Thesis (Ph. D.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 169-178). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph.D.)--Duquesne University, 2004. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references and abstract.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Includes bibliographic references (ℓ. 70-76)

Dissertation submitted in compliance with the requirements for the Master's Degree in Technology: Biotechnology, Durban Insititute of Technology, 2003. / Stimulated by the findings of international researchers, that the sulfate-reducing microorganism Desulfovibrio desulfuricans could be incriminated in the process of mercury bio-methylation, it was decided to test this hypothesis on sediments from selected areas of Durban Bay where elevated levels of the bio-hazardous heavy metal had previously been detected. The Environmentek Division of the Council for Scientific and Industrial Research (Durban) is involved in an ongoing chemical assessment of heavy metal contamination (including levels of mercury) in the sediments of this estuary, but nothing is currently understood about the form in which mercury exists or the biological processes that could be determining its fate. The purpose of this project was to attempt to answer some of these questions. The study involved attempting to isolate, identify and quantify microorganisms of the species Desulfovibrio desulfuricans, Escherichia coli and Clostridium perfringens in one hundred and eighty sediment samples taken from three designated sites in the bay. Each sample was additionally analysed for total and methyl mercury and sulfate content, as well as a number of physical parameters. Based on the outcome of the initial survey, it was envisaged that further laboratory experimentation would be conducted to determine whether or not isolates were responsible for the production of the highly toxic organic mercury and whether this process was occurring in situ in the sediments. The findings of this project were contrary to what had been expected. Total mercury concentrations (apart from one instance) did not appear to be appreciably elevated in the areas under study. Similarly, the levels of methyl mercury were fourrd to be either diminished or absent. Numbers of D. desulfuricans were low and not uniformly distributed throughout the sediments. Cl. perfringens was more in evidence, but counts were not perceptibly increased. Sulfate levels were consistently high, indicating significantly impaired rates of sulfate reduction. Difficulty experienced in sub-culturing / M

Thesis (Ph. D.)--University of Illinois at Chicago, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Illinois at Chicago, 1999. / Includes bibliographical references.

"Professional paper presented in partial fulfillment of the requirements for the degree of Master of Science, Environmental Studies, the University of Montana, Missoula, MT, spring 2007." / Title from PDF title page (viewed on Aug. 12, 2007). Includes bibliographic references (p. 67-69).

Orientadores: Pedro Sérgio Fadini, José Roberto Guimarães / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-16T04:17:25Z (GMT). No. of bitstreams: 1 Silva_LeonardoAugustoSilvestre_M.pdf: 5806444 bytes, checksum: 66a71a65fd0f1a54aff06733e84a328e (MD5) Previous issue date: 2006 / Resumo: Neste trabalho, o objetivo principal foi a construção e otimização de câmaras visando a quantificação dos fluxos de mercúrio dissolvido gasoso (MDG), na interface água / atmosfera em lagos da Bacia Hidrográfica do Rio Negro - AM. Foram realizados trabalhos de campo utilizando-se câmaras construídas em acrílico incolor nos quais foram determinadas as concentrações de mercúrio na atmosfera externa e interna da câmara. O ar foi bombeado através de colunas preenchidas com areia de quartzo recoberta com ouro, capazes de pré-concentrar o MDG por amalgamação. A quantificação do mercúrio foi realizada empregando-se a técnica de Espectrometria de Fluorescência Atômica do Vapor Frio (CVAFS), em um equipamento operando embarcado. Em campanha realizada no mês de Janeiro de 2003, os fluxos de MDG registrados no Lago Araca (águas brancas) foram, em pmol m-2 h-1: -20,68; + 8,16 e - 0,54 em períodos sem incidência de luz, e + 29,54 ; + 32,72 em períodos iluminados. Já no Lago Iara (águas negras), os valores encontrados para MDG em períodos sem incidência de luz foram: + 28,77; + 19,00 ; + 22,35, assim como + 5,39 e - 4,85 em períodos iluminados. Os resultados sugerem que os fluxos de MDG nos lagos da Bacia do Rio Negro seguem a tendência de serem invasivos para períodos não iluminados e evasivos para períodos iluminados em águas brancas, mas evasivos para períodos não iluminados e invasivos para períodos iluminados em águas negras / Abstract: The scope of this work was the construction and optimization of fluxes chambers for the determination of dissolved gaseous mercury (DGM) in the water atmosphere interface, in lakes belonging to the Negro River basin - AM. Field work was carried out using a plexiglass flux chambers for the determination of inner and outer atmospheric gaseous mercury. The air was pumped through quartz gold-sand columns, preconcentrating the DGM by amalgamation. The mercury quantification was carried out by Cold Vapor Atomic Fluorescence Spectrometry (CVAFS), using equipment on boat. Inthe sampling period of January 2003, the DGM fluxes measured in Araca Lake (white waters) were -20.68, + 8.16 and - 0.54 pmol m-2 h-1, during a period without light incidence, and + 29.54, + 32.72 under light incidence. In the Iara Lake (black waters), the DGM fluxes were + 28.77, 19.00 and 22.35 without light incidence, and + 5.39, - 4.85 in light periods. The results suggest that DGM fluxes in white water lakes show na invasive behaviour in no light periods, as well as an evasive behaviour in light periods. However, the behaviour of DGM fluxes is opposite in black waters / Mestrado / Saneamento e Ambiente / Mestre em Engenharia Civil

Content removed due to copyright restrictions: Anderson, C., Moreno, F., & Meech, J. (2005). A field demonstration of gold phytoextraction technology. Minerals Engineering, 18(4), 385-392. / Mercury (Hg) is a toxic heavy metal that is concentrated in organisms. Injudicious use of Hg and its compounds have resulted in widespread soil contamination. This study investigates the potential use of plants for the remediation of Hg-contaminated mine wastes. Plants can remove soil Hg via phytoextraction and phytovolatilisation. I investigated both of these strategies by focusing on a methodology for Hg analyses in plants and soils with a view to the determination of volatile Hg emitted from plants. Secondly, I determined the feasibility of Hg phytoextraction and phytovolatilisation from contaminated mine wastes. An accurate method for the analysis of Hg in air, plant and various soil fractions was a key component of this study. I developed a hydride-generation atomic absorption spectroscopy method for total Hg analyses in digest and liquid matrices of the aforementioned samples. Quality assurance was ensured by comparing results with those of an external certified laboratory. The maximum discrepancy was 15 %. To measure plant Hg-volatilisation, a method that captures Hg-vapour in solution for subsequent analyses was developed. Initially this system was used to trap Hg vapours released from the root system of Brassica juncea plants grown in hydroponic solutions. A subsequent study improved the Hg trapping system, allowing the capture of volatile Hg from both roots and shoots. Mercury recoveries from the whole plant system (traps + plant + solutions) averaged 90 % using this experimental apparatus. In most contaminated substrates, plant Hg uptake is insignificant, possibly due to the low bioavailability of Hg. This represents an obstacle for effective remediation using phytoextraction. Geochemical studies were carried out in Hg-contaminated substrates to examine the potential of chemical agents to induce Hg solubility and subsequent plant uptake. These studies utilised Hg-contaminated mine tailings collected from three locations: the Tui base-metal mine, in the North Island of New Zealand, the Gold Mountain mine, in North-Central China and, the Serra Pelada artisanal mine site, in Northern Brazil. The results demonstrated that Hg solubility in all tested substrates is increased in the presence of sulphur-containing chemical ligands. The effectiveness of these ligands was influenced by site-specific geochemistry. Plants species were able to accumulate up to 60 mg/kg of Hg in shoot tissues upon addition of sulphur-containing ligands to Tui and Gold Mountain substrates. The degree of plant-Hg accumulation was shown to be dependant on plant species and on the thioligand-induced soluble Hg fraction. Shoot Hg transport was inhibited for Gold Mountain substrate amended with 1.25g/kg of humic acid. The maximum Hg extraction yield for B. juncea plants growing in Tui field sites averaged 25 g per hectare following application of sodium thiosulphate. Volatilisation of Hg vapour from barren substrates occurred as a result of biotic (microorganisms) and abiotic (chemical and photochemical reduction) processes. The presence of B. juncea plants in substrates enhanced the volatilisation process up to 23 fold. Phytovolatilisation was the dominant pathway responsible for between 75 to 99.5 % of the total Hg removed from substrates. It was concluded that Hg removal from contaminated mine wastes can be accomplished by both thioligand-induced phytoextraction and phytovolatilisation. There are risks of groundwater contamination by Hg species mobilised after application of thioligands to substrates. Estimated Hg (0) emissions from plant-based operations at contaminated sites ranged between 1.5 to 3.6 kg of Hg/ha per year. Due to extensive atmospheric dilution, Hg emissions from small-scale phytoremediation operations would not cause serious harm to the local population or the regional environment. Phytoremediation combined with gold-phytoextraction can help to mitigate Hg-pollution in artisanal mine sites in the developing world.