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Recent studies have demonstrated that nanoscale crystalline iron oxide minerals are common in natural systems. The discipline of nanoscience suggests that these particles in the size range of approximately 1-50 nm will have properties that deviate from the bulk properties of the same material and that these properties will change as a function of particle size. This study begins to fill the void of corresponding experimental investigations that apply the principles of nanoscience to the geochemical reactivity of nanominerals. The rate of Mn²⁺(aq) oxidation on hematite with average diameters of 7.3 nm and 37 nm was measured in the presence of O₂(aq). In the pH range of 7-8, the surface area normalized rate was one to two orders of magnitude greater on the 7.3 nm average diameter particles. Based on the application of electron transfer theory, it is hypothesized that the particles with diameters less than approximately 10 nm have surface crystal chemical environments which distort the symmetry of the MnMn²⁺ surface complex, reducing the energy required to reorganize the coordinated ligands after oxidation to Mn³⁺. Cu²⁺, an analog for Mn³⁺, was used to probe for the presence and nature of the proposed changes in surface structure. Cu²⁺ and Mn³⁺ show similar electronic structure changes in response to the surrounding crystal field due to their d-electron configurations and Jahn-Teller coordinative distortions. Batch sorption experiments on hematite nanoparticles revealed a shift in the pH-dependent adsorption of Cu²⁺(aq). Specifically, an affinity sequence of 7 nm > 25 nm = 88 nm was determined based on the shift of the 7 nm sorption edge to approximately 0.8 pH units lower than that for the 25 nm and 88 nm samples. These data support the hypothesis that unique binding sites exist on the 7 nm nanoparticles that are not significantly present on the larger particles. The National Nanotechnology Initiative stresses the need to address the broader societal impacts of nanoscale research. This dissertation embraces this viewpoint through the development and inclusion of "Nano2Earth: Introducing Nanotechnology Through Investigations of Groundwater," a curriculum which combines nanoscience with the Earth sciences for high school students. / Ph. D.

Parkinson's disease (PD) is a neurodegenerative Lewy body disorder characterized by severe motor deficits, followed by cognitive dysfunction with progression of the disease. Environmental exposure has been suggested as a possible contributor to the development of PD and this view is linked to the discovery of the nigrostriatal neurotoxin MPTP. MPTP can induce dopamine specific degeneration within the basal ganglia often resulting in motor deficits similar to PD. MPTP used in the C57BL/6 mouse is a widely used animal model of PD. The pyrethroid permethrin (PM), and the organophosphate chlorpyrifos (CPF), can produce changes in dopaminergic nigrostriatal neurons, the primary target of PD and MPTP-induced neurotoxicity. Such insecticide induced changes in the basal ganglia could exacerbate the onset or severity of PD. Chronic exposure to the metal manganese (Mn) can damage the globus pallidus (GP) of the BG, and produce motor deficits similar to PD. Since the GP is part of the BG circuitry essential for motor control, and is synaptically integrated with the nigrostriatal pathway, Mn may exacerbate MPTP-induced neurotoxicity. Because the BG is disynaptically linked to the mesocortical pathway, a dopaminergic pathway that is important for cognition, Mn induced damage in the BG could indirectly affect the mesocortical pathway as well. This study investigated the pesticides, permethrin and chlorpyrifos, and the heavy metal, manganese as possible environmental compounds that could exacerbate PD in the MPTP treated C57BL/6 mouse. The first part of this dissertation used immunohistochemistry to examine insecticide induced effets on MPTP-induced neurotoxicity in the dorsolateral striatum of the C57BL/6 mouse, the principal target of the nigrostriatal pathway. Tyrosine hydroxylase (TH) was used as a marker for loss of dopaminergic neuropil and glial fibrillary acidic protein (GFAP) was used as a marker of glial activation in the striatum. Three experiments assessed effects of 1) PM (200 mg/kg), 2) CPF (50 mg/kg) & 3) PM + CPF, on MPTP (30 mg/kg) neurotoxicity. Immunohistochemistry revealed a decrease in TH staining and an increase in GFAP staining with MPTP (30 mg/kg). A main effect increase in GFAP was observed for PM (200 mg/kg), but not for CPF (50 mg/kg) or PM+CPF. Insecticides, alone or combined, did not alter MPTP-induced toxicity. . However, the absence of the PM-induced increase in GFAP staining following combined insecticide treatment suggests a neuroprotective effect. The next set of experiments in this dissertation looked at the effect of Mn on MPTP-induced neurotoxicity in the nigrostriatal and mesocortical dopaminergic pathways of the C57BL/6 mouse. Inductively Coupled Plasma atomic emission spectrometry revealed striatal Mn levels were significantly increased with multiple dose 100, 50, and 25 mg/kg MnCl2. Administration of Mn (MnCl2 s.c., Days 1, 4, & 7) in the MPTP (20 mg/kg i.p., Day 8) treated C57BL/6 mouse revealed Mn and MPTP interactions for locomotor activity, grip strength, and repeated measures of learning. Mn attenuated the effect of MPTP on striatal DOPAC, and facilitated the effect of MPTP on cortical DA and DOPAC. Mn also attenuated the MPTP induced decrease in cortical DAT. While these data support the notion that insecticides can produce tissue damage in the nigrostriatal pathway, in this case, these insecticide induced changes were not found to be strong enough to facilitate PD-like tissue damage. While Mn did not always facilitate MPTP neurotoxicity in the mesocortical and nigrostriatal dopaminergic pathways, these results demonstrate Mn and MPTP can interact in a complex way to alter dopaminergic function as well as motor and cognitive behavior. Differences in brain uptake mechanisms and metabolism of Mn and MPTP, could explain why combined administration of Mn and MPTP differentially affect dopaminergic activity in the nigrostriatal and mesocortical pathways. / Ph. D.

Hypolimnetic oxygenation systems, such as linear bubble-plume diffusers, are used to improve raw water quality. Linear bubble-plume diffusers were installed in Spring Hollow Reservoir (SHR) and Carvins Cove Reservoir (CCR). Diffusers induce mixing that aids distribution of oxygen throughout the hypolimnion. The induced mixing also creates an undesirable effect by increasing hypolimnetic oxygen demand (HOD). Nevertheless, oxygenation systems are commonly used and long-term oxygenation is hypothesized to actually decrease HOD. Increased oxygen concentrations in combination with the induced mixing affect the location of the oxic/anoxic boundary relative to the sediment water interface. If the oxic/anoxic boundary is pushed beneath the sediment/water interface, the concentrations of soluble iron and manganese in the bulk water are reduced. This work was performed to further validate a recently published bubble-plume model that predicts oxygen addition rates and the elevation in the reservoir where the majority of the oxygen is added. Also, the first field observations of a theoretically expected secondary plume are presented. Model predicted addition rates were compared to observed accumulation rates to evaluate HOD over a wide range of applied gas flow rates. Observations in both reservoirs showed evidence of horizontal spreading that correlated well with plume-model predictions and of vertical spreading below diffuser elevations, showing oxygen penetration into the sediment. Experimental observations of a theoretically expected secondary plume structure also correlated well with model predictions. Plume-induced mixing was shown to be a function of applied gas flow rates, and was observed to increase HOD. HOD was also observed to be independent of bulk hypolimnion oxygen concentration, indicating that the increase in oxygen concentration is not the cause of the increased HOD. Long-term oxygenation resulted in an overall decrease in background HOD as well as a decrease in induced HOD during diffuser operation. Elevated oxygen concentrations and mixing, which occur naturally during destratification and artificially during oxygenation, were observed to coincide with low dissolved metal concentrations in CCR. Movement of the oxic/anoxic boundary out of the sediment, which is also common during stratified periods, appears to facilitate transport of reduced Mn to the overlying waters. Hypolimnetic oxygenation increased oxygen concentrations throughout the hypolimnion, including down to the SWI, and induced mixing, although not to the extent observed during destratification. Subsequently, elevated Mn concentrations were observed to be restricted to the benthic waters located immediately over the sediments, while bulk (hypolimnion) water Mn concentrations remained low. The good agreement between the model and the experimental data show that the model can be used as a predictive tool when designing and operating bubble-plume diffusers. Linear bubble-plume diffusers provide sufficient horizontal and vertical spreading to enable oxygen to reach the sediments. Hypolimnetic oxygenation, despite the increased HOD, is a viable method to manage the negative consequences of hypolimnetic anoxia in water-supply reservoirs. / Ph. D.

Without proper removal at a water treatment facility, the soluble manganese (Mn) concentration can reach and exceed the Secondary Maximum Contaminant Level (SMCL) of 0.05 mg/L in the water distribution system. At this level, soluble Mn can be oxidized to solid Mn-oxide particulates, leading to water discoloration events and resulting in numerous consumer complaints. Manganese-laden water can severely stain fixtures and laundry as well as increase turbidity and foul tastes. A major discoloration event can cause a decrease in consumer confidence in the quality of water provided to their taps. Currently, there is no other treatment alternative available that can remove soluble Mn with the high efficiency of the "natural greensand effect. Therefore, researchers are developing ways to effectively create the natural greensand effect in a post-filtration sorptive contactor for application at water treatment facilities. The process of adsorption and oxidation of Mn onto oxide-coated media grains in the contactor will be used for the removal of soluble Mn. However, small media grains, such as sand or anthracite, could produce prohibitive head loss in a sorptive contactor. The focus of this research project was to show that Mn could be effectively removed via adsorption onto larger media (2.0-6.4mm) at hydraulic loading rates of 16-24 gpm/ft², thus producing less head loss and furthering the development of soluble Mn sorptive contactors to be implemented in water treatment facilities. Research was conducted by executing laboratory- and pilot-scale experiments using columns packed with oxide-coated media. Three types of media were used: large grain "torpedo sand," pyrolucite granules, and small gravel. Before being packed into the columns, the torpedo sand and gravel media was coated with an oxide coating using a technique previously developed by Merkle (1995). Manganese uptake capacity was determined for each media type prior to use and after a number of contactor column experiments were completed. Water samples were collected during the experiments and analyzed for soluble Mn concentration. The Mn removal profile was determined by taking water samples at a certain time and at various depths in the media bed. Experiments were conducted to determine the removal profile of the media types under different operating conditions. Hydraulic loading rate, influent Mn concentration, influent free chlorine concentration, and pH were the operational parameters varied. The effect of these parameters of the Mn removal profile was evaluated. Although each media type was able to remove some percentage of soluble manganese from the applied water, pyrolucite media was the most effective media, often providing approximately 80-90% removal of initial manganese concentration. The removal performance of the large-sized media beds was affected by operational parameters as expected from knowledge of prior research. The contactor media beds also provided adequate soluble manganese removal under conditions available at the water treatment facility as determined from the pilot-scale experiments conducted at the Blacksburg-Christiansburg-VPI Water Authority Another important and complementing facet of this research was the development of a proven model that would predict soluble Mn removal performance of various oxide-coated media types and the development of recommendations that could be used for implementing and operating such post-filtration sorptive contactors. A model was developed from first principles for the prediction of soluble Mn removal and fitted to the experimental data. The predictive model showed that removal performance depended on the specific surface area of the contactor media, HLR, and the mass transfer coefficient. Recommendations for the operation of a sorptive contactor containing large oxide-coated media include an applied hydraulic loading rate of 16-24 gpm/ft² with an initial free chlorine concentration of 1.0-2.0 mg/L and a slightly alkaline pH of 7.0-8.0. Greater hydraulic loading rates are recommended to provide capital cost savings due to the decreased contactor footprint required. Alkaline pH is recommended for improved Mn removal. Facilities with a slightly acidic pH due to enhanced coagulation practices should consider adjusting the pH of the finished water for corrosion control prior to the Mn removal contactor for improved Mn adsorption performance. / Master of Science

Many treatment facilities remove soluble Mn by an autocatalytic adsorption-oxidation process involving manganese oxide (MnOx(s))-coated filter media and a free chlorine residual known as the natural greensand effect (NGE). In recent years, significant amounts of aluminum (Al) have been found integrated into MnOx(s) coatings on media from drinking water treatment facilities worldwide. The primary objective of this study was to characterize MnOx(s) coatings developed in the presence and absence of Al, and to further define the role played by Al in the coatings' initiation and development. A secondary objective of the study was to examine the potential for pre-filter oxidation of Mn and formation of nano-size MnOx(s) particles, which would be destabilized by Al(OH)3(s) and captured in the filter. This material could act as a seed for coating formation and help explain the integration of Al into MnOx(s) coatings. Bench-scale column tests were conducted to examine Mn removal and backwash composition, while centrifugation and ultrafiltration were utilized to examine the potential for rapid Mn oxidation. Results indicate that the presence of Al augments the initiation and development of MnOx(s) coatings. The backwash solids of columns loaded with Al were composed of a mixture of Mn and Al, suggesting that active adsorption-oxidation sites were present in the Al(OH)3(s) floc captured by the filter. These results suggest at least a small amount of pre-filter MnOx(s) formation by contact with free chlorine; further, that Al(OH)3(s) solids present may destabilize these negatively charged solids into a form that is important to MnOx(s) coating formation. / Master of Science

Elevated manganese (Mn) concentrations have been measured in groundwater within the Roanoke River watershed, Virginia. Concentrations of Mn often exceed the secondary drinking water standard. A historic belt of Mn ores, the James River-Roanoke River Manganese District (JRRRMD), occurs in the eastern part of the watershed. The project objectives were to 1) evaluate the formation of the JRRRMD ore deposits and 2) analyze existing groundwater chemistry data to evaluate sources and processes that control groundwater Mn. Analysis of ore minerals, morphologies, and chemistry provides support that the ore deposits are supergene in origin, consistent with previous work. Spatial correlations between Mn ore locations and stream terrace deposits support a model of ore formation in which Mn-oxides were precipitated near discharge zones as anoxic groundwater mixed with oxic groundwater. Terrace deposits present at elevations higher than modern streams suggests that topography has been inverted, allowing ores to be found at higher elevations than what is typically associated with ores formed in discharge zones. Analysis of groundwater chemistry data shows positive correlations between Mn, calcium and bicarbonate concentrations in groundwater, suggesting that carbonate-bearing lithologies are probable sources of Mn to groundwater. Regionally, groundwater flows toward the Roanoke River where the flowpath terminus is marked by elevated Mn. The inverse correlation of Mn with dissolved oxygen suggests that reducing conditions that develop along flowpaths allow for Mn to persist in groundwater. Overall, results suggest that the same processes that allowed for formation of the JRRRM ore deposits continue to occur today. / Master of Science

Virginia's Coastal Plain region contains the majority of the state's agricultural production despite having low nutrient soils. The soils in this region are predominantly coarse-textured acid soils with low cation exchange capacities (CEC) (< 3 cmol kg-1) and thus frequently exhibit nutrient deficiencies, including cationic nutrients which are not easily lost by leaching in soils with greater CEC. As a result, soils require careful nutrient management to maintain production levels. Soybean (Glycine max), the world's fourth largest crop, shows sensitivity to manganese availability and regularly experiences deficiency symptoms in low-CEC coastal plain soils. Tomato (Solanum lycopersicum) production, one of the 3 largest vegetable production systems in the world, requires careful management of various nutrients, particularly phosphorous, sulfur, and boron, for proper fruit development. Two novel coated fertilizer products consisting of granular KCl coated in a nutrient powder and a sugar-acid chelating agent are investigated as multi-nutrient sources for soybeans and tomatoes. A comprehensive review of the chemistry, behavior, and functionality of key nutrients provided by the fertilizer (P, S, Mn, and B) in both soils and plant tissues and the current state of chelate use in agriculture is provided along with related production issues with tomatoes and soybean. A greenhouse study investigating the ability of the first coated product (Mn + B coated KCl) to provide micronutrients to soybeans was conducted. Using both low and high organic matter (OM) soils (10 g kg-1; 36 g kg-1), Mn + B coated KCl increased soil Mn compared to no fertilizer and uncoated KCl. Additionally, Mn + B coated KCl increased total above ground tissue Mn compared to control and uncoated KCl for the low OM soil but not for the high OM soil, which was likely due to OM leading to the formation of metal-ligand complexes. There were no significant results regarding B concentration in either the soil or plant tissue due to the low application rate provided by the coating. The same fertilizer (Mn + B coated KCl) was investigated under field conditions to determine if increased soil and tissue Mn can be maintained under various environmental factors. Our results found that for all growing seasons and locations, there were no significant treatment differences between months for both Mn and B, but total monthly averages did fluctuate between months, probably reflecting changes in soil moisture and redox status. When averaged across the entire growing season, differences between treatments were inconsistent. Under field conditions, environmental conditions such as soil moisture and leaching likely masked any consistent treatment effects of the coated products. Two potential soil amendments, P + S + B coated KCl and glucoheptonate (GH), were investigated for their ability to provide nutrients to tomatoes. Three greenhouse trials, each lasting 3 weeks, were conducted. In the first trial, P + S + B coated KCl was compared to the current agronomic recommendation rates for P, S, and B. The coated KCl significantly increased soil and plant tissue P and B compared to all but the KCl + P and KCl + B treatments. The second trial was a glucoheptonate rate trial and showed a significant positive correlation between GH rate and soil and tissue B. The third trial combined and compared the coated KCl and GH products and showed that the treatments containing the coated KCl had significantly increased P, S, and B soil and tissue concentrations, with GH application having no synergistic effect / Ph. D. / The majority of the Virginia’s agricultural production occurs on the nutrient poor soils of the coastal plains where nutrient deficiencies are common. As a result, careful nutrient management strategies are required to maintain crop production levels, including major crops like soybean and tomato. Soybean (Glycine max) show sensitivity to manganese (Mn) availability and regularly experience deficiency symptoms in this region. On the other hand, tomato (Solanum lycopersicum) production requires careful management of nutrients such as phosphorous, sulfur, and boron for proper fruit development. In this dissertation, two novel coated fertilizer products, granular KCl coated in a nutrient powder and a sugar-acid chelating agent, are investigated as multi-nutrient sources for soybeans and tomatoes. This dissertation starts with a comprehensive review of the chemistry, behavior, and functionality of key nutrients provided by the fertilizer in soils and plant tissues, followed by a review of the current state of sugar acid use in agriculture. The production systems for soybeans and tomatoes for VA and the USA will also be discussed. The second component of this dissertation is a greenhouse study investigating the ability of the first coated product (Mn+B coated KCl) to provide micronutrients to soybeans. The Mn+B coated KCl significantly increased Mn compared to control and uncoated KCl treatments in the soil for both soil types and in tissue for the low OM soil. The third component of this dissertation investigates the same fertilizer under field conditions. Our results showed that for all growing seasons and locations, there were no significant treatment differences between months for both Mn and B, but monthly averaged concentrations did fluctuate over time, probably reflecting seasonal environmental shifts. When averaged annually, inconsistent differences were seen between treatments. Under field conditions, environmental conditions like increased soil moisture and leaching likely masked any consistent treatment effects of the coated products. The fourth component of this dissertation investigates two potential soil amendments, the second coated KCl product (P+S+B coated KCl) and glucoheptonate (GH), for their ability to provide nutrients to tomatoes. The study consists of 3 separate greenhouse trials, each lasting 3 weeks. In the first trial, P+S+B coated KCl was compared to the current agronomic recommendation rates for P, S, and B. The coated KCl significantly increased soil and plant tissue P and B compared to all but the KCl + P and KCl + B treatments. The second trial was a glucoheptonate rate trial and showed a significant positive correlation between GH rate and soil and tissue B. The third trial combined and compared the coated KCl and GH products and showed that the treatments containing the coated KCl had significantly increased P, S, and B soil and tissue concentrations, with GH application having no enhancing effect.

The Mn oxide (MnOx(s)) surfaces of water treatment filtration media are known to aid in the capture of dissolved Mn species, but the discovery of significant deposits of Al within these coatings raised several questions about the MnOx(s) surface. A series of experiments and analyses were performed to examine the presence of Al within MnOx(s) coatings formed on water treatment filtration media. It was hypothesized that the presence of Al within the MnOx(s) coatings might have an impact on the capture of Mn by the MnOx(s) surface. A 2008 study of oxide coated filtration media found that Mn and Al are present in nearly equimolar quantities within the oxide coatings. This led to questions of how and why the Al became incorporated into the surface. This phenomenon was analyzed by conducting a series of bench-scale column studies, treatment plant data collection, and analysis of the MnOx(s) surface utilizing an electron microscope. The results confirm that Al deposits onto the MnOx(s) media surface by two separate mechanisms; adsorption of dissolved Al species and the deposition of colloidal and particulate Al(OH)3(s) precipitate species onto the surface. Analysis of the MnOx(s) coating with by electron microscopy shows a heterogeneous surface composed of a mix of crystalline Mn oxides existing alongside amorphous Al(OH)3(s) species. The deposition of Al onto the media surface does not have any significant effect on the removal of soluble Mn, but the potential impact that Al might have on the capture of other dissolved species should be explored further. / Master of Science