Conselho Nacional de Desenvolvimento Científico e Tecnológico / Metals environment aquatic contamination has been a growing problem with serious consequences to life of different species over time, even after interrupted their emission into the environment. Among relevance metals, manganese (Mn) has shown importance to be related to several activities such as oil exploration, coal deposits extraction, fertilizer use in agriculture, among others. In living organisms, Mn is an essential trace element for a number of vital functions, and involves energy regulation by blood clotting. On the other hand, high concentrations of Mn can cause irreversible damage to living organisms primarily affecting central nervous system (CNS). Thus, waterborne Mn toxicity can switch from aquatic species, while metal bioaccumulation in marine fish or freshwater has been found around 0.2 to 19.0 mg/kg dry weight. In this study, silver catfish (Rhamdia quelen) were exposed to different Mn concentrations (4.2; 8.4 e 16.2 mg/L), under two different dissolved oxygen levels, normoxia (7.48 ± 0.28) and hypoxia (3.88 ± 0.41) for 15 days. At the end of protocol, Mn bioaccumulation as well parameters of oxidative stress and mitochondrial viability were evaluated in different tissues. In hypoxic conditions, the highest Mn concentration (16.2 mg/L) showed the lowest silver catfish kidney and brain lipoperoxidation (LPO) levels, while brain reduced glutathione (GSH) levels were increased in lower Mn concentration (4.2 mg/L) and kidney catalase activity was reduced in the same metal concentration, in relation to normoxia. Lowest Mn concentration (4.2 mg/L) in hypoxia showed higher gills mitochondrial viability, compared to normoxia. Hematocrit of silver catfish exposed to two highest Mn concentration (8.4 and 16.2 mg/L) was reduced in normoxia conditions while under hypoxia, these values were similar to control. Plasma except, Mn bioaccumulation in liver, kidney and gills were higher in normoxia than hypoxia. From these results is possible to suggest that hypoxia stimulates the development of adaptive mechanisms and/or hormesis in silver catfish exposed to Mn, mainly because the lower metal bioaccumulation occurred in this oxygen level. Contributing with this, under hypoxia, oxidative damage indicators were lower than those observed in normoxia, which were accompanied by changes in antioxidant system represented by GSH and catalase. In conclusion, our results show in the first time that silver catfish exposed to Mn contamination is able to show a better survival under hypoxia. These findings indicate need for continuing studies in search of molecular mechanisms involved in the adaptation and or hormesis processes, which were suggested here. / A contaminação do meio aquático por metais tem sido um problema crescente para à vida de diferentes espécies, mesmo depois de interrompida sua emissão no ambiente. Entre os metais de relevância, o manganês (Mn) apresenta importância por estar relacionado a uma série de atividades tais como exploração de petróleo, extrativismo em jazidas de carvão mineral, utilização de fertilizantes na agricultura, entre outros. Nos organismos vivos, o Mn constitui um oligoelemento essencial para uma série de funções vitais, e envolve desde a regulação da energia até coagulação sangüínea. Por outro lado, quando em concentrações elevadas, o Mn pode causar danos irreversíveis aos organismos afetando principalmente o sistema nervoso central (SNC). A toxicidade do Mn dissolvido na água pode variar entre as espécies aquáticas, a bioacumulação do metal em peixes marinhos ou de água doce tem sido encontrada em torno de 0,2 até 19,0 mg/kg de peso seco. No presente estudo, jundiás (Rhamdia quelen) foram expostos a diferentes concentrações de Mn (4,2; 8,4 e 16,2 mg/L), sob dois diferentes níveis de oxigênio dissolvido: normóxia (7,48±0,28 mg/L) e hipóxia (3,88±0,41 mg/L), durante 15 dias. Ao final do protocolo, a bioacumulação de Mn bem como, parâmetros de estresse oxidativo e a viabilidade mitocondrial foram avaliados em diferentes tecidos vitais. Em condições de hipóxia, a maior concentração de Mn (16,2 mg/L) mostrou os menores níveis de lipoperoxidação (LPO) em rim e encéfalo dos jundiás, enquanto os níveis de glutationa reduzida (GSH) encefálico foram aumentados na menor concentração de Mn (4,2 mg/L) e a atividade da catalase renal foi reduzida nesta mesma concentração de metal, em relação à normoxia. A menor concentração de Mn (4,2 m/L) em hipóxia proporcionou maior viabilidade mitocondrial das brânquias, em relação à normóxia. O hematócrito dos jundiás expostos às duas maiores concentrações de Mn (8,4 e 16,2 mg/L) foi reduzido em condições de normóxia, enquanto sob hipóxia, estes valores foram semelhantes ao grupo sem a presença do metal. Sob normóxia, a bioacumulação de Mn em fígado, rim e brânquias foi maior que sob hipóxia, excetuando o plasma. A partir desses resultados é possível sugerir que a hipóxia pode ter estimulado o desenvolvimento de mecanismos adaptativos ou de hormesis nos jundiás, em presença de Mn na água, principalmente porque neste nível de oxigênio, a bioacumulação do metal ocorreu em menor grau. Contribuindo com este resultado, sob hipóxia, os indicadores de danos oxidativos foram mais baixos que os observados sob normóxia, os quais foram acompanhados de alterações do sistema antioxidante representado pela GSH e catalase. Neste sentido, nossos resultados apontam para uma melhor sobrevivência da espécie em estudo, sob hipóxia, quando exposta ao Mn. Estes achados indicam a necessidade da continuidade dos estudos, em busca dos mecanismos moleculares envolvidos no processo de adaptação aqui sugeridos.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Wastewater disposal often has deleterious impacts on the receiving environment. Low levels of dissolved oxygen are of particular concern. Here I investigate the impacts on dissolved oxygen and carbon chemistry of screened municipal wastewater in the marine waters off Victoria, B.C., Canada. I analyzed data from a series of undersea moorings, ship-based monitoring, and underwater remotely-operated vehicle video. I used these observations to construct a two-layer box model of the nearfield receiving environment. Despite the lack of more advanced treatment, dissolved oxygen levels near the outfalls are well above the commonly used 63 umol kg-1 hypoxic threshold and that the outfalls’ impact on water column oxygen is likely less than a few umol kg-1. Likewise, dissolved inorganic carbon is not elevated and pH not depressed compared to the surrounding region. Strong tidal currents and the cold, well-oxygenated waters of Victoria’s marine environment give these waters a high assimilative capacity for organic waste. / Graduate / 0595 / 0403 / 0543 / jeremykrogh@gmail.com

I investigated seasonal and inter-site variation in factors influencing diel dissolved oxygen (DO) metabolism at four streams in the Virginia Coastal Plain. Data were collected monthly from January to August 2008 to characterize DO metabolism (diel DO amplitude, production, respiration), incident solar radiation (PAR), dissolved nutrients, fine benthic materials (mass, C:N, Chlα) and hydrology (discharge, water transit time, transient storage). Reach-scale metabolism estimates were determined using the one-station diurnal DO technique and transit time and transient storage were determined by conservative tracer additions. Incident solar radiation was the primary determinant of DO metabolism as streams experiencing higher light levels (Herring and Powell Creeks) exhibited greater diel DO amplitudes, production and respiration. Streams with greater riparian shading (Courthouse and Crump Creeks) exhibited lower DO metabolism despite their higher nutrient concentrations. Higher incident solar radiation was associated with greater benthic algal biomass at some (Herring, Crump, and Courthouse Creeks) but not all (Powell Creek) sites. Diel DO amplitudes were significantly and positively correlated with benthic Chlα and incident solar radiation at less shaded sites. These factors were not significant predictors of DO amplitude, production or respiration at more shaded sites.

Questões de aeração forçada ou natural estão intimamente ligadas à capacidade de autodepuração dos corpos hídricos, ou seja, oxidar substâncias agressivas para resultar em baixo teor de toxicidade. Uma das etapas do processamento de efluentes consiste na dissolução de oxigênio em água e, para realizar essa dissolução, utilizam-se aeradores que são unidades (tanques) onde o ar é borbulhado no meio líquido, o qual se desloca em um regime contínuo de escoamento. Esta pesquisa refere-se à obtenção experimental de valores de viscosidade turbulenta para inserção em modelagem fenomenológica da transferência de oxigênio das bolhas de ar para o meio líquido. Tais modelos, se bem realísticos, podem contribuir aos estudos de gestão de recursos hídricos ou em operações nos tratamentos de efluentes líquidos. O método experimental empregado foi a velocimetria por imagem de partículas, no qual foi possível obter velocidades instantâneas do fluido (água). Estas consideram o movimento turbulento, que é o principal responsável pelo transporte de oxigênio da superfície para o seio do corpo hídrico, sendo que essa superfície pode ser livre para o ambiente, ou a superfície de uma bolha. Praticamente, o método consiste em correlacionar posições de partículas traçadoras em suspensão no fluido, as quais são assumidas ter a mesma velocidade do fluido. As posições consecutivas para fornecer a trajetória e a velocidade foram obtidas por imagens capturadas em uma freqüência definida através de uma câmera digital, onde a luz do laser contrastou as partículas em uma área desejada com uma precisão elevada. Então, nessa área (um plano), foi possível correlacionar um perfil de velocidades. Assim, os valores de viscosidade turbulenta foram obtidos para serem usados em modelagem da transferência de oxigênio, os quais poderão contribuir nos estudos de aeração em corpos hídricos. / Problems involving natural or forced aeration are intimately bind to the reaeration of water bodies. Pollutants are oxidized to yield low toxicity conditions. One of the steps of wastewater treatment consists in dissolving oxygen in water. To perform this, aeration tanks are used where bubbling air crosses the continuous liquid flow. This research focuses on the experimental determination of turbulent viscosity values to be used in modeling of oxygen transfer from air bubbles to the bulk liquid. Such models, if realistic enough, may contribute to water resources management studies or in wastewater treatment operations. Particle image velocimetry method was used, by means of which it became possible to obtain instantaneous velocities of the fluid (water). These velocities embody the turbulent flow, which is the main responsible for oxygen transport from the surface to the bulk liquid. This surface may be either facing the atmosphere or the interior of a bubble. In practice, the method consists in correlating tracking particles suspended in the liquid, which are supposed to have the same velocity of the fluid. The successive positions that give path and speed were obtained by images took in predefined intervals by a digital camera. The laser light illuminated the particles in a predefined area with high precision, making possible to determine velocity profiles. Turbulent viscosity values were so determined and may be used in the modeling of oxygen transfer, which may contribute to water body aeration studies.

This pilot study was conducted to determine if an Electron Magnetics Oxygen and Hydrogen (EMOH) device can increase the dissolved oxygen (DO) concentration of a residential surface water. By using EMOH, DO concentration will increase and allow bacteria to remove the substrate that creates blue-green algae for which the City of Boynton Beach (City) receives complaints. Those complaints center on odors and the visual appearance of the ponds. The study was conducted in-situ at the INCA Pond system in the City of Boynton Beach, Florida with data collection taking place bi-weekly, using surface aeration techniques. Water sampling was conducted in the INCA Pond system via a handheld water sensor. Primary variable monitored included: water temperature, barometric pressure, DO concentration, and DO saturation (DOSAT). Biomass of dead algae at the bottom of the pond was also monitored to determine if increased DO concentration aided the biological digestion of the organic matter. Data analysis shows that exposure to EMOH treatment allowed the relationship between DO and temperature to change from a negative correlation (the expected relationship) to a positive trend. Furthermore, pressure and DOSAT became less correlated after exposure to EMOH effluent. In all, EMOH was shown to be an effective means of treating hypoxic pond water. The optimal EMOH effluent discharge is determined to be deep in the subject pond. Backed by research on the surface-air water and bubble-water oxygen transfer coefficients, DO concentration in the subject pond was 110% higher when effluent was directed down toward the floor of the pond. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Since its creation in the late 19th century, mass spectrometry has evolved into one of the most versatile analytical methods in science. To chart this evolution this thesis includes a historical overview of mass spectrometry and a description of the role of mass spectrometry in oceanography. The development and deployment of underwater mass spectrometers (UMS) at the University of South Florida's Center for Ocean Technology has made possible the collection of real-time data with greatly increased spatial and temporal density. The UMS was deployed via both remotely guided surface vehicles (GSV) and ship's cables to monitor a suite of dissolved gases and volatile organic compounds in saltwater and freshwater environments. Spectrometer data in Lake Maggiore, Florida were acquired at a rate of 0.7-3.6 seconds/sample for 2-3 hours. The resulting multi-analyte spectrometer data were recorded in real time with the Global Positioning System (GPS) observations of an associated surface vehicle and transmitted to a remote laptop computer via a wireless Ethernet link. These data were merged to create high-resolution maps of chemical distributions. Of particular interest were the co-varying oxygen and carbon dioxide mass spectrometer signals, diagnostic of photosynthesis-respiration processes, that were collected over a 10,800 square-meter area of the lake. The UMS was also deployed on a shipborne hydrowire in Saanich Inlet, a 200-meter deep fjord in the western Canadian province of British Columbia. The concentrations of a broad suite of dissolved gases were monitored on both downcast and upcast over a total depth range of 200 meters. Spectrometer data were acquired at a rate of 4.2 seconds/sample for the duration of the deployment. Mass spectrometer signals diagnostic of reduced species (CH4, H2S,) in the anoxic waters of the inlet below a depth of 100 meters were consistent with previous descriptions of the fjord's chemistry. The UMS was deployed on a remotely guided surface vehicle on the Hillsborough River in central Hillsborough County. Spectrometer data were acquired at a rate of 0.7 seconds/sample, and geographic location was recorded by an onboard GPS during a 2,640 meter transect of the river. Prior to the deployment, the mass spectrometer was calibrated using certified gas standards. The calibration experiments correlated mass spectrometer ion intensity data with dissolved gas concentrations, whereupon the mass spectrometer data collected during the deployment were reported in units of micromole/kilogram (µmol/kg). The mass spectrometer recorded changes in gas concentrations associated with changing physical conditions and biological activity along the 2,640 meters of the river that was transited by the GSV.

Water resource is one of the most important natural resources on earth. In recent years, due to the discharges of large industrial and domestic waste-water into the nature, water pollution problem is getting more and more serious and how to monitor the quality of water in real time has become a very important research issue. The dissolved oxygen is one of the critical indexes for evaluating the quality of water. Although the conventional dissolved oxygen detectors presented a high sensitivity and high accuracy, the high cost, large dimension, low capability of batch fabrication and real-time monitoring will limit their applications. In this thesis, an extended-gate field-effect transistor (EGFET) based dissolved oxygen microsensor is developed utilizing micro-electromechanical system (MEMS) technology. The gate voltages of EGFET under different concentrations of dissolved oxygen can be detected by the Cr/Au sensing electrode. To further enhance the sensitivity of the proposed microsensor, a polystyrene layer with very high permeation rate of the dissolved oxygen gas is adopted and coated on the surface of Cr/Au layer. The main processing steps of the presented microsensor involve four photolithographic and four thin-film deposition processes. The influence of the channel¡¦s width/length ratio, source/drain geometry and polystyrene additional layer on the sensitivity of the EGFET based dissolved oxygen microsensor are investigated in this study. The chip size of the implemented dissolved oxygen microsensor is 11 mm¡Ñ13 mm¡Ñ 0.5 mm and the sensing area is 1 mm¡Ñ1 mm. As the dissolved oxygen concentration varies from 2 ppm to 6 ppm, a very high sensitivity (35.36 mV/ppm) and sensing linearity (98.83%) of the proposed EGFET microsensor can be demonstrated. In addition, the response time of the presented dissolved oxygen microsensor is only about III 180~200 seconds, hence it is very suitable for developing a real-time monitoring microsystem.

Protection of potable water supplies demands a better understanding of the factors controlling migration of disease causing bacteria in subsurface environments. In this study, the migration behaviour of the waterborne pathogenic microorganisms Escherichia coli O157:H7 and Yersinia enterocolitica was investigated in water saturated granular systems. Both facultative bacteria were grown under aerobic and anaerobic conditions and further acclimatized to a microaerophilic or fully aerated environment for 21 h. Experiments were conducted using laboratory-scale packed columns over controlled extreme dissolved oxygen (DO) concentrations. The observed differences in the transport potential of these pathogens were found to depend strongly on the antecedent growth conditions under the tested environmental settings as well with the environmental DO in certain conditions. Further microbial characterization using cell titrations and FTIR spectroscopy gave a greater insight on the source of the surface charge that was found to dominate the attachment phenomena in sand packed columns. Techniques also revealed a probable role of other cell surface macromolecules (LPS) that could account for non-DLVO behaviour. The results illustrate the importance of considering physicochemical conditions relevant to the natural subsurface environment when designing laboratory transport experiments as evidenced by variations in microbe migration as a function of the DO under growth and acclimation. / Keywords: bacterial adhesion, bacterial transport, DLVO, physicochemical characterization, dissolved oxygen, porous media.

A fuzzy logic controller (FLC) for the dissolved oxygen (DO) concentration of a wastewater bioreactor is presented. The FLC is developed and tested based on simulations using first order plus dead time models obtained from experiments with an actual wastewater bioreactor. The FLC uses feedback of the error in DO concentration and rate of change of the DO concentration and manipulates the stem position of the flow control valves (FCVs) supplying air to the bioreactor. The proposed FLC is tested for robustness across several process models, two of which include proposed worst-case process conditions. The performance of the proposed hand tuned FLC is compared to that of a similarly tuned proportional-integral-derivative controller. The FLC is implemented as a lookup table for speed and ease of deployment. The disturbances present in the experimental step testing data are characterized and used as the basis for disturbing the control loop during controller performance testing. A low-pass filter is then included to subsequently smooth the feedback signal. The nonlinear relationship between the FCV stem position and output flow is modelled and included in the controller performance testing. A genetic algorithm (GA) is developed that manipulates the membership functions of the FLC to yield an optimal controller for the ensemble of process models. The ability of the GA to converge on an optimal FLC is verified through repeated trials. The performance of the GA optimized FLC is observed under realistic process conditions and is benchmarked against a manually optimized PID controller.