Chapter 1 briefly introduces the background, problems, applications as well as recent progress of the nanobubbles research. The relationship between the formation/stabilization of nanobubbles and the long-rang structures of water molecules, particularly the restructuring of water molecules at the water/gas interface, are emphasized. / Chapter 2 introduces the theories of static and dynamic light scattering and Zeta-potential measurements as well as the details of the instrument set-up. In this chapter, the fundamental equations of the scattering theory are figured out basis on the quasi-classical electrodynamics and combination of the statistical mechanics as well as molecular dynamic theory. Finally, the statistical properties of photon counting are discussed. / In chapter 3, aqueous solutions of tetrahydrofuran, ethanol, urea and alpha-cyclodextrin were studied by a combination of static and dynamic laser light scattering (LLS). In textbooks, these small organic molecules are soluble in water so that there should be no observable large structures or density fluctuation in either static or dynamic LLS. However, a slow mode has been consistently observed in these aqueous solutions in dynamic LLS. Such a slow mode was previously attributed to some large complexes or supramolecular structures formed between water and these small organic molecules, Our current study reveals that it is actually due to the existence of small bubbles (∼100 nm in diameter) formed inside these solutions. Our direct evidence comes from the fact that it can be removed by repeated filtration and regenerated by air purging. Our results also indicate that the formation of such nanobubbles in small organic molecules aqueous solutions is a universal phenomenon. Such formed nanobubbles are rather stable. The measurement of isothermal compressibility confirms the existence of a low density micro-phase, presumably nanobubbles, in these aqueous solutions. Using a proposed structural model, i.e., each bubble is stabilized by small organic molecules adsorbed at the gas/water interface, we have, for the first time, estimated the pressure inside these nanobubbles. / In chapter 4, by using a combination of laser light scattering (LLS) and zeta-potential measurements, we investigated effects of salt concentration and pH on stability of the nanobubbles in alpha-cyclodextrin (alpha-CD) aqueous solutions. Our LLS results reveal that the nanobubbles are unstable in solutions with a higher ionic strength, just like colloidal particles in an aqueous dispersion, but become more stable in alkaline solutions. The zeta-potential measurement shows that the nanobubbles are negatively charged with an electric double layer, presumably due to the adsorption of negative OTT ions at the gas/water interface. It is this double layer that plays dual roles in the formation of stable nanobubbles in aqueous solutions of water-soluble organic molecules; namely, it not only provides a repulsive force to prevent the inter-bubble aggregation and coalescence, but also reduces the surface tension at the gas/water interface to decreases the internal pressure inside each bubble. / In chapter 5, the addition of salt can induce slow coalescence of nanobubbles (∼100 nm) in an aqueous solution of alpha-cyclodextrin (alpha-CD). A combination of static and dynamic laser light scattering was used to follow the coalescence. Our results reveal that its kinetic and structural properties follow some scaling laws; namely, the average size (<zeta>) of nanobubbles is related to their average mass (<M>) and the coalescence time (t) as <M> <zeta>dr and <zeta> ∼ tgamma with two salt-concentration dependent scaling exponents (df and gamma) For a lower sodium chloride concentration (C NaCl = 40 mM), gamma = 0.13 +/- 0.01 and df = 1.71 +/- 0.02. The increase of CNaCl to 80 mM results in gamma = 0.32 +/- 0.01 and df = 1.99 +/- 0.01. The whole process has two main stages: the aggregation and the coalescence. At the lower C NaCl, the process essentially stops in the aggregation stage with some limited coalescence. At higher CNaCl leads the coalescence after the aggregation and results in large bubbles. / In this thesis, the nanobubbles in the aqueous solutions have been studied by using combination of static and dynamic laser light scattering (LLS), isothermal compressibility measurements and Zeta-potential measurements. We found that the nanobubbles extensively exist in aqueous solutions and the interface of each nanobubble is negatively charged. The addition of electrolytes can destabilize such interface to induce the coalescence of nanobubbles. / Jin, Fan. / "Aug 2007." / Adviser: Chi Wu. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1030. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 108). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

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Typescript. / Thesis (Ph. D.)--University of Hawaii, 1970. / Bibliography: leaves [76]-79. / vi, 79 l maps, graphs, tables

M.Sc. / Sediment analysis, especially for trace metals, is important since aquatic sediments act as sinks for metals in the environment. Total element analysis yields insufficient information on the bioavailability and the geochemical fate of these metals. Sequential extraction procedures were developed to determine the partitioning of metals in sediment phases. The need for comparability of data produced world-wide led to the development of a sequential extraction procedure, which was proposed by the Community Bureau of Reference as a standard procedure (refered to as the BCR protocol). We contributed to the validation of the BCR procedure by using well-defined in-house model sediments. The results obtained for the model sediments showed that the BCR procedure could distinguish effectively between anthropogenically introduced metals and metals that form part of the mineral structure of the sediment components. The BCR procedure was applied to the sediments of the Vaal Dam and its contributing rivers. The amount of metals extracted in the first three steps of the sequential extraction procedure were low, indicating a very small contribution of anthropogenically introduced metals. It was therefore concluded that these sediments were relatively unpolluted compared to water systems in, for example, Europe.

The purpose of the investigation was to determine the interfering effect on the polarographic method of nitrate analysis of certain chemicals commonly employed in the water purification process. Chemicals tested consisted of coagulants, a disinfectant, and an algaecide. A. “synthetic” water of known chemical consistency was used for diluting purposes. The investigation consisted of two phases; (1) establishing a standard curve with 95 per cent confidence limits of nitrate concentration versus current reading, and ( 2) determining the amount of nitrate recovery in samples containing known nitrate concentrations and certain chemical additives. A further investigation was made of the effect of chemicals revealing a pronounced interference during the initial test. The results obtained indicated that ferric chloride, ferric sulfate, chlorine, and copper sulfate did not interfere with the nitrate analysis. Alum and ferrous sulfate caused a significant interference. The loss in nitrate recovery due to the presence of alum in solution was found to be directly proportional to the alum concentration. Nitrate recovery was reduced from 0 to 10% by alum dosages of 0 to 10 gpg respectively. Although ferrous sulfate caused considerable reduction in nitrate recovery, this is readily explained since ferrous sulfate may be used for the destruction of nitrate in polarographic procedure. When a number of samples were analyzed, the average time required was about 20 minutes per sample. Thus, the time required to perform a nitrate analysis by the polarographic method compares favorably with other methods of analysis. / Master of Science

published_or_final_version / Chemistry / Master / Master of Science

Enteric viruses are viruses which replicate in the intestinal tract of man and animals. One mode of transmission for enteric viruses is the fecal-oral route. Drinking water which has been contaminated with sewage or sewage effluent has been implicated as a means for the spread of enteric viruses. Monitoring water for virus contamination requires two steps: 1) the collection and the concentration of the water sample and 2) the isolation and identification of the virus present. Current methods for the detection of enteric viruses in water requires the use of animal cell culture. This technique has several drawbacks, such as: 1) long incubation periods, up to two and three weeks, before some enteric viruses are detected, 2) not all viruses can be detected in one cell line, and 3) not all viruses have been grown in cell culture. More rapid techniques, such as fluorescent antibody or radioimmunoassay do not have the needed sensitivity to detect the low levels of virus found in contaminated water. These techniques also require the production of an antibody for each different virus type. An alternative technique for the detection of viruses in water was sought. Recent advances in recombinant DNA technology now makes it possible to detect viruses without the use of cell culture or antibodies. Gene probes that hybridize to the RNA of poliovirus and hepatitis A virus were tested for their ability to detect different enteric viruses. The probes were labeled with ³²P dCTP and ³²P dATP to a specific activity greater then 1.0 x 10⁹ cpm/ug DNA. Gene Screen Plus (NEN) was chosen as the hybridization membrane since it was more sensitive to virus detection than the other membranes tested. A dot-blot apparatus (Bio Rad) was used to apply the samples. Results were visualized by autoradiography for thirty-six hours at -70° C. One infectious unit of poliovirus and hepatitis A virus was detected using labeled cDNA probes. Upon comparison, the dot blot assay was as sensitive as tissue culture for the detection of poliovirus in beef extract, secondary effluent, and tapwater. Environmental samples, such as secondary effluent, reclaimed wastewater and unchlorinated drinking water were also assayed for poliovirus and hepatitis A virus with the use of gene probes. The results presented here offer an alternative method for screening water samples for the presence of enteric viruses.