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- Sulfur isotopes (2)
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Articles 1 - 4 of 4
Full-Text Articles in Physical Sciences and Mathematics
Understanding The Physiology Of Extracellular Electron Uptake In Purple Nonsulfur Bacteria, Michael Singh Guzman
Understanding The Physiology Of Extracellular Electron Uptake In Purple Nonsulfur Bacteria, Michael Singh Guzman
Arts & Sciences Electronic Theses and Dissertations
Microbially catalyzed oxidation-reduction reactions drive nutrient cycling and energy flux on Earth. Photoautotrophs, which include the cyanobacteria (oxygenic) and purple and green sulfur bacteria (anoxygenic), transform light energy into chemical energy and are responsible for substantial global primary productivity. Anoxygenic phototrophs, in particular, play a crucial role in biogeochemical cycling in anoxic illuminated environments because of their ability to oxidize an array of inorganic compounds for CO2 fixation. Electron donors include molecular hydrogen, nitrite, and reduced sulfur compounds. Recent evidence has also suggested that solid-phase conductive substances (SPCSs), including rust (mixed-valent iron minerals) and their proxies (poised electrodes), can serve …
The Effect Of Depositional Environment And Early Marine Diagenesis On Carbonate-Associated Sulfate, Jocelyn Ann Richardson
The Effect Of Depositional Environment And Early Marine Diagenesis On Carbonate-Associated Sulfate, Jocelyn Ann Richardson
Arts & Sciences Electronic Theses and Dissertations
The long-term redox state of Earth’s surface environments is governed by the relative burial proportions of redox-sensitive carbon and sulfur species throughout geologic time. The sulfur isotopic signature of seawater sulfate (δ34SSO4) traces the relative proportions of sulfur buried as sulfide (commonly pyrite) and sulfate (as evaporites, barite or carbonate-associated sulfate) and weathering source to the ocean. Thus, δ34SSO4 is a powerful tool to understand the evolution of redox conditions and the marine biogeochemical sulfur cycle. Due to the spatial and temporal extent of carbonates in the rock record, carbonate-associated sulfate (δ34SCAS) is a common proxy for the isotopic composition …
Local Environmental Controls On Sulfur Isotope Ratios In Marine Sedimentary Iron Sulfide Minerals, Roger Nicholas Bryant
Local Environmental Controls On Sulfur Isotope Ratios In Marine Sedimentary Iron Sulfide Minerals, Roger Nicholas Bryant
Arts & Sciences Electronic Theses and Dissertations
The controls on the bulk sulfur isotopic composition of marine sedimentary iron sulfides (often referred to simply as pyrite; δ34Spyr) are poorly understood. Nevertheless, many have employed δ34Spyr in efforts to reconstruct the past operation of the biogeochemical sulfur cycle, from the planetary scale down to individual microbial metabolisms. This practice has been thrown into doubt by a growing body of evidence that suggests δ34Spyr is strongly controlled by local environmental conditions. This dissertation describes efforts to determine the mechanisms responsible for the link between local environmental conditions and δ34Spyr. In order to do this, we developed novel laboratory procedures …
Understanding The Meaning Of Microbialites As Geobiological Archives, Scott Randall Beeler
Understanding The Meaning Of Microbialites As Geobiological Archives, Scott Randall Beeler
Arts & Sciences Electronic Theses and Dissertations
Microbialites, sedimentary structures formed from the interaction of microorganisms with their environment, provide one of the oldest and most complete records of life on Earth, making them an invaluable tool in the field of geobiology. However, much of the information that could be gained from microbialites remains obscured due to our incomplete understanding of how variability in the microbial, geochemical, and physical processes driving their formation affect their morphological and geochemical characteristics. Modern environments of active microbialite formation provide the opportunity to study the relationship between variability in these environmental processes and the resultant mineral product and can act as …