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Inflammation is a critical immune response that protects the host against infection and tissue damage. However, dysregulated inflammation can be damaging to host tissue and can exacerbate disease. The NOD-like receptor pyrin-domain-containing protein 3 (NLRP3) inflammasome is a key orchestrator of inflammation, activating caspase-1-mediated processing and release of the pro-inflammatory cytokines interleukin (IL)-1beta and IL-18, as well as driving gasdermin D (GSDMD)-dependent pyroptotic cell death. In addition to pathogenic stimuli, NLRP3 senses perturbations in cellular and tissue homeostasis. As such, aberrant NLRP3 activation is frequently associated with low-grade, sterile inflammation that contributes to the pathogenesis of many non-communicable diseases, including Alzheimer's, atherosclerosis and diabetes. As such, the NLRP3 inflammasome represents an attractive therapeutic target. In order to facilitate the development of new treatments for diseases in which NLRP3 is implicated, the primary aim of this thesis was to gain further insight into the mechanisms governing NLRP3 inflammasome activation and mature IL-1beta secretion. Growing evidence suggests that chloride (Cl-) efflux is an important cellular event during NLRP3 inflammasome activation. The work conducted in this thesis demonstrates that the volume regulated anion channel (VRAC) is essential for hypotonicity-induced NLRP3 inflammasome activation but is dispensable for NLRP3 inflammasome activation in response to classical NLRP3 agonists such as adenosine triphosphate (ATP), nigericin and silica, suggesting that alternative Cl- channels are involved in the response to these stimuli. Following on from this work, Cl- channels were then explored as therapeutic targets within the NLRP3 inflammasome pathway. Using rational chemical design and iterative screening, a new series of urea-based Cl- channel inhibitors were developed that demonstrate potency and selectivity for the potassium (K+)-dependent pathway of NLRP3 inflammasome activation. In developing these molecules, a specific role for Cl- efflux during the K+-dependent pathway of NLRP3 inflammasome activation was revealed. Finally, we present an inflammasome-free model of unconventional IL-1beta secretion that allows detailed study of the mechanisms underlying IL-1beta release in the absence of GSDMD pore formation and/or pyroptosis. A new proximity labelling method to explore the IL-1beta interactome was also established with the aim of identifying mediators of IL-1beta release in our cell model. In summary, the findings of this thesis provide new insights into the mechanisms governing NLRP3 inflammasome activation and IL-1beta release, and excellent tools to study this inflammatory pathway. In doing so, these studies reveal new therapeutic avenues for selective inhibition of NLRP3/IL-1beta, which may pave the way for new treatments for inflammatory disease.

The mammalian uterus plays a central role in the reproductive process. During pregnancy the organ undergoes a process of remodelling that is not restricted to a change in volume; its behaviour transitions from relative quiescence to regular contraction. This progression is incompletely understood; in particular, questions surround the final stages when the organ transitions from a non-labouring state to a labouring state and complications such as pre-term birth can occur. Pre-term birth is associated with an increased chance of morbidity and mortality for the child and is the leading cause of death in children under 5 worldwide. Up to 13% of births in the developed world are pre-term and the annual cost to society of managing this problem is considerable; in 2006 the financial cost was estimated to be over £2.9 billion in England and Wales alone. In this project a physiologically detailed, multi-dimensional, computational model of the rat uterus, which scales from the single-cell up to a full 3D organ, was developed and used to investigate uterine function. The single-cell model incorporates several changes from the previously published Tong et al 2011 model. The present model includes alternative descriptions of the intracellular ion handling and mechanical systems of the uterine cell, in addition to a reformulated L-Type calcium current, voltage-activated potassium current, calcium-activated potassium current and calcium-activated chloride current. The hypothesis that sodium-channel density can act as a trigger mechanism for initiating labour in late pregnancy was explored. The present model is able to accurately predict and reproduce calcium transients based on experimental patch clamp recordings, as well as the effects of drugs and hormones, including oestradiol, oxytocin, wortmannin and nifedipine. The model was used to investigate the adverse effects of using nifedipine as a tocolytic agent on the cardiovascular system and suggest countermeasures that could permit its use in patients with pre-existing heart conditions: using agonists that target the sodium-potassium pump and SERCA to partially restore vascular function, without impeding nifedipine's tocolytic efficacy. A tissue model was then constructed and used to investigate the synchronisation of electrical activity in myometrial tissue. The primary hypothesis was that heterogeneities within the tissue could evoke the spontaneous and sustained activity required for synchronicity. It was shown that spatial heterogeneity in electrical coupling played an important role in sustaining electrical activity. Spontaneous activity was evoked by using a tissue sample containing cells with heterogeneous excitability, resulting from a stochastic element in the activation potential of their sodium-channels. It was shown that at least 3% - 8% of cells must be pacemaking in order to produce stable electrical waves that propagate successfully in tissue. This work represents an advance in comprehensive uterine cell modelling and extends considerations beyond purely deterministic models, towards models that include stochastic elements, which can uncover complex, non-linear behaviours of uterine electrophysiological systems.

Corrosion of reinforcing steel in concrete due to chloride ingress is one of the main causes of the deterioration of reinforced concrete structures, particularly in marine environments. It is therefore important to develop a reliable prediction model of chloride ingress into concrete, which can be used to predict the chloride concentration profiles accurately to help to assess the service life for reinforced concrete structures. Cementitious materials are porous media with a highly complex and active chemical composition. Ionic transport in cementitious materials is a complicated process involving mechanisms such as diffusion, migration, ionic binding, adsorption and electrochemical interactions taking place in the pore solution of the materials. The process is dependent on not only the microstructural properties of the materials such as porosity, pore size distribution and connectivity but also the electrochemical properties of the pore solution including ionic adsorption and ion-ion interactions. This thesis presents a numerical study on the multi-component ionic transport in concrete with the main focus on the microscopic scale. This study first investigated the impact of the Electric Double Layer (EDL) on the ionic transport in cement-based materials. The EDL is a well-known phenomenon found in porous materials, which caused by the surface charges at the interface between solid surfaces and pore solutions. The numerical investigation is performed by solving the multi-component ionic transport model with considering the surface charges for a cement paste subjected to an externally applied electric field. The surface charge in the present model is taken into account by modifying the Nernst-Planck equation in which the electrostatic potential is dependent not only on the externally applied electric field but also on the dissimilar diffusivity of different ionic species including the surface charges. Some important features about the impact of surface charge on the concentration distribution, migration speed and flux of individual ionic species are discussed. Then a new one-dimensional numerical model for the multi-component ionic transport in concrete to simulate the rapid chloride migration test is proposed. Advantages and disadvantages of the traditional methods used to determine the local electrostatic potential, i.e. electro-neutrality condition and Poisson’s equation, are illustrated. Based on the discussion a new electro-neutrality condition is presented, which can avoid the numerical difficulties caused by the Poisson’s equation, and remain the non-linearity of the electric field distribution. This model with the new electro-neutrality condition is employed to simulate the RCM test to prove its applicability. The new model is promising in solving the multi-component ionic transport problems especially in microscopic scale. Lastly, a one-dimensional numerical investigation on the chloride ingress in a surface-treated mortar with considering the penetration of sealer induced porosity gradient was performed. The numerical model was carefully treated to apply governing equations of ionic transport to this situation of two pore structures, with every parameter clearly defined on the microscopic scale.

Enhanced biological phosphorus removal (EBPR) was researched from the performance of a modified University of Cape Town (UCT), anaerobic-anoxic/nitrifying-aerobic process. The work focussed on high P influent where milk was compared to carbohydrates as exogenous added carbon and typical settled sewage. The results confirmed that at equal COD load in the influent (minimum COD:P (250:5) ratio for EBPR), milk always provided sufficient soluble substrate than the carbohydrate mix, but also improved the EBPR performance. The laboratory scale treated 10L/day where 2 parallel treatment trains for milk and an equivalent carbohydrate mix as supplement to compare and study the P sequestration from hypothesised P ligands in milk and easily assimilable carbon (AOM) after fermentation for biological P uptake. The aerobic bioreactors used submerged flat sheet membranes (AeMBR) to improve the effluent quality and reduce the suspended solid residues. The results suggested extra benefits from adding calcium chloride (CaCl2) (200 ml at 250 mM/day or 200 mg/L treated) to form P complexes both in the anaerobic and aerobic zones (100 ml CaCl2 250mM/zone/day). To complete P removal a calcium phosphate (CaPO4) further treatment stage (post membrane final effluent (F.E.)) was added for nucleation. The combination of, A2O-N, exogenous carbon and calcium addition improved the performance of the EBPR, and enabled the laboratory units to achieve less than the 1 mg/L P required by the EU Directive. The process was tested at higher than normal P loads (maximum 100 mg/L) (domestic wastewater influent 15 mg/L). Experiments with influent P load ≤ 50mg/L, with 1% milk as AOM were compared to the carbohydrate mix and could remove soluble P to less than 1mg/L above 97% and less than 2 mg/L more than 99% of the in the time respectively. With an influent P load of 60mg/L (maximum 100 mg/L), the soluble P in the F.E. with milk was below 5 mg/L and below 8 mg/L with carbohydrates mix. The results showed that most of the phosphorus was retained by the sludge during the anoxic-aerobic phases. The remaining phosphate in the F.E. was able to pass through AeMBR pore size (0.4 μm) and needed to be chelated by the nucleation process. The results indicated this A2O-N modifications achieved stable nutrient removal and also offered the potential for more sustainable phosphorus recovery. The EBPR without AOM was 25% less efficient compared to milk and never achieved the E.U standard of 1mg/L in final effluent. The flat sheet membrane always achieved a NTU final effluent below 1 and the TOC always greater than 90% removal or less than the EU 125 standard regardless of the feeding COD/P ratio.

It has been the purpose of this PhD program to determine whether current laboratory-based methods of investigating Atmospherically-Induced Stress Corrosion Cracking (AISCC) of austenitic Stainless Steels (SS) are adequate in modelling realistic corrosion processes within a marine aerosol environment. Results obtained throughout the study have sought to address three key aims. Mainly, to understand the nature and behaviour of primary marine aerosol containing organic matter present within oceanic surface waters, the interfacial interactions of such aerosol droplets deposited on to austenitic stainless steels and, ultimately, their impact upon AISCC processes. Based upon the work conducted during this research, several conclusions may be deduced. The presence of primary organic components within a sea-salt aerosol leads to a reduction in surface tension at the liquid-vapour interface; highlighting the surface-active nature of algal exudates. Surface-active constituents also have the potential to aggregate at the liquid-solid interface. The inclusion of exudates, therefore, has the potential to maintain an electrolytic environment on an austenitic steel substrate for an elongated time period under ambient conditions. Following subsequent evaporation, organically-enriched seawater droplets typically produce an organic surface film. The results of these interfacial studies have informed AISCC measurements using U-bend specimens, which demonstrate a correlation between cracking and droplet size. Furthermore, the limiting factor for AISCC may not be a function of deposition density as previously thought but rather of droplet surface area.

Chloride-induced corrosion of reinforcing steel in concrete is a worldwide problem. In order to predict how chlorides penetrate in concrete and how other ionic species in con-crete pore solution affect the penetration of chlorides, this thesis presents a numerical study on multi-phase modelling of ionic transport in concrete dominated by migration process. There are many advantages in rapid chloride migration test (RCM) method and numeri-cal approach. However, most of models in the literature predicting chloride diffusivity in concrete are diffusion models, which not consider the action of externally applied electric field. In view of this, the specific aim of this thesis is to develop a rational nu-merical migration model to simulate chloride migration tests. By using this model, the diffusion coefficient of chlorides in concrete will be efficiently predicted. Furthermore, other mechanisms of ionic transportation in composite materials can be scientifically in-vestigated in the meantime. In most existing work, researchers tend to use the assumption of electro-neutrality con-dition, which ensures that no external charge can be imported (Bockris and Reddy, 1998), to determine the electrostatic potential within concrete as well as considering a 1-D problem with only one phase structure and single species (i.e. the chlorides) for pre-dicting the ionic migration. In contrast, this thesis presents a number of sets of multi-phase migration models in more than one dimension and uses the Poisson’s equation for controlling the multi-species interactions. By solving both mass conservation and Pois-son’s equations, the distribution profiles of each ionic species and electrostatic potential at any required time are successfully obtained. Some significant factors, i.e. the influ-ence of dimensions, aggregates, interfacial transition zones (ITZs), cracks and binding effect have also been discussed in detail. The results reveal a series of important features which may not be seen from existing numerical models. For quantitative study, this thesis also provides the prediction method of chloride diffu-sivity not only by the traditional stationary diffusion models but also by the migration models presented in the thesis. The obtained results are compared with three proven analytical models, i.e., Maxwell’s model (Dormieux and Lemarchand, 2000), Brug-geman’s equation (Bruggeman’s, 1935) and the lower bound of the effective diffusion coefficient proposed by Li et al. (2012) as well as validated against experimental data sets of an accelerated chloride migration test (ACMT) brought by Yang and Su (2002).

Galvanic anode technology has in recent years come to the fore as a cost-effective method of successfully mitigating the corrosion of reinforcing steel in concrete structures. Developments in the field of cathodic protection have included the introduction of a novel Hybrid anode system, which uses the same sacrificial anode to pass a short-term impressed current before being connected to the steel directly to provide a long-term galvanic current. Galvanic and hybrid technologies are often seen as less powerful solutions in the treatment of reinforcement corrosion, and the test methodologies which determine the efficacy of cathodic protection systems favour impressed current technologies. The work completed has investigated the application of traditional and novel corrosion assessment techniques to laboratory samples to assess the protection offered by the hybrid treatment methodology in both treatment phases. In addition, the response of both galvanic and hybrid anodes to environmental conditions has been recorded and assessed before being discussed in the context of steel protection criteria. Finally, an investigation is presented into the on-site deterioration of commercially pure titanium feeder wire installed as part of the hybrid anode system and potential solutions to the problem have been documented. The research undertaken found that the hybrid anode system is capable of protecting steel in challenging, aggressive environments. This was confirmed by steel corrosion rate and indicative steel potential measurements. The responsive behaviour investigation showed that the current output of galvanic and hybrid anodes responds rapidly to changes in the corrosion risk posed to the steel and that this has a direct effect on anode system lifetimes. An assessment of the polarisation-based protection criteria applied to steel in concrete has found that the standard inhibits the use of responsive behaviour, and that revisions which consider the present risk of steel corrosion by considering the corrosion current resulting from the relative aggressivity of the concrete environment would be more valid in their application. A cathodic protection system based on the concepts of pit re-alkalisation and pH maintenance can fully utilise galvanic anode responsive behaviour. It was discovered that the deterioration of commercially pure titanium feeder wire seen on site installations was due to anodising in the presence of chloride media which had the potential to lead to pitting corrosion. The pitting risk varied depending on the duration of the treatment and proximity to the installed anode. An anodically grown oxide delayed the onset of corrosion in aqueous KBr solution, but did not significantly increase the pitting potential.

Synaptic transmission in the nervous system involves the activation of receptor proteins that permit rapid transmembrane fluxes of ions. Ionic gradients across the membrane determine the direction and driving force for the flow of ions and are therefore crucial in setting the properties of synaptic transmission. These ionic gradients are established by a variety of mechanisms, including pump and transporter proteins. However, the gradients can be affected by periods of neural activity, which in turn, are predicted to influence the properties of ongoing synaptic transmission. In this thesis I have examined the concentration gradients of two ions that play a fundamental role in synaptic transmission: chloride ions (Cl-) and protons (H+). Type A γ-Aminobutyric acid receptors (GABAARs) are primarily permeable to Cl- and mediate the majority of fast post-synaptic inhibition in the brain. The transmembrane concentration gradient for Cl- is therefore a critical parameter in governing the strength of synaptic inhibition. In the first part of the Thesis I use a combination of experimental and theoretical approaches to demonstrate that influxes of Cl- via activated GABAARs can overwhelm a neurons ability to maintain a stable Cl- concentration gradient. The consequence is that subsequent activation of GABAARs results in weaker inhibition or even excitation, which alters how the neuron integrates synaptic inputs. This process is shown to be dependent upon the level of activity of the GABAAR, the post-synaptic cells membrane potential and the cellular compartment into which the Cl- flows. These principles were extended to demonstrate that popular optogenetic strategies for silencing neural activity have different effects upon GABAAR transmission. A light-activated Cl- pump was shown to cause substantial accumulations in intracellular Cl, which meant that the strength of synaptic inhibition was significantly reduced following light offset. In the second part of the Thesis I use electrophysiological and fluorescence imaging techniques to demonstrate that the activation of GABAARs during epileptiform activity results in pronounced changes to the transmembrane Cl- gradient. Indeed, these changes convert synaptic inhibition into synaptic excitation during the course of a seizure event. As part of this work I characterise a novel, genetically-encoded reporter for measuring intracellular Cl- dynamics in different cell types and subcellular compartments. A significant advantage of this reporter is that it permits the simultaneous quantification of H+ fluxes, which are also shown to change in an activity-dependent manner and which have been a confounding factor for previous Cl- reporters. In the third and final part of the Thesis I use genetically-encoded reporters to investigate activity-dependent changes in intracellular H+ concentration. I demonstrate that markedly different pH changes occur in neurons and astrocytes during epileptiform activity. Whereas neurons become acidic, astrocytes become alkaline and the dynamics of these pH shifts exhibit a very different temporal relationship with the seizure event. In conclusion, this thesis demonstrates that the intracellular concentrations of Cl- and H+ are dynamic variables that evolve across time and space, in an activity-dependent manner. Changes in the transmembrane gradients of these two ions influence ongoing synaptic transmission. Therefore this work has significant implications for our understanding of network activity and the balance of synaptic excitation and inhibition.

Activity-dependent dendritic development is an important process in the maturation of neuronal circuits. The precise morphology of a neuron’s dendritic tree dictates which other cells it is able to interact with and how it will receive and process synaptic information. The aim of this Thesis was to investigate the mechanisms by which dendrites grow and, in particular, how changes in intracellular ion concentrations contribute to these mechanisms. One important activity-dependent signal is calcium as it can translate neuronal activity into morphological changes. Despite this, very little is known about calcium signalling during the period of dendritic development. Using single-cell electroporation of immature CA1 hippocampal pyramidal neurons, I characterised the spatial and temporal properties of local calcium transients in growing dendrites. This revealed a high frequency of transients at shaft filopodia and stable branchpoints, but an almost complete absence from the tips of dendritic branches. Another important factor during development is the intracellular chloride concentration because this regulates neuronal excitability. Prematurely lowering intracellular chloride by expressing the chloride co-transporter KCC2 led to less stable dendritic filopodia and stunted dendritic growth. These effects were independent of local calcium signalling and suggested that chloride regulation itself may be fundamental to normal dendritic growth. To examine this further I developed imaging techniques to measure the spatial and temporal dynamics of chloride in growing dendrites. This work revealed a somatodendritic gradient of increasing intracellular chloride, whereby the highest concentrations were found at sites of growth. Further analysis suggested a close link between local chloride regulation and morphological changes. The dendritic tips that exhibited high intracellular chloride levels and the potential to rapidly modulate these levels, also exhibited the greatest morphological dynamics. These findings have important implications for understanding the mechanisms of dendritic growth and establish the spatiotemporal regulation of chloride as a key parameter.

Distribution of contaminants in the seasonally unsaturated zone of the Chalk aquifer The Chalk is a dual-porosity aquifer in which most of the porosity is found within a fine-grained matrix. Groundwater in this matrix is virtually immobile and flow takes place almost entirely within fissures. The small volume of fissure porosity gives a low unconfined storage coefficient resulting in large changes in water table elevation in response to seasonal recharge. The zone over which the water table fluctuates, the seasonally unsaturated zone (SUZ), has a major influence on the behaviour of dissolved contaminants, initially slowing their movement, through diffusional exchange with the matrix, and at later stages acting as a reservoir of long-term contamination. Detailed profiles of contaminant distribution in matrix porewater through the SUZ have been constructed from cored boreholes at a study site in southern England. The physical and hydraulic environments of the SUZ have also been characterised. The field data have been used to construct a conceptual model of contaminant behaviour in the SUZ and from this a one-dimensional semi-analytical model has been developed to examine the role of matrix diffusion and fluctuating water tables in the distribution of contaminants in matrix porewater in the SUZ. The results of modelling have been compared to data gathered at the field site and similarities found which indicate a correct understanding of the processes involved. The model shows that contaminant distribution in the matrix evolves towards a situation where concentrations are greatest towards the top of the SUZ. The SUZ can thus form a secondary source of contamination, which may persist long after the original source has dissipated. A consequence of this distribution is that contaminant concentrations in groundwater show a characteristic seasonal high at high water stands. The work has examined a particular site but the processes involved are found over the Chalk outcrop, and in other hydrogeological environments characterised by dual porosity and a fluctuating water table.

Stormwater detention basins are commonly used in the Eastern United States to temporarily store and attenuate stormwater runoff, and also serve as habitats for native and exotic plants. However, during winter, these basins receive saline runoff from road salt application, which contributes to Freshwater Salinization Syndrome (FSS). Since limited research has connected direct measurement of soil and stormwater salinities to biodiversity and phytoremediation potential of salt-tolerant plant species, this thesis aimed to fill this gap. We selected a set of detention basins draining mostly pervious areas, parking lots, or roads in Northern Virginia and measured temporal variations in stormwater and soil salinities, depth profiles of soil salinities, plant community composition, and plant tissue ion concentration. The results indicated elevated levels of sodium, chloride, electrical conductivity (EC), and exchangeable sodium percentage (ESP)/sodium adsorption ratio (SAR) in soil and stormwater after road salt application during winter, followed by a decrease during the growing season for basins draining parking lots and roads. A subsequent increase at the end of the season was observed for all site types. While some stormwater samples exceeded toxicity thresholds, most soil samples did not exceed their respective thresholds nor reach saline or sodic conditions, and native and exotic plant species of both salt-sensitive and salt-tolerant classifications were observed at almost all sites, although proportions of each varied by site type. Tissue analysis of select plants revealed ionic concentrations that generally coincided with observed soil and stormwater concentrations at each major site type. These findings have implications for future detention basin planting regimes to mitigate FSS, and the thesis discusses native plants found to provide the most benefit for phytoremediation.

Chloride concentrations in United States lakes have steadily risen over the past several decades as a result of anthropogenic activity, including increased urbanization and its associated chloride discharge.1 Among those waters affected are the Great Lakes, two of which are currently at record chloride levels, and the other three are experiencing increases.2 This is problematic because chloride can have significant harmful effects on aquatic life. Due to the potential harmful effects chloride has on aquatic life, Michigan’s Department of Environment, Great Lakes, and Energy (EGLE) recently developed water quality values (WQV) for chloride. These were developed to reduce overall concentrations in Michigan's surface waters. All surface water systems in the state of Michigan eventually drain into the Great Lakes Basin. While the EPA has set general criteria for chloride concentration levels on a national scale, Michigan has implemented even more conservative values for their surface waters as a means of protecting local aquatic animal and plant life. The Great Lakes have been described as “a crown jewel of North America''.3 They represent the largest group of freshwater lakes in the world by surface area, as well as almost a quarter (21%) of all the planet’s fresh surface water. 4 The Great Lakes and Michigan’s inland waters are important sources of drinking water, economic livelihood, and recreation opportunities for millions of people, including citizens of Michigan’s 12 federally recognized indigenous tribes.3-5 The quality of the surface waters is often a direct reflection of land use activities such as agriculture, mining, and logging practices as well as the level of commercial and residential development that is occurring within the watersheds.6,7 Michigan’s watersheds act as contributors to the water quality of the Great Lakes due to the fact that all waterways in the state eventually drain into either Lake Superior, Lake Michigan, Lake Huron, or Lake Erie.8 A listing of the major watersheds in the state is found in Figure 1.9

The accumulation of salts in plant rootzones, known as “salinization,” is often a gradual process that can degrade soil structure and cause permanent plant damage. Salinization caused by ever increasing water demands and an increasingly dry climate is becoming problematic for agriculture in semi-arid to arid regions, including California’s Central Valley, which produces about one-quarter of the United States' food supply and almost half of its nuts and fruits, including grapes, according to the USGS California website (https://ca.water.usgs.gov). While grapevines are considered moderately salt tolerant (Walker et al. 2002), the current rate of salinization in many of California's vineyards is contributing to reduced crop yields and lower fruit quality (Keller 2020). Once symptoms of salt toxicity appear on the leaves, vine growth and crop yield may already be in serious decline (Fort and Walker 2011). To prevent salt toxicity from occurring in grapevines, the Walker Lab at UC Davis is applying traditional plant breeding techniques to some of the native population of wild North American grapevine species to improve the salt tolerance of commercial rootstocks (Fort et al. 2013). In recent years, the Walker Lab discovered a wild grapevine species called Vitis acerifolia 9018, which has consistently proven to be more salt tolerant than the most salt tolerant commercial rootstocks (Chen 2021). These physiological traits could be bred into existing popular commercial rootstocks to improve their salt tolerance. The research for this thesis was performed to observe the stress response and compare the salt tolerance of the recently discovered salt tolerant wild rootstock V. acerifolia 9018, against commercial rootstocks widely planted in California and other salinization-affected places, including Ramsey, 1103 Paulson and 140 Ruggeri.

Huntington’s disease (HD) has classically been categorized as a neurodegenerative disorder. However, the expression of the disease-causing mutated huntingtin gene in skeletal muscle may contribute to the symptoms of HD, namely those that involve involuntary muscle contraction. In the R6/2 transgenic mouse model of HD, we previously observed ion channel defects that could contribute to involuntary muscle contraction. Here, in R6/2 muscle we investigated the consequence of these ion channel defects on action potentials (APs), the first step in excitation-contraction (EC) coupling. We found that the ion channel defects were associated with depolarizing the baseline membrane potential during AP trains. We also observed changes in the AP waveform in R6/2 muscle, including a prolonged falling phase, which was associated with reduced K + channel expression (another ion channel defect). Next, we investigated the consequence of prolonged APs on intracellular Ca 2+ release flux, the second step in EC coupling. We observed an increase in Ca 2+ release flux duration, which compensated for a reduction in peak Ca 2+ release flux, resulting in normal levels of Ca 2+ available for contraction in R6/2 muscle. Finally, we investigated the consequence of prolonged APs and normal levels of Ca 2+ available for contraction on muscle force generation, the final step in EC coupling. We found that, when accounting for muscle atrophy, the force generated by one AP (twitch) was normal in R6/2 mice. This could be explained by the reduced parvalbumin and normal levels of Ca 2+ available for contraction we observed in R6/2 muscle. We conclude that downregulation of K + channels to prolong APs is a compensatory mechanism for muscle weakness that leads to increased Ca 2+ release duration and force production in R6/2 muscle. This is the first study to examine the entire EC coupling sequence in HD muscle, revealing the importance of the AP waveform in contributing to muscle force generation.

Some of the most common ions in the atmosphere are nitrate (NO3-) and chloride (Cl-) which play key roles in many atmospheric reactions, including ozone depletion. Additionally, they influence the iron equilibria that dictate reaction kinetics. Heterogeneous reactions are heavily influenced by the presence of ions at the air-water interface but there is still not a definitive distinction between the surface propensity of NO3- and Cl-. The impact of NO3- and Cl- on the hydrogen-bonding structure at the air-water interface has been examined using second harmonic generation (SHG) and surface tension measurements. The impact of ferric iron on the propensity of NO3- has also been examined with surface tension by comparison to sodium nitrate. The SHG electric field shows that the hydrogen-bonding structure of NaNO3 and NaCl solutions is significantly different from neat water but shows a slightly different dependence on concentration. Surface tension measurements support this change in structure by displaying significantly different concentration dependence. The introduction of iron has a large impact on the surface as shown by the increased surface tension slope as well. To confirm the presence of iron-anion dipoles, geometry optimization of ferric chloride complexes was performed to obtain dipole moments.

The objective of this dissertation research was to investigate initiation mechanisms for CO2 localized corrosion on mild steel, encompassing the effects of chloride, oxygen, and acetic acid. In CO2 corrosion, iron in steel will be oxidized to ferrous ions under deareated conditions. The ferrous and carbonate ions can combine to form FeCO3 and precipitate once exceeding the solubility limit. When the precipitation of FeCO3 occurs evenly on the steel surface it forms a compact and protective layer. This acts as a diffusion barrier hindering the mass transfer of electrochemical species and covers/blocks the surface making it unavailable for corrosion, which enhances the resistance of mild steel to further uniform CO2 corrosion. However, there are various scenarios where localized corrosion may occur. When the environment becomes more aggressive, the FeCO3 could be partially removed. This leads to localized regions of the bare steel surface that become exposed to the corrosive solution and, subsequently, localized corrosion could be initiated.To study CO2 localized corrosion, two-stage experiments were performed: (1) a uniform protective FeCO3 layer was first formed on a carbon steel with high initial FeCO3 saturation; (2) localized CO2 corrosion scenarios were then developed by adding additional salts (NaCl or NaClO4), oxygen or acetic acid to challenge the protective FeCO3 layer.The experiments were conducted in a two-liter glass cell with a three-electrode system, working electrode (X65 carbon steel), reference electrode (Ag/AgCl saturated electrode), and counter electrode (platinum). Electrochemical measurements (linear polarization resistance) were carried out to observe electrochemical behaviors and calculate the corrosion rates. Weight loss was also used to determine general corrosion rates. Fe2+ concentration was measured using spectrophotometry in order to study the solubilization of FeCO3. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and profilometry by infinite focus microscopy (IFM) were used to determine pitting.The results in non-ideal solutions showed that no localized corrosion was initiated by introducing more salt. The introduction of acetic acid resulted in localized corrosion. When oxygen was introduced, severe pitting occurred. A new water chemistry model based on Oddo & Tomson’s equation was proposed by the author. Based on EQCM results, a new model to calculate the solubility constant of iron carbonate in non-ideal solution at 80℃ was developed based on Sun & Nesic model.

In many source waters across the United States (US), chloride levels are increasing and this change could be problematic for galvanized iron pipe (GIP) installed in consumers' homes and buildings. The higher levels of chloride might increase the rate of galvanic corrosion between the sacrificial zinc coating and the underlying iron (steel) pipe. There are also concerns that the iron in GIP can accumulate lead on its surface from upstream lead service lines, occasionally causing high lead in water from GIP during scale sloughing and associated red water events. The role of high chloride and potential mitigation strategies by orthophosphate and alkalinity on galvanic iron-zinc corrosion in GIP were examined by using new iron and zinc wires, and complementary studies with 85-year-old harvested GIP coupons from the Washington Suburban Sanitary Commission (WSSC). Sequential samplings on a constructed pilot-scale test rig with copper – lead – GIP ¬– brass meter configuration were used to evaluate lead source fingerprinting methods (metal co-occurrence, correlating the plumbing configuration to sample profiling data, and evaluation of lead isotope ratios) and role of flow rate. As chloride concentration increased from 2.6 to 554 mg/L, galvanic current and weight loss of sacrificial zinc increased by about an order of magnitude. Iron leaching also increased by 4.4 times as chloride levels increased by a factor of 12 in WSSC modified water to simulate actual road salt runoff events. Increased orthophosphate or alkalinity could at least partly counter the adverse effects of chloride, as the average iron concentration decreased by 43% as orthophosphate level increased from 3.8 to 11.2 mg/L as P, and average iron concentrations decreased by 32% as alkalinity increased from 50 to 90 mg/L as CaCO3. Applying fingerprinting methods on sequential samples has the potential to determine whether premise plumbing contains GIP and/or lead pipe. Specifically, the metal co-occurrence fingerprinting technique was successful in identifying the location of GIP by the detection of low-level cadmium, and the lead isotope ratio fingerprinting technique was fairly successful in identifying lead pipe. Additionally, our study found that GIP was not contaminated by an upstream lead pipe after five months of conditioning; hence, water discoloration (iron level > 400 ppb) does not always indicate lead problems from GIP. However, with longer exposure of GIP to lead pipe, the magnitude of the problem might increase. As flow rate increased from 0.9 to 2.4 GPM, the median particulate iron release increased by 3.3 times, and the median particulate lead release (>83% particulate lead) increased by 4.9 times.

The winter roadway operations and maintenance community generates a breadth of data detailing the activity and performance of snowplows, deicing practices, and road conditions. While roadway ice clearing is a practical need for communities in temperate climates, one outcome of operations is the distribution of unnaturally high levels of dissolved solids, especially chloride, into environments which are hydraulically connected to maintained roadways and surfaces. The long-term buildup of chloride poses a threat to ecological integrity of freshwater systems. Salt also hastens the oxidation of metals used in the built environment, especially high-iron alloys. A 2007 study of the Twin Cities Metropolitan Area estimated that over a 5-year study period, 70% of road salt applied annually was retained in the landscape or infiltrated to deep groundwater. This research examines the road salt mass balance on a finer scale both spatially and temporally. Continuous monitoring of surface runoff was conducted in a small residential watershed using a novel approach. The results are paired with an analysis of snowplow asset tracking data to estimate what proportion of the total salt added to the catchment in the two-year study enters directly into the stormwater conveyance. Results are followed by a critical discussion of current research and considerations for future research.

Abstract: Contamination of land, water, and air is a widespread concern often associated with anthropogenic activities. Remediation of contaminated sites is necessary to minimize negative impacts on human health and the environment and allow for safe, productive use of land. Although contaminated sites often have fine textured soils and/or multiple contaminants, research on remediation of such sites is lacking. Fine textured soils can make remediation more difficult by hindering movement of contaminants or amendments and by promoting anaerobic conditions. Contaminant mixtures can complicate remediation since each contaminant has unique characteristics to address and can hamper remediation of other contaminants. The objective of this research was to characterize a contaminated site with fine textured soils and multiple contaminants and investigate the potential of various remediation techniques. The research site was the former Ellerslie Waste Management Facility which treated laboratory waste from 1972 to 2007 in Edmonton, Alberta. Prior to 1983, a waste water pond cracked and leaked. Contaminant dynamics over 30 years were characterized by identifying soil and ground water contaminants based on Alberta Tier 1 guidelines, identifying temporal trends with Mann Kendall analysis, and identifying spatial trends with two and three dimensional mapping. The potential of anaerobic biostimulation and bioaugmentation treatment of chloroform were investigated in microcosm experiments using soil from the Ellerslie site and a secondary contaminated site. Microcosms were amended with canola oil, acetate, lactate, nitrate, or sulfate. The soil microbial community was characterized by comparing bacterial and fungal communities from various soil depths in, up gradient, and down gradient of the pond. The potential of chemical reduction treatment of chloroform was investigated in an anaerobic bottle experiment using micro scale zero valent iron with and without soil. The potential of leaching treatment of salinity was investigated in soil column experiments using two soil composites of differing textures with and without calcium nitrate amendment. Of the 18 soil and 37 ground water contaminants identified, chloroform, dichloromethane, and salinity were of greatest concern based on their frequency and magnitude of detection. Temporal contaminant trends were inconsistent, possibly due to heterogeneous contaminant distribution or movement. A clear spatial association with the pond was identified, as expected. There is some evidence of northward chloride and sodium movement with ground water flow. The bioremediation experiments did not yield any meaningful changes in microcosm headspace chloroform or formation of degradation products over time. Biostimulation and bioaugmentation with the inoculation microorganisms used in this research are not likely effective options for the Ellerslie site. This is supported by the lack of chlorinated methane degrading microorganisms enriched in the pond. However, the enrichment of Geobacter species in the pond indicated benzene biodegradation may be occurring. Bacterial richness and diversity were decreased in the pond, likely a result of contaminant toxicity. The fungal community was more similar across the Ellerslie site than the bacterial community. Chemical reduction of nearly 2 g/L chloroform using zero valent iron was rapid and complete. Headspace chloroform was not detected after 0.5 and 2 days in the soil zero valent iron and zero valent iron treatments, respectively. Dichloromethane which formed during the degradation process was removed by day 2 in both treatments. The leaching experiments showed potential for treatment of fine textured soils. Soil electrical conductivity, sodium adsorption ratio, sodium, chloride, and sulfate were greatly reduced by eight rounds of leaching. Greatest salt removal occurred during the first leaching round. Calcium nitrate increased the saturated hydraulic conductivity of the finer textured soil from 4.12 ± 0.46 x 10^-8 to 1.29 ± 0.14 x 10^-7 m/s and increased chloride leaching. The soil and ground water contaminant inventory and knowledge of their spatial distribution will aid in development and application of a site remediation plan. Potential remediation methods include chemical reduction with zero valent iron for chlorinated methanes and leaching for salinity. Zero valent iron treatment could be implemented with a permeable reactive barrier, in situ injection, or ex situ batch reactor. Leaching treatment could be implemented with an interceptor trench or ex situ soil washing. Contaminant maps will be important in guiding soil excavation or placement of in situ remediation infrastructure. Site characterization and remediation methods explored in this research can be applied to similar contaminated sites.

Abstract: The most common detrimental processes that lead to reduction in durability in reinforced concrete elements are shrinkage, sulphate attack and chloride attack. Shrinkage is a dimensional instability chiefly caused by a loss of moisture in the hydrating cement paste. Soluble sulphate ions take part in ettringite-induced expansive reactions in concrete, while chloride ions trigger the corrosion process in embedded steel reinforcement. Cellulose nanofibrils (CNFs) possess unique characteristics, including hydrophilicity, nano-dimensions, and excellent chemical tunability. These features confer upon CNF the ability to control internal moisture movement and also mitigate the ingress of harmful agents, including sulphate and chloride ions, into the cementitious system. A thorough review of the literature confirms that the proposed study is a novel scientific approach. This study explores the feasibility and demonstrates successfully the ability of CNF to address these three durability concerns. Three types of CNFs were used in the study, each one with a distinct amount of carboxylate grafted upon the fibre surface. The CNF was incorporated in cement-based paste and mortar mixtures at various volume fractions. The mixtures were cast to the same workability and water-to-cement ratio, and the mortars had a fixed cement-aggregate ratio. Results show that adding CNF moderately increased the shrinkage as measured at 2-days using image analysis. Similar growth in the drying shrinkage was observed in 90-day trials performed according to ASTM C596. However, CNF additions significantly alleviated bleeding and the shrinkage behavior was strongly influenced by CNF's ability to retain water in the early hours of hydration. Further evidence from the gas-sorption analyses reveals that this water accumulated in fresh mixtures due to CNF led to a larger volume of capillary pores and an increase mainly in the pore gel phase. As seen in the long-term trials, when this cumulative water was lost, there was a rise in shrinkage. This study reveals a retardation in hydration upon adding CNF. However, the samples containing CNF uniformly showed less cracking, which is likely due to fibres bridging the micro- and nano-cracks. The mortars mixtures when dosed with CNF uniformly exhibited noticeable reduction in the ingress of sulphates ions and again, for chlorides ions. Under sulphate exposure, the CNF visibly reduced the penetration of sulphate ions and effected a marked reduction in ettringite as well as the associated ettringite-induced expansion, measured as per ASTM C1012/C1012M. The decrease in the ettringite content (as measured by X-ray analysis) in the CNF-loaded Type GU Portland cement paste mixtures even after 90 days in sulphate solution was comparable to that seen with Type HS Portland cement. At the same time, the compressive strength of CNF-cement mortars was enhanced. Similar improvement was observed in the resistance of mortars loaded with CNF against chlorides ion ingress, as substantiated by the results of the rapid chloride penetrability test (as described in ASTM C1202) and the silver nitrate-based colorimetric method. The performance verified here can be credited to physical and chemical mechanisms trigged by CNF. Despite a slight increase in the capillary pores ranging from 100 nm – 10 μm as seen from the analysis of SEM images, the porosity in the range of 10 nm to 140 nm was moderately reduced as increasingly amounts of CNF were added to cement pastes. As a result, the pore network in this range experienced a rise in the tortuosity and a reduction in the connectivity, which ultimately hindered the ingress of sulphate ions and chloride ions. Concurrently, the negatively charged ionic groups of CNF chemically scavenged some of the calcium cations soluble in the aqueous phase (as evident from the thermogravimetric analysis), which are essential to the ettringite phase formation. This further explains why CNF loadings slowed down the ettringite content. However, the pH of CNF-cement pastes remained unaltered, notwithstanding the reduction in the calcium content in the pore solution. It is safe to say that CNF will not break the protective passive film of the embedded steel bars. The results show CNF as an all-round promising additive to hamper the ingress of deleterious agents in cement-based systems.

Spent dry nuclear fuel (SNF) in the United States is stored in a welded 304/316 stainless steel (SS) shell surrounded by a vented concrete overpack on-site at the commercial reactor where it is generated. The ambient air used to cool the SNF can contain corrosive aerosols (i.e. Cl-) that have been shown to deposit on the outside surface of the SS canister. At sufficiently high humidity levels and temperatures below ~80°C, these deposits can absorb moisture from the air leading to atmospheric corrosion concerns. While most research has focused on the initial stages of atmospheric corrosion ranging from 1 day to 1 week under singular microliter-sized droplets, there is a gap in understanding the effect of atmospheric exposure on pitting corrosion under nano to microscale aerosol droplets for longer periods of time. The current research aims to understand the effect of time, humidity, salt loading density, and surface roughness on the corrosion morphology and pitting damage distribution of 304 SS in atmospheric environments under aerosol size ASTM D1141-98 seawater droplets. Two salt loading densities, 10 and 300µg/cm2, were deposited on ground and polished coupons via printing then exposed to 40 and 76% RH at 35°C for interval times up to 1 year. The distribution and morphology of corrosion damage was characterized using a combination of optical profilometry, electron microscopy, and focused ion beam milling. Low pit counts (< 1 pit/cm2) or no corrosion was found on samples with a polished surface or low salt loading density (10 µg/cm2) after one year of atmospheric exposure. Conversely, ground surfaces loaded with 300 µg/cm2 of sea salt loading density showed pitting damage as early as one week, and the degree of damage was directly related to humidity. Ground surfaces exposed to 40% RH resulted in irregularly-shaped pits with rough surfaces due to selective dissolution of slip bands associated with the deformed, ground steel surface. At 76% RH, pits were characteristically hemispherical with relatively smooth, but faceted surfaces. Additionally, small cracks were found to emanate from pit edges only when exposed at 40% RH. Higher pit number densities were observed at 40% RH due to the discrete droplets that remain intact during the exposure time, which allows for a higher number of pit initiation sites. The limited volume of electrolyte and area coverage, as well as the concentrated brine chemistry (indicative of deliquesced electrolytes), is used to explain the mechanisms leading to limited corrosion damage on polished surfaces and at low salt loading densities as well as the unique morphologies and cracking observed on ground surfaces.

Road salts, brines, and other de-icers are used to melt snow and ice on roads and sidewalks. The runoff resulting from this process is high in salt ions such as sodium, chloride, calcium, magnesium, and potassium. These ions end up in our waterways, and contribute to the problem of increasing salinity in freshwater ecosystems. In this study, two constructed freshwater wetlands near Kent State University were monitored for one year by measuring specific conductance with in situ conductivity sensors and concentrations of road salt ions in surface water with IC and ICP-OES. This data set allowed us to assess seasonal and temporal trends in road salt runoff, as well as possible mechanisms of salt storage and cycling within the wetlands. We found that the wetlands were a considerable sink for road salt ions over the course of the year. Moreover, the degree to which each wetland retained the ions was not the same. The wetland with continuous flow and comparatively less storage space retained less of the ions than the intermittently flowing, deeper wetland. Additionally, we found that there are cation dynamics in which road salt-derived sodium exchanges with cations sorbed to soils, causing a net release of calcium and magnesium from one of the wetlands. The notable imbalance in the salt budget of these wetlands, despite their differences in flow regime, is symptomatic of unsustainable road salt practices in these and similar watersheds. Should this pattern continue, there could reach a point where the wetlands could no longer store the influx of salt ions each year, resulting in a large release of saline water into downstream freshwater ecosystems. These findings can be used to inform management decisions not only in Kent, Ohio, but also in any city to better balance ecosystem function with public safety.

Field trials were conducted in 2016, 2017 and 2018 with dark fire-cured, dark air-cured, and burley tobacco at Princeton, Murray and Lexington Kentucky. Tobacco variety used in 2016 was a low converter (LC) variety, varieties used in 2017 and 2018 were LC and higher converter (HC) varieties. Potassium sources used at all locations and in all years were potassium sulfate (K2SO4) and potassium chloride (KCl). Application rates used at all locations and in all years were 93, 186, 279 kg K ha-1along with an untreated control that received no potassium. In all trials, tobacco that was treated with either potassium source yielded numerically higher than the untreated control. In seven out of 10 trials, LC varieties had a higher moisture content than HC varieties. Tobacco treated with KCl had higher chloride levels than tobacco treated with K2­SO4.Quality grade index was similar for tobacco treated with KCl compared to tobacco treated with K2SO4. In all trials, tobacco treated with KCl had numerically lower Tobacco Specific Nitrosamines (TSNA) levels than tobacco treated with K2SO4. Reductions in TSNA levels were 30% lower in tobacco treated with KCl compared to tobacco treated with K2SO­4.

In California, a multiyear drought from 2009 to 2016 forced avocado growers to re-evaluate their water management practices. Groundwater, which accounts most of the state’s water supply, was in direct competition with urban and environmental demands for water. California production accounts for 90% of the avocados produced in the United States avocado which is an economically important commodity to the state. When faced with fluctuations in water availability, reliability, and quality, avocado growers must consider the effects of these changes on long term yield and profits. The dissertation research was divided into two projects which were organized into two main chapters. Research in chapter 2 used a survey instrument distributed to growers to learn about their use of irrigation management practices. The results of this research identified key determinants underlying which combinations or “bundles” of technologies and management practices were implemented by California avocado growers during the current drought. Results indicated that the likelihood of adopting more advanced water-saving technologies and management practices increased with the shift in the location of the orchard from cooler coastal counties to hotter and drier inland areas, with the increased proportion of grower income derived from avocado production, and the greater level of importance the grower placed on information obtained from cooperative extension services; it decreased with increased irrigation complexity and grower age. Results indicated that the likelihood of adopting more advanced water-saving technologies and management practices increased with the shift in the location of the orchard from cooler coastal counties to hotter and drier inland areas, with the increased proportion of grower income derived from avocado production, and the greater level of importance the grower placed on information obtained from cooperative extension services; it decreased with increased irrigation complexity and grower age. Research in chapter 3 was a field study of the impacts of quantity and quality of irrigation water on avocado orchards. The overall goal of the research was to determine how water quality and soil hypoxia effect leaf chloride, manganese, iron and yield on ‘Hass’ avocado trees grafted on different rootstocks. A second objective was to determine whether tree uptake of iron and manganese is affected by hypoxia and whether the concentrations of these nutrients in leaf tissues may serve as surrogate markers for avocado tree exposure to hypoxia over time. The research was conducted over multiple years in three orchards, which were representative of the spatial and climatic variations of the avocado-growing regions in California. In each orchard, in situ soil monitoring equipment for continual recording of soil salinity, volumetric water content, soil temperature, soil water potential and irrigation frequency were installed. Soil hypoxia appeared to have no statistically significant effect on leaf chloride accumulation in this dataset. Leaf manganese accumulation proved to be a better marker for soil hypoxia followed by leaf iron. Results indicate that irrigation salinity may be an environmental factor that effects alternate bearing in ‘Hass’ avocado. Results may help guide avocado growers in irrigation management and emphases the importance of understanding microsite variability with an orchard. The combined results from projects one and two will help guide grower irrigation practices for optimizing both yields and profitability in relation to water quality and soil type.

Given the state of aging infrastructure in the United States, reinforcement corrosion is proving to be costly in direct maintenance and replacement costs, as well as indirect costs, such as traffic delays and loss of productivity. Seismicity complicates this issue due to the looming threat of extreme loading on the heavily-used bridge structures that connect our communities. It is important to understand mechanisms of corrosion damage and their impacts on structural behavior in order to ensure that future repairs and new designs are sustainable, long-term solutions. The research presented in this dissertation investigates the combined action of corrosion and seismic loading on bridge columns. Fiber reinforcement is proposed as a means of extending the service life of reinforced concrete components and providing resistance to damage from environmental and mechanical action. Hybrid Fiber Reinforced Concrete (HyFRC) and its self-consolidating variant, SC-HyFRC, were utilized in these experiments to investigate their durability against the expansion of corrosion products and their ductility during mechanical loading. Of specific interest in this research is the intersection between corrosion damage in reinforced concrete and HyFRC column elements and mechanical behavior under seismic loading.Steel reinforced self-consolidating concrete (SCC) and SC-HyFRC columns are exposed to corrosion damage through long term exposure in a chloride-contaminated environment, in which 2% chloride by weight of binder materials was admixed when column elements were cast to investigate the corrosion propagation phase in isolation. Corrosion rate and surface cracking behavior was monitored during a 125-week corrosion exposure period. Mechanical behavior was then investigated through compressive testing of corrosion-damaged column elements and tensile testing of corroded reinforcing steel. While the SC-HyFRC clearly exhibited less corrosion damage compared to the SCC control specimen, the large difference in compressive strength between the SC-HyFRC and SCC implies that a difference in their matrix/rebar interfaces made a comparison in their crack propagation behavior less conclusive. Hybrid Simulation (HS) is utilized to investigate the system-level seismic performance of reinforced concrete structures with corrosion damaged components. This technique combines physical testing with computer simulation to impose realistic, dynamic loading conditions on a physically manageable test-specimen. An HS test procedure was developed to investigate the seismic behavior of a single-column highway bridge, where the lower portion of the column serves as the experimental element. The setup was validated and calibrated using a steel hollow structural section (HSS) column element. The HS procedure was also utilized with reinforced concrete and HyFRC column elements that were exposed to an applied current to accelerate corrosion damage prior to testing. HyFRC columns were more effective at preventing spalling as well as retaining their stiffness following severe seismic damage, even with pre-existing corrosion damage.Many reinforced concrete bridges are simultaneously exposed to the combined hazard of seismicity and corrosion damage. It is of great importance to improve the understanding of existing infrastructure so that we can develop efficient and long-lasting repair or replacement strategies to keep communities safe while more effectively utilizing innovative materials to extend the service lives of structures. HS improves accuracy by incorporating the true behavior of a physical specimen into a numerical model to capture the full response of the structure, even if some components are difficult to explicitly model. This also increases efficiency of experimental testing as a large portion of the structure can remain as a computational model, eliminating the need perform expensive system-level tests.

In urban areas, increased runoff from storm events is a significant concern due to flooding, erosion, ecosystem disturbance, and water quality problems. Phosphorus (P) and nitrogen (N) are key limiting nutrients that lead to eutrophication and harmful algal blooms in Lake Erie and other freshwater systems, and urban landscapes are locally important sources of nutrients to downstream water bodies. Green infrastructure (GI) is one increasingly popular solution being used in urban areas to address the water quantity and quality issues that urban runoff creates. Green roofs and bioretention cells are widely used forms of GI designed to decrease and slow down runoff through evapotranspiration and infiltration. I compared the hydrologic effectiveness of a co-located extensive green roof and two bioretention cells in northeastern Ohio, in order to understand their relative capacities to decrease and slow down stormwater runoff, when subjected to the same weather conditions. I also monitored the green roof to understand its effects on water quality, in terms of P and N.From June 2015 to November 2016, 93 storms from 2.5 to 62 mm, were monitored. To assess the hydrologic performance of each site, I measured rainfall, underdrained outflow, groundwater levels in the bioretention cells, and soil moisture on 1–5 minute intervals. To assess water quality for the green roof, I collected precipitation and samples from the green roof downspout. I measured chloride (Cl-) phosphate (PO43-), total P, nitrate (NO3-), ammonium (NH4+), and total N concentrations using ion chromatography and a colorimetric assay.The bioretention cells performed similarly to each other, despite slightly different designs, and they had superior performance to the green roof. The paved lot bioretention cell showed 77% volumetric and 85% peak flow reduction and the gravel lot bioretention cell showed 78% volumetric and 82% peak flow reduction. The green roof only reduced 59% of its water input and 69% of peak flow. Overall, precipitation amount and peak rain intensity were the most significant predictors of hydrologic performance.The green roof exported PO43- with an average storm event mass balance of -20,115% and retained NO3- with an average mass balance of +77%. As much as half of the total P outflow concentrations consisted of PO43-. However, outflow PO43- concentrations did decrease by ~3x after fertilizer application ceased in 2016. Many cities are aggressively promoting green roofs as part of their stormwater management policies. If these policies result in many green roofs that are directly connected to downstream water bodies, phosphorus export may exacerbate water quality problems in urban areas. Re-consideration of the maintenance and construction of green roofs may be required before further adoption of the practice.

The service life of reinforced concrete structures is dependent on the integrity of the steel within the concrete. Over time, due to exposure, chloride and other minerals can penetrate the concrete. Once these materials get to the reinforcing steel, the chloride and oxygen start to corrode and deteriorate the steel. This deterioration will cut the service life of a bridge down dramatically. To prevent this, the permeability of concrete was studied to determine the service life of one of the new Class-M concretes and a Self-Consolidating Concrete (SCC) mix designs; both developed to produce higher quality concrete. This paper looks at the previous research done into the cementitious replacement of sla SCC's an effect on permeability. A replacement of cement with 50% slag was used to create the slag concrete, and a 9% addition of silica fume was used for the SCC concrete. During this study, three different concrete mix designs were included, concrete with 50% slag replacement, an SCC, and an ordinary Portland cement (OPC) concrete. The permeabilities of these three concrete mixes were tested using three different methods. A ponding experiment, which allows salty water to slowly penetrate concrete samples, the Rapid Chloride Penetration Testing, which uses current to push chloride through a concrete sample, and lastly, a Virtual RCPT method, which is a computer model that uses the mix design quantities to predict the permeability of concrete. The diffusion chloride coefficients of the concrete were obtained. These results were then used with the Life 365 software and a NIST service life prediction model to predict the service life of each concrete mix design. The results show that OPC has a service life in the range of 16-22 years. Slag has a service life range between 47-48.5 years, and SCC has a range of 60-252 years. This shows that OPC has the lowest service life range when looking at chloride permeability and that SCC produces the largest service life.

Chloride toxicity is recognized as yield limiting problem in soybean [Glycine max (L.) Merr.] production. Limited information is available to accurately diagnose and manage Cl toxicity. The only recommendation for Cl toxicity management is to plant an excluder cultivar, however the cultivar Cl sensitivity rating system (excluder, includer, and mixed) does not appear to capture the variability in cultivar Cl tolerance. The objectives of this research were to i) develop critical tissue-Cl concentrations in which yield loss occurs for excluder and includer cultivars and ii) investigate the variability in cultivar Cl ratings. A study was conducted across five site-years using six soybean cultivars including three Cl-includer and three Cl-excluder cultivars. Solution containing Cl was applied to the soil beginning at late vegetative growth with final rates ranging from 0 to 1010 kg Cl ha-1. Critical trifoliolate leaflet-Cl concentrations at the R3 stage were developed by regressing relative soybean yield across leaf-Cl concentration for each cultivar Cl rating. For the second objective, composite trifoliolate leaflet and individual trifoliate leaf samples were collected during reproductive growth from variety trials and analyzed for Cl concentration. The research verified that the yield of Cl-includer cultivars is reduced more (4-20%) than Cl-excluder cultivars (0-8%) in high Cl environments. Relative grain yield declined linearly for cultivars within each Cl rating group with 5% yield loss expected when Cl concentrations at the R3 stage averaged 3923 mg Cl kg-1 for Cl includers and 1885 mg Cl kg-1 for Cl excluders. Across more than 100 cultivars sampled in three Arkansas Soybean Performance Tests, tissue-Cl concentration ranged from 5000 mg Cl kg-1 and showed no clear groupings of the three cultivar Cl-traits suggesting that many cultivars labeled as includers are a mixture of includer and excluder plants. Chloride concentrations of 528 individual plants from eleven cultivars showed 34% and 31% of the plants had Cl concentrations ≤500 or 1000-2000 mg Cl kg-1 with only one cultivar having a pure population of Cl excluder plants. A new rating system is warranted to more accurately characterize the proportion of Cl include and excluder plants of each cultivar.

This thesis explores the effects of pH and chloride on Cu transformations in aqueous solutions typical of both natural waters and physiological conditions: i) The effect of pH on the interaction between Cu and H2O2 in 0.7 M NaCl solution was investigated. A speciation-kinetic model was developed to explore the mechanism. While the rate of Cu(I) oxidation by H2O2 did not change with pH, the rate of reduction of Cu(II) by H2O2 was highly pH dependent due to changes in Cu and H2O2 speciation. ii) The production of oxidizing intermediates increased with increasing pH, with their reactivity assessed by phthalhydrazide hydroxylation and formate degradation experiments, both in presence and absence of additional probe compounds. By comparing observed reactivity with that expected for HO• it was shown that a higher oxidation state of copper, Cu(III), not HO•, is the oxidant formed between pH 6 and 8. Model simulations under experimentally inaccessible environmental conditions showed that Cu(III) production rates did not vary strongly with pH, despite large changes in cycling of Cu between its +I and +II oxidation state. iii) The impact of Cu on Menadiol (MNH2Q) oxidation was examined between pH 6.0 and 7.5. The oxidation of MNH2Q occurred in the open air and the autoxidation rate by O2 increased with pH, with Cu significantly accelerating the oxidation. The results were well-described by a kinetic model where mono-deprotonated menadiol caused the pH dependence, Cu(II) initiated the MNH2Q oxidation, and semiquinone and superoxide played important roles. The high [Cu(I)]ss attained in the system and the production of H2O2 also lead to formation of Cu(III). iv) The impact of chloride and the well-characterized Suwannee River Fulvic Acid (SRFA) on Cu-transformations was investigated. High chloride concentrations lead to highly-reactive Cu(II) complexes but more stable Cu(I) complexes with respect to reaction with all reductants/oxidants in the system. In the absence of O2, SRFA acted like a hydroquinone in the reduction of Cu(II); in the presence of O2 additional reactions mediated by superoxide that consumed the SRFA reductant needed to be considered, as well as complexation of Cu(I) by an oxidized SRFA moiety. A kinetic model that incorporated these key features described the key observations.

The two major construction materials in civil engineering, cement, and steel, are studied using Density Functional Theories (DFT) simulation and empirical methods, respectively. In this thesis, DFT method is used for the study of cement material reactivity study to get access to the electronic-scale investigation; for steel corrosion research, 3-dimensional topography at high resolution is captured for nanoscale pitting evolution observation. The simulation work aims at understanding how to enhance Ordinary Portland Cement (OPC) reactivity and reduce energy consumption as well as reduce CO2 emission from cement industry. Ca2SiO4 (C2S) is the second major phase in OPC clinker, however, it reacts with water at a slow rate and does not contribute early-age strength to concrete structures. To uncover the nature of this low reactivity, 3 major polymorphs of C2S naming γ-, β- and α'L-C2S crystal structures are calculated to determine the least stable phase, revealing that the stability of three C2S ranks in the sequence of γ- > β- > α'L-C2S. As β-phase is the dominant C2S, points defects with foreign ions (K+, Na+, Mg2+, Sr2+, B3+, Al3+, Fe3+, Ge4+) have been introduced into β- C2S crystal structure in order to improve the instability and potentially reactivity. From the doped β- C2S structure, at the same molar concentration, B element shows the highest instability, following by Al element; Na and Mg elements exhibit little trend to activate β- C2S. Ionic size and doping preference have been further studied to uncover the rule of doping in β- C2S as well as future doped structure design. The doping preference in β- C2S crystal structure highly correlates to the ionic size difference between the foreign ion and the substituted ion. Ions with smaller ionic size difference from foreign ions are easy to be replaced. The investigated aspects include lattice parameter, mechanical performance, DOS, PDOS, liner charge distribution, coordination number with oxygen atoms, formation enthalpy as well as vacancy formation enthalpy. Results show that Mg atoms introduced the most instability to doped structures at the same oxide concentration (in mass).Steel corrosion, specifically, rebar in the concrete structures, has aroused increasingly research interest in order to improve the understanding its nature as well as to protect steel from rapid failure. For steel corrosion study, AISI 1045 medium carbon steel has been selected to conduct pitting corrosion initiation and propagation observation using Vertical Scanning Interferometry (VSI). The corrosion environments are at neutral pH with/without 100 mM NaCl for comparison. Over time, the 3D steel surface morphology is captured with VSI for pitting corrosion analysis at the nanoscale. The comparing items include corrosion product chemical composition, pit initiation mechanism, pit density, average pit depth, and surface height change frequency distribution. Evolution of pitting corrosion over large surface areas has been examined. Special efforts have been paid to quantify the pitting nucleation, growth, and propagation rate. Chloride ions enhance the corrosion rate significantly by shortening the initiation time as well as increase the pit density, pit depth as well as steel surface height retreat. For both with and without chloride ion cases, the surface defects, e.g., MnS inclusions initiate pitting corrosion. Initial pits remove passivation film around themselves, where more pits will generate and propagate. In this study, the pitting corrosion follows the adsorption mechanism. This study provides new insights into steel corrosion at neutral pH environment and extends the understanding of the nature pitting corrosion process.In sum, from the results of DFT simulation of doped C2S structures, it can be concluded that the introduced instability highly depends on the ionic size mismatch between dopants and the ions being replaced. In steel corrosion study, it is found Cl- ions accelerate pitting corrosion by such factors: (i) destabilization of passivation films, (ii) prevention of repassivation, and, (iii) preservation of aggressive microenvironments within the pits. Both of the studies can be helpful to enhance the performance of reinforced concrete structures.

The Clinch River (CR) and North Fork Holston River (NFHR) contain some of the most diverse freshwater mussel assemblages in the United States; however, both rivers are experiencing declines in mussel populations. The first component of this study used histological evaluations and water quality data to determine whether mussels were negatively impacted in the CR zone of decline (ZD) and to inform future management of freshwater mussels in the river. In the 91 kilometer (km) section from Carbo, Virginia (CRKM 431) downstream to Speers Ferry, Virginia (CRKM 340), referred to as the ZD, mussel density decreased >90% from 1979 to 2014 at key sites such as Semones Island (CRKM 378.3) and Pendleton Island (CRKM 364.2). Laboratory propagated mussels were placed in cages in the river for one year from June 2012 to May 2013 at four sites within the ZD and four sites in reaches where mussel populations remain stable or are increasing, a zone of stability (ZS). The survival, growth and histological results indicated that there are continuing impacts to mussels in the ZD. Research investigating impacts to the ZD and methods to improve water quality in this zone are needed. The laboratory component of this study examined sublethal effects of potassium (K⁺), chloride (Cl⁻), and un-ionized ammonia (NH₃-N) on mussel tissues at concentrations relevant to those found in the NFHR. Historical industrial activities at Saltville, Virginia, as well as continued pollution of the NFHR from chemical waste ponds at this location, are believed to be significant contributors to mussel declines. Contaminant seepages from the waste ponds that include Cl⁻, K⁺, and NH₃-N have been shown to be toxic to adult and juvenile mussels. A three-month laboratory study was conducted to assess impacts to organ tissues (gills, digestive glands, kidneys, and gonads) of adult Villosa iris exposed to environmentally relevant concentrations of K⁻ (4 and 8 mg/L), Cl⁻ (230 and 705 mg/L), and NH₃-N (0.014 and 0.15 mg/L) using histological evaluations. No detectable differences were observed among the histological endpoints from mussels held in treatments and control (p>0.05). The study design was modified and repeated using increased concentrations of K⁺ (8, 16, and 32 mg/L) and Cl⁻ (705, 1410, and 2820 mg/L) for a two-month exposure period. Due to issues with maintaining NH3-N in mussel holding chambers, the second study did not the second study did not include NH₃-N exposures. Control mussels in both studies had a higher abundance of lipofuscin in kidneys and degraded cytoplasm in the digestive gland diverticula compared to baseline mussels, indicating that captivity influenced mussel tissues. Future studies are needed to more thoroughly address these captivity effects. Both survival and histological data in the second test showed a significant negative effect of the increased concentrations of Cl⁻ and K⁻, which were representative of those found at some sites in the NFHR downstream of Saltville, Virginia.

Halide perovskites have garnered much attention in recent years as a potential material for photovoltaics, semiconductors, transparent conductors, thermistors, and electromagnetic radiation detectors. Lead halide perovskites with the formula APbX3, where A = Cs+ and X = Cl-, Br-, or I- have been shown to adopt a distorted perovskite structure (space group Pnma) with desirable band gaps and electronic properties for photovoltaic and detector applications. Experiments were conducted herein to better understand the stability limit of the lead halide perovskite structure through A-site substitution with a smaller Rb+ ion. Variable X-ray powder diffraction measurements were used to identify and characterize perovskite phase transitions at elevated temperatures for RbPbCl3, RbPbBr3, and RbPbI3, all of which form non-perovskite compounds at room temperature. Solid solutions Rb(x)Cs(1-x)PbCl3 and Rb(x)Cs(1-x)PbBr3 were synthesized as a means to stabilize the high temperature perovskite phases observed in the variable temperature experiments, and to further study the effects of octahedral tilting on the band gap of the compound. The RbPbX3 (X = Cl-, Br-, and I-) phases do not form as perovskites at room temperature, but RbPbCl3 and RbPbBr3 undergo phase transitions to perovskite structures at higher temperature. RbPbCl3 transitions first at 320 °C to a tetragonally distorted perovskite structure (space group P4/mbm) then to the cubic perovskite structure (space group Pm-3m) at 340 °C. RbPbBr3 also undergoes two phase transitions, first to an orthorhombically distorted perovskite structure (space group Pnma) at 250 °C then to a tetragonally distorted perovskite structure (space group P4/mbm) at 350 °C. Solid solutions of Rb(x)Cs(1-x)PbCl3 and Rb(x)Cs(1-x)PbBr3 resulted in a orthorhombic perovskite structure (space group Pnma) at room temperature. The orthorhombic distortion increased as the Rb+ content increased, due to increased tilting of the lead-centered octahedra. For the Cl- solid solution, the perovskite structure was retained for Rb+ substitution up to a value of x = 0.9, while for the Br- solid solutions a perovskite structure could be obtained up to x = 0.6. As the Rb+ substitution increases, the band gap of the compound increases. The band gap of the Rb(x)Cs(1-x)PbCl3 (x = 0 - 0.6) solid solution increases from 2.97 eV to 3.08 eV, while the Rb(x)Cs(1-x)PbBr3 solid solutions increases from 2.13 eV to 2.30 eV across the same x = 0 - 0.6 range. The increase is a result of greater octahedral distortions, which were characterized by measuring the Pb-X-Pb bond angles.

In this study, phenol was used in a sodium chloride or sulfate matrix as a representative pollutant to systematically study which operating conditions have the largest impact on chlorine forms in an electrochemical treatment system. Initially, an HPLC method was developed and validated to simultaneously determine phenol and potential intermediates from hydroxylation and hypochlorination pathways during electrooxidation in the presence of chloride. In a combined-reactor configured with a boron-doped diamond (BDD) anode, samples were analyzed to identify and quantify organic intermediates and inorganic chlorine species generated during the electrooxidation of phenol. Ionic strength was kept constant at 50 mM and the applied current density was 12 mA/cm2. The effects of chloride-to-phenol ratio on contaminant removal efficiency and byproduct formation were studied. Experimental results showed that phenol was removed faster at higher chloride-to-phenol ratios but more chlorinated intermediates and chlorate were produced. The impact of initial chloride concentration on the chlorate formation rate was stronger than its impact on phenol removal rate. Analysis of variance (ANOVA) was used to evaluate the statistical significance of operational factors in a full 24 factorial design. Factors studied were anode type (BDD vs. graphite), initial phenol concentration (0.25 – 0.5 mM), initial chloride concentration (5 – 50 mM) and applied current density (12 – 25 mA/cm2), on responses such as phenol removal rate and chlorate production rate. Results showed that anode type and chloride concentration had the most significant effects either individually or interactively on the phenol removal rate, and that chloride concentration had a considerable effect on the chlorate production rate. Additionally, applied current density had a significant effect on the free chlorine production rate after breakthrough if and when it occurred with BDD in the presence of excess chloride. A 23 factorial design with a given reactor configuration with either BDD or graphite anode was optimized using response surface methodology (RSM) with respect to phenol removal and control of chlorate production. Linear regression results showed that the phenol removal rate was highest at low phenol concentration and high chloride concentration, whereas low chloride concentration minimized chlorate production. In addition to the ANOVA analyses, kinetics of the electrochemical oxidation of phenol and intermediates formed in the presence of chloride were explored for the different anodes at various chloride-to-phenol ratios. Comparison of rate constant k values of the first-order reactions showed that hypochlorination and hydroxylation pathways were in competition and hypochlorination pathway was more favored and 2-chlorophenol was the most dominant species in most cases. Mass balances around carbon and chlorine for measured species were also considered. Lack of closure for both indicated possible formation of other by-products that were not identified by HPLC. LC-QTOF-MS was used to qualitatively investigate the unknown by-products formed during phenol electrooxidation in the presence of chloride at two levels (5 mM and 50 mM) using the BDD anode. Results showed formation of chlorinated dimers and trimers of phenol, including potential formation of polychlorinated dibenzo-p-dioxins (PCDDs).

Because breaking and making of chemical bonds lies at the heart of chemistry, this thesis focuses on dynamic studies of labile molecules in solutions using ultrafast transient absorption spectroscopy. Specifically, my interest is two-fold: (i) novel reaction intermediates of polyhalogenated carbon, boron and phosphorus compounds; (ii) photophysics and photochemistry of labile copper(II) halide complexes.Excitation of CH2Br2, CHBr3, BBr3, and PBr3 into n(Br)σ*(X-Br) states, where X=C, B, or P, leads to direct photoisomerization with formation of isomers having Br-Br bonds as well as rupture of one of X-Br bonds with the formation of a Br atom and a polyatomic radical fragment, which subsequently recombine to form similar isomer products. Nonpolar solvation stabilizes the isomers, consistent with intrinsic reaction coordinate calculations of the isomer ground state potential energy surfaces at the density functional level of theory, and consequently, the involvement of these highly energetic species on chemically-relevant time scales needs to be taken into account.Monochlorocomplexes in methanol solutions promoted to the ligand-to-metal charge transfer (LMCT) excited state predominantly undergo internal conversion via back electron transfer, giving rise to vibrationally hot ground-state parent complexes. Copper-chloride homolitical bond dissociation yielding the solvated copper(I) and Cl- atom/solvent CT complexes constitutes a minor pathway. Insights into ligand substitution mechanisms were acquired by monitoring the recovery of monochloro complexes at the expense of two unexcited dichloro- and unsubstituted forms of Cu(II) complexes also present in the solution.Detailed description of ultrafast excited-state dynamics of CuCl42-complexes in acetonitrile upon excitation into all possible Ligand Field (LF) excited states and two most intense LMCT transitions is reported. The LF states were found to be nonreactive with lifetimes remarkably longer than those for copper(II) complexes studied so far, in particular, copper blue proteins. The highest 2A1 and lowest 2E LF states relax directly to the ground electronic state whereas the intermediate 2B1 LF state relaxes stepwise through the 2E state. The LMCT excited states are short-lived undergoing either ionic dissociation (CuCl3- + Cl-) or cascading relaxation through the manifold of vibrationally hot LF states to the ground state.

Reinforced concrete is a structure material made up of concrete with relatively lower tensile strength containing reinforcements with higher tensile strength and better ductility, which are embedded into fresh concrete to resist tensile stress in certain regions of concrete. Steel reinforced concrete is most widely used around the world in civil engineering structures, water conservancy and highway construction due to its durability strength and reasonable cost. However, reinforced concrete structures such as bridges and parking lots slabs inevitably experience variable loads and constant degradation from the aggressive environments, such as marine and deicing salts. Therefore, it is imperative to study the synergic impact of different types of loadings and exposure to chloride ions on the corrosion of steel rebars. Clear understanding of such processes assists improving the resiliency of the structures and helps extending the service life of the constructions by modifying the design codes of structural steel, which will thus improve the durability and safety of next generation of sustainable infrastructures. In addition, it is necessary to understand the fundamental mechanism of steel passivation and depassivation processes in concrete under stresses, then more reliable and robust service life modeling tools can be made to help engineers predict the state and performance of rebar in concrete structures. Hence, in order to obtain detailed understanding of the effect of both tensile and compressive stresses on passive film and the depassivation process, experiments were performed on steel immersed in concrete simulated pore solution under different types and degrees of loadings. Simulated concrete pore solution was chosen in order to obtain the results in a reasonable time frame required for this project. Several electrochemical measurement techniques were used. Besides, Mott-Schottky technique was utilized to investigate the semi-conductive behavior of the passive film, which is formed on the surface of the steel rebars. Results indicate that steel specimens in chloride free pore solution under tensile loadings passivate more rapidly compared to those under compressive loadings. However, the situation in chloride contaminated solution is different and steel under tensile stress exhibit more corrosion than that under compressive stress and no load.

Carbon steel is susceptible to stress corrosion cracking (SCC) in fuel grade ethanol. Dissolved oxygen and corrosion potential have been identified as the critical factors. The threat of SCC prevents the use of the cost-efficient pipeline system for long distance transport of ethanol. Simulated fuel grade ethanol (SFGE) was used in the laboratory. Due to the high electrical resistivity of SFGE, adding non-complexing supporting electrolyte is considered to be the most practical method for accurate potential control. TBA-TFB was found to be the best suitable supporting electrolyte in deaerated FGE among the salts that were tested. Carbon steel exhibits passivity and high corrosion potential in aerated SFGE. Deaerated conditions are of interest so that the effects of high potential on SCC susceptibility can be determined separately from other possible effects of dissolved oxygen. In slow strain rate (SSR) tests, cracking was reproduced at applied potential without oxygen in the deaerated SFGE + TBA-TFB, which indicates that the role of oxygen in ethanol SCC might be a simple oxidizing agent. However, the passivation effect of oxygen is also required to prevent lateral corrosion at crack tip. A potential range for ethanol SCC was determined by SSR tests at different potentials. No experimental evidence was found to support the proposed role of oxygen to react with ethanol to form an aggressive oxidation product. The presence of chloride causes decreasing corrosion potential and enhanced pitting corrosion. The chloride effect on ethanol SCC was investigated both in aerated SFGE at open circuit and deaerated SFGE at applied anodic potentials over a wide range of chloride concentration. A minimum concentration of chloride is required for SCC of carbon steel, but it is not the controlling factor for crack growth. There is no upper limit of chloride concentration for cracking in aerated SFGE, but a window of chloride concentration in deaerated SFGE at applied potential. The dissolution based SCC mechanism has been identified for carbon steel in ethanol environment. SSR testing with periodic potentiodynamic scans at different stains and strain rates show that the anodic current difference between plastic and elastic region has a peak in the cracking potential range. The notched SSR testing is more sensitive to ethanol SCC susceptibility, and it generates more consistent results of current evolution. A high R-ratio and low cyclic frequency crack growth rate (CGR) test was intended to mimic the actual loading condition of pipelines in service at accurately-controlled fracture mechanics conditions. The measured CGR at applied potentials matches the cracking susceptible potential region. An oxygen depletion induced dissolution model and the traditional film rupture induced dissolution model were proposed to explain the mechanism of ethanol SCC. A few models based on oxygen diffusion and consumption were considered in an attempt to explain the differences of the two proposed mechanisms. Complete oxygen depletion is less likely to occur at crack tip.

The transport and adsorption phenomena in cement-based materials are the most important processes in the durability of concrete structures or nuclear waste containers, as they are precursors to a number of deterioration processes such as chloride-induced corrosion, sulfate attack, carbonation, etc. Despite this importance, our understanding of these processes remains limited because the pore structure and composition of concrete are complex. In addition, the range of the pore sizes, from nanometers to millimeters, requires the multi-scale modeling of the transport and adsorption processes. Among the various environments that cement-based materials are exposed to, aqueous and saline environments represent the most common types. Therefore, this dissertation investigates the adsorption and transport phenomena of cement-based materials exposed to an aqueous and saline environment from atomic to macro-scales using different arrays of novel spectroscopic techniques and simulation methods, such as scanning transmission X-ray microscopy (STXM), X-ray absorption near edge structure (XANES), molecular dynamics (MD), and finite element method (FEM). The structure and transport of water molecules through interlayer spacing of tobermorite was investigated using MD simulations because the interlayer water of calcium silicate hydrate (C-S-H) gel influences various material properties of concrete. The adsorption processes of cementitious phases interacting with sodium and chloride ions at the nano-scale were identified using STXM and XANES measurements. A mathematical model and FEM procedure were developed to identify the effect of surface treatments at macro-scale on ionic transport phenomena of surface-treated concrete. Finally, this dissertation introduced a new material, calcined layered double hydroxide (CLDH), to prevent chloride-induced deterioration.

Incorporation of silver nanoparticles (AgNPs) into an increasing number of consumer products has led to concern over the potential ecological impacts of their unintended release to the environment. Dissolution is an important environmental transformation that affects the form and concentration of AgNPs in natural waters; however, studies on AgNP dissolution kinetics are complicated by nanoparticle aggregation. Herein, nanosphere lithography (NSL) was used to fabricate uniform arrays of AgNPs immobilized on glass substrates. Nanoparticle immobilization enabled controlled evaluation of AgNP dissolution in an air-saturated phosphate buffer (pH 7, 25 °C) under variable NaCl concentrations in the absence of aggregation. Atomic force microscopy (AFM) was used to monitor changes in particle morphology and dissolution. Over the first day of exposure to ≥10 mM NaCl, the in-plane AgNP shape changed from triangular to circular, the sidewalls steepened, and the height increased by 6-12 nm. Subsequently, particle height and in-plane radius decreased at a constant rate over a 2-week period. Dissolution rates varied linearly from 0.4 to 2.2 nm/d over the 10-550 mM NaCl concentration range tested. NaCl-catalyzed dissolution of AgNPs may play an important role in AgNP fate in saline waters and biological media. This study demonstrates the utility of NSL and AFM for the direct investigation of un-aggregated AgNP dissolution.

Bacteria were previously isolated from two separate sites, one contaminated with lead and the other with Polycyclic Aromatic Hydrocarbons (PAHs). Alcaligenes sp. AO22 and Arthrobacter sp. E9 were identified from the lead contaminated site, while Stenotrophomonas maltophilia was identified from the PAH contaminated site. Minimum Inhibitory Concentration assays (MICs) were previously performed on Alcaligenes sp. AO22 and Arthrobacter sp. E9 and they were found to be resistant to varying levels of heavy metals and polymerase chain reactions suggesting the presence of mercury (mer), copper (pco) and cadmium, zinc and cobalt (czc) resistance genes. S. maltophilia VUN 10010, was previously investigated for its ability to degrade pyrene and other HMW PAHs as a sole carbon and energy source. The purpose of the current project was to further characterise the MICs of these isolates, along with biofilm capabilities. The genetic basis of their heavy metal resistance was also investigated.

As stagnant water contacts copper pipe and lead solder (simulated soldered joints), a corrosion cell is formed between the metals in solder (Pb, Sn) and copper. If the resulting galvanic current exceeds about 2 µA/cm², a highly corrosive microenvironment can form at the solder surface, with pH

Tetrachloroethene and trichloroethene are among the most prevalent groundwater contaminants found at hazardous waste sites throughout the United States. Since implementing some of the common treatment methods to remediate these hazardous waste sites would exceed hundreds of billions of dollars, there is considerable interest in reducing costs while achieving remediation regulations. Under anaerobic conditions, these compounds can undergo reduction reactions known as reductive dechlorination. This occurs when an electron donor provides the reducing equivalents needed to replace the chlorine atoms with hydrogen atoms. The daughter products from higher chlorinated ethenes are ethene and ethane which can be used to document the process with a simple mass balance. However, at many hazardous waste sites, the sum of the daughter products often does not account for the amount of tetrachloroethene and trichloroethene consumed. At least two explanations have been offered for this phenomenon. First, downgradient sampling of plumes may not be accurately representing where the plume is. Second, it is possible that the lesser chlorinated products, in particular vinyl chloride (VC) and ethene, could be undergoing anaerobic or aerobic oxidation. If this occurs, CO2 and Cl- are the major daughter products. While both are nonhazardous, it is far more difficult to show that these compounds were formed from VC and ethene, rather than other compounds. Bio-oxidation of ethene and the aerobic biodegradation of VC at levels that are too low to be accurately measured in the field are possible explanations for the lack of mass balances. Additionally, the pathways for catabolism of both compounds have been proposed and they share considerable overlap. The first step involves insertion of an oxygen atom from O2 via an alkene monooxygenase, forming an epoxide followed by a series of reactions forming acetyl coenzyme A, a central intermediate in metabolic processes. Since an oxygenase is required to initiate aerobic oxidation of VC, oxygen must be available as a reactant. Substitution of nitrate for oxygen as the electron acceptor would decrease the amount of oxygen required for growth on VC. The overall purpose of this project was to improve the methods needed to document the fate of VC and ethene in situ. The specific objectives were 1) to document in microcosms the anaerobic oxidation of VC, using groundwater from a hazardous waste site where the field evidence suggests that bio-oxidation is occurring; 2) to document in microcosms the anaerobic oxidation of ethene, using uncontaminated soil as a source of inoculum, under a variety of anaerobic conditions; 3) to determine if microbes subjected to anaerobic conditions for longer than one year are then able to aerobically oxidize VC; and 4) to determine if nitrate can replace oxygen as a terminal electron acceptor under oxygen-limited conditions that still permit the use of oxygen as a reactant for the alkene monooxygenase. In approximately eight of the 83 microcosms prepared with first flush groundwater from a hazardous waste site, significant levels of VC bio-oxidation occurred. However, there was considerable uncertainty whether the process observed was anaerobic or aerobic, as a consequence of oxygen leaking into the bottles. Lines of evidence in support of each scenario were reviewed. Overall, the weight of evidence suggests the activity was aerobic. Some of the considerations include the detection of low levels of oxygen by analysis of headspace samples (coupled with controls that indicated these measurements were not false positives), the pink color of resazurin during most of the time when VC was consumed, consumption of methane during or after the VC was consumed (methane is generally recalcitrant under anaerobic conditions), and the ability of microbes that grow aerobically on VC to use oxygen to the point when it is no longer detectable. Incubation of five of the active microcosms is on-going, to further assess the question of aerobic versus anaerobic activity. Anaerobic oxidation of ethene was observed in microcosms amended with Fe(III) and Fe(III) chelated with ethylenediaminetetraacetic acid (EDTA), and in a chlororespiring enrichment culture amended with sulfate. Ethene oxidation occurred when the concentration of ethene in the headspace was increased to 1% (v/v) or higher. Prior to that, ethene was stoichiometrically reduced to ethane. Oxidation was not observed in unamended microcosms and ones with nitrate and glucose added. Unlike the results with VC, there was a high level of confidence that oxidation occurred under anaerobic conditions. Compared to VC, the rate of ethene oxidation was considerably slower. Also, oxidation activity often slowed down after 10% or less of the ethene was consumed. This type of pattern suggested the process may be cometabolic, although additional studies are needed to verify this. Also, confirmation of oxidation is needed using [14C]ethene. Microcosms were prepared with soil and groundwater from a hazardous waste site and incubated under anaerobic conditions for 1.7 years, with no evidence for biodegradation of VC. When oxygen was added to the microcosms, only two of the 12 exhibited biodegradation of VC, along with methane. The results of this study indicate that aerobic biodegradation of VC may not always occur when soil and groundwater have been subjected to anaerobic conditions for an extended period, in this case 1.7 years. The results of this study indicated that nitrate did not substitute for oxygen as a terminal electron acceptor under conditions with limited oxygen (but enough to allow functioning of the alkene monooxygenase) and an excess of nitrate. However, the results may be specific to the enrichment culture that was tested, which was able to biodegrade VC aerobically and also use acetate as a substrate under denitrifying conditions. If this process is possible, it would decrease the stoichiometric amount of oxygen needed for VC oxidation. The inconsistencies in observations of anaerobic bio-oxidation of VC leave many questions unanswered. Considerable uncertainties also remain for the occurrence of anaerobic oxidation of ethene. As promising as previous studies appear, the hallmark of advances in science is reproducibility. Until the results of others can be replicated under conditions that are unquestionably anaerobic, the uncertainties surrounding anaerobic oxidation of VC and ethene will persist. As a consequence, so too, will the uncertainties associated with explaining the lack of mass balances in situ for remediation of PCE and TCE.

Lead corrosion in premise plumbing systems from materials, such as lead pipes, soldered joints, and brass, can cause elevated lead in drinking water. This work examined mechanisms by which galvanic corrosion of lead solder:copper joints is accelerated by high chloride, low sulfate, and high nitrate in the water. Galvanic corrosion studies conducted using simulated copper plumbing joints showed lowered pH and concentrated anions at the lead solder surface. A combination of low pH and high chloride can prevent passivation of the solder surface, indefinitely sustaining high corrosion rates and lead contamination of potable water supplies. The mass of lead leached to water correlated with predictions based on Faraday's law, although a portion of the oxidized lead remained attached to solder in a scale layer. When the level of sulfate in water increased relative to chloride, galvanic currents and associated lead contamination could be greatly reduced. The impact of chloride-to-sulfate mass ratio (CSMR) on lead leaching from 50:50 lead:tin solder galvanically coupled to copper was examined at the bench scale.The CSMR can be affected by coagulant changeover, use of desalinated water, anion exchange, brine leaks, and other treatment changes. Consistent with prior experiences, increasing the CSMR in the range of 0.1 to 1.0 produced dramatic increases in lead leaching from this source. Above this range, while lead leaching was generally very high, there was little correlation between lead release and CSMR. The impact of nitrate was tested at the bench scale using synthesized water. Results consistently showed that increasing nitrate in the range of 0 to 10 mg/L NO??N, could dramatically increase lead leaching from simulated soldered pipe joints. Although higher nitrate slightly increased the galvanic current, the main factor affecting lead release appears to be initiation of non-uniform corrosion, with small pieces of solder detaching into the water. Under some circumstances, the decay of chloramine after it leaves the treatment plant, and formation of nitrate via nitrification, can markedly increase corrosivity of distributed water to lead solder. The bench scale experiments conducted in this work illuminated many issues related to accelerated lead corrosion of solder. However, future research is necessary to further elucidate the mechanisms behind nitrate-accelerated corrosion, as well as methods for inhibition of corrosion due to chloride and nitrate.

The LIC-310 prestressed adjacent box-beam bridge was removed on July 2007 after 27 years of services because of serious corrosion, cracking, and spalling of its beams observed during its inspections. A number of its beams were examined through visual inspection and the forensic investigation. The investigation revealed that the amount of chloride at different locations of the tested beams was greater than the threshold level. The compressive strength of concrete obtained by both destructive and nondestructive methods exceeded the minimum required concrete compressive strength of 5500 psi. Furthermore, the tensile capacity of prestressing strands was much lower than the requirements for all but one beam. Further investigation after cutting the beams revealed the existence of further corrosion, cracking, and spalling in the beams. Besides, strand cover, surface, and overall conditions of the beams detected by GPR were closely comparable to other destructive and nondestructive findings. Also, it was learned that the beams were built close to specifications. Finally, it was discovered that corrosion reduced the capacity of Beams 4, 15, and 18 as much as 34%, 41%, and 59%, respectively.

This study involves the design and fabrication of an Ion-Sensitive Field Effect Transistor (ISFET), which is aimed to be incorporated into the multisensory chips fabricated at RIT. ISFETs are used for various purposes in biomedical, medicine, and chemical applications and have advantages such as small size, low power consumption, robustness, and fast response time, over the ion-selective electrode (ISE) counterparts. The capability of fabricating ISFETs in a standard CMOS process let them to be used in sensor systems together with the dedicated signal processing circuitry which in turn makes portable applications possible. The ISFET fabricated in this study have a SiO2 gate oxide and on top of that a Si3N4 layer. The latter layer, in addition to passivating the device, serves as a pH sensitive membrane. The overall process has 5 mask levels and the electrical tests, which were performed using buffer solutions with varying pH values, indicated that the transistor can be employed to measure the pH of solutions. ISFETs were also tested against environmental conditions such as temperature, long term exposure to various pH-valued solutions and it is found out that the FETs are quite robust in terms of temperature stability and long term drift. In addition to their pH sensing properties, these devices were also taken one step ahead to sense chloride ion (Cl-) concentration via preparing a Cl--sensitive membrane stacked on top of the Si3N4 layer. Electrical tests, which were performed in solutions with various Cl- concentrations, showed that the modified ISFETs are also Cl- sensitive.

Salt is widely used for ice and snow control on roads in the US, Canada and other parts of the world affected by adverse winter driving conditions. The primary product applied in North America for deicing of roads is sodium chloride (NaCl), a readily available and inexpensive material. The use of sodium chloride as a road deicing chemical has increased dramatically in the northern areas of the United States over the last 50 years with about 23 million tons used in 2005. The primary objective of my research was to determine how road salt applications influenced the water quality in a major metropolitan area (Twin Cities metropolitan area (TCMA) of Minneapolis/St Paul, Minnesota, USA). This objective was met by collecting and analyzing data from area lakes, streams and rivers and through the development 0 Dimensional (0D) and 1 Dimensional (1D) models. It was determined that on average over 70% of the chloride applied annually in the TCMA was retained in the watershed instead of entering the Mississippi River and eventually exported to the Gulf of Mexico. Salinity cycles were observed in area lakes with high concentration in the winter followed by lower concentrations in the spring and summer. Mean annual concentrations in 38 lakes in the TCMA rose on average 1.4 mg/L per year over 22-years matching a similar trend in the amount of rock salt the state of Minnesota purchased over the same time period. Salt water inflows changed the natural mixing behavior of area lakes. In some lakes monomictic behavior developed with mixing events only occuring in the fall. The presence of a saline layer at the bottom of the lake prohibited dissolved oxygen from reaching the benthic water layer in the spring extending the anoxic period of this water layer by 6 months. Simulations conducted without the presence of a saline layer showed complete mixing and oxygenation of the benthic layers in the spring and fall. Rising Cl concentrations in lakes are expected to continue. If the annual inputs of salt to the lakes were stopped it would take 10 to 30 years to reach chloride concentrations equal to predevelopment concentration. Chloride retention in urban areas where road salt is applied should cause much concern. Mitigation measures, best management practices (BMPs) for road salt application and alternatives to NaCl need to be examined.

Swollen cells expel osmolytes to decrease volume in a process referred to as Regulatory Volume Decrease, or RVD. The plasma membrane current ICl,swell is ubiquitously expressed in mammalian cells and contributes significantly to RVD. In a variety of cell types, activation of ICl,swell is enhanced by nucleotide signaling. In this study, we used human astrocytoma cells to examine whether nucleotide signaling is necessary or sufficient for ICl,swell activation. Three clones of the 1321N1 human astrocytoma cell line were used for voltage clamp recordings. One clone was transfected with P2Y1 receptors, another with P2Y2 receptors and a third was devoid of any P2Y receptors (Parental). In physiological solutions, hyposmotic exposure (HOE) caused increased membrane conductance in each cell line. HOE also depolarized the reversal potential in P2Y1 and P2Y2, but not in Parental, cell lines. In solutions containing no permeable cations, HOE activated ICl,swell in morphologically round cells of each cell line and in morphologically flat P2Y1 and P2Y2 cells. However, morphologically flat Parental cells did not demonstrate HOE-induced ICl,swell activity. Exogenous ATP activated a chloride current with an electrophysiological profile different from ICl,swell. I conclude that P2Y nucleotide signaling may play a role in gating ICl,swell, but is not necessary for its activation. P2Y receptor stimulation is sufficient to activate a chloride current, but whether the response is mediated by P2Y1 or P2Y2 receptors requires further investigation.