Master of Science (MS), Wright State University, 2021, Earth and Environmental Sciences

The Theis Environmental Monitoring and Modeling Site is a field research facility, located on the Great Miami River in southwest Ohio, dedicated to the study of hyporheic zone processes. The site is underlain by an aquifer on the order of 21 meters thick, comprised of fluvial deposits. The permeability of the aquifer sediments was quantified both from one large scale hydraulic test (~100 m radial distance) and from grain-size analysis of 119 small-scale core samples (~20 cm length each). The permeability determined from the large-scale hydraulic test is 98.9 Darcies. The test also gave a value for specific yield of 0.25. The geometric mean of the small-scale measurements is 88.3 Darcies, close to the value of the large-scale measurement, and within the central tendency of the distribution of previously published measurements. The aquifer contains an inferred hierarchy of sedimentary architecture, with compound bar deposits comprising unit bar deposits, and unit bar deposits comprising stratasets with different grain-size facies, including sand, gravelly sand, sandy gravel, and gravel. The stratasets are less than a meter thick and less than 10 meters in length. Intervals of sand facies make up 18.5% of the aquifer, have a mean thickness of 0.75 m (standard deviation (σ) of 0.37 m), a mean permeability of 86.8 Darcies (σ of 47.8 Darcies), and a mean porosity of 36% (σ of 4%). Intervals of gravelly sand facies make up 25.2% of the aquifer, have a mean thickness of 0.96 m (σ of 0.46 m), and a mean permeability of 73 Darcies (σ of 49.9 Darcies), and a mean porosity of 28% (σ of 3%). Intervals of sandy gravel facies make up 36.1% of the aquifer, have a mean thickness of 1.00 m (σ of 0.79 m), and a mean permeability of 84.9 Darcies (σ of 49.7 Darcies), and a mean porosity of 25% (σ of 3%). Intervals of gravel facies make up 20.2% of the aquifer, have a mean thickness of 1.10 m (σ of 0.74 m), and a mean permeability of 670 Darcies (σ of 1170 Darcies), and a me (open full item for complete abstract)

Committee: Robert W. Ritzi Jr., Ph.D. (Committee Chair); David A. Schmidt Ph.D. (Committee Member); David F. Dominic Ph.D. (Committee Member) Subjects: Geological; Geology; Hydrologic Sciences; Hydrology

Doctor of Philosophy, The Ohio State University, 2020, Earth Sciences

Upland catchments play an outsized role in the processing and export of water, sediments, nutrients, and organic matter, thus strongly influencing downstream water quality. In Chapter 1, an overview of biogeochemical cycling within upland fluvial sediments is presented, focusing on key regional biogeochemical cycling patterns and solute export processes. Additionally, anthropogenic influences on this environment, such as historical mining activities and climate change, are briefly reviewed in this chapter. Chapter 2 explores the relationship between spatial hydrologic heterogeneity and microbial community assembly and functional potential within the hyporheic zone. The region of groundwater and river water mixing, known as the hyporheic zone, is a hotspot of microbial activity that influences solute export and cycling in rivers. Hyporheic mixing patterns can vary over small spatial scales, leading to heterogeneity in fluid chemistry and microbial community composition and function. Here, we integrate new mass-spectrometry data, metagenomic insights, and ecological models with previous analyses of microbial community composition and dissolved organic matter (DOM) quality to understand spatial relationships between hyporheic flow and microbial community assembly, metabolism, and DOM processing at high-resolution (100 locations) along a 200 m meander of East River, Colorado (USA). Ecological modeling revealed a strong linkage between community assembly patterns and underlying hydrologic and geochemical drivers, including the impact of physical heterogeneity (riverbed grain size) on microbial community structure. Geochemical profiles associated with upwelling groundwater suggest the influence of underlying geology, specifically Mancos-derived solutes, in driving community assembly. Distinct microbial community profiles and functional potential in zones of upwelling groundwater suggest that groundwater chemistry may have a greater influence on biogeochemical cycling wi (open full item for complete abstract)

Committee: Michael Wilkins (Advisor); Steven Lower (Advisor); Audrey Sawyer (Committee Member); Elizabeth Griffith (Committee Member) Subjects: Biogeochemistry; Earth; Ecology; Environmental Geology; Environmental Science; Geobiology; Geochemistry; Geology; Hydrology; Limnology; Microbiology; Mineralogy

Master of Science, The Ohio State University, 2016, Earth Sciences

In coastal rivers, tidal pumping enhances the exchange of oxygen-rich river water across sediment-water interfaces, controlling nitrogen cycling in suboxic riverbed sediments. I developed a one-dimensional, coupled fluid flow and solute transport model that quantifies the influence of tidal pumping on redox zonation and nitrate removal in the hyporheic zones of coastal rivers, and applied it to the tidal freshwater zone (TFZ) of White Clay Creek (Delaware, USA). At high tide when oxygen-rich river water infiltrates into the bed, denitrification rates decrease by ~20% relative to low tide when nitrate-rich anoxic groundwater discharges to the channel. Tidal pumping deepens the aerobic zone by a factor of 6, decreasing denitrification rates by 10%. Therefore, along TFZs nitrate removal rates decrease as tidal amplitude increases due to enhanced oxygen exchange across the sediment-water interface. Sensitivity analyses suggest that denitrification hot spots in TFZs will occur in less permeable, organic-rich sediment under lower tidal ranges and higher rates of ambient groundwater discharge. Tidal pumping is not efficient at removing surface water nitrate but removes up to 81% of groundwater nitrate that would discharge to White Clay Creek. Given the high population densities of coastal watersheds and thus the tendency towards high nitrate inputs from groundwater to rivers, the hyporheic zones of TFZs play a critical role in mitigating new nitrogen loads to coasts.

Committee: Audrey Sawyer PhD (Advisor); William Lyons PhD (Committee Member); Joachim Moortgat PhD (Committee Member) Subjects: Earth; Environmental Geology; Geology; Hydrology

Master of Science, The Ohio State University, 2015, Earth Sciences

Hydraulic conductivity (K) heterogeneity and channel morphology both control surface water-groundwater exchange (hyporheic exchange), which influences stream ecosystem processes and biogeochemical cycles. Here I show that K heterogeneity is the dominant control on exchange rates, residence times, and patterns in hyporheic zones with sharp lithologic contrasts. I simulated hyporheic exchange in a representative low-gradient stream with 300 different bimodal K fields composed of sand and silt. K realizations span five sets of sand-silt ratios and two sets of low and high K contrasts (one and three orders of magnitude). K heterogeneity increases interfacial fluxes by orders of magnitude relative to homogeneous cases, drastically changes the shape of residence time distributions, and decreases median residence times. The positioning of highly permeable sand bodies controls patterns of interfacial flux and flow paths. These results are remarkably different from previous studies of smooth, continuous K fields that indicate only moderate effects on hyporheic exchange. The results also show that hyporheic residence times are least predictable when sand body connectivity is low. As sand body connectivity increases, the expected residence time distribution (ensemble average for a given sand-silt ratio) remains approximately constant, but the uncertainty around the expectation decreases. Including strong heterogeneity in hyporheic models is imperative for understanding hyporheic fluxes and solute transport. In streams with bimodal sediments, characterizing stark facies contrasts is more critical for predicting hyporheic exchange metrics than characterizing channel morphology.

Committee: Audrey Sawyer Dr. (Advisor); Michael Wilkins Dr. (Committee Member); Franklin Schwartz Dr. (Committee Member) Subjects: Geology; Hydrology

Doctor of Philosophy, The Ohio State University, 2013, Geological Sciences

My dissertation research utilizes stable isotopes as tracers of water and solute sources to study specific geochemical (solute origin) and hydrological (glacier meltwater source across a season comparing water contributions from hyporheic zone and/or glacier melt and residence time of precipitation within a managed water supply) problems within McMurdo Dry Valleys (MCM), Antarctica, and Central Ohio, USA. In Chapter II, δ11B isotopic and dissolved B measurements are used to infer the origin of B within MCM aquatic system. Boron stable isotopic values span the range of +12.3‰ to +51.4‰, varying from glacier meltwater streams to the hypolimnion of a highly evaporated hypersaline lake. These data demonstrate that the major sources of B are chemical weathering of alumniosilicates within the stream channels, and a marine source, either currently introduced by marine-derived aerosols or from ancient seawater. In-lake processes create a more positive δ11B through adsorption or mineral precipitation. The glacier meltwater streams, Lakes Fryxell, Hoare, and upper waters of Lake Joyce display a mixture of these two sources, with Lake Joyce bottom waters primarily of marine origin. Lakes Bonney and Vanda and Blood Falls brine are interpreted as having a marine-like source changed by in-lake processes to result in a more positive δ11B, while Don Juan Pond displays a more terrestrial influence. In Chapter III, δ18O and δD are used to trace water source variation via hyporheic zone or glacier melt within two MCM streams over an entire melt season. The isotopic variation of these streams was more negative at the beginning of the season and more positive later. D-excess measurements were used to infer mixing between hyporheic storage and glacier meltwater. It was supported that Von Guerard Stream has a large, widespread hyporheic zone that changes with time and discharge amounts. The chemistry of Andersen Creek also displayed hyporheic zone influence at certain times of (open full item for complete abstract)

Committee: William Berry Lyons (Advisor); Anne E. Carey (Committee Member); Bryan G. Mark (Committee Member); John Olesik (Committee Member) Subjects: Environmental Geology; Environmental Science; Geochemistry; Geology; Hydrologic Sciences

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

Excess nitrogen in rivers and lakes is a well known problem which leads to eutrophication and can leave water bodies neither aesthetically pleasing nor a healthy ecosystem. 95% of all stream miles in the United States are small streams, and they have a significant capability to prevent excess anthropogenic nitrogen from reaching larger, impaired bodies. Instead of modifying natural streams to test engineering solutions and toxicity of pollutant loads, stream mesocosms and computer models have been used to analyze the processes of natural streams. A computer model was developed using nutrient data obtained from a stream mesocosm at the USEPA's Experimental Stream Facility (ESF) in Milford, OH to examine the processing of nitrogen by the stream mesocosm, and by extension, natural streams. The model showed that, for the ESF mesocosms, sediment, temperature, and light are very important factors in determining how much nitrogen is either stored or passed on to receiving bodies.

Committee: Paul Bishop PhD (Committee Chair); Margaret Kupferle PhD, PE (Committee Member); Christopher Nietch PhD (Committee Member) Subjects: Environmental Engineering