Deep-water formation supplies oxygen-rich water to the deep sea, spreading throughout the ocean via the global thermohaline circulation. Models suggest that gases in newly formed deep-water do not come to equilibrium with the atmosphere. However, direct measurements during wintertime convection are scarce, and the controls over the extent of this disequilibria are poorly quantified. Here we show that oxygen is consistently undersaturated at -6.3% to -7.6% in the Labrador Sea at the end of convection, when convection reaches deeper than 800 m. Deeper convection resulted in greater undersaturation while convection lasting later in the year resulted in values closer to equilibrium, from which we produce a predictive relationship. We use dissolved oxygen data from six profiling Argo floats in the Labrador Sea between 2003 to 2016, allowing direct observations of wintertime convection. Four of the six optode oxygen sensors displayed in situ drift of -2.98 μmol O2 kg-1 year-1 on average, which we corrected to stable deep-water oxygen values from repeat hydrography. Observations of low oxygen intrusions during restratification and a simple mixing calculation demonstrate that lateral processes act to lower the oxygen inventory of the central Labrador Sea. This suggests that the Labrador Sea is a net sink for atmospheric oxygen, but uncertainties in parameterizing gas exchange limit our ability to quantify the net uptake. Our results constrain the initial oxygen concentration of Labrador Sea Water and allow more precise estimates of oxygen utilization and nutrient regeneration in this water mass. / Graduate

[pt] Estudos prévios relacionam a ocorrência de episódios de mortandade de peixes em corpos hídricos como a Lagoa Rodrigo de Freitas (LRF) com a rápida disponibilização de espécies poluentes e nutrientes naturais na coluna d água especialmente durante altas precipitações de chuva, quando ocorre transbordo dos rios poluídos da bacia sobre a água da Lagoa, ocasionando uma demanda de oxigênio dissolvido maior do que o normal para depuração de tais espécies. Nesse contexto existe interesse em evitar episódios críticos de insuficiência de OD na água dos corpos hídricos que possam advir de tais eventos. Estudos realizados no presente trabalho tiveram como objetivo caracterizar as águas de rios da Sub-bacia hidrográfica da LRF através de DBO, COT, SST, Ptotal no canal a montante de deságue para a Lagoa em períodos de chuva e de tempo seco; e avaliar um possível tratamento que proporcione a depuração acelerada dos poluentes utilizando peróxido de hidrogênio, fornecendo oxigênio para as águas poluídas através do processo de decomposição do oxidante. Avaliaram-se diferentes dosagens de H2O2 em tempo reacional de 24h de acordo com limites de ecotoxicidade conhecidos. Testes realizados em amostras de rio coletadas em dias de baixa precipitação contendo concentrações de DBO de até 2,2 mg/L mostraram uma velocidade de decaimento de H2O2 inferior ao para amostras tanto coletadas também em dia de baixa precipitação porém com elevada DBO (24,0 mg/L), quanto para dia de alta precipitação (13,2 mm em 24 h) com relevante concentração de material orgânico. Observou-se uma dosagem suficiente de 15,0 mg/L para as amostras coletadas em baixa precipitação e alta DBO, e dosagem suficiente de 3,0 mg/L para amostras coletas em maior evento de precipitação (13,2 mm em 24 h), acima das quais, não ocorre mais aumento significativo da velocidade de decaimento da [H2O2] e também de velocidade de contribuição de OD para a água. Concluiu-se que a adição de H2O2 nas águas de rios durante eventos de poluição causados por chuvas intensas ou lançamento de esgoto pode contribuir para evitar episódios críticos de insuficiência de OD em rios poluídos por material orgânico e na pluma de poluentes que pode ser formada por transbordo dos rios para a LRF. / [en] Previous studies have associated the occurrence of episodes of death of fish in water bodies such as the Lagoa Rodrigo de Freitas (LRF) to to the rapid availability of pollutants and natural nutrients in the water column species especially during high rain precipitation events, which occur when the rivers overflow and pollute the water of the lagoon, causing a biochemical oxygen demand higher than usual for the rate of natural depuration of the contaminating species. In this context there is interest in avoiding critical episodes DO deficiency in the water bodies that may arise from such events. Studies conducted in the present work aimed at characterizing the rivers of sub-basin of LRF through BOD, TOC, TSS, Ptotal on the canal that overflows into the lagoon in periods of rain and dry weather; and evaluate a possible treatment offering the accelerated depuration of pollutants using hydrogen peroxide, providing oxygen to the polluted water through the self-decomposition process. The study evaluated the effect of different doses H2O2 in 24 hours of reaction time according to known ecotoxicity limits. In tests on samples collected from rivers in days of little rain containing BOD concentrations up to 2.2 mg / L, H2O2 showed a decay rate lower than those of other samples also collected on days of low precipitation, but with high BOD (24, 0 mg / L), and days of high rainfall (24 hours 13.2 mm), with a significant concentration of dissolved organic contaminants. A maximum sufficient dose of 15.0 mg / L was found for the low and high samples precipitation BOD, and a maximum sufficient dose of 3.0 mg / L for most of the samples collected during the precipitation event (13.2 mm 24 hours), above which there is no significant increase over the rate of decomposition of [H2O2], and the rate of generation of DO in the water. It was concluded that the addition of H2O2 into the waters of rivers during pollution events caused by heavy rains or sewage release can help to avoid critical episodes of DO deficiency in polluted rivers by organic matter and pollutant plume that can be formed by overflow of those rivers to the LRF lagoon.

Dans le cadre du projet européen « Optimized Products for Elderly Populations (OPTIFEL) » (ou « produits optimisés pour des gens âgés »), des produits alimentaires sont conçus pour les besoins particuliers des personnes âgées. Puisque cette population est souvent mal-nourrie, l’objectif du projet consistait à produire des aliments riches en nutriments et appétants. Ce but a été mis en œuvre en enrichissant des produits à base de fruits et légumes avec des protéines, des minéraux et vitamines, dont la vitamine C et les folates. Cependant, les deux dernières vitamines sont connues pour être fragiles et pour être rapidement perdues lors du chauffage. Pour atteindre le but de la supplémentation, c’est-à-dire augmenter l’absorption des nutriments, l’étude de leur stabilité est d’une grande importance. Ce travail, en particulier, a été dédié à l’étude de la stabilité de la vitamine C et des folates lors du réchauffage des aliments. Le réchauffage des aliments nécessite de respecter une température minimum de 60°C afin d’éviter la croissance des bactéries sporulées. Une deuxième contrainte, qui se démarque des méthodes de cuisson, est la durée du maintien en température. Selon que le réchauffage se déroule à la maison ou dans un système de restauration collective en liaison chaude, le temps de réchauffage est de courte durée ou peut atteindre quelques heures. La pomme et la carotte ont été choisies en tant qu’exemple d’un fruit et un légume pour le projet OPTIFEL et aussi pour le travail présent. La pomme et la carotte sont des produits qui sont appréciés à travers l’Europe et contiennent des quantités naturelles négligeables en vitamine C et folates. La stabilité de la vitamine C a fait objet de nombreuses études dans la littérature. Cependant, les facteurs qui impactent sa stabilité ont été principalement examinés en solution modèle et leur importance respective dans un vrai aliment manque d’études. Bien que la disponibilité de l’oxygène ait un impact primordial, et qu’il soit connu que l’oxygène est soluble jusqu’à 100°C, sa disponibilité dans le milieu alimentaire est très mal connue pendant le chauffage à des températures intermédiaires. L’acide folique est un vitamère synthétique, qui est habituellement utilisé pour la supplémentation mais qui a l’inconvénient de pouvoir masquer un déficit en vitamine B12. C’est pourquoi le vitamère naturellement abondant, l’acide 5-méthyltétrahydrofolate, a été proposé comme alternative pour l’enrichissement. Son inconvénient majeur, outre le prix, est qu’il est fragile et se dégrade rapidement en l’absence de réducteurs. L’objectif de cette thèse de doctorat consistait à comprendre la stabilité de la vitamine C et de l’acide 5-méthyltétrafolique à des températures intermédiaires. Une attention particulière a été portée à la stabilité dans des matrices alimentaires et à la disponibilité de l’oxygène. Dans un premier temps, la stabilité de la vitamine C et de l’acide 5-méthyltétrahydrofolique a été étudiée à une échelle laboratoire. Ensuite, l’impact des différentes méthodes de réchauffage a été examiné. Le travail a été divisé en quatre chapitres. Le premier chapitre a été consacré à l’étude de la stabilité de la vitamine C. Dans le deuxième chapitre, la disponibilité de l’oxygène a été étudiée. La troisième étude a été dédiée à la stabilité de l’acide 5-méthyltétrahydrofolique. Et dans le quatrième chapitre, trois méthodes de réchauffage ont été comparées. / The European project « Optimized Products for Elderly Populations (OPTIFEL) » was launched to ameliorate elderlies’ nutritional status. Since this population often suffers from malnutrition, it was envisaged to conceive food products based on fruit and vegetables, with a dense nutritive value. Therefore, products were enriched with important nutrients, among vitamin C and folates. To comply with the intention of supplementations consisting in an increased intake of nutrients, the study of their stability, especially of easy degradable molecules, is of utmost importance. The present work in particular, was dedicated to the stability of vitamin C and 5-methyltetrahydrofolate when food is warmed-up that is heated at an intermediate temperature range (60-80°C). It turned out that the deterioration pace of vitamin C is principally influenced by the filling volume of recipients on a lab-scale. A negligible effect was found for the food matrix meaning that products based on apples and carrots can interchangeably be used for fortifications. Concentration adaptions are easy to control as the degradation loss per time in the concentration range 2-5 mmol/kg, is independent of the initial concentration. Increasing temperature in the range 60-80°C, does not have an impact in a real food matrix either. The latter indicates that another factor, probably oxygen, becomes limiting as enhancing the supply of energy does not increase degradation rates anymore. Thus, by heating products at 80°C, the microbial safety margin can be increased while the nutritional value is kept as if heated at 60°C. From literature it is known that degradation at this temperature range only proceeds via the aerobic degradation pathway. It has been shown in the present work that in food products, the oxygen availability decreases down to anaerobic conditions, also near the surface, during heat treatments at 80°C while oxygen in model solutions stays abundant. Hence, the headspace gains in importance during long warm holding of real food products and dynamics of oxygen and ascorbic acid might determine degradation paces. However, oxygen is not alone responsible for the degradation initiation since ascorbic acid in ultrapure water does not degrade at 80°C during 8 h, even if oxygen is abundant during the whole length of time. An additional trigger, as Fe3+ ions or maybe also other constituents in food matrices, must be present. An interaction between oxygen and the trigger might result in the generation of reactive oxygen species that finally deteriorate the vitamin. For complete stabilization of 5-methyltetrahydrofolate, the amount of ascorbic acid is crucial in contrast to the food matrix that is used for supplementation. The protective effect of ascorbic acid is however time-limited even if it remains in excess. The duration of complete stability can be prolonged by increasing the initial ascorbic acid concentration. Heat treatments under real conditions that is when food products are warmed-up by a microwave, an Actifry ® device or held warm by a water bath, lead to minor to negligible vitamin losses. These are good news for the project since the vitamin amount that is added, is preserved during warming-up of products and must not be controlled. The results indicate the complexity of vitamin degradation since the stability depends crucially on the experimental set-up. It can be concluded that predictive modeling should be performed under real conditions. Vitamin C and 5-methyltetrahydrofolate, which are generally referred to be very susceptible to oxygen and heat, are fairly stable under reheating conditions in real food products.

Aucune étude physicochimique majeure des eaux du fleuve Chari n’a été réalisée malgré le fait que depuis l’indépendance du Tchad (1960), quelques usines agroalimentaires, des hôpitaux, des usines textiles, des abattoirs… se soient installés sur ses rives. Les résultats des analyses obtenus après un suivi de 2008 à 2010 ont montré la présence des métaux traces dans le Chari. Sur l’ensemble des échantillonnages d’eau analysés, le fer est l’élément métallique majeur devant le manganèse, le zinc et le nickel. Ces résultats varient en fonction des périodes de prélèvement (saison des pluies ou saison sèche). La plupart des valeurs obtenues dépassent largement les seuils acceptables selon les recommandations de l’OMS. La présence des métaux traces dans le Chari résulte aussi bien du processus naturel que de l’activité humaine. Bien que les concentrations de Ni, Cr, Co, Mn et Zn ne soient pas aussi élevées que celle du fer, le profil de répartition de ces éléments entre les différents sites montre une certaine similarité. Les valeurs moyennes de pH indiquent que les effluents ont un caractère légèrement alcalin, tandis que celles relatives à l’oxygène dissous sont satisfaisantes. De ce fait, les eaux du Chari sont impropres, du point de vue physicochimique voire potentiellement dangereuse pour la santé environnementale et humaine. La lutte contre les pollutions doit être entreprise le plus précocement possible / No physicochemical major study of water of the Chari river was carried out in spite of the fact that since the independence of Chad (1960), some food agro factories, hospitals, textile factories, slaughter-houses… were installed on its banks. Also, this work aims to the “contribution to the analytical study of the pollutants (particularly heavy metals) in waters of the Chari river crossing the town of N’Djamena” using the suitable chemical techniques. The results of the analyses obtains after a follow-up from 2008 to 2010 showed the presence of trace metals in the Chari river. On the whole of analyzed water samplings, iron is the major metal element in front of manganese, zinc and nickel. These results vary according to the periods of taking away( rainy season or dry season). The majority of the values obtained largely exceed the acceptable thresholds according to recommendations of WHO. The presence of trace metals in the Chari river results as well from the natural process as of human activity. Although the concentrations of Ni, Cr, Co, Mn, Cu and Zn are not as high as those of iron, the profile of distribution of these elements between the various sites shows a certain similarity. The average values of pH indicate that the effluents are slightly alkaline, while those relating to dissolved oxygen are satisfactory. So the waters of Chari are unsuitable, from the physicochemical point of view, even potentially dangerous for environmental and human health. The control of pollution must be undertaken the most preciously as possible

No description available.

Aquaculture is a multibillion-dollar industry that meets the demand for marine food while enhancing sustainability. Farmers in this area encounter a finite number of issues. The difficulties experienced by aquafarmers in assessing water quality are described in the chapter 3 of  this report. Farmers' traditional methods for measuring water quality are inefficient and time-consuming. To address the concerns related to pH, dissolved oxygen, and turbidity, we developed a system that would allow farmers to monitor water quality in aquafarms in real time. This report presents a thorough illustration of how we created the system. To test water quality in real time, we placed pH, TDS, and dissolved oxygen sensors connected to Arduino in various liquids and the observation and results can be seen in chapter 5. We calibrated the sensors used in the system design to achieve the precise values. The results were then displayed on a webpage after the system connected to the internet.

Nitrogen removal from wastewater has been exstensively addressed by scientific literature in recent years; one of the most widely implemented technologies consists of the combination of partial nitritation and anaerobic ammonium oxidation (ANAMMOX). Compared to traditional nitrification and denitrification techniques such solution eliminates the requirement for an external carbon source and allows for a reduced production of excess sludge; furthermore, it brings down the costs associated to aeration by 60-90% and the emissions of CO2 by 90%. Similar techniques can turn out to be particularly interesting when stringent environmental regulations have to be met. At present, most of the dedicated research dwells on wastewater at high temperatures, high nitrogen loads and low organic content, as it is typical of sidestream effluents; this project, instead, is focused on mainstream wastewater, characterized by lower temperatures and nitrogen content, but higher COD values. At the center of the thesis is the application of a one-stage reactor treating synthetic mainstream municipal wastewater. The chosen approach consisted in maintaining low DO values, allowing for both for the establishment of a proper reaction environment and for the out-selection of nitrite oxidizers; granular biomass was employed for the experiment, aiming at effective biomass retention. The HRT value was gradually decreased, with a minimum at 6 hours. Resulting nitrogen removal rates proved to be satisfactory, with a maximum TN removal efficiency of 54%. Retention of biomass was also positively enhanced throughout the experiment, and yielded a final SRT value of 15.6 days. The whole process was then inserted into a more complete framework, accounting for possible energetic optimizations of similar treatment plants. Employing COD fractionation as a primary step paves the way for anaerobic digestion side processes, which can produce methane and ultimately provide energy for the main nitrogen removal step. Therefore, envisioning energy-sufficient water treatment processes seems a more and more feasible and realistic possibility.

No description available.

Irrigation of the municipal cemetery in Brigham City, Utah resulted in stained headstones in 2001 and 2002. The water used in the irrigation came from Mantua reservoir, a medium sized impoundment situated near the mouth of Box Elder Canyon. In order for Brigham City to establish a city wide secondary pressurized irrigation system using water from Mantua reservoir, the cause and the source of staining problem must be determined. Previous research (Wallace 2006) determined that the source of the staining was the reduction of iron found in Mantua Reservoir sediments that occurred when seasonal variations in the reservoir caused anaerobic conditions. The reduced iron then dissolved in the water and was used in the irrigation system, causing re-oxidation of the iron. The oxidized iron then precipitated out on the headstones causing the staining. The purpose of this investigation is to determine the iron oxidation kinetics after the re-aeration of the water which will help determine appropriate mitigation methods. A secondary purpose is to confirm the Mantua reservoir's capacity to become anaerobic, resulting in the conditions which cause staining. Using laboratory investigations and computer modeling, I determined that on re-aeration, fifty percent of the dissolved iron in the water precipitates in five hours. Using first-order kinetics to model this process, I found the rate constant of the kinetic reaction to be 0.0029 min-1. Fitting a geochemical computer model of the iron oxidation kinetics in Mantua reservoir, which uses a higher-order kinetics model to better model this process, to experimental kinetic data yielded a rate constant of 4x1013 /atm x min. I also recreated the staining process in the laboratory using concrete. This was successful and provided visual evidence that the iron precipitates out of the water and stained the concrete within a couple of hours of application. Field data collected from Mantua reservoir showed that the dissolved oxygen concentration in the reservoir drops regularly below levels consistent with equilibrium to the atmosphere. While my field measurements did not record anaerobic conditions, based on the patterns shown, this study shows that it would be possible for anaerobic conditions to occur during warmer weather.

Raceway ponds can be used to cultivate microalgae for purposes such as wastewater treatment and feedstock for animal feeds and biofuels. Besides nitrogen assimilation in biomass, nitrification can be a wastewater treatment mechanism but one that is hindered by the low nighttime dissolved oxygen concentrations (DO) common in wastewater treatment raceways. The large diel difference in pond conditions and changing influent wastewater quality also raises the question of the optimal frequency and timing of grab sample collection, to obtain representative water quality data. Three sets of triplicate pilot raceways (1,000-L, 0.30-m deep, fed primary clarifier effluent) were operated at an inland central California wastewater treatment plant. Two pilot pond experiments were conducted to determine the effect of (1) night aeration (1800 to 0600) on nitrification, biomass productivity, DO, and BOD5 treatment and (2) sampling frequency (diel, consecutive daily, and once-per-week; 1x/week) on the resulting mean biomass concentration (ash-free dry weight; AFDW) values. The two pond sets with night aeration both displayed a higher nitrification rate than control ponds. Night aeration in well-mixed, 3.7- to 5.4-day hydraulic residence time (HRT) pilot-ponds receiving influent from facultative pond-fed head tank (HT) effluent 16 to 20 hours per day lead to 8.8% more nitrification than night aeration in 2-day HRT ponds fed primary effluent wastewater (PEFF) eight hours per day during late-spring and summer. The cBOD5 concentration in HT was 61% less than PEFF, indicating that low cBOD5 concentrations in influent waters likely promote nitrification when night aeration is provided. Ponds increased in DO by 15% over a 24-hour period on average and by 57% at nighttime hours from 0600 to 1800, suggesting that night aeration significantly increased DO in ponds over a 24-hour period and at nighttime hours when DO may be limited for nitrifying bacteria. However, night aeration is likely to have a negative effect on productivity; the pond set with the highest nitrification experienced a 16% decline in productivity, and the pond set with the lowest nitrification displayed a 6% decline in productivity with night aeration installed. In the sampling frequency study, productivity from samples collected 1x/week at 0900 PST± 2 hour was compared to productivity determined from samples collected at the consecutive daily frequency for four to six consecutive days at 0900 PST± 2 hour and to samples collected at equal time intervals over 24 hours (diel) to determine the optimal sampling frequency. Based on AFDW concentrations, gross productivities were compared to evaluate the effect of sampling frequency. Average diel productivity from three diel experiments, conducted June 2015, December 2015, and July 2016, indicate 1x/week samples might overestimate productivity; however, at most, the difference was 11%. Average consecutive daily productivity from the five experiments, conducted February, March, June, and July of 2016, indicate 1x/week samples may underestimate productivity. The difference was also, at most, 11%. Because the 1x/week samples led to higher productivities than the diel samples and lower productivities than the consecutive daily samples, it seems likely that over many months, the 1x/week sampling frequency represents actual productivity with reasonable accuracy.