Matching Items (4)
Filtering by
- All Subjects: Analytical Chemistry
- All Subjects: Nitrogen
- Genre: Academic theses
- Creators: Anbar, Ariel D
Description
Carbonaceous chondrites (CCs) present a unique opportunity for learning about the earliest organic chemistry that took place in our Solar System. The complex and diverse suite of meteoritic organic material is the result of multiple settings and physicochemical processes, including aqueous and thermal alteration. Though meteorites often inform origin-of-life discussions because they could have seeded early Earth with significant amounts of water and pre-biotic, organic material, their record of abiotic, aqueous, and organic geochemistry is of interest as well.
CC materials previously resided on asteroidal parent bodies, relic planetesimals of Solar System formation which never accreted enough material to develop long-lived, large-scale geological processes. These bodies were large enough, however, to experience some degree of heating due to the decay of radiogenic isotopes, and the meteorite record suggests the existence of 100-150 parent bodies which experienced varying degrees of thermal and aqueous alteration for the first several 10 Myr of Solar System history.
The first chapter of this dissertation reviews literature addressing aqueous alteration as an essential participant in parent body geochemistry, organic synthesis, or both (though papers which address both are rare). The second chapter is a published organic analysis of the soluble organic material of Bells, an unclassified type 2 chondrite. Analytical approaches to assess terrestrial contamination of meteorite samples are also reviewed in the first chapter to allow introduction in chapter 3 of kinetic modeling which rules out certain cases of contamination and constrains the timing of thermal and aqueous alteration. This is the first known application of isoleucine epimerization for either of these purposes. Chapter 4 is a kinetic study of D-allo-isoleucine epimerization to establish its behavior in systems with large, relative abundances of alloisoleucine to isoleucine. Previous epimerization studies for paleontological or geological purposes began with L-isoleucine, the only protein amino acid of the four isoleucine stereoisomers.
Kinetic model calculations using isoleucine stereoisomer abundances from 7 CR chondrites constrain the total duration of the amino acids' residence in the aqueous phase. The comparatively short timescales produced by the presented modeling elicit hypotheses for protection or transport of the amino acids within the CR parent body.
CC materials previously resided on asteroidal parent bodies, relic planetesimals of Solar System formation which never accreted enough material to develop long-lived, large-scale geological processes. These bodies were large enough, however, to experience some degree of heating due to the decay of radiogenic isotopes, and the meteorite record suggests the existence of 100-150 parent bodies which experienced varying degrees of thermal and aqueous alteration for the first several 10 Myr of Solar System history.
The first chapter of this dissertation reviews literature addressing aqueous alteration as an essential participant in parent body geochemistry, organic synthesis, or both (though papers which address both are rare). The second chapter is a published organic analysis of the soluble organic material of Bells, an unclassified type 2 chondrite. Analytical approaches to assess terrestrial contamination of meteorite samples are also reviewed in the first chapter to allow introduction in chapter 3 of kinetic modeling which rules out certain cases of contamination and constrains the timing of thermal and aqueous alteration. This is the first known application of isoleucine epimerization for either of these purposes. Chapter 4 is a kinetic study of D-allo-isoleucine epimerization to establish its behavior in systems with large, relative abundances of alloisoleucine to isoleucine. Previous epimerization studies for paleontological or geological purposes began with L-isoleucine, the only protein amino acid of the four isoleucine stereoisomers.
Kinetic model calculations using isoleucine stereoisomer abundances from 7 CR chondrites constrain the total duration of the amino acids' residence in the aqueous phase. The comparatively short timescales produced by the presented modeling elicit hypotheses for protection or transport of the amino acids within the CR parent body.
ContributorsMonroe, Adam Alexander (Author) / Pizzarello, Sandra (Thesis advisor) / Williams, Peter (Thesis advisor) / Anbar, Ariel D (Committee member) / Shock, Everett L (Committee member) / Arizona State University (Publisher)
Created2014
Description
Molybdenum (Mo) is a key trace nutrient for biological assimilation of nitrogen, either as nitrogen gas (N2) or nitrate (NO3-). Although Mo is the most abundant metal in seawater (105 nM), its concentration is low (<5 nM) in most freshwaters today, and it was scarce in the ocean before 600 million years ago. The use of Mo for nitrogen assimilation can be understood in terms of the changing Mo availability through time; for instance, the higher Mo content of eukaryotic vs. prokaryotic nitrate reductase may have stalled proliferation of eukaryotes in low-Mo Proterozoic oceans. Field and laboratory experiments were performed to study Mo requirements for NO3- assimilation and N2 fixation, respectively. Molybdenum-nitrate addition experiments at Castle Lake, California revealed interannual and depth variability in plankton community response, perhaps resulting from differences in species composition and/or ammonium availability. Furthermore, lake sediments were elevated in Mo compared to soils and bedrock in the watershed. Box modeling suggested that the largest source of Mo to the lake was particulate matter from the watershed. Month-long laboratory experiments with heterocystous cyanobacteria (HC) showed that <1 nM Mo led to low N2 fixation rates, while 10 nM Mo was sufficient for optimal rates. At 1500 nM Mo, freshwater HC hyperaccumulated Mo intercellularly, whereas coastal HC did not. These differences in storage capacity were likely due to the presence in freshwater HC of the small molybdate-binding protein, Mop, and its absence in coastal and marine cyanobacterial species. Expression of the mop gene was regulated by Mo availability in the freshwater HC species Nostoc sp. PCC 7120. Under low Mo (<1 nM) conditions, mop gene expression was up-regulated compared to higher Mo (150 and 3000 nM) treatments, but the subunit composition of the Mop protein changed, suggesting that Mop does not bind Mo in the same manner at <1 nM Mo that it can at higher Mo concentrations. These findings support a role for Mop as a Mo storage protein in HC and suggest that freshwater HC control Mo cellular homeostasis at the post-translational level. Mop's widespread distribution in prokaryotes lends support to the theory that it may be an ancient protein inherited from low-Mo Precambrian oceans.
ContributorsGlass, Jennifer (Author) / Anbar, Ariel D (Thesis advisor) / Shock, Everett L (Committee member) / Jones, Anne K (Committee member) / Hartnett, Hilairy E (Committee member) / Elser, James J (Committee member) / Fromme, Petra (Committee member) / Arizona State University (Publisher)
Created2011
Description
Volcanic devolatilization is one of the major processes in the global nitrogen cycle. Past studies have often estimated the magnitude of this flux using volcanic emission measurements, which are limited to currently active systems and sensitive to atmospheric contamination. A different methodological approach requires appropriate analytical parameters for nitrogen analysis in silicate glasses by secondary ion mass spectrometry (SIMS), which have not yet been established. To this end, we analyze various ion implanted basaltic and rhyolitic glasses by SIMS. We demonstrate that water content significantly affects the ion yields of 14N+ and 14N16O−, as well as the background intensity of 14N+ and 12C+. Application of implant-derived calibrations to natural samples provide the first reported concentrations of nitrogen in melt inclusions. These measurements are from samples from the Bishop Tuff in California, the Huckleberry Ridge Tuff of the Yellowstone Volcanic Center, and material from the Okaia and Oruanui eruptions in the Taupo Volcanic Center. In all studied material, we find maximum nitrogen contents of less than 45 ppm and that nitrogen concentration varies positively with CO2 concentration, which is interpreted to reflect partial degassing trend. Using the maximum measured nitrogen contents for each eruption, we find that the Bishop released >3.6 x 1013 g of nitrogen, the Huckleberry Ridge released >1.3 x 1014 g, the Okaia released >1.1 x 1011 g of nitrogen, the Oruanui released >4.7 x 1013 g of nitrogen. Simple calculations suggest that with concentrations such as these, rhyolitic eruptions may ephemerally increase the nitrogen flux to the atmosphere, but are insignificant compared to the 4 x 1021 g of nitrogen stored in the atmosphere.
ContributorsRegier, Margo Elaine (Author) / Hervig, Richard L (Thesis advisor) / Roggensack, Kurt (Committee member) / Till, Christy B. (Committee member) / Arizona State University (Publisher)
Created2016
Description
A novel technique for measuring heavy trace elements in geologic materials with secondary ion mass spectrometry (SIMS) is presented. This technique combines moderate levels of mass resolving power (MRP) with energy filtering in order to remove molecular ion interferences while maintaining enough sensitivity to measure trace elements. The technique was evaluated by measuring a set of heavy chalcophilic elements in two sets of doped glasses similar in composition to rhyolites and basalts, respectively. The normalized count rates of Cu, As, Se, Br, and Te were plotted against concentrations to test that the signal increased linearly with concentration. The signal from any residual molecular ion interferences (e.g. ²⁹Si³⁰Si¹⁶O on ⁷⁵As) represented apparent concentrations ≤ 1 μg/g for most of the chalcophiles in rhyolitic matrices and between 1 and 10 μg/g in basaltic compositions. This technique was then applied to two suites of melt inclusions from the Bandelier Tuff: Ti-rich, primitive and Ti-poor, evolved rhyolitic compositions. The results showed that Ti-rich inclusions contained ~30 μg/g Cu and ~3 μg/g As while the Ti-poor inclusions contained near background Cu and ~6 μg/g As. Additionally, two of the Ti-rich inclusions contained > 5 μg/g of Sb and Te, well above background. Other elements were at or near background. This suggests certain chalcophilic elements may be helpful in unraveling processes relating to diversity of magma sources in large eruptions. Additionally, an unrelated experiment is presented demonstrating changes in the matrix effect on SIMS counts when normalizing against ³⁰Si⁺ versus ²⁸Si²⁺. If one uses doubly charged silicon as a reference, (common when using large-geometry SIMS instruments to study the light elements Li - C) it is important that the standards closely match the major element chemistry of the unknown.
ContributorsCarlson, Eric Norton (Author) / Hervig, Richard L (Thesis advisor) / Roggensack, Kurt (Committee member) / Burt, Donald M (Committee member) / Arizona State University (Publisher)
Created2021