Theses and Dissertations at Montana State University (MSU)
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Item SR and U isotopes reveal interactions of surface water and groundwater along the mountain headwaters to intermountain basin transition (Hyalite Canyon and Gallatin Valley, MT)(Montana State University - Bozeman, College of Agriculture, 2018) Miller, Florence Rita; Chairperson, Graduate Committee: Stephanie A. Ewing; Stephanie A. Ewing, Robert A. Payn, James B. Paces, Sam Leuthold and Stephan Custer were co-authors of the article, 'SR and U isotopes reveal the influence of lithologic structure on stream-groundwater interaction along a mountain headwater catchment (Hyalite Canyon, MT)' submitted to the journal 'Water resources research' which is contained within this thesis.; Stephanie A. Ewing, Robert Payn, Sam Leuthold, Stephan Custer, Tom Michalek and James B. Paces were co-authors of the article, 'SR and U isotopes reveal mixing patterns of groundwater and surface water influenced by human management in an intermountain basin (Gallatin Valley, MT)' submitted to the journal 'Journal of hydrology' which is contained within this thesis.Mountainous regions of the western United States are characterized by steep, rapidly eroding mountain headwater streams transitioning to more depositional intermountain basins. The character and flux of water across these process domains is subject to projected changes in mountain headwater snowpack and agricultural and urban land use in rapidly developing intermountain basins. Here we evaluate controls on water/rock, water/substrate, and surface/groundwater interactions within Hyalite Creek and the Gallatin Valley of southwest Montana. We use solute loads and geochemical tracers (87 Sr/86 Sr, Ca/Sr, and [234U/238U]) as indicators of such interactions. Surface water, groundwater, and soil samples were collected between 2016 and 2018. Stream water in upper Hyalite Creek had low 87 Sr/86 Sr values typical of volcanic and sedimentary host rock units, and low [234 U/238 U] values consistent with shorter flow path soil, shallow aquifer or runoff water. Middle Hyalite Creek had increased [234 U/238 U] values, reflecting groundwater inflows from the Madison Group limestones. Lower Hyalite Creek had an increase in 87 Sr/86 Sr values and decrease in [234 U/238 U] values, indicated contributions from Archean gneiss fracture flow. Using mixing models, we estimate inflows from the Madison contribute ~4% during summer baseflow conditions and inflows from the Archean contribute ~2% to ~8% of streamflow during summer and winter baseflow conditions. At the mountain front, diverse Ca/Sr, 87Sr/86Sr, and [234U/238U] ratios were observed as a result of convergent flow in mountain headwaters catchments. In the intermountain basin, divergent flow at the mountain front recharges valley aquifers and combines with infiltration through soils. With distance down-valley, we observe intermediate values of Ca/Sr, 87 Sr/86 Sr, and [234 U/238 U], suggesting mixing of diverse source waters. Higher concentrations of Sr, alkalinity, and Ca/Sr and 87 Sr/86 Sr ratios consistent with soil carbonates suggest water infiltration through soil facilitated the influence of soil secondary carbonates on groundwater geochemistry. Additionally, increased water movement through soil facilitates the increase in anthropogenic loading of NO3- and Cl- in surface and groundwaters. Our results provide novel quantification of groundwater contribution to streamflow in mountain headwaters, and elucidate water quality and quantity controls from the mountain front across the intermountain basin, including valley aquifer recharge, infiltration through soils, and anthropogenic solute influxes to groundwater.Item Soil storage on steep forested and non-forested mountain hillslopes in the Bitterroot Mountains, Montana(Montana State University - Bozeman, College of Letters & Science, 2018) Quinn, Colin Aidan; Chairperson, Graduate Committee: Jean DixonMountain hillslopes are dynamic settings with discontinuous soils affected by a suite of variables including climate, lithology, hydrology, and vegetation. Our study seeks to understand how forest cover influences soil and rock distribution at decadal to century timescales. We focus on a series of post-glacial hillslopes in Lost Horse Creek of the Bitterroot Mountains, Montana. In this system, avalanche paths maintain parallel, topographically similar swaths of forested and non-forested slopes with uniform aspect, lithology, and climate. We combine field observations, fallout radionuclide analysis (210 Pbex & 137 Cs), and remote sensing data to understand both landscape- and fine-scale patterns in soil and rock distribution. Local soil and rock measurements indicate more extensive soil cover (forest = 94.4 + or = 2.6%; non-forest = 88.3 + or = 1.9%) and thicker soils (6cm greater median) in the forested system. We compare landcover-classified rock to topographic metrics from LiDAR data and find a doubling of rock cover (from 40% to 80%) as hillslope angles transition across slopes of ~24-42 ?. Topographic roughness, calculated as the standard deviation of slope, is predictive of only ~60% of total landscape rock cover, but can identify large boulders and coarse-scale outcrops with higher accuracy (79%). These calibrated remote sensing metrics indicate higher rock cover in non-forested regions (34%, compared to 20% in forested areas), though with high uncertainty. Additionally, we measure fallout-radionuclide inventories in soils to explore variations in decadal transport processes and soil residence times. We find distinct 210 Pb and 137 Cs behaviors in forested and non-forested systems, controlled both by unique partitioning of each nuclide within organic and mineral soil horizons, but also due to depth-driven differences in their physical mobility. Average 210 Pb ex inventories in non-forested soils are 33% lower, and half as variable as soils in the forested region (10.45 + or = 0.97 and 15.49 + or = 1.91 kBq/m 2 respectively), while 137 Cs inventories are indistinguishable (4.04 + or = 0.34 and 3.73 + or = 0.42 kBq/m 2). Together, our spatial, field, and isotope analyses suggest forested systems have greater soil storage and longer residence times than non-forested soils, mediated by differences in surface erosion processes within a larger fire disturbance landscape.Item Hyperthermal reactions of O(p3sP) with hydrogen and methane(Montana State University - Bozeman, College of Letters & Science, 2004) Garton, Donna Joan; Chairperson, Graduate Committee: Lee SpanglerHyperthermal reactions of O(3P) occur at the surfaces and in the exhaust gases of spacecraft that travel through the residual atmosphere of the Earth at high altitudes (200-600 km). These reactions may degrade materials through oxidation and erosion, or they may yield internally excited reaction products which emit radiation and contribute to the “signature” of a rocket plume. Crossed-beams experiments were used to study model reactions of O(3P) with H2, D2, CH4, and CD4 at center-of-mass collision energies in the range 8-75 kcal mol^-1. Interpretation of the experimental results has been strengthened by theoretical calculations carried out by collaborators. A study of the OH scattered flux as a function of collision energy has led to the determination of an experimental excitation function in the threshold region for the O(3P)+H2 → OH+H reaction. The experimental excitation function clearly matched the theoretical prediction, which confirmed that the laser-detonation source produces O(3P) atoms. The excitation function for the O(3P) + H2 reaction and the dynamics of the O(3P) + D2 reaction, observed experimentally for the first time, demonstrate that these reactions proceed mainly on triplet potential energy surfaces, with little or no intersystem crossing. Experiments on the reactions of O(3P) with methane have revealed a previously unobserved reaction pathway, which involves H-atom elimination: O(3P) + CH4 → OCH3 + H. The excitation function for this reaction has been measured, and the reaction barrier has been determined to be ∼46 kcal mol^-1. In addition, the expected H-atom abstraction reaction, O(3P) + CH4 → CH3 + OH, has been observed, and the dynamics have been investigated. Theoretical calculations identify a triplet-singlet curve crossing below the triplet barrier for the H-atom elimination reaction, but the observed dynamics indicate reaction exclusively on the two lowest-lying triplet surfaces. While it remains to be seen whether intersystem crossing will affect the outcome of other reactions involving hyperthermal atomic oxygen, unknown reactions which have high barriers are likely to be common in extreme environments such as low-Earth orbit, where spacecraft surfaces and exhaust gases suffer high-energy collisions with ambient atomic oxygen.Item Radiocesium in Montana soils and applications for soil erosion measurement(Montana State University - Bozeman, College of Agriculture, 1984) Arnalds, Olafur Gestur; Chairperson, Graduate Committee: Gerald A. NielsenRadiocesium levels in soils were measured at eleven sites throughout Montana. Cesium was mostly confined to the top of the soil profile. Both lateral and vertical displacement of cesium was attributed to mechanical movement of soil particles. The areal activity of cesium was strongly correlated to annual precipitation (R^2 = 0.92). An equation is given to predict cesium activity from annual rainfall. Methods of calculating soil erosion and deposition are discussed and performed for a wind erosion study site in Pondera County and a small watershed in Teton County. The results indicate that deposition at the wind erosion study site can be quantified. Soil deposition of 70 to 1290 m^3 ha^-1 was measured on the leeward sides of a fence and tree windbreaks while an average of 450 m^3 was lost from the windward sides. An average of 740 m^3 ha^-1 was lost since 1962 from an adjacent wind eroded field. This amounts to 34.8 Mg ha^-1 yr^-1. Soil loss since about 1962 ranged from 300 to 820 m^3 ha^-1 within the upper areas of the watershed studied. A pond at the outlet of the watershed and deposition areas at the toeslope accounted for a relatively small fraction of the soil loss within the watershed. Most of the losses are likely to be from wind erosion. Length of slopes or position within the field were more related to erosion than was steepness of slopes, Estimates of erosion rates based on 137Cs ranged from 16.5 Mg ha^-1 yr^-1 at the summit of the watershed to 45.1 Mg ha^-1 yr^-1 at the midslope. Predictions by conventional methods (wind erosion equation and the Universal Soil Loss Equation) agreed rather closely with the estimates from 137Cs.Item The separation of boron isotopes using ion-exchange chromatography(Montana State University - Bozeman, College of Engineering, 1990) Paulson, Gerald ThomasItem A study of the isotope shift in chromium(Montana State University - Bozeman, College of Letters & Science, 1964) Lincoln, Charles AlbertItem Separation of boron isotopes by gas phase membrane permeation of BF₃(Montana State University - Bozeman, College of Engineering, 1989) Herbst, Ronald ScottItem Reactive scattering of oxygen and chlorine atoms on hydrocarbon surfaces(Montana State University - Bozeman, College of Letters & Science, 1998) Garton, Donna Joan