Master of Science, The Ohio State University, 2016, Evolution, Ecology and Organismal Biology

Terrestrial land use is intimately connected to the amounts and characteristics of organic and inorganic carbon (C) exported to aquatic ecosystems. However, the effect of land use on the contributions of various potential C sources to headwater streams is poorly established quantitatively. In this study we examined the fluxes and δ13C and Δ14C signatures of dissolved inorganic C (DIC), dissolved organic C (DOC), and particulate organic C (POC) exported from headwater streams of six watersheds of differing land use in a long-term experimental watershed. We employed Bayesian modeling (MixSIR) to determine relative contributions of potential C sources to DIC, DOC, and POC. Agricultural activity (i.e., tilled and non-tilled corn planting) increased watershed C export fluxes by 50-400% due to a 4-9-fold greater export of terrestrial plant-derived biomass C and a 5-15-fold greater export of soil C, compared to all other land uses (i.e., pasture, mixed land use, and forested). In addition, the sources of C contributing to exports from the forested watershed differed from watersheds with both agricultural land uses and those with pasture or mixed land uses. By scaling our results to the Mississippi River Basin watershed, we estimate that historic conversion of land to tilled agricultural practices may have increased the terrestrial-aquatic C flux by 11.4 ± 0.5 Tg•C•yr-1 (nearly six-fold). If non-tilled practices were implemented across all agricultural land in the Mississippi watershed, we estimate that C exports to inland waters and subsequent CO2 release to the atmosphere could be reduced by as much as 60%.

Doctor of Philosophy, University of Toledo, 2014, College of Natural Sciences and Mathematics

Severe weather and climate anomalies have been observed increasingly in recent decades in United States. Large uncertainties still exist about to what extent ecosystems may respond to such drastic variability of external environmental forcing in terms of their carbon sequestration rates. Challenges also remain in predicting and assessing the potential impact of climate variability and anomaly under anticipated climate change. This study targeted the three most prevalent ecosystems (i.e., a deciduous woodland, a conventional cropland, and a coastal freshwater marsh) in northwestern Ohio, USA. Using the eddy covariance method and supplementary measurements, I examined the effects of recent climatic variability and anomalies (2011-2013) on ecosystem carbon fluxes (i.e., net ecosystem CO2/CH4 exchanges (FCO2/FCH4) and lateral hydrologic fluxes of dissolved organic carbon (FDOC), particulate organic carbon (FPOC), and dissolve inorganic carbon (FDIC)). Gross ecosystem production (GEP) and ecosystem respiration (ER) were the two largest fluxes in the annual carbon budget at all three ecosystems. Yet, these two fluxes compensated each other to a large extent and their balance – FCO2 – depended largely on the interannual variability of these two large fluxes. Around 57-58%, 91-96%, and 77-78% of the interannual FCO2 variability was attributed to functional changes of ecosystems among years, suggesting that the changes of ecosystem structural, physiological, or phenological characteristics played an important role in regulating interannual variability of GEP, ER and FCO2. Freshwater marshes deserve more research attention for their high FCH4 (~50.8±1.0 g C m-2 yr-1) and lateral hydrologic carbon inflows/outflows. Lateral hydrologic flows were an important vector in re-locating carbon among ecosystems in the region. Considerable hydrologic carbon flowed both into and out of the research marsh (108.3±5.4 and 86.2±10.5 g C m-2 yr-1, respectively). Despite marshes accounting for (open full item for complete abstract)

MS, University of Cincinnati, 2013, Engineering and Applied Science: Mechanical Engineering

The discovery of Carbon Nanotubes (CNTs) has sparked tremendous interest among the scientific community due to its extraordinary mechanical properties like high strength and elastic modulus and semiconductor like properties. Though spinning the CNTs into continuous yarns enabled the use of CNTs at macroscale, current spinning techniques are not able to reproduce the properties comparable to those observed at nanoscale. Motivated by this gap, a modeling approach is established to address the subject of transferability of the high strength properties from individual CNT to carbon nanotube (CNT) yarns. More specifically, a number of key factors that contribute to the reduced strength of the twisted CNT yarns are investigated. First of all, the effects of Stone-Wales defects on the strength of individual nanotubes are studied. It is found that the tensile strength of the individual CNT is not highly sensitive to the Stone-Wales defects even with relatively high ratio of defects percentage. Subsequently, molecular dynamics and mechanics simulation are performed to evaluate the load transfer mechanism and tensile strength in a bundle of CNTs. The goal is to find the most favorable twist angle for maximum tensile strength and maximum load transfer ability in between the CNTs in CNT bundles. Both small and large bundles have been studied to examine whether the results are scalable. This thesis concludes with a comparison of the simulation results with the analytical studies based on the mechanics of ropes.

Master of Arts, Miami University, 2006, Geography

This study investigated the variability of soil organic carbon within the Old Woman Creek watershed and the influence of landuse, soil texture, geomorphic surface and depth on SOC variability. Soil samples were collected at 0-30cm and 30-60cm depths in forest, pasture, conservation tillage and conventional tillage sites in both the Lake Plain and Till Plain. The Lake Plain had higher SOC than the Till Plain, and geomorphic surface had a greater affect at the 30-60cm depth than the 0-30cm depth. SOC was higher at the 0-30cm depth than the 30-60cm depth. Forest and pasture landuses had higher SOC than conservation and conventional tillage landuses. Conventional tillage had higher SOC than conservation tillage. Linear regression models and soil survey data were used to extrapolate SOC data to the watershed. Linear regression models could be useful estimators of SOC when used with site-specific data.

Doctor of Philosophy, Case Western Reserve University, 2022, Macromolecular Science and Engineering

The oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are critical electrocatalytic reactions for clean and renewable energy technologies, such as fuel cells, metal-air batteries, and water-splitting. Current commercial applications of these reactions utilize noble-metal-based catalysts (e.g., Pt, Pd, RuO2, IrO2). The high cost of these precious metal-based catalysts and their limited reserve have precluded these renewable energy technologies from large-scale applications. Therefore, research efforts have focused on the development of alternative catalysts that are readily available and cost-effective, with superior electrocatalytic performance compared to noble-metal-based catalysts. In 2009, nitrogen-doped carbon nanotubes (N-CNTs) were discovered to demonstrate electrocatalytic ORR activity attributed to the doping-induced charge transfer from carbon atoms adjacent to the nitrogen atoms to change the chemisorption mode of O2. More recent studies have further demonstrated that certain heteroatom-doped carbon nanomaterials can even act as multi-functional metal-free electrocatalysts for ORR/OER/HER, leading to the potential development of low-cost, highly efficient, and multi-functional electrocatalysts for advanced clean and renewable energy technologies. The work presented herein develops new carbon-based metal-free electrocatalysts (C-MFECs) by utilizing different design strategies. Chapter two demonstrates carbonization of a newly-synthesized pair of enantiotopic chiral metal-organic frameworks (MOFs) to produce Co-coordinated N-doped carbon materials with a hierarchical rod-like morphology and remarkable bi-functional electrocatalytic activity and stability for both OER and ORR – comparable to both commercial RuO2 for OER and Pt/C electrocatalysts for ORR. The observed excellent electrocatalytic activities were attributed to their unique hierarchical rod-like structure with homogeneously distributed cob (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2020, Environment and Natural Resources

Urban, or anthropogenic, soils are those which are highly influenced by human activity. These soils are spatially complex due to the physical disturbances to which they are subjected through direct anthropogenic impacts. Human intervention and their impacts on urban soils are the predominant cause of the unique characteristics of urban soils, which are not present in natural, undisturbed environments. Changes in landscape vegetative cover from natural to urban environments could have a negative effect on biodiversity by loss of habitat, the capacity of soil to store C, and reduction of biomass. To better classify, characterize, map and determine carbon fractions of urban soils this research's main objectives were to: (1) find relatively undisturbed soils in the urban study area to use as a reference for future studies and use USDA soil taxonomic methods to characterize and classify these urban soils; (2) determine if mid-DRIFTS can serve as a rapid method for calcite and dolomite assessment in urban soils when compared to the volumetric calcimeter method, and if acid pre-treatment effectively removes calcite and dolomite from urban soil samples; (3) compare four methods to determine organic carbon in highly disturbed environments and compare methods to determine organic carbon in soil with inorganic carbon present and (4) develop a classification of urban soils based on taxonomic distance, create a map of The Ohio State University soils, and develop a measure of soil disturbance by comparing the urban soil classification to an anthroposequence. In Chapter 2, historical Ohio State University campus maps were used to locate and sample areas where minimally disturbed soils might be found. These pedons, inadvertently presented different stages of an anthroposequence. Pedon 1 showed a mostly homogeneous parent material. Pedon 2 had large concentrations of inorganic C derived from the calcareous glacial outwash parent material. Foreign materials and disrupted horiz (open full item for complete abstract)

MARCH, University of Cincinnati, 2019, Design, Architecture, Art and Planning: Architecture

The impacts on the environment of carbon being produced by the building industry have been known for some time now. The United States is by far one of the biggest carbon emitters on the planet and our building industry is one of the main contributors. Between manufacturing, transportation of materials, construction, building maintenance, and end of life processes buildings consume around 48% of total U.S. energy use. This energy use is predominately fueled by carbon emitting fossil fuel sources. This thesis will analyze the architectural implications of carbon neutral building by creating a low-carbon baseline through analyses, using a life cycle assessment tool. The baseline analyses will aim to reduce the embodied and operational carbon impacts of the building by analyzing the massing, location (suburban/urban), wall assemblies, structural material, and energy efficiency. The results of the low-carbon baseline building will produce the lowest total carbon emissions for each category listed previously; while also giving visualization to the architectural implications. The concurrent design portion will try to put these lessons to use by designing a building that is low in embodied carbon, low in operational carbon and high in carbon sequestration.

Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Materials Engineering

The purpose of this research was to develop novel nanoparticle-enabled material shields and conductors for use in electrical coaxial cables, and to create appropriate methods to characterize their response to high frequency electromagnetic fields. In addition, techniques to distinguish the effects of mechanical degradation on electrical properties were developed. Traditional electrical measurements methods are ineffectual to such characterization due to limitations with frequency range, sample geometry, field impingement, and false assumptions of field coupling to non-metal center conductors. In this study, a reverberation chamber was used to develop a novel measurement method using conduction characterizations from a network analyzer. Samples were fatigued to identify the effects of heavy use and mechanical degradation on shielding effectiveness and system characterization, including impedance, voltage standing wave ratio, return loss, and insertion loss. The novel measurement of shielding effectiveness as well as system characterizations was used to determine the effect of material properties on cabling functionality, both electrical and mechanical and their inter-relationship. The results showed that the combination of carbon nanotube yarn center conductors and carbon nanotube tape shields led to more signal attenuation and therefore much higher characteristic impedance. Utilizing the novel method to measure the shielding effectiveness allowed for the incorporation of these differences in power transmission while simultaneously analyzing the immunity of the three-dimensional shield within a high frequency field. The carbon nanotube tape shields provided lightweight and efficient shielding at higher frequencies (towards 5 GHz) due to a decreasing skin depth at higher frequencies. A braid architecture, that which was incorporated in the silver coated copper clad steel shield, proved to withstand mechanical fatigue better, while the carbon nanotube helical tap (open full item for complete abstract)

Master of Science (M.S.), University of Dayton, 2017, Renewable and Clean Energy

Despite the availability of cost-effective alternatives to highly carbon-intensive practices, the world continues to invest in fossil fuel energy systems. For universities that have pledged to become carbon neutral, this concept of carbon lock-in raises the stakes of their carbon commitments, presenting challenges to traditional practices in facilities planning and operations. Building upon past research on carbon lock-in effects on college campuses, this thesis seeks to identify the University of Dayton's over-committed emissions under a business-as-usual scenario and chart out a course for decarbonization pathways that would unlock those emissions that are hardest to avoid. I find the business-as-usual scenario results in high carbon liability at the neutrality date, which represents high costs to offset carbon emissions or purchase other “end-of-pipe” solutions. I also discuss decarbonization pathways that could unlock these over-committed emissions. Future work should explore some of the carbon unlocking strategies discussed here so the university can begin to integrate them into its climate action plan and construction policies. Additionally, this perspective on carbon lock-in will be useful to administrators and facilities managers at other institutions concerned about carbon neutrality and high carbon liabilities associated with existing and future carbon-emitting infrastructure.

Master of Science (MS), Ohio University, 2016, Mechanical Engineering (Engineering and Technology)

The aim of this work was to investigate the use of a catalytic material to accelerate the formation of carbonic acid in a thin liquid film using a vertical membrane mass transfer system. Results comparing the rate of formation of Total Inorganic Carbon (TIC) for similar experimental conditions between the non-catalytic and the catalytic mass transfer systems indicated a statistically significant increase in carbonic acid formation with catalytic mass transfer system. The increased rate of TIC accumulation in the media indicated that the catalytic galvanized mesh potentially accelerated the rate limiting step, i.e. the formation of carbonic acid on the thin liquid film.

Master of Science, The Ohio State University, 2015, Evolution, Ecology and Organismal Biology

Tree root exudation of soluble organic carbon (SOC) is often considered an important but under-assessed component of terrestrial net primary productivity that also strongly influences rhizosphere and soil biogeochemical processes. Although riparian and bottomland systems are often considered “hot spots” of biogeochemical activity that are potentially supported by root exudate SOC, in situ tree root exudation rates of SOC have not been previously reported for these systems. Additionally, there is an outstanding need to understand the δ13C signatures of root exudates in relation to not only different plant components such as leaves and roots but also different ecosystem pools of C, such as CO2 emitted from soil. In the present study we used an in situ method to collect root exudate SOC in order to assess root exudation rates in a bottomland forest for Acer saccharinum, Populus deltoides and Platanus occidentalis trees over five sampling dates ranging from mid-summer to late-autumn. Leaves from Acer negundo, Acer saccharinum, Lonicera maackii, Populus deltoides and Platanus occidentalis were also collected. δ13C values were determined for all of the root exudates, roots and leaves collected in this study. Exudation rates and δ13C values were evaluated in relation to leaf and root morphology, leaf and root C and N contents and a number of environmental parameters (e.g. vapor pressure deficit) and net ecosystem exchange (NEE). Findings indicate that exudation rates and δ13C values of leaves and roots were significantly correlated to time-lagged measurements of NEE, suggesting a strong link between exudation rates and δ13C values of leaves and roots and photosynthetic rates. Various time lagged environmental parameters (e.g., vapor pressure deficit) were correlated to the δ13C of exudates, leaves and roots—suggesting a rapid transfer of recent photosynthate from the canopy to roots and root exudates and relatively rapid turnover of C in leaves. When pooled toge (open full item for complete abstract)

Master of Science, University of Akron, 2015, Applied Mathematics

Having already shown great potential for novel engineering applications, graphene and other carbon-based nanostructures (CNSTR) are being investigated for use in nanotechnology and Nanoelectromechanical Systems. For the design of nanoscale devices, it is important to understand the geometries and behavior of CNSTR. We study an atomistic energy-based model for graphene. We model a graphene sheet as a two-dimensional sheet of atoms in ℜ³. We derive an expression for the total internal energy of a CNSTR considering only the energy of covalently bonded atoms, the energy of the local interaction between non-bonded atoms, and the energy due to the bending of adjacent atomic bonds. The configuration of a CNSTR is initialized, and we run simulations using gradient flow dynamics to minimize total energy and determine equilibrium configurations. Predictions from our model show that the structure of the final configuration depends on the relative strengths of the forces as well as the initial configuration.

Doctor of Philosophy (Ph.D.), University of Dayton, 2014, Materials Engineering

Coiled carbon filaments have one of the most attractive three-dimensional forms in carbon materials due to their helical morphologies. Because of their shape and carbon structure, they exhibit excellent mechanical and electrical properties such as superelasticity, low Young's modulus, relatively high electrical conductivity, and good electromagnetic (EM) wave absorption. Therefore, they are good candidates as fillers in composite materials for tactile sensor and electromagnetic interference shielding. In medical areas of interests, coiled carbon filaments can be used as micro and nano heaters or trigger for thermotherapy and biosensors using EM wave exposure because absorbed EM waves by coiled carbon filaments are converted into heat. Although various shapes of coiled carbon filaments have been discovered, optimum synthesis conditions and growth mechanisms of coiled carbon filaments are poorly understood. The study of growth kinetics is significant not only to analyze catalyst activity but also to establish the growth mechanisms of coiled carbon filaments. The establishment of growth mechanisms would be useful for determining optimum synthesis conditions and maximizing the quantity of carbon filaments synthesized for a given application. In the first study, tip grown single helical carbon filaments or carbon nanocoils (CNCs) were synthesized by a chemical vapor deposition method using tin-iron-oxide (Sn-Fe-O) xerogel film catalyst. The Sn-Fe-O catalyst was prepared by a low-cost sol-gel method using stannous acetate and ferric acetate as precursors. The growth kinetics of CNCs were monitored by a thermogravimetric analyzer, and the experimental result was correlated using a one-dimensional kinetic model, corresponding to one-dimensional tip growth. In the second study, bidirectionally grown double helical filaments or carbon microcoils (CMCs) were synthesized using a chemical vapor deposition method. CMCs obtained at two reaction temperatures were compared (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2014, Environmental Science

For more than three decades the practice of creating and restoring wetlands has focused on offsetting lost habitat and ecosystem function, and on water quality improvement. For the past decade wetland research has shifted to the role of wetlands in climate change with most studies dealing with one component of the carbon cycle. This dissertation developed a detailed carbon budget of the two flow-through experimental wetlands at The Ohio State University's Olentangy River Wetland Research Park (ORWRP) in Columbus, Ohio, USA. The two 1-ha flow-through riverine wetlands were created in 1994 (one planted and the other naturally colonized) adjacent to a third-order stream in central Ohio. The dissertation also investigated previous methods used for estimating methane emissions at the experimental wetlands to better permit comparison of data for almost a decade, and estimated the influence the autochthonous productivity had on carbon exported from these two wetlands. Detailed carbon budgets from 2008 to 2010 were created for the two wetlands. Measurements were taken of dissolved non-purgeable organic carbon (NPOC), dissolved inorganic carbon (DIC), fine particulate organic carbon (FPOM), and coarse particulate organic carbon (CPOM). Methane emissions, soil sequestration, aquatic primary productivity, and macrophyte above-ground net primary productivity were also included in the carbon budget based on other studies. The carbon budget successfully balanced inputs (1,838 ± 41 g C m-2 year-1) and export/sequestration (1,846 ± 59 g C m-2 year-1) with only a 0.5 % over estimation of export in relation to input and 12.8 % of the input carbon from both hydrologic and biologic inputs accumulating into the wetland soil. FPOM and CPOM concentrations and exports were positively correlated with hydrologic flow under most circumstances; NPOC and DIC concentrations were usually negatively or poorly correlated with hydrologic flow. In all seasons, except winter, the change of total carbo (open full item for complete abstract)

MS, University of Cincinnati, 2010, Engineering and Applied Science: Electrical Engineering

Carbon nanotubes have excellent electrical and mechanical properties, which are ideally suited for field emission and sensor/actuator applications. The catalyst layer needed for CNT growth (Fe, Ni or Co) once coated on the substrate is subject to an annealing step, which results in the formation of tiny globules of randomly aligned particles. CNTs finally grow on these randomly placed catalyst particles after the substrate annealing. The disadvantage of the bottom-up approach is that the catalyst globules are susceptible to migration on the substrate during thermal annealing and the CNT growth process. The scope of this thesis includes: (1) Patterning arrays of nano-/micro- features by e-beam lithography, (2) shallow etches of the holes by plasma etching in these features (3) deposition of the catalyst material into the shallow holes, (4) CNT growth, and (5) characterization of the patterned nano/micro-scale CNT catalysts and CNT growth. The main objective in this thesis is to immobilize the catalysts on the substrate at a specific location with an array of shallow holes. We believe this will localize and anchor the catalyst producing patterned arrays of CNT's. This method process will also be compared with the current methods of catalyst immobilization developed by Dr. Shanov's group where an alumina layers acts as the catalyst anchor layer. Also CNT growth is compared and with a substrate with no immobilization of the catalyst. The differences in catalyst morphology between annealing the substrate in air and nitrogen will also be compared. All the comparisons are done across different diameters of patterned features on the substrate. This new process will allow for the controlled patterning of CNT growth and enable CNT's to be integrated into manufacture able devices.

Doctor of Philosophy, The Ohio State University, 2011, Environmental Science

In an attempt to slow the increase in atmospheric CO2 enrichment, researchers are looking at the capacity of world soils to sequester carbon (C) and mitigate global climate change (GCC). Analyses of U.S. turfgrass soils throughout diverse ecoregions indicated that home lawns sequester soil organic carbon (SOC). Rates of SOC sequestration to 15 cm depth ranged from 0.01% yr-1 to 0.70% yr-1 with the majority of lawns sequestering SOC to concentrations of 2-3%. Notably high SOC concentrations were observed in Minneapolis, MN (5.6%), Wooster, OH (3.4%), Denver, CO (3.2%), and Duluth, MN (3.1). In contrast, notably low concentrations were observed for soils located in Atlanta, GA (1.5%). Differences in SOC concentration and pool were attributed to differences in climatic and soil properties across ecoregions. The mean annual temperature (MAT) was negatively correlated with SOC concentration and pool, while both mean annual precipitation (MAP) and soil bulk density (ρb) indicated a nonlinear interaction with optimal SOC concentrations at MAP of 60-70 cm yr-1 and ρb of 1.4-1.5 Mg m-3. Additionally, soil nitrogen (N) concentration was positively correlated with both SOC concentration and pool. Rates of SOC sequestration ranged from 0.9 Mg C ha-1 yr-1 to 5.4 Mg C ha-1 yr-1, with a national average of 2.8 ± 0.3 Mg C ha-1 yr-1. Differences in rates of SOC sequestration were also attributed to differences in MAP, soil N concentrations, and ρb, however, SOC sequestration rate was also positively correlated with fine soil texture content and pH. The potential C sink capacity of soils was determined and ranged from 20.8 ± 1.0 Mg C ha-1 in Portland, ME to 96.3 ± 6.0 Mg C ha-1 in Minneapolis, MN, with an average across ecoregions of 45.8 ± 3.5 Mg C ha-1. The hidden carbon costs (HCC) of home lawn maintenance due to fertilizer use (0.06 Mg Ce ha-1 yr-1) and mowing fuel combustion (0.19 Mg Ce ha-1 yr-1) produced a mean total emission across sites of 0.25 Mg Ce ha-1 yr-1. Accounting fo (open full item for complete abstract)

Master of Science, The Ohio State University, 2009, Natural Resources

This study was composed of two research components that examined the effects of tallgrass prairie land use changes on soil organic C (SOC). The central objective of the first study was to examine changes in SOC and a suite of soil quality parameters in former agricultural soils now under restored tallgrass prairie. This research was conducted at the Prairie Nature Center, on the OSU Marion campus in northwest Ohio. Soils from 31 year, 13 year, and 8 year- old prairies, and adjacent agricultural and lawn soils were analyzed. These soils demonstrated significant increases in SOC concentration, particulate organic matter (POM), water stable aggregation (%WSA), aggregate mean weight diameter (MWD), total porosity (ft), and available water capacity (AWC), and significant decreases in soil bulk density (ρb) associated with time under tallgrass prairie. The second research component observed long and short-term effects of the conversion of remnant tallgrass prairies to wheat production, in north central Kansas. Total C, microbial biomass C (MBC), and a particle size fractionation of SOC were used as indices of change. Long-term sites showed changes in all fractions analyzed, while only MBC showed significant change in the short-term study. This study provides further evidence that perennial plant communities store and cycle C, and maintain ecosystem processes at far greater levels than annual plant communities.

Doctor of Philosophy, The Ohio State University, 2008, Geological Sciences

Tropical small mountainous rivers (SMRs) may transport up to 33% of the total carbon (C) delivered to the oceans. However, these fluxes are poorly quantified and historical records of land-ocean carbon delivery are rare. Corals have the potential to provide such records in the tropics because they are long-lived, draw on dissolved inorganic carbon (DIC) for calcification, and isotopic variations within their skeletons are useful proxies of palaeoceanographic variability. The ability to quantify riverine C inputs to the coastal ocean and understand how they have changed through time is critical to understanding global carbon budgets in the context of modern climate change. A seasonal dual isotope (13C & 14C) characterization of the three major C pools in two SMRs and their adjacent coastal waters within Puerto Rico was conducted in order to understand the isotope signature of DIC being delivered to the coastal oceans. Additionally a 56-year record of paired coral skeletal C isotopes (δ13C & Δ14C) and trace elements (Ba/Ca, Mn/Ca, Y/Ca) is presented from a coral growing ~1 km from the mouth of an SMR. Four major findings were observed: 1) Riverine DIC was more depleted in δ13C and Δ14C than seawater DIC, 2) the correlation of δ13C and Δ14C was the same in both coral skeleton and the DIC of the river and coastal waters, 3) Coral δ13C and Ba/Ca were annually coherent with river discharge, and 4) increases in coral Ba/Ca were synchronous with the timing of depletions of both δ13C and Δ14C in the coral skeleton and increases in river discharge. This study represents a first-order comprehensive C isotope analysis of major C pools being transported to the coastal ocean via tropical SMRs. The strong coherence between river discharge and coral δ13C and Ba/Ca, and the concurrent timing of increases in Ba/Ca with decreases in δ13C and Δ14C suggest that river discharge is simultaneously recorded by multiple geochemical records. Based on these findings, the development of coral-b (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2008, Geological Sciences

The latest Ordovician (444 million years ago) was a critical period in Earth history. This was a time of significant climatic global change with large-scale continental glaciation. Moreover, the end-Ordovician mass extinction is recognized as the secondmost devastating mass extinction to have affected the Earth. The anomalous Late Ordovician icehouse period has perplexed many researchers because all previous model and proxy climate evidence suggest high levels of atmospheric CO 2during the Late Ordovician glaciation. Also associated with this period is a large positive carbon isotope(a 13C) excursion (up to +7‰) that represents a global perturbation of the carbon cycle. Additionally, a large decrease (0.001) in seawater 87Sr/ 86Sr occurs several million years prior(~460 million years ago);this could reflect an increase in atmospheric CO 2uptake due to weathering of volcanic rocks involved in uplift of the early Appalachian Mountains. To address these Ordovician anomalies, well-studied, thick, and continuous Late Ordovician limestone sequences from eastern West Virginia, south-central Oklahoma, central Nevada, Quebec (Canada), Estonia, and China have been sampled. Carbon and strontium isotopic ratios have been measured on samples from these localities of which Estonian and Chinese sample sites represent separate paleocontinents (Baltica and South China) and are compared with other data sets from North America. These data test previous interpretations that the well-documented latest Ordovician carbon isotope excursion coincides with maximum glaciation. They support a hypothesis that the large positive carbonate carbon isotope excursion was coincident with a warm interglacial(high CO 2levels) period that separated two major glacial advances (with lowered CO 2levels). There are clear parallels between the Late Ordovician and the Late Cenozoic (the most recent) greenhouse to icehouse transitions, with silicate weathering providing the initiator and positive feedback on c (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2007, Environmental Science

Rapid urbanization is increasing turfgrass covered soils throughout the United States. Research on carbon (C) dynamics in turfgrass systems can enable their exploitation as sinks of atmospheric C. In the first study long term (15years) effect of management programs that differed in the application of nitrogen (N) fertilizer, and pesticides on soil organic C (SOC) and turf quality in Kentucky bluegrass lawns was evaluated. The SOC pools in turfgrass systems can be influenced by the amount of N applied and weeds with their N fixing ability and broad leaf cover can reduce turfgrass aesthetic quality but play an important role in the biomass returned to the soil and therefore contribute to C sequestration. In the second study C cost occurring from the use of fossil fuels required for the production, transport, storage, and application of fertilizers, pesticides, and mowing was calculated and compared to the gain of SOC using a sustainability index. Greater sustainability of turfgrass systems for C can be achieved by reducing or replacing the use of mineral with organic fertilizers, replacing chemical with biological pesticides, mowing less often, and returning clippings. In the third study soil carbon dynamics and litter decomposition as affected by grass species perennial ryegrass (PR) and tall fescue (TF) with low and high endophyte infection were evaluated. The SOC along with its labile fractions microbial biomass C (MBC) and dissolved organic C (DOC), soil surface CO2 flux, and litter bag decomposition in the field were analyzed and found to be not different between treatments. The last study determined the spatial variability in SOC pools in urban landscapes. The SOC was more variable across a residential neighborhood block in the City of Wooster than across the lawns in the study region of Wayne and Holmes County, OH. Considering the average SOC pool of 25 Mg ha-1in the 0-12 cm depth and the total turf area for Ohio lawns at 6733 km2, we calculated the total Ohio (open full item for complete abstract)