Selenium (Se) is a micronutrient, yet elevated Se can be toxic to aquatic organisms. The range of Se concentrations within which Se uptake goes from insufficient to toxic is very narrow. It is thus important to understand the Se biogeochemical cycle in aquatic systems. In this thesis, the study focuses on changes in Se speciation during uptake by green algae. An optimized method was adopted to quantify and speciate Se in water using flow-injection atomic fluorescence spectroscopy coupled with high-pressure liquid chromatography. Details on the method are given here. For the uptake experiments, the uptakes of four Se species (selenite (Se-IV), selenate (Se-VI), selenocystine (Se-Cys) and selenomethionine (Se-Met)) by the green algae Chlamydomonas reinhardtii were compared. This thesis reports that the algae take up higher amounts of organic Se than inorganic Se. Selenomethionine (Se-Met) had the most rapid uptake, during which Se-Cys was produced. For all experiments, Se-IV was produced and found to sorb onto the algae cells, revealing that Se-IV is an important intermediate compound. Mass balance calculations revealed that more than 90% of Se was lost during uptake, probably to the atmosphere. This study also investigated the release of Se during algae decay to simulate the fate of Se during early-diagenesis. Selenium-rich algae cells were mixed with estuarine sediments at the sediment–water interface in a series of column incubations experiments. During the 7-week incubations, Se speciation was measured at the water–sediment interface and in pore water samples. We found that all the Se released to the pore water was in the form of Se-Cys. Although preliminary, these results highlight the key role of organic-Se species in the biogeochemical cycle of Se in the aquatic environment.

The Alberta Basin has been the subject of various diagenetic studies but the precise understanding of the processes behind deep burial cementation remains unclear. This study investigates late-diagenetic calcites from the Devonian Southesk-Cairn Carbonate Complex with the purpose of constraining temperature, relative timing and chemistry of the paleo-fluids involved during calcite precipitation. Two types of late-diagenetic calcites were petrographically andgeochemicallycharacterized.Whereascalcite-Iresultedfrom thermochemical sulfate reduction, calcite-II precipitated with no or little oxidized organic carbon present. As shown by the Sr isotopic signatures, some reservoirs were exposed to radiogenic Sr-bearing fluids. A slight trend of increasing fluid inclusion homogenization temperatures with depth is only seen in calcite-I, and bitumen reflectance also increases with depth following a normal burial gradient. These results, however, are not conclusive to interpret the influence of tectonically-driven fluids during deep burial.

Thesis (M.S.)--University of Adelaide, Dept. of Geology and Geophysics, 1991. / Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 258-282). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 258-282). Also available on the Internet.

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: 31-34)

Thesis (M. Sc.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Aug. 25, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Earth & Atmospheric Sciences, University of Alberta." Includes bibliographical references.

Thesis (Ph.D.) -- Memorial University of Newfoundland, 1986. / Typescript. Abstract in English and French. Bibliography : leaves 416-444. Also available online.

Thesis (M.S.)--Brigham Young University. Dept. of Geology, 2007. / Includes bibliographical references (p. 41-44).

Thesis (M.Sc.)--Memorial University of Newfoundland, 2006. / Restricted until October 2007. Bibliography: leaves 182-200. Also available online.