Matching Items (34)
Description
Archean oxidative weathering reactions were likely important O2 sinks that delayed the oxygenation of Earth’s atmosphere, as well as sources of bio-essential trace metals such as Mo to the biosphere. However, the rates of these reactions are difficult to quantify experimentally at relevantly low concentrations of O2. With newly developed O2 sensors, weathering experiments were conducted to measure the rate of sulfide oxidation at Archean levels of O2, a level three orders of magnitude lower than previous experiments. The rate laws produced, combined with weathering models, indicate that crustal sulfide oxidation by O2 was possible even in a low O2 Archean atmosphere.
Given the experimental results, it is expected that crustal delivery of bio-essential trace metals (such as Mo) from sulfide weathering was active even prior to the oxygenation of Earth’s atmosphere. Mo is a key metal for biological N2 fixation and its ancient use is evidenced by N isotopes in ancient sedimentary rocks. However, it is typically thought that Mo was too low to be effectively bioavailable early in Earth’s history, given the low abundances of Mo found in ancient sediments. To reconcile these observations, a computational model was built that leverages isotopic constraints to calculate the range of seawater concentrations possible in ancient oceans. Under several scenarios, bioavailable concentrations of seawater Mo were attainable and compatible with the geologic record. These results imply that Mo may not have been limiting for early metabolisms.
Titanium (Ti) isotopes were recently proposed to trace the evolution of the ancient continental crust, and have the potential to trace the distribution of other trace metals during magmatic differentiation. However, significant work remains to understand fully Ti isotope fractionation during crust formation. To calibrate this proxy, I carried out the first direct measurement of mineral-melt fractionation factors for Ti isotopes in Kilauea Iki lava lake and built a multi-variate fractionation law for Ti isotopes during magmatic differentiation. This study allows more accurate forward-modeling of isotope fractionation during crust differentiation, which can now be paired with weathering models and ocean mass balance to further reconstruct the composition of Earth’s early continental crust, atmosphere, and oceans.
Given the experimental results, it is expected that crustal delivery of bio-essential trace metals (such as Mo) from sulfide weathering was active even prior to the oxygenation of Earth’s atmosphere. Mo is a key metal for biological N2 fixation and its ancient use is evidenced by N isotopes in ancient sedimentary rocks. However, it is typically thought that Mo was too low to be effectively bioavailable early in Earth’s history, given the low abundances of Mo found in ancient sediments. To reconcile these observations, a computational model was built that leverages isotopic constraints to calculate the range of seawater concentrations possible in ancient oceans. Under several scenarios, bioavailable concentrations of seawater Mo were attainable and compatible with the geologic record. These results imply that Mo may not have been limiting for early metabolisms.
Titanium (Ti) isotopes were recently proposed to trace the evolution of the ancient continental crust, and have the potential to trace the distribution of other trace metals during magmatic differentiation. However, significant work remains to understand fully Ti isotope fractionation during crust formation. To calibrate this proxy, I carried out the first direct measurement of mineral-melt fractionation factors for Ti isotopes in Kilauea Iki lava lake and built a multi-variate fractionation law for Ti isotopes during magmatic differentiation. This study allows more accurate forward-modeling of isotope fractionation during crust differentiation, which can now be paired with weathering models and ocean mass balance to further reconstruct the composition of Earth’s early continental crust, atmosphere, and oceans.
ContributorsJohnson, Aleisha (Author) / Anbar, Ariel D. (Thesis advisor) / Till, Christy (Committee member) / Hartnett, Hilairy (Committee member) / Romaniello, Stephen J. (Committee member) / Sharp, Thomas (Committee member) / Arizona State University (Publisher)
Created2020
Description
My dissertation research broadly focuses on the geochemical and physical exchange of materials between the Earth’s crust and mantle at convergent margins, and how this drives the compositional diversity observed on the Earth’s surface. I combine traditional petrologic and geochemical studies of natural and experimental high-pressure mafic rocks, with thermodynamic modeling of high-pressure aqueous fluids and mafic-ultramafic lithologies allowing for more complete understanding of fluid-melt-rock interactions. The results of the research that follows has important implications for: the role of lower crustal foundering in the geochemical origin and evolution of the modern continental crust (Chapter 2; Guild et al., under review), metasomatic processes involving aqueous metal-carbon complexes in high pressure-temperature subduction zone fluids (Chapter 3; Guild & Shock, 2020), natural hydrous mineral stability at the slab-mantle interface (Chapter 4; Guild, et al., in preparation) and water-undersaturated melting in the sub-arc (Chapter 5; Guild & Till, in preparation).
ContributorsGuild, Meghan Rose (Author) / Till, Christy B. (Thesis advisor) / Shock, Everett L (Committee member) / Hervig, Richard L (Committee member) / Hartnett, Hilairy (Committee member) / Clarke, Amanda (Committee member) / Arizona State University (Publisher)
Created2020
Description
Organic compounds are influenced by hydrothermal conditions in both marine and terrestrial environments. Sedimentary organic reservoirs make up the largest share of organic carbon in the carbon cycle, leading to petroleum generation and to chemoautotrophic microbial communities. There have been numerous studies on the reactivity of organic compounds in water at elevated temperatures, but these studies rarely explore the consequences of inorganic solutes in hydrothermal fluids. The experiments in this thesis explore new reaction pathways of organic compounds mediated by aqueous and solid phase metals, mainly Earth-abundant copper. These experiments show that copper species have the potential to oxidize benzene and toluene, which are typically viewed as unreactive. These pathways add to the growing list of known organic transformations that are possible in natural hydrothermal systems. In addition to the characterization of reactions in natural systems, there has been recent interest in using hydrothermal conditions to facilitate organic transformations that would be useful in an applied, industrial or synthetic setting. This thesis identifies two sets of conditions that may serve as alternatives to commonplace industrial processes. The first process is the oxidation of benzene with copper to form phenol and chlorobenzene. The second is the copper mediated dehalogenation of aryl halides. Both of these processes apply the concepts of geomimicry by carrying out organic reactions under Earth-like conditions. Only water and copper are needed to implement these processes and there is no need for exotic catalysts or toxic reagents.
ContributorsLoescher, Grant (Author) / Shock, Everett (Thesis advisor) / Hartnett, Hilairy (Committee member) / Gould, Ian (Committee member) / Arizona State University (Publisher)
Created2020
Description
Dissolved organic matter (DOM) can have numerous effects on the water chemistry and the biological life within an aquatic system with its wide variety of chemical structures and properties. The composition of the dissolved carbon can be estimated by utilizing the fluorescent properties of some DOM such as aromatic amino acids and humic material. This experiment was used to observe how organic matter could influence hydrothermal systems, such as Sylvan Springs in Yellowstone National Park, USA. Using optical density at 600 nm (OD 600), excitation-emission matrix spectra (EEMS), and Illumina sequencing methods (16S rRNA gene sequencing), changes in dissolved organic matter (DOM) were observed based on long term incubation at 84ºC and microbial influence. Four media conditions were tested over a two-month duration to assess these changes: inoculated pine needle media, uninoculated pine needle media, inoculated yeast extract media, and uninoculated yeast extract media. The inoculated samples contained microbes from a fluid and sediment sample of Sylvan Spring collected July 23, 2018. Absorbance indicated that media containing pine needle broth poorly support life, whereas media containing yeast extract revealed a positive increase in growth. Excitation-Emission Matrix Spectra of the all media conditions indicated changes in DOM composition throughout the trial. There were limited differences between the inoculated and uninoculated samples suggesting that the DOM composition change in this study was dominated by the two-month incubation at 84ºC more than biotic processes. Sequencing performed on a sediment sample collected from Sylvan Spring indicated five main order of prokaryotic phyla: Aquificales, Desulfurococcales, Thermoproteales, Thermodesulfobacteriales, and Crenarchaeota. These organisms are not regarded as heterotrophic microbes, so the lack of significant biotic changes in DOM could be a result of these microorganisms not being able to utilize these enrichments as their main metabolic energy supply.
ContributorsKnott, Nicholas Joseph (Author) / Shock, Everett (Thesis director) / Hartnett, Hilairy (Committee member) / Till, Christy (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Freshwater ecosystems are increasingly threatened by anthropogenic eutrophication (Kolzau et al., 2014) and require mitigation efforts to prevent oxygen depletion and subsequent biodiversity loss. Tres Rios Constructed Treatment Wetland (CTW) relies on wetland ecosystem functioning to reduce nutrient concentrations in order to meet regulatory guidelines. I investigated the impact of solar irradiance, temperature, and nutrient availability on aquatic net primary productivity, ecosystem respiration, and nutrient cycling using statistical analysis and quantitative modeling informed by field data generated by ASU’s Wetland Ecosystem Ecology Lab (WEEL) in partnership with the City of Phoenix Water Services Department. I found that the extent of daily solar insolation controls Aquatic Net Primary Productivity (ANPP) rates and the seasonal aquatic nutrient processing capacity of Tres Rios, resulting in the following approximate relationship: ANPP = 0.001344(W/m²) - 0.32634 (r² = 0.259; p = 0.005).
This formula was used to estimate the nutrient uptake performance of aquatic primary producers from sampling observations; ANPP accounted for 16.26 metric tons of system wide N uptake, while aquatic ER contributed 6.07 metric tons N of nighttime remineralization and 5.7 metric tons of N throughout the water column during the day. The estimated yearly net aquatic N flux is 4.49 metric tons uptake, compared to about 12 metric tons yearly N uptake by the vegetated marsh (Treese, 2019). However, not accounting for animal respiration results in an underestimation of system-wide N remineralization, and not accounting for soil processes results in an underestimation of N uptake.
This formula was used to estimate the nutrient uptake performance of aquatic primary producers from sampling observations; ANPP accounted for 16.26 metric tons of system wide N uptake, while aquatic ER contributed 6.07 metric tons N of nighttime remineralization and 5.7 metric tons of N throughout the water column during the day. The estimated yearly net aquatic N flux is 4.49 metric tons uptake, compared to about 12 metric tons yearly N uptake by the vegetated marsh (Treese, 2019). However, not accounting for animal respiration results in an underestimation of system-wide N remineralization, and not accounting for soil processes results in an underestimation of N uptake.
ContributorsEvans, Joseph Barrett (Author) / Childers, Daniel (Thesis director) / Hartnett, Hilairy (Committee member) / Watts College of Public Service & Community Solut (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Tempe Town Lake is the site of fifteen years’ worth of chemical data collection by ASU researchers. In 2018 the dataSONDE, an instrument capable of measuring different water quality parameters every thirty minutes for a month at a time was installed in the lake. The SONDE has the potential to completely reduce the need for sampling by hand. Before the SONDE becomes the sole means of gathering data, it is important to verify its accuracy. In this study, the measurements gathered by the SONDE (pH, dissolved oxygen, temperature, conductivity and colored dissolved organic matter) were compared to measurements gathered using the verified methods from the past fifteen years.
ContributorsSauer, Elinor Rayne (Author) / Hartnett, Hilairy (Thesis director) / Glaser, Donald (Committee member) / Shock, Everett (Committee member) / Historical, Philosophical & Religious Studies (Contributor) / School of Molecular Sciences (Contributor) / School of Life Sciences (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2020-12
Description
Dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) are crucial nutrients for autotrophic and heterotrophic microbial life, respectively, in hydrothermal systems. Biogeochemical processes that control amounts of DIC and DOC in Yellowstone hot springs can be investigated by measuring carbon abundances and respective isotopic values. A decade and a half of field work in 10 regions within Yellowstone National Park and subsequent geochemical lab analyses reveal that sulfate-dominant acidic regions have high DOC (Up to 57 ppm C) and lower DIC (up to 50 ppm C) compared to neutral-chloride regions with low DOC (< 2 ppm C) and higher DIC (up to 100 ppm C). Abundances and isotopic data suggest that sedimentary rock erosion by acidic hydrothermal fluids, fresh snow-derived meteoric water, and exogenous carbon input allowed by local topography may affect DOC levels. Evaluating the isotopic compositions of DIC and DOC in hydrothermal fluids gives insight on the geology and microbial life in the subsurface between different regions. DIC δ13C values range from -4‰ to +5‰ at pH 5-9 and from -10‰ to +3‰ at pH 2-5 with several springs lower than -10‰. DOC δ13C values parkwide range from -10‰ to -30‰. Within this range, neutral-chloride regions in the Lower Geyser Basin have lighter isotopes than sulfate-dominant acidic regions. In hot springs with elevated levels of DOC, the range only varies between -20‰ and -26‰ which may be caused by local exogenous organic matter runoff. Combining other geochemical measurements, such as differences in chloride and sulfate concentrations, demonstrates that some regions contain mixtures of multiple fluids moving through the complex hydrological system in the subsurface. The mixing of these fluids may account for increased levels of DOC in meteoric sulfate-dominant acidic regions. Ultimately, the foundational values of dissolved carbon and their isotopic composition is provided in a parkwide study, so results can be combined with future studies that apply different sequencing analyses to understand specific biogeochemical cycling and microbial communities that occur in individual hot springs.
ContributorsBarnes, Tanner (Author) / Shock, Everett (Thesis advisor) / Meyer-Dombard, D'Arcy (Committee member) / Hartnett, Hilairy (Committee member) / Arizona State University (Publisher)
Created2023
Iron Cycling May Lower Methane Fluxes at an Impounded Marsh: Evidence from the Herring River Estuary
Description
Wetlands produce approximately one third of total global methane emissions and sequester significant amounts of CO2. Salt marshes make up 5% of total wetland area, and therefore are key factors affecting global methane and CO2 emissions. Many marshes are anthropogenically managed either by diking, draining, impoundment, or otherwise restricting tidal exchange. This causes marsh freshening, increases methane emissions, and releases sequestered carbon, all of which can lead to a warming effect on the climate by the greenhouse effect. We studied the formerly impounded Old County salt marsh, found in the Herring River Estuary of Wellfleet, Massachusetts, USA. The USGS Woods Hole Coastal and Marine Science Center installed two eddy covariance flux towers in the Herring River Estuary. These showed that Old County had low methane fluxes (17 nmol/m2/s) compared to another site in the same estuary (112 nmol/m2/s). The question became; why did Old County experience lower methane emissions? We then did a focused study on the Old County location to investigate. We sampled various biogeochemical parameters including pH, salinity, ORP, dissolved Fe, sulfate, chloride, CH4, DOC, and DIC from pore water samples taken June 2022. We also measured extractable iron from a 2015 archived sediment core at Old County. Specifically, we explored the role of Fe in reducing methane through Fe coupled anaerobic oxidation of methane (Fe-AOM). The porewater depth profiles ranged from 10cm to 242 cm in depth and showed Old County as acidic (pH of 3-6.5), mostly fresh, anoxic, highly reducing, and high in dissolved organic carbon (DOC; 2,000-10,000 μM). I divided the depth profiles into two distinct zones, one above 50 cm and one below 50 cm. Overall, Fe-AOM was likely to occur below 50 cm because dissolved Fe increased as CH4 decreased, which is the expected pattern for Fe-AOM. Also, because the ratio of the calculated methane flux (-0.552 nmol m-2 s-1) to the dissolved Fe (0.072 nmol m-2 s-1) was 7.6, which closely matched the 1 to 8 stoichiometry of the Fe-AOM reactions.
ContributorsEinecker, Rachel (Author) / Hartnett, Hilairy (Thesis director) / Anbar, Ariel (Committee member) / Eagle, Meagan (Committee member) / Barrett, The Honors College (Contributor) / School of Molecular Sciences (Contributor)
Created2023-12
Description
With the ability to observe the atmospheres of terrestrial exoplanets via transit spectroscopy on the near-term horizon, the possibility of atmospheric biosignatures has received considerable attention in astrobiology. While traditionally exoplanet scientists looking for life focused on biologically relevant trace gases such as O2 and CH4, this approach has raised the spectre of false positives. Therefore, to address these shortcomings, a new set of methods is required to provide higher confidence in life detection. One possible approach is measuring the topology of atmospheric chemical reaction networks (CRNs). To investigate and assess this approach, the ability of network-theoretic metrics to distinguish the distance from thermochemical equilibrium in the atmosphere of hot jupiters was tested. After modeling the atmospheres of hot jupiters over a range of initial conditions using the VULCAN modeling package, atmospheric CRNs were constructed from the converged models and their topology measured using the Python package NetworkX. I found that network metrics were able to predict the distance from thermochemical equilibrium better than atmospheric species abundances alone. Building on this success, I modeled 30,000 terrestrial worlds. These models divided into two categories: Anoxic Archean Earth-like planets that varied in terms of CH4 surface flux (modeled as either biotic or abiotic in origin), and modern Earth-like planets with and without a surface flux of CCl2F2 (to represent the presence of industrial civilizations). I constructed atmospheric CRNs from the converged models, and analyzed their topology. I found that network metrics could distinguish between atmospheres with and without the presence of life or technology. In particular, mean degree and average shortest path length consistently performed better at distinguishing between abiotic and biotic Archean-like atmospheres than CH4 abundance.
ContributorsFisher, Theresa Mason (Author) / Walker, Sara I (Thesis advisor) / Hartnett, Hilairy (Committee member) / Line, Michael (Committee member) / Shkolnik, Evgenya (Committee member) / Okie, Jordan (Committee member) / Arizona State University (Publisher)
Created2023
Description
Bacillus sp. BSC154 was isolated from a biological soil crust near Moab, Utah. The strain appears to be capable of chemotaxis and biofilm production. The BSC154 genome contains iron siderophore production, nitrate reduction, mixed acid-butanediol fermentation, and assimilatory and dissimilatory sulfate metabolism pathways.
ContributorsBailey, Alexis (Author) / Kellom, Matthew (Author) / Poret-Peterson, Amisha (Author) / Noonan, Kathryn (Author) / Hartnett, Hilairy (Author) / Raymond, Jason (Author) / College of Liberal Arts and Sciences (Contributor)
Created2014-11-13