Thesis (doctoral)--Ludwig Maximilians-Universität zu München, 1979.

Bachelor-Arbeit Univ. St. Gallen, 2005.

Thesis (M.S. in geology)--Washington State University, December 2005. / Includes bibliographical references.

Master-Arbeit Univ. St. Gallen, 2006.

Thesis (Ph. D.)--Catholic University of America. / "Literature cited": p. 21-22.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1961. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis--Universiteit van Utrecht. / Bibliography: p. 101-104.

Thesis (M.A.)--Eastern Illinois University, 1976. / Includes bibliographical references (leaves 87-89).

The thesis reviews literature relating to lead in the environment with particular reference to the distribution and pathways of lead in the soil and plant ecosystem. Methods of conducting large area soil surveys and assessing the distribution of lead and other heavy metals including cadmium, copper and zinc are also examined. A survey was conducted over a 370 km2 area of North East Derbyshire, England. Maps showing the distribution of the metals reveal anomalously high concentrations related in many instances to past industrial activity. A simple reliable and rapid acid digestion procedure was developed and the procedure evaluated through an interlaboratory survey involving 22 laboratories. This demonstrated that analysts should seek to improve analytical performance through achieving better interlaboratory correlation rather than intralaboratory precision. A stratified random sampling protocol was developed and evaluated which allowed an estimate of precision to be placed on the results of the trace metal soil survey. An assessment was carried out of the contribution that lead fromaerially deposited dust and soil sources makes to the distribution of lead in potato plants. A micro sampling cup technique was developed which permitted (for the first time as far as can be ascertained) the analysis of lead in discrete sections of solid plant tissue from single plants grown under field conditions. This overcomes the problems of sensitivity which normally requires that samples are bulked or dosed with lead salts. Results are presented for the distribution of lead in potato plants grown in several field locations and in soils containing varying concentrations of lead. The major source of lead in the plants via the soil with aerial sources having a negligible effect on tissue distribution. Comparisons are made between results obtained by conventional flame atomic absorption spectrometry and the microsampling cup procedure.

Made available in DSpace on 2014-06-11T19:35:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2000-12-01Bitstream added on 2014-06-13T18:46:22Z : No. of bitstreams: 1 silva_map_dr_araiq.pdf: 1825634 bytes, checksum: b8f8252c49c068a4dfd8208ba58028e3 (MD5) / Vidros e vitrocerâmicas foram obtidos dos sistemas oxifluoretos envolvendo os fluoretos de chumbo e cádmio e um óxido conhecido como formador de vidros: SiO2, B2O3, P2O5, e TeO2. Os domínios vítreos foram estabelecidos e um grande número de composições incluindo alta concentração de metais pesados leva à formação de vidros estáveis. A estrutura amorfa foi estudada por técnicas espectroscópicas de determinação de estruturas a curtas distânicas (Espalhamento Raman e Absorção de Raios X). Além dos óxidos, o papel de formador desempenhado pelos átomos de cádmio foi também identificado. Atenção especial foi direcionada aos processos de cristalização. Fluoreto de chumbo cúbico β-PbF2, telurito de chumbo PbTe3O7 (fase cristalina de uma vitrocerâmica transparente), óxido de telúrio tetragonal α-TeO2 e soluções sólidas do tipo Pb1-xCdxF2 foram obtidos como produtos da cristalização, dependendo da composição e do tratamento térmico. A adição de íons terras-raras leva ao controle do processo de cristalização. Na presença do íon nucleante apenas a forma β-PbF2 foi identificada. Os íons terras raras apresentamse concentrados na fase cristalina e as propriedades espectroscópicas são aquelas apresentadas em um meio cristalino, sugerindo interessantes aplicações destes materiais na indústria tecnológica. / Glasses and glass-ceramics have been obtained in oxyfluoride systems involving lead and cadmium fluorides and one of the well-known glass former oxides SiO2, B2O3, P2O5, GeO2 and TeO2. Vitreous domain were established and a wide range of compositions including high heavy metal contents lead to stable glasses. Amorphous structures have been studied by short-range order spectroscopy techniques (Raman scattering and x-ray absorption) and molecular basic structures have been identified. Besides the usual oxides, the role of glass former could also be proposed for cadmium ions. Special attention has been paid for crystallization process. Cubic lead fluoride, cubic lead tellurite, tetragonal tellurium oxide and a solid solution of the type Pb1-xCdxF2 are obtained as crystallization products depending on the composition and temperature of heat treatments. Pb1-xCdxF2 solid solutions are well known superionic materials and obtaining this solid solution as a crystal phase could be very interesting for applications concerning ionic electrical conduction properties. The addition of rare earth ions led to the control of the crystallization process. In the presence of the nucleating ion only the cubic form β-PbF2 was identified. Rare earth ions are concentrate in the crystal phase and crystal like spectroscopic properties were observed suggesting interesting applications for these perfectly transparent glass ceramics in photonics.