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%.

Committee: James Bauer (Advisor); Andréa Grottoli (Advisor); Peter Curtis (Committee Member); Kathleen Knight (Committee Member) Subjects: Biogeochemistry; Environmental Science; Freshwater Ecology

Master of Science (MS), Bowling Green State University, 2020, Geology

Conventional tillage, a soil preparation practice to produce a fine seedbed, can disturb the soil profile by promoting soil compaction and soil organic matter (SOM) degradation. In contrast, conservation tillage, such as no-till and minimal tillage (30% or more crop residue) have the potential to sustain or increase soil organic carbon (SOC). Additional benefits of conservation tillage include; improvement to soil structure, reducing soil erosion, greater water retention, buffering soil temperatures, and greater crop residue retention. Conservation tillage practices promote nutrient retention in soils. Furthermore; Fe- and Mn-(oxy)hydroxide minerals play an important role in SOC stabilization and sequestration, which also promotes nutrient adsorption. This study aimed to 1) quantify SOC under varying agricultural managements, 2) qualitatively describe the degree of aromaticity and recalcitrance of SOC using fluorescence spectroscopy, 3) correlate SOC quantity with nitrogen and phosphorous retention in soils, and 4) understand the mineral phases responsible for the stabilization and sequestration of SOC, as well as phosphate and nitrate using a four-step chemical sequential extraction. Results showed that no till and minimal tillage sites consistently had greater SOC and fluorescence intensity in the humic-like acids region, when compared to conventional tilled fields. The SOC quality was obtained using relatively quick and cost-effective methods. No till and minimal tillage enhanced SOC stabilization. In addition, conservation tillage practices retained the largest total nitrogen and total phosphorous concentrations at all studied depths (0-30 cm), when compared to conventional tilled fields. Sequential extraction results showed that SOC was stabilized in the following order: crystalline Fe-oxides > amorphous Fe-oxides > Mn-oxides. Fe- and Mn-(oxy)hydroxide minerals can promote the stabilization and long-term sequestration of SOC via the formation of inner sphere (open full item for complete abstract)

Committee: Angélica Vázquez-Ortega Dr. (Advisor); Andrew Gregory Dr. (Committee Member); Ganming Liu Dr. (Committee Member) Subjects: Geology

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)

Committee: Jiquan Chen (Advisor); Johan Gottgens (Advisor); Richard Becker (Committee Member); Ankur Desai (Committee Member); Ge Sun (Committee Member) Subjects: Ecology; Environmental Science

Master of Science, The Ohio State University, 2024, Civil Engineering

Estuarine marshes occur at the interface of terrestrial riverine flows and oceans or lakes. As such, they play a crucial role in the movement, storage, and fluxes to the atmosphere, of carbon. We monitored CH4 fluxes, and the concentration of dissolved organic carbon (DOC) in the Old Woman Creek (OWC) estuary, Ohio. Gas exchange chamber measurements and sampling of surface water for DOC concentration were conducted simultaneously at three locations with distinct hydraulic characteristics: the outflow, mid-flow, and backflow areas, and at three different relative depths (deep, intermediate, and shallow) within each location. Samples were conducted monthly, over the summer and autumn of 2023 (i.e., month 1 to month last). We investigated the temporal and spatial correlation between DOC and CH4 fluxes in OWC, with a focus on the inflow dynamics from nearby rivers and the wetland's hydrological regime. We hypothesized that the high CH4 flux levels observed in OWC are driven by the wetland's intake of DOC, and short-term depth changes (due to barrier opening and closing) and long-term depth changes (due to changes in water levels and inundation) influences methane emissions. We found that DOC in the wetland's inflow positively correlates with the river stage, but contrary to our initial hypothesis, elevated DOC levels within the wetland did not significantly contribute to methane emissions. However, we found that DOC concentrations varied by depth, but not temporally when other factors (temperature, depth, river stage) were considered. Spatially, the outflow area had the highest DOC concentration, with deep depths in each hydrological location exhibiting higher DOC concentrations. CH4 fluxes varied spatially, with the outflow area recording the least methane emissions, while the mid-flow area exhibited higher methane concentrations. Intermediate depths in each hydrological location recorded higher methane emissions. Interestingly, we found that long-term trends of CH4 fl (open full item for complete abstract)

Committee: Gil Bohrer (Advisor); Andy May (Committee Member); James Stagge (Committee Member) Subjects: Atmospheric Sciences; Biogeochemistry; Climate Change; Environmental Engineering; Environmental Science; Freshwater Ecology

Master of Science, Miami University, 2022, Biology

Lakes in the northeastern US are browning or increasing in dissolved organic carbon (DOC) as they recover from acidification and experience an increase in precipitation from climate change. DOC attenuates ultraviolet radiation (UV), reducing exposure of lake zooplankton to damaging wavelengths in browner lakes. Additionally, some zooplankton can detect and avoid UV. DOC's role in the cladoceran Holopedium's survival was tested by exposing organisms to natural solar radiation in the presence vs. absence of DOC. It was hypothesized that when exposed to natural UV, the presence of DOC would increase survival in Holopedium. Additionally, if Holopedium could behaviorally detect and avoid UV or visible light was also investigated. Survival was significantly higher in treatments exposed to UV in the presence vs. absence of DOC. There was no evidence of behavioral response to UV or visible light. These results convey the importance of DOC protecting Holopedium from UV damage as they can inhabit in the surface waters of some lakes, partially due to a defense against tactile predators. Browning may also mediate the potential for resource partitioning between Holopedium and its competitor Daphnia. Predicted increases in browning caused by climate change may continue to alter these patterns.

Committee: Craig Williamson (Advisor); María González (Committee Member); Thomas Fisher (Committee Member) Subjects: Biology; Climate Change; Ecology; Limnology

Doctor of Philosophy, The Ohio State University, 2022, Earth Sciences

Climate change causes extreme precipitation patterns that result in flood and drought conditions and compromise water quantity and quality. Ireland is one of the many countries that face increasing water stress from inconsistent surface water supply and anthropogenic modification of water systems. My dissertation research generates scientific evidence to promote the development of sustainable water resource management in Ireland. The overall goal of my research is to identify the anthropogenic and natural influences on Irish river chemistry and investigate alterations to river chemistry during drought and flood conditions. Surface water samples were collected from rivers in the Shannon, Corrib, and Burrishoole catchments during the 2018 summer drought and 2020 winter flood to investigate climatic, anthropogenic, and environmental drivers of river chemistry. Stable isotopes (δ18O, δ2H, δ15N, δ34S) were used to discern [1] the impact of drought on water river resources and [2] source of nitrate (NO3-) and sulfate (SO42-) to rivers. These data were paired with [3] optical measurements of dissolved organic matter to identify characteristics and reactivity of dissolved organic carbon (DOC) and [4] concentrations of major ions, filterable iron, DOC, and nutrients to identify ‘hotspots' (elevated concentration and flux) of chemical transport. Results of δ18O–H2O and δ2H–H2O analyses show that the 2018 summer drought conditions increased surface water evaporation across Ireland, but that water stress was greatest in the location with the highest population, rather than greatest evaporative deficit. δ15N–NO3- values suggested river NO3- were derived from two primary sources: manure and soil organic nitrogen. δ34S–SO42- data suggested that river SO42- were derived from a mixture of precipitation and reduced S species. DOC pools from peatlands had lower reactivity than DOC from pasturelands. During the 2020 winter flood event, rivers in the lower Shannon catchment, with the gr (open full item for complete abstract)

Committee: Anne Carey (Advisor); William Lyons (Committee Member); Thomas Darrah (Committee Member); Franklin Schwartz (Committee Member) Subjects: Earth; Geochemistry; Hydrology

MS, Kent State University, 2021, College of Arts and Sciences / Department of Earth Sciences

The Huff Run Watershed, located in Mineral City, Ohio, was mined for coal, limestone, and clay from 1853 to the late 1970s. Mine spoil is left scattered on the surface of about one third of the watershed, contributing to metal leaching to the watershed. Although the mine spoil has had time to become vegetated, camouflaging itself among the native landscape, the disturbed pyrite from coal layers is exposed to water and oxygen leading to a chain of chemical reactions, resulting in the production of potentially acidic and metal-rich porewater, which can infiltrate into the groundwater and streams. Remediation efforts for this watershed have totaled around 4.5 million dollars, but most of the remediation is focused on the point sources of contamination. Runoff from the spoil is a nonpoint source of contamination, and most areas are left untreated. These untreated areas can affect the immediate area and many kilometers downstream of the leaching. For this project, soil samples were collected from a vegetated mine spoil hill and a vegetated shale hill in this watershed, to make a physical and chemical comparison of the soils and their pore water. Solid phase characterization included particle size analysis, bulk X-ray powder diffraction, and loss on ignition (LOI). Soil pore water was collected from suction lysimeters installed at different depths (10, 40, 80, and 120 cm) at the two sites. Field-based water quality analyses included pH, dissolved oxygen (DO), electrical conductivity, and temperature; collected samples were analyzed for metals by inductively coupled plasma-optical emission spectrometry (ICP-OES), anions by ion chromatography, and dissolved organic carbon (DOC). The speciation of Al, Fe, and Mn was also determined by a sequential extraction procedure. The particle size distribution showed a sandy loam, with an overall average of 4.4% clay, 47.7% silt, and 47.9% sand in the high wall (HW) and 6.3% clay, 41.8% silt, and 51.9% sand in the mine spoil (open full item for complete abstract)

Committee: David Singer (Advisor); Elizabeth Herndon (Committee Member); David Costello (Committee Member) Subjects: Geochemistry; Geology

Master of Arts, Miami University, 2021, Geography

Previous research has indicated that agricultural land-use often reduces water quality in streams. This includes: 1) an increase in total suspended solids (TSS) due to elevated soil erosion and 2) changes in dissolved organic carbon (DOC) concentrations. The goal of this study is to determine if a forested state park can mitigate these potentially negative impacts. This study examines spatial and temporal dynamics of TSS and DOC in four streams, located in an agriculturally impacted watershed in SW Ohio, as they flow from agricultural land-cover through a naturally forested state park. Eight surface water sites were sampled bimonthly over a one-year period from December 2019 to December 2020. Each water sample was processed to quantify concentrations of TSS and DOC. In addition to examining the impact of land use, this study also examined the effect of discharge and the normalized difference vegetation index (NDVI) on changes to TSS and DOC concentrations. A significant increase in TSS concentrations was found within the state park. The changes in TSS concentrations were not significantly related to stream discharge nor NDVI. A significant decrease in DOC concentrations was found in two streams within the state park. Discharge was negatively correlated with changes in DOC concentrations in three of four streams. The results suggest that small streams in the U.S. Midwest are able to reduce fluvial DOC concentrations in agricultural watersheds within naturally forested areas. Further research is needed to determine why TSS concentrations increased within the forested state park.

Committee: Bartosz Grudzinski (Advisor); Jessica McCarty (Committee Member); Fadel Megahed (Committee Member); Michael Vanni (Committee Member) Subjects: Geography; Geomorphology; Hydrology

Doctor of Philosophy, The Ohio State University, 2021, Civil Engineering

Dissolved organic matter (DOM) is ubiquitous in natural and engineered aquatic systems. DOM can be problematic during drinking water treatment due to its ability to scavenge oxidants and react with chlorine to form carcinogenic disinfection byproducts (DBPs). Drinking water treatment plant operators aim to minimize DBP formation by removing DOM (alum coagulation and activated carbon sorption) or altering DOM composition (permanganate oxidation). While permanganate pre-oxidation has been claimed widely to be an effective strategy to reduce DBP formation, its impact on drinking water treatment and subsequent DBP formation remains poorly understood. Here, a novel ultrahigh resolution mass spectrometric approach was used to characterize DOM by combining data from multiple ionization techniques to provide greater insight on DOM molecular level changes induced by treatment. In Chapter 2, this approach was applied along with Fourier Transform-infrared spectroscopy and ultraviolet-visible spectroscopy to understand which DOM components react with permanganate for two DOM isolates (a terrestrial isolate and a microbial isolate). Aromatic and nitrogenous components were found to react with permanganate and help explain previously observed trends between permanganate-DOM reaction rates and SUVA-254 values as well as why algal-derived DOM can efficiently scavenge permanganate. In Chapter 3, the impact of permanganate pre-oxidation on the response of DOM to subsequent treatments was investigated using ultrahigh resolution mass spectrometry and bulk characterization techniques for three DOM isolates that represented different DOM source types: terrestrial, algal-impacted, and wastewater effluent-impacted. Permanganate pre-oxidation enhanced removal of aromatic components by coagulation and activated carbon sorption because it added negatively charged functional groups that interacted more favorably with sorption sites. It was also observed that complimentary treatments (i.e., coa (open full item for complete abstract)

Committee: Allison MacKay (Advisor); John Lenhart (Committee Member); Linda Weavers (Committee Member); James Cowan (Committee Member) Subjects: Environmental Engineering

Master of Science, The Ohio State University, 2020, Food, Agricultural and Biological Engineering

In the first chapter of my thesis, I investigate the water quality improvement that can be expected from grass filter strips in agricultural headwater streams. Grass filter strips consist of herbaceous vegetation planted at the edge of agricultural fields next to a stream or river, intended to control non-point source pollution by trapping sediments, nutrients, and pesticides flowing into streams. Because they take agricultural land out of production, grass filter strips have been incentivized in the United States, and so it is important to know their effectiveness. My study objective was to understand the impacts of riparian habitat types on nutrient concentrations over time in agricultural headwater streams. Eight streams within the Upper Big Walnut Creek Watershed in central Ohio were selected, possessing unplanted riparian habitats with remnant vegetation, grass filter strips, or forested riparian habitats. Weekly water samples for the measurement of nutrient concentrations were collected from each stream reach from March 2007 to February 2017. Annual mean nitrogen and phosphorus concentrations did not differ (P > 0.05) among riparian habitat types. Dissolved organic carbon was influenced through the interaction effects of riparian habitat type and year and riparian habitat type and season. Forested riparian habitat types may be used to manage DOC levels in agricultural headwater streams. Grass filter strips were not more effective in reducing nitrogen and phosphorus concentrations than filter strips having other vegetation. In the second chapter of my thesis, I study the ability of a less rigorous estimation of stream discharge to replicate state-of-the-art discharge estimates and, when combined with water quality sampling, nutrient loads. Estimation of stream and river discharge is important for understanding its impact on water quality, habitat, living organisms present in the water, and the surrounding ecosystem. Since state-of-the-art monitoring techniques (open full item for complete abstract)

Committee: Margaret Kalcic (Advisor) Subjects: Agricultural Engineering; Agriculture; Aquatic Sciences; Ecology; Environmental Engineering; Environmental Science; Hydrologic Sciences; Hydrology; Natural Resource Management

PhD, University of Cincinnati, 2016, Arts and Sciences: Geology

Dissolved organic carbon (DOC) is a critical nutrient in aquatic ecosystems, but can also be a pollutant in drinking water. Controlled by a combination of catchment wide and instream processes, the bioavailability, reactivity, and concentration of DOC is readily altered by natural and anthropogenic processes within rivers and the greater watershed area. However, little is known about natural or anthropogenic controls on DOC in dryland areas where water resources are limited and increasingly endangered. To address this, we examined the major contributors of DOC within and to a dryland river—the Middle Rio Grande (MRG) in central New Mexico. This was achieved via synoptic sampling of storm event flow in an urban storm drainage system, water in agricultural conveyances, and monthly sampling of the mainstem. We measured DOC concentration, determined its source (terrestrial or instream), and explored its chemical structure (aliphatic v. aromatic) as an indicator of lability. We found that during storm events, DOC entering the river from the storm drainage system is derived from a combination of terrestrial and instream sources. The connection of the landscape to the river via storm event runoff controls when during the storm event DOC from these two sources reaches the river. We found that the agricultural system is a net DOC sink because of water loss during irrigation. The agricultural irrigation system also acts a biogeochemical hotspot where DOC is rapidly cycled. As a result labile DOC is introduced in the agricultural system's conveyances and DOC effluent from the agricultural systems is more labile and bioavailable than DOC in the mainstem. Within the Middle Rio Grande, we find that despite the addition of DOC from storms and agricultural systems, DOC concentration and character remains largely consistent over time and as the river moves north to south. Additionally, in the MRG DOC concentration is uncoupled from discharge. Thus, we hypothesize that anthropogenic (open full item for complete abstract)

Committee: Aaron Diefendorf Ph.D. (Committee Chair); Thomas Lowell Ph.D. (Committee Member); J Barry Maynard Ph.D. (Committee Member); David Byer Nash Ph.D. (Committee Member); Jodi Shann Ph.D. (Committee Member) Subjects: Geochemistry

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

Emission and uptake of greenhouse gases and the production and transport of dissolved organic matter in different wetland plant communities are key wetland functions determining two important ecosystem services, climate regulation and nutrient cycling. The objective of this dissertation was to study the variation of methane emissions, carbon sequestration and exports of dissolved organic carbon (DOC) in wetland plant communities of a subtropical climate in south Florida. The plant communities selected for the study of methane emissions and carbon sequestration were located in a natural wetland landscape and corresponded to a gradient of inundation duration. Going from the wettest to the driest conditions, the communities were designated as: deep slough, bald cypress, wet prairie, pond cypress and hydric pine flatwood. Methane fluxes from the different communities did not show a discernible daily pattern, in contrast to a marked increase in seasonal emissions during inundation. Median and mean + standard error fluxes in g CH4-C.m-2.d-1 were higher in the deep slough (11 and 56.2 + 22.1), followed by the wet prairie (9.01 and 53.3 + 26.6), bald cypress (3.31 and 5.54 + 2.51) and pond cypress (1.49, 4.55 + 3.35) communities. The pine flatwood community acted as a net sink (0.0 and -1.22 + 0.81). Seasonality in methane emissions was positively correlated with the water levels, but not with soil temperature. However, longer inundation periods did not necessarily result in higher methane emissions. The mean carbon concentration from the surface to the depth of maximum 137Cs activity between communities was similar in the deep slough, bald and pond cypress (446, 405 and 369 g-C Kg -1, respectively). However, carbon sequestration rates (g-C.m-2.yr-1) were highest in the deep slough (104 + 14), followed by the pond cypress (60 + 9), bald cypress (30 + 2), wet prairie (24 + 1) and pine flatwood (15 + 1) communities, without an apparent relationship with the duration of the in (open full item for complete abstract)

Committee: William J. Mitsch Ph.D (Advisor); Gil Bohrer Ph.D (Advisor); James Bauer Ph.D (Committee Member); Jay Martin Ph.D (Committee Member) Subjects: Biogeochemistry; Climate Change; Ecology; Environmental Engineering; Environmental Management; Environmental Science; Environmental Studies; Hydrology; Natural Resource Management; Water Resource Management

Doctor of Philosophy, The Ohio State University, 2012, Geological Sciences

Coral reefs are declining globally due to a combination of direct and indirect human impacts. Much of this decline can be attributed to prolonged exposure to elevated sea surface temperatures which induces coral bleaching – a process whereby corals lose their endosymbionts and/or their endosymbiotic pigments resulting in corals that appear pale or white. Corals have extremely different responses to bleaching events: some corals bleach and die, others bleach and recover, and some do not visibly bleach at all. In the absence of abundant photosynthetically fixed C, corals may rely on one or more of the following strategies to sustain themselves and promote recovery: (1) catabolize stored energy reserves, including lipids, carbohydrates, and/or proteins, (2) reduce respiration rates, (3) decrease skeletal growth, (4) increase heterotrophy or (5) shuffle or change their endosymbiont type(s). Although mounding species of coral have been shown to survive bleaching events in greater abundance than branching species, the underlying mechanism(s) for mounding coral resilience is unknown. Furthermore, controlled bleaching and recovery experiments coupled with detailed carbon budgets that incorporate autotrophy and multiple heterotrophic sources (i.e. zooplankton and dissolved organic carbon) do not exist for Caribbean corals. Therefore, two controlled tank experiments, one in Hawaii and the other in Puerto Morelos, Mexico were conducted to understand the bleaching and recovery responses in the Hawaiian coral Porites lobata and the three Caribbean corals Montastraea faveolata, Porites astreoides, and Porites divaricata. Four major findings were observed: 1) Bleaching resilience in the mounding coral P. lobata is due to it harboring a thermally tolerant endosymbiont type combined with an ability to actively metabolize zooplankton acquired C and utilize DOC as a significant fixed C source, 2) Bleached P. astreoides were capable of meeting greater than 100% of metabolic demand by i (open full item for complete abstract)

Committee: Andrea Grottoli Dr (Advisor); James Bauer Dr (Committee Member); Yo Chin Dr (Committee Member); Ozeas Costa Dr (Committee Member); Meg Daly Dr (Committee Member) Subjects: Biological Oceanography

Doctor of Philosophy, The Ohio State University, 2006, Chemistry

Biomass burning and fossil fuel combustion have resulted in the global distribution and accumulation of black carbon in soils and sediments. Black carbon is currently produced at an estimated rate of 1014 g per year, but little is known about its environmental fate and reactivity. Most of this black carbon is charcoal formed by forest fires. The original research in this dissertation is divided among two overarching themes involving the organic geochemistry of the charcoal deposited to soils by biomass burning. The first theme is oriented toward understanding the importance of environmental charcoal as a geosorbent for hydrophobic contaminants (PAHs). The sorption capacity of environmental charcoal differs significantly from that of recently deposited or lab-generated chars. The competitive sorption of natural organic matter is implicated as the cause of diminished sorption capacity. New sorption models are proposed to address the prediction of PAH uptake by fire-impacted soils. The second research theme deals with the environmental fate of charcoal black carbon. Advanced imaging and magnetic resonance techniques were used to compare and contrast the morphology and chemical composition of recently-formed forest fire charcoals to those aged in soil. The colonization of charcoal particles by filamentous microorganisms was an intriguing observation that motivated an investigation of the feasibility of enzymatic charcoal degradation. The lignolytic fungal enzyme, laccase, causes a modest but discernable oxidation and humification of soil charcoal. The spectroscopic analyses also extend to natural waters of a fire-impacted watershed as a potential conduit for the export of charcoal black carbon from soils. Condensed aromatic leachates from the soil charcoal are prevalent in the dissolved organic matter of the soil pore, river, and ground water.

Committee: Patrick Hatcher (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2003, Chemistry

There is currently little molecular level information available for dissolved organic matter (DOM). In this study, electrospray ionization mass spectrometry (ESI-MS) with ultra-high resolution has been used to study DOM at a molecular level. High resolution mass spectra of DOM routinely contains several thousand peaks with a multitude of peaks in each nominal mass region. To study the spectra at the molecular level, the individual peaks need to be examined, a process that is arduous and time consuming. In this study, use of the van Krevelen diagram is demonstrated as an innovative graphical interpretation tool for ultra-high resolution mass spectrometric data of DOM. Plotting of ESI-FT ICR-MS data from DOM indicates that lignin or tannin type molecules compose the main portion of readily ionizable DOM molecules. In addition, many peaks corresponding to hydrogen deficient molecules are observed. These hydrogen deficient molecules found in DOM samples can be related to black carbon derived material. The process of consumption and utilization of DOM by microorganisms is investigated by employing plug-flow thin film bioreactors and ultra-high resolution mass spectrometry of DOM from inflow and outflow water samples. It is shown that the DOM molecules are subject to modifications to lower molecular weight molecules by micro-organisms. Applying van Krevelen analyses for mass spectral data reveals that relative importance of the peaks with low H/C ratios (especially the peaks in the region that has been assigned to black carbon molecules) are generally increased from inflow to outflow water samples. This is consistent in two sets of bioreactor samples collected from two different locations. The current study clearly demonstrates that the method employed in a significant “breakthrough” in the ability to recognize such a biologically refractory form of DOM.

Committee: Patrick Hatcher (Advisor) Subjects: Chemistry, Analytical

Doctor of Philosophy, Miami University, 2011, Ecology, Evolution and Environmental Biology

This dissertation consists of four independent yet interrelated research chapters, each of which addresses a topic under the umbrella of understanding the patterns, causes, and consequences of changes in ultraviolet (UV) transparency in freshwater ecosystems. Chapter 1: Differences in UV transparency and thermal structure between alpine and subalpine lakes: implications for organisms. This chapter addresses the important role of water temperature and UV transparency in structuring alpine lake ecosystems and the consequences of these forces for aquatic organisms that inhabit them. This chapter includes data I collected on a suite of alpine and subalpine lakes throughout graduate school as well as longer term data on these lakes. This chapter was published in Photochemistry and Photobiological Sciences in 2009 (Rose et al. 2009). Chapter 2: Patterns of spatial and temporal variability of UV transparency in Lake Tahoe, California-Nevada. This chapter examines how UV transparency varies relative to longer wavelength photosynthetically active radiation (PAR, 400-700nm) along inshore-offshore transects in the lake and vertically within the water column as well as temporally throughout 2007. This chapter was published in Journal Geophysical Research, Biogeosciences in 2009 (Rose et al. 2009b). Chapter 3: Allochthony Indicators in Freshwaters: Separating the Signals. This chapter compares the utility of several traditional and novel indicators of allochthony including DOC:Chl a, a440:Chl a, stable hydrogen isotopes of seston, measurements of the fluorescence index, the spectral slope region S350-400nm and the ratio of diffuse attenuation coefficients (Kds) at 320:380nm UV. We found significant relationships between most indicators and evidence to support S350-400nm and 320:380nm UV Kd ratios as indicators across a broad gradient of lakes. This chapter is currently in preparation for submission to Limnology and Oceanography. Chapter 4: The Role of UV and Fish in Regulatin (open full item for complete abstract)

Committee: Craig Williamson E (Advisor); A Bailer John (Committee Member); Melany Fisk C (Committee Member); James Oris T (Committee Member); Jasmine Saros E (Committee Member) Subjects: Ecology

Master of Arts, Miami University, 2008, Geography

We use remote sensing and geographic information system (GIS) tools to develop simple predictive models to define relationships between watershed variables known to influence lake DOC concentrations and lake water color in the Absaroka-Beartooth Wilderness in Montana and Wyoming, USA. Variables examined include watershed area, topography, and vegetation cover. The resulting GIS model predicts DOC concentrations at the lake watershed scale with a high degree of accuracy (R2 = 0.92; p = <0.001) by including only two variables: vegetation cover (representing sites of organic carbon fixation) and areas of low slope (0-5%) within the watershed (wetland sites of DOC production). Modeling with Advanced Land Imager satellite remote sensing data provided a somewhat weaker relationship between water color and DOC concentrations (R2 = 0.672; p = <0.001). We compare model predictions to each other to determine success of DOC modeling methods (R = 0.761; p = <0.001).

Committee: Robbyn Abbitt (Advisor); Craig Williamson (Committee Member); William Renwick (Committee Member); Mary Henry (Committee Member) Subjects: Ecology; Environmental Science; Geography; Hydrology; Remote Sensing

PHD, Kent State University, 2012, College of Arts and Sciences / Department of Biological Sciences

Dissolved organic carbon (DOC) is the dominant form of organic matter in aquatic ecosystems and bacteria play a key role in its mobilization to higher trophic levels. The DOC pool is often divided into broad classes such as labile or recalcitrant, based on its ease of uptake by bacteria; or as autochthonous and allochthonous, based on its production within or outside the ecosystem. In this dissertation, I examined the relationship between the composition of the DOC pool and bacterial community structure and function. The three research chapters address this relationship in different freshwater ecosystems. In the first research chapter, the effect of presence or absence of Microcystis, a dominant primary producer in the western basin of Lake Erie as well as an autochthonous DOC source, on bacterial community structure and heterotrophic productivity was studied. This study revealed that bacterial responses were independent of the presence of the dominant primary producer. In second research chapter, the effect of compositional diversity of DOC within labile and recalcitrant categories, on stream bacterial community structure and denitrification rates was investigated. Use of different compounds within each category, administered individually and in mixtures, contributed to the heterogeneity. Results of this study suggest molecular heterogeneity of DOC can lead to differences in bacterial structure and denitrification potential. In my final research chapter, bacterial responses to differences in proportion of autochthonous and allochthonous DOC between a river and reservoir ecosystem were compared. The findings of this study demonstrated that, rather than the proportion of the two DOC sources, each source, considered individually, played a more important role in determining bacterial response. Regardless of the study, in all cases bacterial community structure was not linked to function, emphasizing the requirement to study both. The results indicate that differences i (open full item for complete abstract)

Committee: Dr. Laura Leff (Committee Chair); Dr. Adam Leff (Committee Member); Dr. Darren Bade (Committee Member); Dr. Elizabeth Griffith (Committee Member); Dr. Roger Gregory (Committee Member) Subjects: Ecology

PHD, Kent State University, 2006, College of Arts and Sciences / Department of Biological Sciences

Pelagic, heterotrophic bacteria are essential to lake ecosystem processes, serving as decomposers, nutrient re-mineralizers, and food web links to higher trophic levels. Understanding how phosphate is apportioned to plankton is important since phosphorus is often a limiting nutrient in lakes. The microbial shunt hypothesis (MSH) proposes that available carbon, as well as phosphate, may influence the apportionment of phosphate to plankton communities. The effects of labile dissolved organic carbon (LDOC) on phosphorus dynamics were examined at stations with diverse trophic states and LDOC regimes in Lake Erie to test the assertions of the microbial shunt hypothesis (MSH). More phosphate was apportioned to bacterioplankton at stations with the lowest trophic state index (TSI) and more phosphate was apportioned to phytoplankton at stations with the highest TSI. The highest bacterial P-quotas and phosphate uptake velocities (PUV) were observed at stations with the lowest LDOC concentrations. The lowest P-quotas and PUV were observed at stations with the highest LDOC concentrations. These results were consistent with the MSH. LDOC concentration was not related to TSI. Low P-quotas and low PUV were observed at many stations with low LDOC. These observations were inconsistent with the MSH. An inactive metabolic state in bacteria may explain these inconsistencies. A change in LDOC utilization was observed amongst bacterial assemblages from different stations suggesting that LDOC availability is dependent upon the local bacterial community composition. The biotic and abiotic factors controlling bacterial bioenergetic processes – bacterial productivity (BP), bacterial respiration (BR), and bacterial growth efficiency (BGE) were examined at diverse trophic states in Lake Erie. Bacterial abundance and the condition of the algal community, based on chlorophyll a concentration, most influenced BP and BGE. LDOC concentration most influenced BR. These results suggest that algal-bac (open full item for complete abstract)

Committee: Robert Heath (Advisor) Subjects: Biology, Ecology

Master of Science in Engineering, University of Akron, 2011, Civil Engineering

Dissolved organic carbon (DOC) poses many challenges for drinking water treatment plants (WTP) as its reaction with chlorine produces disinfection by-products (DBP) which are undesirable because if their harmful effect on humans and is also regulated by the United States Environmental Protection Agency (U.S. EPA). Parallel factor (PARAFAC) analysis, fluorescence regional integration (FRI), excitation-emission matrices (EEM) maximum peaks and ultra-violet absorbance (UVA) are all optical analysis methods used to characterize DOC and its contribution to disinfection by-product (DBP) formation. Multifactor linear regression models were developed from these optical analysis methods to predict DOC concentrations and DBP formation from raw water and coagulated water collected from a WTP. This comprehensive study utilized 492 total samples collected from January 2010 to July 2011that were used in the DOC analysis while 88 total samples (September 2010 to July 2011) were used for the DBP analysis. The models were evaluated statistically to determine which of the optical analysis techniques performed the best in predicting DOC concentration and DBP formation. PARAFAC analysis had the highest linear correlations of all the models tested and had statistically significant components characterizing the nature of DOC and the precursors to DBP formation. The speed, sensitivity and low cost of PARAFAC analysis shows great promise for incorporation of PARAFAC components into a WTP operation helping them make more informed and science-based decisions to treatment train processes.

Committee: Christopher Miller Dr. (Advisor); Stephen Duirk Dr. (Committee Member); Chelsea Monty Dr. (Committee Member) Subjects: Environmental Engineering