The lack of availability of a single, complete paper on the analysis of a digital data acquisition system for in situ oceanographic measurements brought about the present work. In order to compile an accurate technical paper on such a complex system, it was necessary to design, construct, and calibrate a system for the in situ measurement of various physical and chemical properties of sea water. A unique digital encoding circuit was developed which utilizes the basic principles of null balance, resistance ratio bridge and potentiometer measurements. The circuit is a uniquely loaded binary ladder resistance network. Variation of the loading allows resistance ratio and potentiometric measurements to be made over different ranges with a constant high degree of resolution. The developed system has the capability of measuring any parameter which can be converted into a varying voltage, current, or resistance. The range over which the measurement can be made is adjustable; and the resolution equals ± 0.006% of the full range value. The resolution is constant over the full range, as a result of the analog-to- digital converter linearity characteristics. / Graduation date: 1968

Phosphate, silicate and nitrate concentrations in the sea off the coast of Oregon were determined to study their seasonal distribution patterns. The water samples were collected monthly along the east-west hydrographic line off Newport, Oregon, from the shore to 165 miles (310 km) offshore. The samples were analyzed by both a Technicon Autoanalyzer® and by manual methods. Phosphate in January was greater than 0.5μM at the surface, increasing to a 3.3μM maximum at 1000m. A phosphate maximum occurred at 1000m throughout the year. With the onset of photosynthetic activity, there was a general decrease in surface concentrations. Concentrations decrease to less than 0.1μM in October with surface concentrations increasing in November and December, reaching a maximum in January. Silicate concentration was approximately 170μM at 2600m during the entire year. In January, surface silicate increased from less than 5μM offshore to 13μM nearshore; a weak silicate minimum was observed at a depth of 60m offshore and at 5m near the coast. In March nearshore surface concentrations were greater than 15μM due to increased coastal river runoff; the silicate concentrations of Oregon coastal rivers were 150-250μM. In July, a pronounced minimum occurred at 40-50m depth, where the concentration was less than 2μM. Summer surface concentrations were less than 2M offshore, increasing to 40μM nearshore as a result of coastal upwelling. Surface concentrations in October were generally less than 5FIM along the Newport hydrographic line with increased near shore concentrations due to river runoff. The nitrate maximum of 40-45μM existed at 1000- 1200m. In January surface concentrations ranged from 3μM offshore to 6μM nearshore. March values were lower, ranging from 11μM offshore to 5μM nearshore at NH-3 (6 km). In July patches of nitrate-free water were observed at 40-50m depth offshore, disappearing at 25 miles (46 km) off the coast, at station NH-25, as a result of the influence of upwelled and nitrate containing water. Late in October, nitrate concentrations were higher, 5-6μM, near the coast, and dropping to less than 0.1μM offshore. Patches of nitrate-free water were found from May to November. The existence of nitrate-free water near the surface indicated that the feature was formed by the photosynthetic activities of phytoplankton. The formation of the silicate minimum and oxygen maximum below or near the bottom of the Columbia River Plume during summer months indicated intense photosynthetic activity. Neither preformed phosphate nor preformed nitrate changed with depth below the layers of active photosynthetic processes. Preformed phosphate was generally 1.0-1.2μM below 200m with variation occurring in surface waters. For surface values, 1.2μM, the highest of the year, was observed in July in upwelled water; 0.4μM, the lowest, also occurred in July within the influence of the Columbia River Plume. The vertical distribution of preformed nitrate seemed to be random and may have reflected analytical techniques. The range was between 5 and 10μM with a maximum at 12μM. The 5μM values were found at approximately 200m with a maximum observed at 1000m deep. The highest surface values of preformed nitrate, 2.0-5.0μM, were observed in January and the lowest, 1.0-1.5μM, in July. March and October values were between the above extremes (1.1-2.0μM). / Graduation date: 1970

Marine microorganisms play a significant role in the cycling of nutrients in the open ocean through production, consumption, and degradation of organic matter (OM). Carbon (C), nitrogen (N), and phosphorus (P) are essential ingredients in every known recipe for life. However, the cycling of each of these elements proceeds at different rates such that the ratio of C:N:P can vary widely between particulate, dissolved, organic, and inorganic pools. To better understand the mechanisms controlling these transformations, this study investigated the bacterial remineralization of photosynthetically-derived organic matter derived from cultures of Trichodesmium IMS101, Thalassiosira weissflogii, Prochlorococcus MED4, and particulate material collected from the surface waters of an upwelling regime. Experiments were conducted at sea for a short duration (<6d) and in the laboratory for longer periods (<150 days). In all treatments, across experiments, we observed rapid and selective P remineralization independent of the type of organic material added. Full solubilization and remineralization of P typically occurred within a week. Conversely, N remineralization was slower, with only 39-45% of particulate N (PN) remineralized in shorter (6d) experiments and 55-75% of PN remineralized in <150d experiments. Nitrification was observed after 70-98 days depending on the remineralizing bacteria (isolated from either the Oregon coastal upwelling regime or the North Pacific Subtropical Gyre (NPSG). Notably, these events did not transform the full complement of ammonium to nitrate. This differential lability between N and P led to rapid changes in the N:P ratio of inorganic pools as organic matter was depolymerized by varying bacterial populations. The variable input of potentially limiting elements could have consequences for primary productivity and particle export. Finally, we observed that in short-term experiments with heterotrophic bacteria collected from the NPSG, the N:P ratio of remineralization (11 ± 2.2) was independent of the N:P of added organic material (5-23). This uniformity of inorganic ratios implies differential lability and N:P composition of residual semi-labile and refractory organic matter. Formation of refractory C and N rich organic matter, often termed the microbial pump, is a significant pathway for the transport and sequestration of elements in the aphotic zone of the ocean interior. The experimental results reported here suggest that differential supply of POM leads to rapid and preferential P remineralization, N:P remineralization independent of the N:P of added substrates, and variable N:P of residual organic matter. These findings help constrain our knowledge of elemental cycling in the marine environment. / Graduation date: 2013

The aim of this study is to develop a seawater desalination system that uses sea-wave energy as the sole energy source for system operation. This system is composed of a sea-wave energy acquisition system, a reverse-osmosis device, and a proposed mechanism linking the system to function synchronously. The relationships between various system parameters and system characteristics are analyzed. The limitations and constraints of system operations are then suggested. For the purpose of comparison, another system, which indirectly drives the reverse-osmosis system through an additional stage of energy storage, is introduced. To analyze the system dynamic properties, the following steps are implemented. First, a mathematical model than can properly describe the system characteristics is derived. This model is found to be a nonlinear one, which increase the difficulties of system analysis enormously. However, it is also noted through a preliminary examination that the effect of system nonlinearity becomes insignificantly if the system parameters are properly adjusted. Under these parameters, the linearied model is analyzed. The effects of different system parameters on the amount of energy acquisition and desalinated water are investigated. The analysis indicates that the amount of energy acquisition or desalinated water is closely related to both the selected energy acquisition system and the desalination system. For a given energy acquisition system and sea wave condition, an improper system parameter selection of desalination system will either make the whole system operation inefficient or devastate the functioning of acquisition system. This suggests that certain parameters of the desalination system must be adjustable in a real operation. The study also shows that the linearied system can be approximated by a model with two degrees of freedom. This model may offer the convenience for the optimization of system parameters.

Wreckage of ‘Carnauba’, a 1930s vintage Sikorsky S-38 aircraft, a beloved icon of SC Johnson's early history, was found on July 5, 2000, in seawater off of an Indonesian island of West Irian Jaya. The company decided to recover this aircraft from seawater, conserve it, and display it in its museum, as part of their rich heritage. The objective was to study the aluminum alloy used on the aircraft for its chemical and mechanical properties, suggest the corrosion mechanism of aluminum alloy 2024 in seawater, and recommend preservation methods for the same. Chemical analysis performed on the samples collected from the site revealed that copper was the primary alloying element. Copper is responsible for increasing the strength. However, copper is also the reason for pitting corrosion of the aluminum alloy, causing material loss and reducing the structural stability of the wreckage. Copper forms intermetallics with other elements, such as magnesium and aluminum, and is distributed in the aluminum matrix heterogeneously. In order to study the corrosion mechanism of aluminum alloy 2024, it was subjected to potentiodynamic tests in sodium chloride solution. In the presence of an electrolyte like seawater, the difference between the potentials of these intermetallics and the surrounding aluminum matrix creates a galvanic cell. The galvanic cells serve as sites for localized corrosion. Chloride ions are responsible for pitting of alloy 2024. A pitting potential of around -600mV was observed when sodium chloride was used as an electrolyte. The average corrosion rate measured for wrought aluminum alloys was around 0.05 mm/year. The thesis provides guidelines or recommendations for the procedure to be followed in recovering aircraft from seawater, and retain it in its as found condition. Recommendations about various measurements like pH, dissolved oxygen, salinity, pressure, temperature, and velocity need to be taken and the visual assessment needs to be done before the aircraft is hauled from the seawater were specified. After the aircraft has been recovered, recommendations for handling, cleaning, and prevention of corrosion using coatings such as carnauba wax and inhibitors such as chromates, have been stated.

Ozone is a powerful oxidant which can be use for bacterial inactivation, deodorizing, and bleaching. In aquatic farms, it can improve larvae hatching and keep water quality under control. The primary object of this research is to investigate the influence of ozone solubility by the concentrations chloride¡]Cl-¡^and bromide¡]Br-¡^in seawater. The indigo colorimetric method was used to detect the variation of total residual oxidants¡]TROs¡^after ozonation. The bacteriocidal effects of ozone with added Cl- or Br- were tested on three common marine fish pathogens. The results showed that the ozone solubility in reverse osmosis¡]RO¡^treated water was about 2.3 mg/L, and rapidly decreased to 0.5 mg/L when ozonation stopped. The process of ozonation in seawater from start to equilibrium, the TROs concentration could reach 8.5 mg/L and then decreased slowly to a stable concentration of about 6 mg/L. When Cl- was added in RO water, the TROs concentration varied from 2 to 3.5 mg/L, and rapidly disappeared after stop ozonation. It was concluded that Cl- could not effectively increase ozone solubility in seawater. In contrast, adding Br- in RO water not only efficiently increased the solubility of ozone but also maintained the TROs concentrations after stop ozonation, and the TROs concentrations were proportional to the Br- concentrations. The same trends were also observed in seawater added with Br-. In the bacteriocidal effect of ozone, compare with pure seawater, adding of Br- in seawater could effectively reduce the TROs concentrations needed to completely inhibit each pathogen. Such practice may be extended to aquatic farms to eliminate or reduce the bacterial pathogens in seawater.

Thesis (M. Phil.)--University of Hong Kong, 1987.

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In spite of abundant water resources, world is suffering from the scarcity of usable water. Seawater Reverse Osmosis (SWRO) desalination technology using polymeric membranes has been recognized as a key solution to water scarcity problem. However, economic sustainability of this advanced technology is adversely impacted by the membrane fouling problem. Fouling of RO membranes is a highly studied phenomenon. However, literature is found to be lacking a detailed study on kinetic and dynamic aspects of SWRO membrane fouling. The factors that impact the fouling dynamics, i.e., pretreatment and water quality were also not adequately studied at full–scale of operation. Our experimental protocol was designed to systematically explore these fouling aspects with the objective to improve the understanding of SWRO membrane fouling mechanisms. An approach with multiple analytical techniques was developed for fouling characterization. In addition to the fouling layer characterization, feed water quality was also analysed to assess its fouling potential. Study of SWRO membrane fouling dynamics and kinetics revealed variations in relative abundance of chemical and microbial constituents of the fouling layer, over operating time. Aromatic substances, most likely humic–like substances, were observed at relatively high abundance in the initial fouling layer, followed by progressive increase in relative abundances of proteins and polysaccharides. Microbial population grown on all membranes was dominated by specific groups/species belonging to different classes of Proteobacteria phylum; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age and with the position of membrane element in RO vessel. Our results demonstrated that source water quality can significantly impact the RO membrane fouling scenarios. Moreover, the major role of chlorination in the SWRO membrane fouling was highlighted. It was found that intermittent mode of chlorination is better than continuous mode of chlorination of seawater, as anti–biofouling strategy. It was also confirmed that significant biofilm development was inevitable even with the use of chlorine to disinfect SWRO membranes. Our findings on the dynamic patterns of SWRO membrane fouling should help in further elaborating research projects focusing on the development of better strategies to minimize this troublesome phenomenon.

No description available.