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School of Environmental Studies

Meet Our Current PhD Students 

Meet our current students and read about their research below.

PhD Student Samantha Allen at Collins River Samantha Allen- Integrated Research

Sam's research proposal is titled “Integrated Analysis of Hydrology, Anthropogenic Threats and Species Distributions within Stream Ecosystems of a Major Military Base” . It focuses on using GIS and statistical modeling to analyze the aquatic resources at Arnold Air Force Base. She hopes to explore the potential to use GIS techniques in innovative ways to study Karst ecosystems as well as stream habitats and species. 

Abigail G. Blake-Bradshaw- PhD StudentAbigail G. Blake-Bradshaw- Biology

Abby’s research is titled: Mallard (Anas platyrhynchos) wintering ecology and the effects of sanctuary and disturbance. Abby is studying wintering waterfowl ecology and is interested in assessing impacts of anthropogenic disturbance on wintering mallards.  In particular, she is determining factors that influence sanctuary use in west Tennessee, a current and historically important region for waterfowl hunting. She aims to provide information to better understand and manage sanctuaries to meet wintering waterfowl needs.

SOES PhD Student Peter BlumPeter Blum- Biology

Peter's research is titled: "Transfer of PCBs from Emergent Insects to Terrestrial Consumers in Historically Contaminated Streams and Reservoir". His dissertation focuses on how stream insects that develop in polychlorinated biphenyls (PCBs) contaminated sediments can transfer PCBs to terrestrial consumers when they emerge as winged adults. Gray bats (Myotis grisescens) utilize emergent aquatic insects in their diet, which provides a route for PCB exposure and a potential concern for their conservation. Because PCBs are resistant to decomposition, historical contamination of PCBs at Wood’s Reservoir and several streams near Arnold Air Force Base may be sources of PCB exposure to local gray bat colonies. His research investigates how much insect biomass is emerging from these streams and reservoirs sites as a potential food source for bats, the PCB flux from these emergent aquatic insects, and how nutrient stoichiometry (the ratios of major nutrients in insects) affects PCB biomagnification.

Martine Patiance Bowombe-Toko- Agriculture

Martine is originally from Mbanga (Littoral region, Cameroon) and her research study focuses on preventing or controlling periodical cicada oviposition damage associated with nursery tree crops. Her dissertation is titled, "Determining control strategies for periodical cicadas in commercial ornamental nursery plants in Tennessee."  To accomplish this goal, two major priorities will be addressed: 1) evaluation of new or current insecticide treatments to manage periodical cicada adults using cage studies in shadehouse settings and 2) assessment of nursery tree damage by periodical cicada adults (Brood X, 2021) in cooperating East Tennessee field nurseries. However, with limited nurseries located so far, they will include the insurance assessment reports from the 2011 emergence, to return in 2024, and from the 2008 emergence to return in 2025.

Robert Brown PhD StudentRobert Brown- Biology

Dissertation title: Linking Nutrient Removal Pathways with Riverine Nutrient Subsidies in Restored Floodplain Wetlands  Abstract: Intact soil core incubations with nutrient rich water provide valuable estimates of potential nitrogen (N) and phosphorus (P) cycling rates at the interface of aquatic and terrestrial ecosystems. These data facilitate understanding of management practices that enable soils to remove N and P from floodwater and reduce impacts of agricultural runoff on downstream ecosystems. My research focuses on: 1) scaling-up N and P removal rates from soil core incubations across representative management areas enrolled in the USDA Wetlands Reserve Program; 2) identifying tradeoffs between desirable N removal (N2 gas production) and greenhouse gas emissions (N2O gas production); and 3) placing N and P removal rates measured in the laboratory within context of natural floodwater by measuring nutrient concentration patterns across a reconnected floodplain forest and six tributaries of the Mississippi River.

PhD Student Sabrina BuerSabrina Buer- Integrated Research

Sabrina's research is titled, "Experimental and Modeling Approaches for Using Platinum-Doped Thin Film Photocatalysis for Simultaneous Contaminant Degradation and Hydrogen Production in Wastewater Treatment Systems." As the amount of human and industrial waste in the environment increases, the need for more effective and efficient water treatment methods is higher than ever.  Current wastewater treatment processes have been found to be ineffective against a growing number of contaminants, including pharmaceutical compounds.  Sabrina’s work focuses on the need for a safe and environmentally-friendly method of removing pharmaceutical compounds from surface and drinking water sources, and will address this issue from two perspectives: 1) The photocatalytic degradation of acetaminophen via UV-C radiation and a titanium dioxide photocatalyst, and 2) The development of a mathematical model to provide essential information regarding reactor volume, the amount of photocatalyst (titanium dioxide) needed for degradation, and the time it would take to achieve complete contaminant degradation.      

Bryant Davis- Integrated Research

Bryant's project is entitled Geochemical Fingerprinting of Natural Waters in Middle Tennessee. He is currently using an ion chromatograph to obtain both cationic and anionic species in surface waters, but he hopes to expand this technique to a recently purchased inductively coupled plasma mass spectrometer.

PhD Student Cody Godwin Cody Godwin- Biology

Cody's research is called, "Impacts of Snake Fungal Disease in Tennessee, Variation in Snake Immunology, Physiology and Demographic Structure." . Cody studies Snake Fungal Disease (SFD), a mycosis effecting numerous North American snakes, including snakes in Tennessee. His dissertation focuses on the immunological, physiological, and population effects the novel fungal pathogen, Ophidiomyces ophiodiicola, has on snakes in Tennessee. In addition to studying SFD, he also collaborates with a team of researchers in the outback of Australia studying the nesting and spatial ecology of the perentie (Varanus giganteus). His primary interests are herpetology, natural history, reptile and amphibian pathogens and immunology, physiology, reproductive ecology, and conservation.

PhD Student Brooke GrubbBrooke Grubb- Biology

Dissertation title: An interdisciplinary approach to understanding ecology and genetics of a narrow endemic crayfish species, Faxonius wrighti.
Brooke is studying the taxonomic validity, habitat needs, conservation genetics, and movement of Faxonius wrighti (Hardin Crayfish).  Her work will involve aspects of landscape ecology and genomics to understand how the environment influences crayfish movement, genetic structure, and generate predictive models under different climate change scenarios to highlight populations at increased risk of extirpation. Her research will aid in the generation of a species status assessment (SSA) used to make federal listing and management decisions.

Rachel Kaiser PhD StudentRachel Kaiser- Geoscience

Rachel's dissertation is titled, "An Interdisciplinary Approach Towards Understanding Antibiotic Resistance in Urban karst Groundwater Systems." Rachel's research is studying the prevalence of antibiotic resistance in groundwater resources, particularly urban karst areas, in correlation with environmental determinants, including water quality and spatio-temporal trends, to understand the resistome in urban karst environments. This understanding, along with a global and national antimicrobial resistance policy and program analysis, will also contribute to the development of an integrated framework of antimicrobial resistance stewardship for water resources utilizing the four pillars of surveillance, innovation, mitigation, and prevention.  

PhD Student Nick MasteoNicholas Masto- Biology

Nick's dissertation is titled, "Annual cycle ecology of mallards from the Mississippi Alluvial Valley." Nick is studying movements, habitat selection, and other behaviors of mallards (Anas platyrhynchos) across their annual life cycle (i.e., migration, wintering, breeding) using state-of-the-art GPS-GSM telemetry units. 

Haley Lawsone- PhD StudentHaley Lawson- Chemistry

Haley's research is titled "Demethylation of Amphetamine-type Stimulants by Ultraviolet Light During Tertiary Treatment at the Cookeville Wastewater Treatment Plant." It focuses on how methamphetamine and MDMA will degrade when exposed to UV light in wastewater treatment plants.  The mechanism of this degradation is unknown and will be studied. This mechanism will allow us to know what by-products are being produced and released in the environment.

Current PhD Student Chioma OnwuchekwaChioma Onwuchekwa- Chemistry

Chioma is from Imo State (South -East Nigeria) and she has lived most of her life in Lagos, South-Western Nigeria. Her doctoral research aims to better understand how and/or if the wastewater treatment plant contributes to the occurrence of microplastics in the environment, and the role of microplastics as possible vectors for pollution (focus on psychostimulants) in the environment. This portion of the research entails investigating the adsorption of selected psychostimulants onto microplastic pellets and determining the concentration via LC-MS. 

PhD Student Kenny Pierce GreenhouseKenny Pierce- Agriculture

Kenny's research is titled: "Development of rapid-screening protocols for predicting allelopathic interactions among cover crops, weeds, and market crops." Allelopathy is broadly defined as the biochemical interactions between all types of plants, including microorganisms. Because allelopathic effects include both inhibitory and stimulatory responses and may be species and cultivar specific, a method for rapidly screening crops and weeds for allelopathic interactions is needed. The objective of this research is to establish growth chamber and greenhouse protocols for rapidly screening plant species and cultivars for allelopathic interactions that are consistent with allelopathic interactions observed in field production situations.  

PhD Student Kitty PhillipsCatherine "Kitty" Phillips - Integrated Research

The title of Kitty's dissertation is "Ethnobotany Among Cherokee and Chocktaw Women: Medical and Spiritual Uses." The basic premise of he4r research is to explore the plants and methods used by the Cherokee and Choctaw women to cure ills, to prevent illness, to heal wounds, and for overall health.  She will explore which methods worked and why. In addition, she is researching the spiritual or ritualistic uses of plants in their culture.  She also want to determine the overlap between the uses.

Richard Pirkle- Biology

Canada geese in the Upper Cumberland region of Tennessee have been intensively banded over the past two decades. Richard's research involves the analysis of this long-term dataset for patterns that explain Canada goose dispersal, reproduction, and molt site fidelity. In particular, he is interested in how stress may impact nesting physiology and influence social structure amongst unrelated Canada geese. He is also interested in the impact of increased hunting mortality due to banding. 

PhD Student Sunil RawalSunil Rawal- Integrated Research

Sunil's dissertation is titled, "Advanced Oxidation of Acetaminophen for Wastewater Treatment: Testing A New Approach for Degradation by Photocatalytic Methods via TiO2 Films." Abstract: Traditional Waste Water Treatment Plants (WWTP) have not been designed to handle pharmaceutical-based contaminants and, therefore, cannot completely eliminate drugs residues. As a result, pharmaceutical metabolites can be found in ground water, surface water and even in drinking water in low concentrations. The application of titanium dioxide (TiO2) photocatalysis, for water purification, is a widespread technique due to it is chemically inert, cost-effective, non-toxic, and environmentally friendly. In this contribution, transparent, anatase-form TiO2 thin films were prepared via the sol-gel method and deposited onto glass microscope slides, using a novel spraying technique, with coatings ranging from one to ten. Furthermore, characterization of the coated TiO2 thin film slides was performed by using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The slides were used to determine the photocatalytic degradation rate of acetaminophen with different pH ranges (acidic, basic and neutral), different contaminant concentrations, and different slides conditions. The most favorable photocatalytic degradation outcome Acetaminophen of ~ 44% was accomplished by using six glass slides with ten coating layers of TiO2 in a neutral medium. It was observed that over a period of 90- minute intervals the increase in number of thin film slides displayed a considerable increase in the degradation rate due to the increase in surface area, that helps to form more active sites. The global reaction rate constants for both four and six thin film glass slides increase with the increases in the coating layers. Further, a successful comparison was conducted to test the degradation of acetaminophen with different advanced oxidation processes to degrade acetaminophen, including the following: UV, UV/H2O2, and UV/H2O2/TiO2.

PhD Student Phillip RobersonPhillip Roberson- Geology

Phillip's research focuses on understanding ancient reef-like structures known as Waulsortian mounds. He will be examining the paleoecology, stratigraphy, and geochemistry of these mounds to better understand how and why they formed. 


PhD Student Christopher WatersChristopher Waters- Biology

Chris's research is titled, "Metabarcoding environmental DNA to examine pollinator communities across the range of Physaria globosa (Brassicaceae).” and is part of the recovery and conservation efforts for a federally endangered mustard species called Short’s bladderpod (Physaria globosa(Desv.) O'Kane and Al-Shehbaz). The primary goal of Chirs's research is to investigate and monitor pollinator communities across the range of Short’s bladderpod via metabarcoding environmental DNA (eDNA) on flowers. As insects visit flowers they can leave behind small fragments of DNA in saliva or shed hairs that can be extracted from the flowers and identified to species or taxonomic group. This method allows us to identify and monitor the pollinator community composition across the range of Short’s bladderpod more efficiently compared to traditional sampling techniques.

Spencer Womble-PhD StudentSpencer Womble- Biology

The title of Spencer's dissertation is "Factors Influencing Nutrient Flux Rates in Restored Agricultural Floodplain Wetlands in western Tennessee and Kentucky, USA". His research focuses on how wetland hydrology influences nutrient retention in restored agricultural floodplain wetlands in the upper Mississippi Alluvial Valley. Soil cores are collected from various restored wetland habitats across western Kentucky and Tennessee and incubated with high nutrient water to estimate maximum nutrient flux rates for each habitat. Environmental data from each sampling location are also collected to see which factors correlate with nutrient flux rates. Further, Spencer is using remotely sensed data to examining how cycles of wetting and drying in areas where soil cores are collected affect nutrient flux rates.



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