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Description
The biological carbon pump in the ocean is initiated by the photosynthetic fixation of atmospheric carbon dioxide into particulate or dissolved organic carbon by phytoplankton. A fraction of this organic matter sinks to depth mainly in the form of microaggregates (5-60 μm) and visible macroaggregates. These aggregates are composed of cells, minerals, and other sources of organic carbon. Exopolymeric substances (EPS) are exudated by heterotrophic bacteria and phytoplankton and may form transparent exopolymeric particles (TEP) that act as a glue-like matrix for marine aggregates. Heterotrophic bacteria have been found to influence the aggregation of phytoplankton and in some cases result in an increase in TEP production, but it is unclear if marine heterotrophic bacteria can produce TEP and how they contribute to aggregation. Pseudoalteromonas carrageenovora, Vibrio thalassae, and Marinobacter adhaerens HP15 are heterotrophic marine bacteria that were found associated with sinking particles in an oligotrophic gyre station in the subtropical North Atlantic. These bacteria were grown in axenic cultures to determine growth, TEP production, and aggregation. They were also inoculated into roller tanks used to simulate open ocean conditions to determine their ability to form macroaggregates. Treatments with added kaolinite clay simulated aeolic dust input from the Sahara. M. adhaerens HP15 had the highest TEP concentration but the lowest cell-normalized TEP production at all growth stages compared to the other bacteria. Additionally, M. adhaerens HP15 also had the lowest microaggregate formation. The cell-normalized TEP production and microaggregate formation was not significantly different between P. carrageenovora and V. thalassae. All bacteria formed visible macroaggregates in roller tanks with clay addition and exhibited high sinking velocities (150-1200 m d-1) that are comparable to those of aggregates formed by large mineral ballasted phytoplankton. Microaggregates in the clay treatments declined during incubation, indicating that they aggregated to form the macroaggregates. The findings from this study show for the first time that heterotrophic bacteria can contribute to aggregation and the export of organic carbon to depth in the ocean.
ContributorsLivar, Britni (Author) / Neuer, Susanne (Thesis advisor) / Hartnett, Hilairy (Committee member) / Cadillo-Quiroz, Hinsby (Committee member) / Arizona State University (Publisher)
Created2022
Description
I present results of field and laboratory experiments investigating the habitability of one of Earth’s driest environments: the Atacama Desert. This Desert, along the west coast of South America spanning Perú and Chile, is one of the driest places on Earth and has been exceedingly arid for millions of years. These conditions create the perfect natural laboratory for assessing life at the extremes of habitability. All known life needs water; however, the extraordinarily dry Atacama Desert is inhabited by well-adapted microorganisms capable of colonizing this hostile environment. I show field and laboratory evidence of an environmental process, water vapor adsorption, that provides a daily, sustainable input of water into the near (3 - 5 cm) subsurface through water vapor-soil particle interactions. I estimate that this water input may rival the yearly average input of rain in these soils (~2 mm).
I also demonstrate, for the first time, that water vapor adsorption is dependent on mineral composition via a series of laboratory water vapor adsorption experiments. The results of these experiments provide evidence that mineral composition, and ultimately soil composition, measurably and significantly affect the equilibrium soil water content. This suggests that soil microbial communities may be extremely heterogeneous in distribution depending on the distribution of adsorbent minerals.
Finally, I present changes in biologically relevant gasses (i.e., H2, CH4, CO, and CO2) over long-duration incubation experiments designed to assess the potential for biological activity in soils collected from a hyperarid region in the Atacama Desert. These long-duration experiments mimicked typical water availability conditions in the Atacama Desert; in other words, the incubations were performed without condensed water addition. The results suggest a potential for methane-production in the live experiments relative to the sterile controls, and thus, for biological activity in hyperarid soils. However, due to the extremely low biomass and extremely low rates of activity in these soils, the methods employed here were unable to provide robust evidence for activity. Overall, the hyperarid regions of the Atacama Desert are an important resource for researchers by providing a window into the environmental dynamics and subsequent microbial responses near the limit of habitability.
ContributorsGlaser, Donald M (Author) / Hartnett, Hilairy E (Thesis advisor) / Anbar, Ariel (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2022
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
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
Description
As air quality standards become more stringent to combat poor air quality, there is a greater need for more effective pollutant control measures and increased air monitoring network coverage. Polluted air, in the form of aerosols and gases, can impact respiratory and cardiovascular health, visibility, the climate, and material weathering. This work demonstrates how traditional networks can be used to study generational events, how these networks can be supplemented with low-cost sensors, and the effectiveness of several control measures. First, an existing network was used to study the effect of COVID-19 travel restrictions on air quality in Maricopa County, Arizona, which would not have been possible without the historical record that a traditional network provides. Although this study determined that decreases in CO and NO2 were not unique to the travel restrictions, it was limited to only three locations due to network sparseness. The second part of this work expanded the traditional NO2 monitoring network using low-cost sensors, that were first collocated with a reference monitor to evaluate their performance and establish a robust calibration. The sensors were then deployed to the field to varying results; their calibration was further improved by cycling the sensors between deployment and reference locations throughout the summer. This calibrated NO2 data, along with volatile organic compound data, were combined to enhance the understanding of ozone formation in Maricopa County, especially during wildfire season. In addition to being in non-attainment for ozone standards, Maricopa County fails to meet particulate matter under 10 μm (PM10) standards. A large portion of PM10 emissions is attributed to fugitive dust that is either windblown or kicked up by vehicles. The third part of this work demonstrated that Enzyme Induced Carbonate Precipitation (EICP) treatments aggregate soil particles and prevent fugitive dust emissions. The final part of the work examined tire wear PM10 emissions, as vehicles are another significant contributor to PM10. Observations showed a decrease in tire wear PM10 during winter with little change when varying the highway surface type.
ContributorsMiech, Jason Andrew (Author) / Herckes, Pierre (Thesis advisor) / Fraser, Matthew P (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2023
Description
The prevalence and unique properties of airborne nanoparticles have raised concerns regarding their potential adverse health effects. Despite their significance, the understanding of nanoparticle generation, transport, and exposure remains incomplete. This study first aimed to assess nanoparticle exposure in indoor workplace environments, in the semiconductor manufacturing industry. On-site observations during tool preventive maintenance revealed a significant release of particles smaller than 30 nm, which subsequent instrumental analysis confirmed as predominantly composed of transition metals. Although the measured mass concentration levels did not exceed current federal limits, it prompted concerns regarding how well filter-based air sampling methods would capture the particles for exposure assessment and how well common personal protective equipment would protect from exposure. To address these concerns, this study evaluated the capture efficiency of filters and masks. When challenged by aerosolized engineered nanomaterials, common filters used in industrial hygiene sampling exhibited capture efficiencies of over 60%. Filtering Facepiece Respirators, such as the N95 mask, exhibited a capture efficiency of over 98%. In contrast, simple surgical masks showed a capture efficiency of approximately 70%. The experiments showed that face velocity and ambient humidity influence capture performance and mostly identified the critical role of mask and particle surface charge in capturing nanoparticles. Masks with higher surface potential exhibited higher capture efficiency towards nanoparticles. Eliminating their surface charge resulted in a significantly diminished capture efficiency, up to 43%. Finally, this study characterized outdoor nanoparticle concentrations in the Phoenix metropolitan area, revealing typical concentrations on the order of 10^4 #/cm3 consistent with other urban environments. During the North American monsoon season, in dust storms, with elevated number concentrations of large particles, particularly in the size range of 1-10 μm, the number concentration of nanoparticles in the size range of 30-100 nm was substantially lower by approximately 55%. These findings provide valuable insights for future assessments of nanoparticle exposure risks and filter capture mechanisms associated with airborne nanoparticles.
ContributorsZhang, Zhaobo (Author) / Herckes, Pierre (Thesis advisor) / Westerhoff, Paul (Committee member) / Shock, Everett (Committee member) / Fraser, Matthew (Committee member) / Arizona State University (Publisher)
Created2023
Description
The origin of life remains unknowable to current science. Scientists cannot see into the origin of life on Earth, and until humanity discovers life elsewhere in the universe and begin to compare this alien life to Earth, it is likely to be undiscoverable. However, alien life may be so different from life as it is currently known that it may not be recognizable when it is found. Therefore, astrobiology needs a universal theory for life to avoid detection methods being biased towards Earth-based life. This also extends to the instrumentation sent into space, which should be built to detect universal properties of life. Assembly theory, a novel measure of complexity and arguably the only testable agnostic biosignature in current science, is used here to provide precision requirements for mass spectrometry instrumentation on future spaceflight missions with the goal of finding life elsewhere. Universal properties are not only applicable to the origins of life, but also to technologically advanced societies. Predictable patterns are found in today’s industrially based society, such as energy usage as a function of population density. These patterns may serve as the basis for technosignatures that are evidence of advanced extraterrestrial civilizations. Patters found in patent chemistry are explored, as well as predictions of chemical complexity based on assembly theory, to determine how complex chemistry is built by human society and which statistical patterns may be found in extraterrestrial civilizations. Moving beyond astrobiology, science cannot be done in a vacuum but must be communicated and taught to others. Topics such as a universal definition of life, biosignatures, and increasing complexity mean nothing without interest and engagement from others, particularly students. To this end, transformative pedagogical tools are used, particularly sociotransformative constructivism (sTc), to build and teach an Earth Science and Astrobiology curriculum to a classroom of high school incarcerated students. The impact of this class on their science learning and how they personally identify as scientists is studied.
ContributorsMalloy, John (Author) / Walker, Sara (Thesis advisor) / Reano, Darryl (Committee member) / Hartnett, Hilairy (Committee member) / Trembath-Reichert, Elizabeth (Committee member) / Cronin, Leroy (Committee member) / Arizona State University (Publisher)
Created2023
Description
Lithium (Li) is a trace element in kerogen, but the content and isotopic distribution (δ7Li) in kerogen has not previously been quantified. Furthermore, kerogen has been overlooked as a potential source of Li to sedimentary porefluids and buried sediments. Thus, knowing the content and isotopic composition of Li derived from kerogen may have implications for research focused on the Li-isotopes of buried sediments (e.g., evaluating paleoclimate variations using marine carbonates).The objective of this work is to better understand the role of kerogen in the Li geochemical cycle. The research approach consisted of 1) developing reference materials and methodologies to measure the Li-contents and δ7Li of kerogen in-situ by Secondary Ion Mass Spectrometry, 2) surveying the Li-contents and δ7Li of kerogen bearing rocks from different depositional and diagenetic environments and 3) quantifying the Li-content and δ7Li variations in kerogen empirically in a field study and 4) experimentally through hydrous pyrolysis.
A survey of δ7Li of coals from depositional basins across the USA showed that thermally immature coals have light δ7Li values (–20 to – 10‰) compared to typical terrestrial materials (> –10‰) and the δ7Li of coal increases with burial temperature suggesting that 6Li is preferentially released from kerogen to porefluids during hydrocarbon generation. A field study was conducted on two Cretaceous coal seams in Colorado (USA) intruded by dikes (mafic and felsic) creating a temperature gradient from the intrusives into the country rock. Results showed that δ7Li values of the unmetamorphosed vitrinite macerals were up to 37‰ lighter than vitrinite macerals and coke within the contact metamorphosed coal.
To understand the significance of Li derived from kerogen during burial diagenesis, hydrous pyrolysis experiments of three coals were conducted. Results showed that Li is released from kerogen during hydrocarbon generation and could increase sedimentary porefluid Li-contents up to ~100 mg/L. The δ7Li of coals becomes heavier with increased temperature except where authigenic silicates may compete for the released Li. These results indicate that kerogen is a significant source of isotopically light Li to diagenetic fluids and is an important contributor to the global geochemical cycle.
ContributorsTeichert, Zebadiah (Author) / Williams, Lynda B. (Thesis advisor) / Bose, Maitrayee (Thesis advisor) / Hervig, Richard (Committee member) / Semken, Steven (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2022
Description
The Greater Obsidian Pool Area just south of the Mud Volcano area in Yellowstone National Park is an active and ever-changing hot spring region. Situated next to a lake in a meadow between several hills of glacial deposits, north of the Elephant Back rhyolite flow, a diverse group of hot springs has been developing. This study examines the geologic and geomorphic context of the hot springs, finding evidence for a previously undiscovered hydrothermal explosion crater and examining the deposits around the region that contribute to properties of the groundwater table. Hot spring geochemical measurements (Cl- and SO4-2) taken over the course of 20 years are used to determine fluid sourcing of the springs. The distribution of Cl-, an indicator of water-rock interaction, in the hot springs leads to the theory of a fissure delivering hydrothermal fluid in a line across the hot spring zone, with meteoric water from incoming groundwater diluting hot springs moving further from the fissure. A possible second dry fissure delivering mostly gas is also a possible explanation for some elevated sulfate concentrations in certain springs. The combination of geology, geomorphology, and geochemistry reveals how the surface and subsurface operate to generate different hot spring compositions.
ContributorsAlexander, Erin (Author) / Shock, Everett (Thesis director) / Whipple, Kelin (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor) / School of Molecular Sciences (Contributor)
Created2022-05
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