Excess nutrients entering aquatic systems cause negative effects downstream. Oxidation-reduction potential (Eh) is an inexpensive proxy which can be used to define the potential nutrient reducing capacity of a system, in particular denitrification. My thesis attempts to determine effects of hydrology and vegetation manipulations on Eh in an agricultural drainage ditch with weirs using continuous automated data loggers to monitor the system. Accuracy and precision of the continuous automated data loggers was confirmed through laboratory and field testing. Effects of hydrology and vegetation on Eh were quantified during testing from May-September 2012 in east-central Mississippi. Vegetation affected Eh (t=-1.75, P=0.08, df=9,754) whereas changes in hydrology also affected Eh (t=7.05, P<0.001, df=9,754). Modeling of these variables indicated the interaction of hydrology and vegetation was the most influential factor measured. Through management of hydrology and vegetation in ditches, Eh can be managed to create conditions conducive for denitrification.

Forest rings are large features common in Ontario’s boreal forests that comprise circular topographic depressions in carbonate mineral soil that are filled with peat. This thesis documents differences in peat and soil chemistry along transects across the “Bean” and “Thorn North” rings, which are centered on accumulations of CH4 and H2S, respectively. Within the mineral soil, ring edges are characterized by strong negative anomalies in pH, ORP and carbonate, as well as positive anomalies of Al, Fe and Mn in the results of aqua regia and hydroxylamine-hydrochloride digestions. Within the peat, positive carbonate and pH anomalies are recorded. This antithetic relationship suggests vertical migration of carbonate species from clay to peat. An inverse relationship exists between ORP, versus redox inferred from aqua regia. Strong ORP lows occur where oxidized products show highest concentrations. This is interpreted to reflect the proliferation of autotrophic organisms occupying the strong redox gradient at the ring edge.

Forest rings are large features common in Ontario’s boreal forests that comprise circular topographic depressions in carbonate mineral soil that are filled with peat. This thesis documents differences in peat and soil chemistry along transects across the “Bean” and “Thorn North” rings, which are centered on accumulations of CH4 and H2S, respectively. Within the mineral soil, ring edges are characterized by strong negative anomalies in pH, ORP and carbonate, as well as positive anomalies of Al, Fe and Mn in the results of aqua regia and hydroxylamine-hydrochloride digestions. Within the peat, positive carbonate and pH anomalies are recorded. This antithetic relationship suggests vertical migration of carbonate species from clay to peat. An inverse relationship exists between ORP, versus redox inferred from aqua regia. Strong ORP lows occur where oxidized products show highest concentrations. This is interpreted to reflect the proliferation of autotrophic organisms occupying the strong redox gradient at the ring edge.

The uranium price decline has negatively impacted on the uranium mining industry. This decline in price requires that uranium metallurgical processes be made to operate more efficiently. Some key parameters that influence the dissolution and kinetics of leaching uraninite (one of the main minerals from which uranium can be extracted) are pH, oxidationreduction potential and iron concentration. A good understanding of the effect these parameters have on the leach kinetics would lead to an efficient operation of metallurgical processes. The objective of this work was therefore to investigate the effects of these key drivers on leach kinetics of Rӧssing Uranium ore. Added to this, was an attempt to come up with a mathematical model which can successfully replicate the leach kinetics. A series of laboratory leach experiments were performed on Rӧssing ore where the pH, oxidationreduction potential and total iron were varied, one at a time, to establish the effects they have on the leach kinetics and on the uranium extraction. Analysis of the data collected from this study showed that the leach kinetics are more dependent on the oxidation-reduction potential, followed by the iron concentration and least affected by the pH. It was further shown that oxidation-reduction potential is a function of total iron. An integral method was used to analyse the kinetic data. A literature study reveals that uraninite dissolution follows first order kinetics, but of interest in these results was that the uranium dissolution was found to closely follow the second order. Further research is recommended to look at ascertaining these results. Two models were developed, one using regression and the other by curve fitting method. Both models could fit the experimental data well enough. / Dissertation (MSc)--University of Pretoria, 2016. / Materials Science and Metallurgical Engineering / MSc / Unrestricted

Background: Physically injured elder adults present challenges in the emergent injury phase. Oxidative stress contributes to cellular deterioration, resulting in decreases in physiological reserve. Imbalance of oxidative stress pathways lead to damage and drive the aging process and frailty. Goals of this study were to determine if a new plasma biomarker of oxidative stress is related to: 1) oxidation reduction status in patients who have experienced traumatic injury as well as healthy community dwellers, 2) outcomes of patients who have experienced trauma, 3) frailty measured by established frailty scales in healthy community dwellers. Methods: Prospective study included 1) trauma patients ≥65 admitted to Level I trauma center 2) age, gender matched healthy, community-dwelling participants. Plasma samples tested in duplicate for capacity oxidative reductive potential (cORP, μC; antioxidant reserve), and static oxidative reductive potential (sORP, mV; the current state of oxidative stress). Frailty assessments were performed in healthy participants using established frailty scales. ORP measurements were analyzed using correlation analyses. Univariate analysis analyzed cORP and sORP for differences by the variables gender, age, smoking, diabetes, statin use, vitamin use and any alcohol use in both the injured and healthy populations. Results: 186 subjects included in study (N=93 for both groups). Trauma groups's cORP values were significantly lower in patients with diabetes (p<0.05) and patients that smoked (p<0.01). Similarly the healthy group's cORP was significantly lower for those who smoked and those with diabetes (p<0.05). Non-vitamin use in the healthy group was related to lower cORP values (p<0.05). Trauma patients who smoked and those with diabetes exhibited higher sORP values (p<0.05). In the healthy group, sORP did not differ when considering the variables. No12significant differences were found based on gender, statin or alcohol use for either group. Significant correlation was found for both sORP and cORP with CSHA Clinical Frailty Scale in the healthy group. Conclusion: Findings suggest that the variables of smoking and diabetes are contributory to frailty trajectory. Data suggest the capacity to tolerate oxidative stress, measured by cORP, is lower in aged individuals that smoke or are diabetic and contributes to frailty as a result of oxidative damage.

INTRODUCTION: Inflammatory bowel disease (IBD) is a complex, chronic, autoimmune disease of the gastrointestinal tract. Reactive oxygen species (ROS), a product of active leukocytes, have been implicated in the pathogenesis of IBD. The ability to reliably measure ROS in blood, urine, and stool samples could represent a new approach to assessing disease activity and response to therapy in pediatric patients with IBD. OBJECTIVES: To assess the relationship between redox measurements and clinical disease activity in pediatric patients with IBD. METHODS: Biological specimens, including stool, urine, blood plasma, and intestinal aspirates, were collected from patients at Boston Children’s Hospital. Each sample’s oxidation-reduction potential was measured by two oxidation-reduction potential probes (an Arrowdox probe and a Mettler Toledo probe). Probes were directly immersed into the sample, returning a millivolt measurement of oxidation-reduction potential. Linear regression was performed to explore the relationship between patient-reported outcome measures (PROMs) and redox measurements of biological specimens. Patients were also stratified by disease severity, and ANOVA testing was performed to test for differences in oxidation-reduction potential observed in patients with remittent, mild, moderate, and severe disease activity. RESULTS: Redox values in stool, urine, plasma, and intestinal aspirate did not significantly correlate with PROMs or differ significantly among groups categorized by disease severity. CONCLUSIONS: Measurements of oxidation-reduction potential from stool, urine, plasma, and intestinal aspirate do not appear to be useful for assessing disease severity in pediatric patients with inflammatory bowel disease.

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Constructed wetlands and the soil filters are water treatment devices using the filter material that in most cases consists of natural river gravel, coarse sand or crushed stone. Master´s thesis deals with the research of cleaning effect of unconventional filtration materials, or more precisely with examination to load real waste water in a filtration column, to prove their ability to be used as an alternative medium that can ensure better cleaning effect. For the research work following metallurgical industry materials were used: fine slag and coarse slag 8-16 mm, materials from the natural character: zeolite, keramzit, a plastic material: PUR-foam. Also the traditional materials of fine gravel and coarse gravel were tested to compare the cleaning efficiency. Both the hydraulic and the cleaning efficiency of all above mentioned materials were tested. The examined hydraulic parameters are particularly porosity, hydraulic conductivity and suspended solids, turbidity and oxidation-reduction potential of both the inflow and outflow of the filter columns were determined. Accredited laboratory set the inflow and outflow of the filter columns BOD5, CODCr, total phosphorus, total nitrogen, nitrite, nitrate, ammonia and dissolved oxygen. By evaluating the results of the measurements it is determined which materials are suitable to be applied in the constructed wetlands and the soil filters. This filtration column was modeled by program HYDRUS and the result was compared with real results.

Philosophiae Doctor - PhD / The aim of this thesis is first, to evaluate various culture conditions to improve embryo development, and secondly, to analyze spent culture media for any biomarkers that may be predictive of embryo health. Single-step and sequential culture media were compared in both Planer and EmbryoScope™ incubators. Single-step media resulted in better blastocyst development compared to sequential media and the EmbryoScope™ incubation system showed slight improvements in embryo development than the Planer system. The benefits of supplementing the culture medium with either insulin or insulin-like growth factor 1 (IGF-1) or culturing in a 2% O2 environment, using two different strains of mice (hybrid and C57), as well as the suitability of these strains for quality control were compared. In insulin, hybrid embryos were slower to blastulate and had a lower blastocyst rate, whereas C57 embryos were slower to the morula and faster to blastocyst stages, and lower blastocyst rate than the controls. IGF-1 showed no difference in time-lapse morphokinetics (TLM) or blastocyst rates compared to controls in both hybrid and C57 embryos. Under 2% O2, hybrid embryos showed no significant difference in TLM up to the 8-cell stage, but slowed down afterwards, resulting in blastocysts with significantly lower cell counts than the 6% O2 group. The C57 embryos were slower to reach morula and expanded blastocyst, and had lower blastocyst rates in 2%O2 vs 6%O2. The C57 strain had significant slower overall embryo development for all time points than hybrid embryos in insulin, IGF-1 and ultra-low O2, as well as lower blastocyst rates. Measurement of growth differentiation factor 9 (GDF-9) and oxidation-reduction potential (ORP) in spent media as markers for embryo health were evaluated. Day 5 human blastocysts yielded higher pregnancy rates and GDF-9 levels in spent media compared to Day 6 blastocysts, but TLM parameters showed no impact on pregnancy outcome. In Day 6 blastocysts, the non-pregnant group showed significantly faster embryo development compared to the clinically pregnant group up to the 8-cell stage and start of blastulation. GDF-9 did not show any significant differences between non-pregnant and pregnant groups of Day 5 or Day 6 embryo transfers. ORP in spent media from good quality Day 3 embryos that developed into blastocysts were significantly higher than from those that did not, with no difference in control medium ORP. Spent media from arrested embryos showed lower ORP than their corresponding controls. Arrested embryos had slower development at syngamy, morula, blastulation and blastocyst stages. The single step medium in the EmbryoScope™ is the preferred choice for embryo culture. Insulin or IGF-1 media supplementation or 2% O2 culture did not provide any benefit to embryo development. The C57 mouse strain is more sensitive and may be better to detect changes in culture conditions, and therefore better model for quality control assays. GDF-9 values decrease from Day 5 to Day 6 which gives new insight to understanding the role of GDF-9 during embryogenesis. ORP in spent media indicate that embryos that developed into blastocysts did not contribute to ROS, but maintained ORP balance.