https://etd.auburn.edu/handle/10415/2 2026-08-11T23:03:01Z https://etd.auburn.edu/handle/10415/10641 Description, Phylogenetics and Population Genetics of the Brassy Jumprock Allen, Benjamin The Brassy Jumprock (Moxostoma sp.) is a known yet undescribed species of freshwater fish, recognized as distinct since 1956 but left without a valid name due to prolonged taxonomic confusion. The species is herein described as Moxostoma braesium, and its morphology, meristics, distribution, ecology, phylogenetic placement and population structure are documented. A total of 215 specimens were examined and compared with the morphologically similar, co-occurring, congeners M. rupiscartes and M. lachneri. Moxostoma braesium is distinguished from other co-occurring Moxostoma by the presence of 16 circumpeduncular scales and sub-plicate lips. Greater overall body depth and several meristic characters separate it from both M. rupiscartes and M. lachneri, while it can be individually separated from M. rupiscartes by shorter pectoral fins and from M. lachneri by a narrower head width. Phylogenetic relationships were inferred from RADseq SNPs under both diploid and tetraploid genotyping assumptions using maximum likelihood and Bayesian methods. Moxostoma braesium was recovered as monophyletic in all analyses and, under tetraploid assumptions, as sister to all remaining sampled Moxostoma. Population genetic analyses supported a single ancestry cluster, and the early branching position recovered is consistent with biogeographic patterns documented for other similarly distributed southern Atlantic Slope fishes. 2026-08-11T00:00:00Z https://etd.auburn.edu/handle/10415/10640 Mechanistic Controls on the Fate, Transport, and Destruction of Per- and Polyfluoroalkyl Substances in Soil–Water Systems Song, Ziteng Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic contaminants that pose long-term risks to groundwater, drinking water, agricultural soils, and aquatic environments. Their environmental behavior is controlled by a complex combination of molecular structure, soil properties, dissolved organic matter (DOM), and treatment-system chemistry. Because many PFAS are resistant to natural attenuation and conventional treatment, effective management requires both mechanistic understanding of their fate and transport in soil--water systems and the development of technologies capable of destructive removal. This dissertation investigates the environmental and engineered controls on PFAS mobility, retention, sorption, and degradation, with emphasis on the roles of dissolved organic matter and chitosan-modified biochar. The first part of this work examines how dissolved organic matter controls PFAS transport in soil. Saturated column experiments were conducted using a clayey agricultural soil and a mixture of six PFAS, including short- and long-chain carboxylates and sulfonates. Four dissolved organic matter sources, including biosolids, Suwannee River natural organic matter, Pahokee peat, and Leonardite, were used to represent organic materials with distinct optical and chemical properties. Results showed that PFAS transport was strongly dependent on both PFAS molecular structure and dissolved organic matter composition. Long-chain PFAS, especially sulfonates, exhibited greater retardation, stronger tailing, and lower mass recovery than short-chain compounds. Dissolved organic matter altered PFAS mobility in source-dependent ways: some organic matter types enhanced retention and irreversible sequestration of long-chain PFAS, whereas more aromatic and humified dissolved organic matter reduced retention relative to DOM-free controls. Optical indicators, including SUVA254, humification index (HIX), and fluorescence index (FI), were useful predictors of PFAS transport behavior, demonstrating that DOM quality, rather than concentration alone, is a key control on PFAS leaching potential. The second part of this dissertation evaluates engineered biochar as a platform for PFAS sorption and destructive treatment. Biochar was modified using iron oxide, zero-valent iron/chitosan, and chitosan to improve PFAS removal from water. Among the tested materials, chitosan-modified biochar showed the strongest PFAS sorption performance, largely due to favorable surface charge and enhanced interactions with anionic PFAS. When combined with UV/sulfite advanced reduction processes, chitosan-modified biochar significantly improved PFAS degradation and defluorination by concentrating PFAS near reactive radical species. This biochar-enabled advanced reduction system enhanced PFOS destruction and reduced the strong pH dependency commonly observed in UV/sulfite treatment. The third part of this work extends the chitosan-modified biochar/UV-sulfite system to PFAS with different structures and to more environmentally realistic water chemistries. The system was tested for PFBS, PFHxS, PFOS, and PFOSA under varying ionic strength, nitrate, humic acid, and simulated groundwater conditions. Results demonstrated that degradation and defluorination were strongly influenced by PFAS chain length, headgroup chemistry, and matrix composition. Long-chain PFAS generally showed stronger adsorption and more effective degradation, while environmental constituents affected treatment efficiency by altering PFAS adsorption, radical availability, and interfacial reactions. Nitrate, in particular, promoted PFAS adsorption onto chitosan-modified biochar and indirectly enhanced defluorination under certain conditions, whereas natural organic matter had concentration-dependent effects. Overall, this dissertation provides an integrated understanding of PFAS behavior across natural and engineered soil--water systems. It shows that interfacial processes govern both PFAS transport in soils and PFAS destruction in treatment systems. Dissolved organic matter can either mobilize or immobilize PFAS depending on its composition, while engineered biochar can be used to capture PFAS and promote destructive transformation. These findings improve the mechanistic basis for predicting PFAS leaching in amended soils and support the development of low-cost, biochar-enabled treatment strategies for PFAS-contaminated water. 2026-08-10T00:00:00Z https://etd.auburn.edu/handle/10415/10639 School Gardening as Experiential Learning: A Qualitative Study of Extension Educators' Observations of Youth Learning Outcomes in Alabama Shealey, Tansia The purpose of this study was to examine how school gardening is described as influencing youth learning based on Alabama Cooperative Extension System educators’ observations. Specifically, this study explored theoretical perspectives related to student learning, reviewed existing research on garden-based education, and utilized narrative inquiry to examine Alabama Cooperative Extension System educators’ stories and observations of in school gardening and how it is described as influencing youth learning and development outcomes. Through an integrative approach, the study synthesized findings from prior qualitative research with interview data collected from seven educators to provide a comprehensive understanding of how gardening functions as an instructional tool in school settings. The researcher identified supporting literature describing student learning and behavior changes associated with gardening experiences and its perceived positive effect. Therefore, the research’s use of narratives offers insight on the learning effect of school gardening as told by Alabama Cooperative Extension System team members and Alabama educators working with students. The findings revealed notable similarities between the reviewed literature and the educators’ narratives of experience. Consistent with data in this research, interview subjects stated that the schools at which they worked lacked formal in-school gardening curricula, gardening was nevertheless employed to support student learning related to plant growth, scientific processes, and behavioral development. Educators also described observable changes in students’ social behaviors, including increased peer interaction, collaboration, and engagement during garden‑based activities. Interview data further indicated that Alabama Cooperative Extension educators frequently described students as understanding scientific concepts while participating in gardening. Participants shared narratives describing how students applied vocabulary, exhibited curiosity, and engaged in hands‑on problem solving during garden lessons. Moreover, at least two educators described noticeable behavioral improvements among students who had previously been withdrawn or disengaged from learning. These observations aligned with the broader qualitative literature, which suggests that garden‑based learning environments support both cognitive and socio‑emotional development. Overall, the findings from the literature review and educator interviews suggest that educators perceive that in-school gardening programs positively influence student learning and behavior; however, the limited interview data underscores the need for additional research. Broader studies incorporating diverse educational contexts and extended observation periods are warranted to further examine the social and educational effects of gardening on student learning outcomes 2026-08-10T00:00:00Z https://etd.auburn.edu/handle/10415/10638 Development and Evaluation of a Novel Bioprocessing Technique for Valorizing Brewer’s Spent Grains as a Model High Protein Lignocellulosic Waste Stream Shelley, Madison This work utilizes brewers spent grain (BSG) as a low-cost feedstock for the development of a novel processing technique for producing high yield hydrogel polymers from high protein lignocellulosic biomass. BSG accounts for approximately 85% of the solid waste generated by breweries, resulting in an annual global production of 39 million tons per year. The primary limitation preventing adoption as feedstock for bioconversion is it moisture content of 80% significantly increasing it’s transportation and drying cost. Due to breweries high volume of BSG’s production the majority ends up in landfills. A novel processing technique was developed to valorize BSG into functional materials (BSGHP). The final BSGHP, created by a combination of mechanical and chemical pretreatment, followed by wet fractionation, and subsequent secondary treatment and mechanical post treatment before recombination, was characterized to determine potential applications. The subsequent processing techniques were evaluated at final coagulation pH’s of 3.5 and 3.8 to determine how coagulation pH effects BSGHP performance. The BSGHP hydrogel network can be described as a naturally derived, mixed interpenetrating matrix composed of both physical and chemical crosslinks, in which cellulose fibers, proteins, and lignin rich components collectively contribute to network formation and structural integrity. Due to their amphiphilic nature, dissolved phenolics provide hydrophobic properties that counteract fibrillated celluloses hydrophilic nature, thereby increasing the lifespan of BSGHP when undergoing degradation. The dual entanglement and partial cross linking between the cellulose fibers and microfibrillated cellulose within the BSGHP matrix, 3 creates structural reinforcement, enabling progressive load transfer and preventing structural collapse. Based on mechanical analysis, BSGHP is best suited as a replacement for cork-based materials such as protective packaging and structural paneling, due to its higher compressive strain deformation and superior energy adsorption capability. The coagulation pH was also adjusted to 4.5 for evaluation of the BSG matrix base as a hydrogel-controlled release fertilizer (CRF). The 4.5 pH BSG-controlled release fertilizer (CB-CRF) acted as a control and was compared against a formulation containing a 2:1 ratio of gelatin and kappa carrageenan, comprising 14 wt% of the total gelatin kappa carrageenan blend BSG CRF (GKB-CRF). Both CRFs were subjected a 30 day nutrient-release study, along with a 15 day soil moisture content study, and a 15 day soil pH leachate study. Soil leachates were analyzed for nitrogen, phosphorous, and potassium concentrations on Days 3, 5, 10, 15, and 30 for the slow-release study and Days 3, 6, 9, and 15 for the soil moisture content and soil pH studies. The additives in GKB-CRF resulted in greater microbial activity leading to greater nutrient mineralization but faster degradation. Whereas the CB-CRF exhibited more linear nutrient release profile, consistent with those reported for CRFs in the literatures, while retaining much of its nitrogen content after the 30 days period. Both CRFs were determined to be suitable bases for a hydrogel-CRF matrices with low solubility of phosphorous and potassium amendments added. However, CB-CRFs appears more suitable for extended life-cycle crops like tomatoes and wheat, whereas the GKB-CRFs are better suited for short life-cycle crop production like spinach and radishes. 2026-08-10T00:00:00Z