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The presence of hydrogen sulfide in a ground water source is noted by its rather obnoxious odor, similar to a "rotten egg". Concentrations as low as 0.05 ppm are noticeable, therefore, almost its entire removal is demanded prior to potable consumption. Hydrogen sulfide is formed primarily by the decomposition of organic matter in anaerobic conditions. Removal of this gas has been accomplished by means of aeration, detention, and chlorination over the years. The mechanisms behind each of these processes are complex and discussed in this paper. During the course of this investigation, a literature survey concerning the mature and sources of hydrogen sulfide, its removal by aeration and detention, and the experimental methodology has been conducted. Samples were collected from two ground water locations in Central Florida, namely City of Apopka Terrace Plant, and the City of Maitland Thistle Plant. These samples were taken before and after aeration and detained in containers similar to the storage tank dimensions. These samples were tested for Hydrogen Sulfide and pH with respect to time. The aerators were determined to remove 13 to 15 percent H2S, respectively. The pH values ranged between 7 - 8 prior to detention and rose slowly during H2S ionization to 8-8.6. Both locations were evaluated to determine the most economic operating conditions. Ideally, Apopka should be removing between 30 - 40 percent by means of aeration, and Maitland, between 40 - 50 percent. Chlorination will remove the remaining H2S. Although the existing aerators were operating less than their optimum removal range, they should remain in service. This is based on deducting the aerator "sunk costs" from the economic evaluation. Efforts should be encouraged to improve aerator efficiencies by increased agitation, contact time, and weir overflow rates in the aerator trays. These measures should increase the H2S reaction rate and improve its removal. Detention only removes the odor problem, but the chlorine demand still remains, as exerted by the forms HS- and S=.

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<p>Microorganisms are the most abundant living things on the planet and they drive many important environmental processes. They can do this by coupling reduction – oxidation (redox) reactions. In such reactions, the oxidation of reduced organic matter is coupled with the reduction of another compound, which serves as the electron acceptor. All microbes contain lipids in their cells; phospholipids are the main components of the cell membrane where they make up a consistent component of cell mass. Therefore, in situations where direct cell count is unrealistic, lipid analysis can be used to provide information on microbial communities. Because they hydrolyze shortly after cell death,PLFAs indicate only viable cell biomass, and PLFA analysis provides valuable insight on cell density distribution across a site. One application of PLFA analysis is within this thesis, where it was used to investigate the microbial community at Mildred Lake, Syncrude’s primary tailings settling basin. At Mildred Lake, Syncrude is constructing a freshwater fen over the deposited composite tailings (CT) as part of their reclamation process. Understanding the microbial biogeochemical cycling associated with these reclamation activities is an important component for management decisions affecting the site and thus, inform future reclamation activities.</p> <p>PLFA analysis on samples from the site showed variable concentrations equivalent to estimated cell densities on the order of 107 decreasing to 106 in the CT.These cell density ranges are expected for oligotrophic systems. Phospholipids can also be biomarkers if they are indicative of a specific group of microbes. The study at Mildred Lake identified biomarkers for sulfate reducing bacteria (SRBs). The presence of these biomarkers provided a basis for the hypothesis that sulfide detected at the site was potentially from SRBs.</p> <p>This thesis provides information on the fundamental concepts of lipids and the application of lipid analysis on the environmental samples from the Mildred Lake site to understand its microbial community and cycling of sulfur to prevent potential environmental issues associated with the generation of sulfide.</p> / Master of Science (MSc)

Hydrogen sulfide (H2S) is an endogenously produced signaling gas involved in numerous cellular functions. At the appropriate concentration, exogenous administration of this gasotransmitter regulates vasodilation, promotes angiogenesis of endothelial cells, and generally exhibits beneficial effects as an anti-inflammatory and antioperoxidative agent. H2S is also capable of acting as a gaseous chemotherapeutic agent. Therefore, the therapeutic potential of exogenous delivery of H2S is vast. The delivery of H2S is complicated by its gaseous nature. Under physiologically relevant conditions, H2S is rapidly depleted from solution by oxidation and/or degassing. Therefore, direct exogenous delivery is difficult. To date, most studies have employed Na2S as a convenient H2S source. However, the rapid surge in H2S concentration upon Na2S dissolution followed by its rapid decline poorly mimics the sustained production of low concentrations of H2S that occurs in biological systems. We synthesized a library of S-aroylthiooximes (SATOs)—H2S-releasing compounds that more aptly mimic in vivo H2S concentrations. SATOs are synthesized via reaction of a S-aroylthiohydroxylamine and an aldehyde or ketone. SATOs release H2S in response to a thiol functionality. H2S release from SATOs could be controlled, with H2S release half-lives on the order of minutes to hours. SATO chemistry was utilized to prepare H2S-releasing polymers. Copolymers prepared using RAFT polymerization could be functionalized with SATOs with conversions > 99%, and these polymers released H2S on a similar timescale to our small molecule donors, confirming the viability of SATO formation as a post-polymerization modification strategy. SATO-functionalized polymer amphiphiles were prepared that self-assembled into micelles or vesicles based on their composition. H2S was released from these polymer assemblies more slowly than from the small molecules and statistical polymers. These H2S-releasing micelles were employed in in vitro cytotoxicity studies. H2S released from the micelles was found to be selectively toxic to human colon cancer cells compared with healthy fibroblasts. These polymeric micelle donors outperformed existing H2S donors in terms of their toxicity towards cancer cells. The observed enhanced toxicity was suspected to arise from the slow and sustained release of H2S from the micelles. / Ph. D.

Hydrogen Sulfide (H2S), is a negative off aroma produced during yeast fermentation and is common in cider and leads to consumer rejection. H2S has a very low odor detection threshold (ODT) and is often described as "rotten egg". H2S is produced when juice is deficient in yeast nutrients, such as amino acids and yeast assimilable nitrogen (YAN), which is a common problem in apples since they naturally low in nutrients. The purpose of this research was to investigate the effects of yeast nutrient addition to cider fermentation by adding four different nitrogen-rich supplements and evaluating the effects on H2S production, fermentation kinetics, and aroma quality during cider. Three yeast strains (M2, EC1118 and ICV OKAY), four yeast nutrients (Fermaid K, Fermaid O, Experimental Nutrient, and DAP) and single addition versus split addition of nutrient were tested. For single addition, all nutrient was added pre-fermentation and for split additions, the first addition was pre-fermentation and the second at one-third total soluble solid (TTS) depletion as measured by °Brix. Sensory evaluation was conducted on selected treatments. The greatest H2S was produced by M2 yeast strain (525 .63 ± 53.31 µg mL-1) while the least H2S on average was produced by EC1118 (118.26 ± 26.33 µg mL-1) and ICV OKAY produced an intermediate amount of H2S (209.26 ± 31.63 µg mL-1). Significant differences were observed between treatments and total H2S production within yeast strains. Yeast strain had the largest effect on H2S production. The second largest effect was yeast nutrient type. Classical text analysis of descriptions of cider aroma were evaluated and 25 attributes were chosen to describe the ciders. Check- all-that-apply (CATA), a rapid sensory technique that askes panelists, revealed that there was no clear pattern between variables tested. This work demonstrates that yeast nutrient type and yeast strain affect H2S production during cider fermentation. These findings provide a basis for improving the effectiveness of strategies used to prevent H2S production in cider fermentation. / Master of Science in Life Sciences / Cider, an alcoholic beverage made from fermenting apple juice, has grown in popularity and production in the United States in recent years. With increased in production and sales there is increase demand for high quality cider, but cider is prone to sensory faults. A common fault in cider aroma includes negative off aromas know as volatile sulfur compounds (VSCs). These aromas are often described as "rotten eggs", or "cabbage" and lead to consumer rejection of the product. One of the most recognized VSCs is hydrogen sulfide (H2S) which has a characteristic smell of "rotten eggs". These negative off aromas are thought to be produced during yeast fermentation under nutrient lacking conditions. Apples, depending on cultivar, ripeness, and other factors, naturally lack yeast assimilable nitrogen, vitamins, amino acids, and other nutrients needed for a successful yeast fermentation leading to off aromas. Yeast nutrients can be added to apple juice to increase nutrient availability, but little research has been focused on nutrient addition and timing of additions to prevent H2S production in cider. Most research focused on H2S production has been studied in wine must or grape juice. This knowledge may be limited when applying practices to apple juice due to differences in juice chemistry. Providing cider makers with specific scientific strategies to prevent off aromas, such as H2S, is important to the continued growth of the cider industry. This research is focused on exploring aroma quality and H2S prevention strategies in cider by evaluating how yeast nutrient addition via four exogenous nitrogen rich yeast nutrient and timing of yeast nutrient addition affect H2S production, fermentation kinetics, and consumer perception of aroma in cider fermentation.

In advanced stages, cardiac disease causes millions of deaths each year. Superoxide anions (O₂^.-) and their derivative peroxynitrite (ONOO^-) contribute to cardiac disease pathogenesis, yet strategies to reduces these reactive oxygen species through antioxidants in large scale clinical trials have largely been unsuccessful. Better understanding of pathways regulating enzymatic sources of O₂^.- like NADPH oxidases, uncoupled nitric oxide synthases (NOSs) and mitochondrial oxidases are required to regulate myocardial oxidative stress in patients with advanced stages of cardiac disease. Hydrogen sulfide (H2S) is a gaseous signalling molecule generated by transsulfuration pathway enzymes cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (MST). H₂S regulates oxidative stress in animal models and shows promise for cardiovascular therapeutic strategy. This thesis investigates whether H₂S/CSE biology is related to human myocardial redox state in a cohort of individuals with advanced cardiac disease (Oxford Heart, Fat, Vessels Cohort; Ox-HVF). Individuals with varying levels of myocardial oxidative stress and function were extensively phenotyped for H₂S biology. Individuals with high myocardial oxidative stress from NADPH oxidases and NOSs were found to have high expression of myocardial CSE. To examine first the positive association with NADPH oxidase activity, CSE expression was examined after myocardial oxidative injury and CSE was found to be redox-sensitive. Furthermore, direct effects of two exogenous H₂S donors (NaHS and GYY4137) demonstrated a direct regulation of O₂^.- from NOSs in myocardium from individuals with advanced cardiac disease, further supporting H₂S's direct role in the regulation of NOS biology. Finally, identification of a SNP in CSE further demonstrated CSE's causal role in the regulation of O2.- generation from mitochondrial oxidases. Taken together, we demonstrate for the first time that H₂S and CSE biology are linked to human myocardial redox state and have a causal role in redox regulation in the human heart. These findings suggest H₂S/CSE biology are important endogenous regulators of myocardial redox state in humans and continued exploration of these pathways may develop novel therapeutic strategies against myocardial oxidative stress in cardiac disease.