Physical Sciences and Mathematics Commons^™

Agricultural Irrigation Induced Evaporation In A Temperate Study Area: A Stable Isotope Approach, Lincoln Grevengoed

Masters Theses

In regions where groundwater is used for irrigation, significant water losses take place due to evaporation. Previous studies demonstrated the utility of stable oxygen and hydrogen isotopes in estimating evaporative water loss experienced during return flow back to an aquifer. Unlike arid regions where the other studies took place, this study examined the region around Kalamazoo, Michigan, the United States, which experiences a more temperate climate. Irrigation in the Kalamazoo area primarily uses center-pivot systems supplied by wells, unlike flood irrigation in previous study areas. Water samples were taken periodically from wells close to center-pivot irrigation systems. Water losses due …

Impact Of Interlayer Cation Composition And Strongly Bound Water On Smectite ẟ²H, As Determined By A Modified Tcea Method, Nadine J. Kanik

Electronic Thesis and Dissertation Repository

Interlayer cation composition and cation hydration enthalpy can potentially affect the excess hydrogen-yield and δ²H of smectitic clays. Complexities arise from condensed atmospheric water adsorbed on the clay, as it constitutes a potential additional source of hydrogen when attempting to measure the δ²H of structural OH groups. To approach this problem, the δ²H of different cation-saturated, dried forms of six Clay Minerals Society Source Clay smectites were measured. A modified sample drying and on-line High-Temperature-Conversion-Elemental-Analysis (TCEA) Continuous-Flow-Isotope-Ratio-Mass-Spectrometry protocol, facilitated isotopic measurements. A stronger interlayer cation hydration enthalpy (Ca²⁺>Na⁺>K⁺), …

Plio-Pleistocene Antarctic Ice-Ocean Interactions In The Ross Sea, Catherine Prunella

USF Tampa Graduate Theses and Dissertations

Warm, intermediate-depth Southern Ocean waters are implicated in recent Antarctic ice mass loss. Direct observations of Antarctic Ice Sheet (AIS) retreat are temporally limited, necessitating paleoceanographic records of ocean-ice interactions during past warm climate intervals. Deepsea and ice-proximal sediments record orbitally-paced glacial-interglacial fluctuations in AIS volume during the Plio-Pleistocene (last 5 million years; Ma), but the total contribution of the AIS and the role of ocean heat in these fluctuations remain unresolved. To address the response of Antarctica’s ice sheets to changing ocean temperatures during the Plio-Pleistocene, International Ocean Discovery Program (IODP) Expedition 374 recovered sediments from the Ross Sea …

Triple Oxygen Isotope Composition Of Carbonates, Jordan A.G. Wostbrock

Earth and Planetary Sciences ETDs

This dissertation presents a method of analyzing the triple oxygen isotope compositions of carbonates, presents an empirical calibration of the carbonate-water equilibrium fractionation line, presents a triple oxygen isotope equipped fluid-rock mixing model for carbonates to see-through diagenesis, and applies all these findings to ancient carbonate samples. Using modern carbonates and associate water, the following equations are calculated to describe equilibrium triple oxygen isotope fractionation of carbonates:

1000lnalpha¹⁸O_cc-wt=2.84x10⁶/T²-2.96 1),

Theta_cc-wt=-1.39/T+0.5305 2).

Using these fractionation equations provides an extremely useful tool to determine whether a carbonate sample is altered or preserves …

Paleoproductivity Of Late Holocene Lake Huron, Jamal Khaled Nigim

Electronic Thesis and Dissertation Repository

The paleolimnology of North America’s Lake Huron is described using lead-210 dating, mineralogy, magnetic susceptibility, total organic carbon (TOC), total nitrogen (TN), carbon:nitrogen (C/N) ratio, grain size, and the δ¹³C_OM and δ¹⁵N_TN of organic matter. Sediment cores from Lake Huron’s 6 depositional basins and Georgian Bay span the Medieval Warm Period, Little Ice Age, and Canadian-European settlement. The main organic matter source is lacustrine algae, as indicated by δ¹³C_OM, δ¹⁵N_TN and C/N. Prior to the 19th century, primary production changes are reflected only by small variations in …