difenoconazole remains a viable dry rot management fungicide. In vitro resistance of F. sambucinum was found in 67% of isolates tested while 43% of F. oxysporum isolates tested were resistant to the fungicide. However, in an experiment testing efficacy of fludioxonil as a seed treatment, in vitro resistance of F. oxysporum to fludioxonil had much less impact on disease levels in fludioxonil-treated seed tubers than F. sambucinum. Data from the two-year field trial indicated fludioxonil-resistant F. sambucinum isolates may increase dry rot incidence and severity in the field and decrease marketable and overall yield when a fludioxonil seed treatment is used. Thiabendazole resistance was found to persist in PNW F. sambucinum isolates, with 71% of isolates tested considered resistant. These findings emphasize the importance of variety selection and fungicide resistance management plans when addressing problems associated with Fusarium dry rot.doctoral, Ph.D., Plant Sciences -- University of Idaho - College of Graduate Studies, 2023-0

Abelian Surfaces with Complex Multiplication Admitting Nonprincipal Polarizations

The theory of complex multiplication of abelian varieties is a useful field of study with applications ranging from the explicit construction of abelian extensions CM-fields to the explicit description of L-functions of abelian varieties in ways which are much easier to carry out than the more general case. In the literature the most commonly studied abelian surfaces are those with a principal polarization. In the present thesis we extend this analysis to describe abelian surfaces with complex multiplication which carry a nonprincipal polarization. We provide a complete characterization of which types of polarizations are possible on abelian surfaces which have complex multiplication by a given quartic CM-field K as well as how to construct them when they do exist. We also derive several necessary conditions for such abelian surfaces to exist as well as provide an existence theorem in limited circumstances.doctoral, Ph.D., Mathematics & Statistical Sci -- University of Idaho - College of Graduate Studies, 2023-0

Leachate Experiments to Evaluate Weathering of Waste Rock for Backfill Aquifers in Restored Open Coal Mine Pits, Powder River Basin, USA

Open-pit mining companies utilize waste rock for landscape restoration which may include the construction of backfill aquifers. Chemical weathering and contaminant transport can be altered in backfill aquifers because of the mining of the waste rock that produces newly available mineral surfaces and nanoparticles that can impact water quality. Waste rock from the Cordero Rojo open-pit coal mine in the Powder River Basin was exposed to benchtop weathering experiments for 20 weeks at temperatures of 5 °C and 20 °C. Leach columns containing 4 kg of waste rock were saturated and drained twice weekly. Collected leachate was analyzed for Eh, pH, alkalinity, specific conductance, and cation and anion concentrations as unfiltered and 0.45-μm and 0.2-μm filtered concentrations. During the experiment, leachate Eh and pH substantially varied during the first 50 days, which corresponds to a period of high specific conductance and alkalinity values. Correspondingly, anion and cation concentrations were the largest during this early weathering stage and the filter fractions indicated multiple weathering processes, such as particle transport, salt dissolution, and sulfide oxidation. After this early weathering stage, all environmental parameters slowly evolved towards a chemical equilibrium of neutral, oxidizing, and low solute conditions. This evolution was reflected in the decline and stabilization or non-detection of metal(loid) concentrations reflective of a shift to primarily bulk aluminosilicate weathering. Over the course of the experiment, the solute trend of certain elements indicated particular weathering processes— cadmium and nanoparticle transport, selenium and salt dissolution, and arsenic and the oxidation of pyrite. Elements that are found in multiple sources, such as iron, indicated multiple weathering processes that occurred in the early weathering stage and throughout the experiment. The mining of the overburden formations created newly available mineral surfaces and nanoparticles that could release elements into solution that were not expected to be present given historical aquifer water quality for the overburden formations.masters, M.S., Geography & Geological Science -- University of Idaho - College of Graduate Studies, 2023-0

Corrosion Behavior in Friction Stir Processed Austenitic Stainless Steel

Chloride induced stress corrosion cracking (CISCC) is particularly deleterious to 300series stainless steels. Examples of CISCC have been reported on the surfaces of Type 304, 304L, and 316L stainless steel components in a variety of environments where chloride is present. Localized pitting generally precedes CISCC, and therefore improving the pitting resistance of a material generally improves resistance to CISCC. Friction stir processing is a proposed technique to repair and mitigate material chloride induced stress cracks by adding molybdenum to the base material. Molybdenum improves pitting resistance and that is why it is used in this experiment. Friction stir processed samples were made by adding 316L and molybdenum powder to 304L stainless steel via friction stir processing. By using electrochemical techniques, an evaluation of the friction stir processed samples was performed to evaluate corrosion resistant qualities of the material. Cyclic polarization results suggests that the addition of the molybdenum through FSP was not beneficial to pitting resistance of the samples. The FSP 304L sample had a pitting potential around 0.3342 V where as the FSP 304L+Mo sample only had a pitting potential of around 0.2872 V. Friction stir processing was beneficial in decreasing the corrosion current and in the case of the FSP 304L+Mo increasing the linear polarization significantly. U-bend samples were also made and tested in an open circuit potential and a 0.2 V static potential. The FSP 304L+316L and FSP 304L+Mo were more noble than the 304L in the open circuit potential analysis and did not fail in the u-bend test yet the surface crack density was higher in the FSP samples. The expirement was terminated at 2472 hours and the FSP 304L+316L and FSP 304L+Mo were removed from the 2.5 M sulfuric acid + 0.5 M sodium chloride solution with no failure. By contrast, the 304L base u-bend sample had a low surface crack density yet failed at 267.5 hours. The potentiostatic analysis revealed that the FSP 304L+Mo sample had improved passivation kinetics.masters, M.Engr., Nuclear Engr & Industrial Mgmt -- University of Idaho - College of Graduate Studies, 2023-0

Economic Impacts of Grazing Production Systems on Cow-Calf Ranches in Southern Idaho under Market Variability

Livestock and land management decisions made by ranchers in the Mountain West have current impacts on ranch profitability as well as long-run impacts on sustainability of the operation. As a result, it is critical for ranchers to understand the economic impacts of management decisions to choose strategies that minimize economic and operational risk. Here, we use a multi-period mathematical optimization model to estimate the economic outcomes of two summer grazing management practices- non-irrigated range land and irrigated pasture grazing, given cattle price projections over a 40-year planning horizon. The model is parameterized for 150- and 300- head operations, using enterprise budgets for Lemhi County, Idaho, and grazing and animal outcome data from the Nancy M. Cummings Research, Extension and Education Center. We also simulated 40-year price trends using historical cattle price data. We find that simulated operations that utilize summer grazing of range lands result in the highest overall profit, regardless of ranch size. We also find that the average annual returns for large ranches that only utilize irrigated pasture are negative. While the average annual returns for small ranches utilizing irrigated pasture are positive, the returns are significantly lower than ranches that use range lands for summer grazing. Our results indicate the economic significance of range land grazing and forage production for the profitability of ranch operations and their resilience to exogenous impacts on production.masters, M.S., Agricultural Economics & Rural Soc -- University of Idaho - College of Graduate Studies, 2023-0

An All-Optical 4-Bit Adder Composed of Fabry-Perot Devices

This work models an all-optical 4-bit adder comprised of Fabry-Perot devices. Each device is composed of 2 silver mirrors on either side of a cavity made of a nonlinear Kerr material. These devices are optically bistable and suitable for fast logic operations on the order of picoseconds. An amplifying buffer is used between devices to adjust the transmitted signal’s amplitude to the desired value, and to provide control for logic operations. This work uses the method of finite-difference time-domain (FDTD) in one-dimensional (1D) space to demonstrate the feasibility of the proposed idea.doctoral, Ph.D., Electrical and Computer Engineering -- University of Idaho - College of Graduate Studies, 2023-0

The Optimization of Biochar for the Removal of Phosphorus from Water

Phosphorous (P) pollution from anthropogenic activities is contributing to increases in eutrophication in freshwater systems. In addition, the demand for plant-available P sources continues to increase globally. Biochar, a substance created through biomass pyrolysis, has shown potential for removing P from wastewater. Numerous published studies indicate that chemically modified biochar is more effective at P removal than unmodified biochar. To identify the most suitable type of biochar for future modification for P removal and storage, several characterization experiments were conducted. After conducting the characterization experiments on fourteen biochar types, four were chosen for further experimentation. These biochars were then chemically altered to optimize P adsorption. The modification agents used were Ca, Mg, Fe cations, and cationic polymers. 4% Fe-modified biochar was determined to be the best and it was incorporated into a bench scale continuous flow reactor with dairy effluent wastewater to simulate real wastewater treatment applications. The biochar was then recovered from the reactor and experiments were done to determine the quantity of recoverable plant available P and total P. The Fe-modified biochar treatment had a significant increase in plant available P from 27 to 138 mg/kg. However, this was still lower than the initial value of unmodified biochar, which was 646 mg/kg and increased to 680 mg/kg after treatment. Total P was highest in the Fe-biochar post-treatment with the flow reactor at 1224 mg/kg, while the unmodified biochar had a total P of 993 mg/kg. Results from the research will enable P recycling using modified biochars that can be used as a soil amendment. To test biochar use for P recycling, a pilot study was conducted at Elk Mountain Farms, Idaho, to assess the effectiveness of Fe-modified biochar in removing P from groundwater impacted by agriculture. The University of Idaho Clean Water Machine, which uses reactive filtration technology, was utilized to remove and recover P from groundwater. The water samples showed that for 4% Fe-modified Pacific Biochar, total P in the water dropped from 0.166 mg/L to 0.019 mg/L between the influent and effluent samples, while ortho-phosphate decreased from 0.102 mg/L to 0.008 mg/L. Total P for the unmodified biochar dropped from 0.091 mg/L to 0.025 mg/L between the influent and effluent samples, and ortho-phosphate decreased from 0.049 mg/L to 0.003 mg/L. Both the unmodified biochar and the Fe-modified treatment showed an increase in total P after being used in the reactive filtration. The unused unmodified biochar had an initial P amount of 725 mg/kg, which increased to 1108 mg/kg after water treatment. Similarly, the Fe-modified treatment had an initial P amount of 614 mg/kg, which increased to 995 mg/kg after water treatment. These results indicate that biochar has the potential to be used to remove P from water, especially if the biochar is modified to do so.masters, M.S., Soil & Water Systems -- University of Idaho - College of Graduate Studies, 2023-0

Depletion Chain Simplification With Pseudo-Nuclides to Model Decay Effects

This work introduces the novel usage of pseudo-nuclides to model decay effects in nuclear fission reactor systems which are otherwise absent from simplified depletion libraries. Pseudo-nuclides are artificial nuclides which, when added to a simplified depletion library, can preserve quantities of interest, such as decay energy release or decay photon activity, which are otherwise significantly under-predicted by simplified libraries. Several dozen pseudo-nuclides are capable of accurately modeling decay effects of hundreds of short-lived radionuclides. The computational resources needed to model the decay effects in depletion systems with simplified depletion libraries with pseudo-nuclides are significantly less than those needed when using simplified depletion libraries without pseudo-nuclides. When compared to the similar method of decay heat precursors for a given system, pseudo-nuclides allow for smaller depletion libraries to be generated because of their ability to more accurately model the fission product irradiation effect on decay heat.doctoral, Ph.D., Nuclear Engr & Industrial Mgmt -- University of Idaho - College of Graduate Studies, 2023-0