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Mn is a geochemically important element that contributes significantly to the cycling of heavy metals. During precipitation, Mn oxyhydroxides scavenge many heavy metals, including Pb, in a variety of natural environments. Because of this phenomenon, the precipitation of Mn oxyhydroxides may provide a remediation technique for removing Pb from contaminated aqueous solutions. Therefore, this study was undertaken to provide a quantitative understanding of the coprecipitation of Pb with Mn oxyhydroxides to demonstrate their capacity to remove Pb permanently from contaminated solutions. To accomplish this, a series of factorial experiments with varying initial Mn and Pb concentrations were run in the presence of a borate buffer or a bicarbonate buffer. All experiments were run in batch reactors, in the presence of a quartz substrate, at 25 degrees celcius, at pH 8.5, and were continuously stirred. Initial Mn and Pb concentrations were varied by half log units from 100 to 0 mg/L and from 3 to 0 mg/L, respectively. Solutions were analyzed for Mn using the formaldioxime colorimetric method and for Pb using AA. Precipitates on quartz surfaces were analyzed by SEM, XPS, and XRD for precipitate identification and morphology. The amount of Mn and Pb associated with the quartz sand was determined by dissolving the precipitates from selected quartz samples using concentrated nitric acid. Finally, a different set of precipitate-coated quartz grains were leached in pH 5 acetic acid solution to assess the metal retention capacity of the precipitated material. Mn oxyhydroxides precipitated onto the quartz sand in both the borate and bicarbonate buffered experiments. SEM and XPS data revealed tiny crystallites in etch pits on the quartz surfaces that contained predominantly Mn3+. XRD analysis did not produce an X-ray pattern for these Mn oxyhydroxides but did identify the suspended Pb precipitates as hydrocerrusite and Pb(HBO3)2 in the borate buffered experiments and hydrocerrusite in the bicarbonate buffered experiments. Much more Mn and Pb are associated with the quartz surfaces in the borate buffered experiments, but no Pb was associated with quartz surfaces initially (< 6 hrs. of reaction time). Leaching of precipitates resulted in extracted Mn in both experiments but Pb was extracted in only the bicarbonate buffered experiments. The Mn precipitation rate was greater in the borate buffered experiments and higher initial Mn and Pb concentrations appear to increase the precipitation rate in both sets of experiments. These results indicate that Mn oxyhydroxides nucleated onto suspended Pb precipitates. The growing Mn oxyhydroxide particles were attracted to the quartz sand, carrying along the Pb precipitates. Further precipitation of Mn oxyhydroxides on the quartz surfaces trapped the Pb. This process was much more significant in the borate buffered experiments where much more Mn precipitated. The greater amount of Mn oxyhydroxide growth acts as a barrier protecting the Pb from the pH 5 leaching solutions. As a result, Pb was retained by the sand grains from the borate buffered experiments during leaching while significant amounts of Pb (35-100%) was extracted from the sand produced by the bicarbonate experiments. These results strongly suggest that coprecipitation of Pb with Mn oxyhydroxides in the presence of a borate buffer and a quartz substrate may be a remediation tool for Pb contaminated aqueous solutions. Not only will this process remove aqueous Pb2+ from solution but it appears it will also substantially incorporate colloidal Pb particles as well. / Master of Science

The Asbestos Hazard Emergency Response Act (AHERA) requires public schools to manage asbestos containing materials. Twenty five years after AHERA was enacted public schools continue to struggle with documenting and managing asbestos containing material assets. In addition, the manufacturing of lead based paint (LBP) was banned over thirty years ago yet public schools continue to have to manage LBP assets with no guidelines specific to public schools. When compared to current civil infrastructure asset management systems, AHERA and the HUD guidelines lack a rating system based on visual inspection data. The development of a condition index algorithm and risk of failure model would provide school planners an efficient management tool to predict the future condition of asbestos containing material and lead based paint assets. As a result, school planners would be able to prioritize maintenance, repair, and abatement projects based on the risk to the indoor air quality of their facilities and more efficiently utilize their limited resources to mitigate such risks. This paper presents initial work toward the development of a visual condition index algorithm and a risk of failure model to support prioritization of maintenance, repair, and abatement projects. The condition assessment categories provided by AHERA and HUD were adapted and incorporated in an evaluation form created to assist in rating the various stages of accessibility, deterioration, and detection of typical ACM and LBP building components. The evaluation form can be utilized by inspection and school personnel when reclassifying ACM and LBP components during semi-annual inspections of their facilities and also ensure the repeatability of the condition assessment and risk of failure methodologies. A risk of failure model was developed utilizing the FMEA process, specifically the calculation of a risk priority number (RPN). Three schools were selected for a field pilot study to develop the accessibility, deterioration, detection, and RPN algorithms and evaluate for repeatability. The algorithms will provide a quantitative and consistent means for documenting the condition and RPN of asbestos containing material and lead based paint assets and allow the condition of these assets to be monitored and reclassified over a period of time. / Ph. D.

In natural systems, the solution concentration and hence, potential bioavailability of trace metals is primarily controlled by adsorption-desorption reactions at the mineral-water interface. While many studies have been conducted to understand the adsorption of trace metals to soil minerals, less is known about long-term adsorption/desorption processes. In this study, we examined the influence of mixing and sorption period on the desorption of lead from goethite. Lead sorption was rapid and essentially complete in 1 h, with no change in the quantity of lead adsorbed over the 6 month sorption period. Desorption of lead was slower than the adsorption reaction and was best modeled by two first order equations. At all sorption densities, the desorption of lead followed the order Short-term (24 h) > Long-term non-stirred (6 months) > Long-term stirred (6 months). However, statistical analysis indicated that these differences were not statistically significant. Furthermore, the desorption rate coefficients were very similar for all the experiments indicating that there was no significant residence time effect in this study. However, a sample from a previous study that was allowed to age 5 years and then analyzed by the desorption procedure did have statistically significant differences between the long-term (5 years) and the short-term (5 months). These results suggest that longer adsorption periods, perhaps a number of years, may be necessary to determine if residence time effects are an artifact of the experimental conditions or truly the length of the adsorption period. / Master of Science

[pt] O lead é um elemento fundamental da notícia de jornal. Este estudo adota uma abordagem contrastiva e interdisciplinar, analisando, por meio de definições jornalísticas e descrições lingüísticas, um corpus de 200 leads em inglês e português, retirados de dois jornais americanos e dois brasileiros, em dois períodos: 12 a 14 de setembro de 2001 e 29 e 30 de novembro de 2001. Através da análise de gêneros discursivos, o lead é definido como um subgênero do gênero notícia (Biber, 1988, Swales, 1990). Uma analogia é feita, também, entre o lead e o conceito de Tema da gramática funcional, conforme definido por Halliday (1985). Finalmente, este trabalho apresenta uma proposta de classificação dos leads de acordo com sua estrutura e função, dividindo-os em quatro categorias: objetivo, frase de efeito, contextualizado e intergênero. Testes estatísticos foram aplicados ao corpus para investigar a variação quanto a língua, editoria, jornal e período. Resultados indicam predominância dos leads objetivos, especialmente em português. Os leads em inglês mostraram variação em relação ao período, sendo mais freqüentes os leads intergênero durante o período após 11 de setembro de 2001. A comparação entre leads brasileiros e americanos comprova que os leads variam de acordo com a editoria para a qual são produzidos, havendo predominância de leads objetivos na editoria de Economia, por exemplo, e maior variação nas editorias de Esportes e Cultura. Também foram constatadas variações quanto à extensão, em períodos, dos leads em português e em inglês. / [en] Leads are fundamental elements of the news story. This study follows an interdisciplinary approach, analyzing the lead through journalistic definitions and linguistic descriptions. The corpus was composed of 200 leads in English and Portuguese, collected from two American newspapers and two Brazilian newspapers, in two different periods: 12 to 14 September, 2001, and 29 and 30 November, 2001. Using genre analysis theory, leads are defined, in this dissertation, as a subgenre of the news story genre (Biber, 1988, Swales, 1990). Also it is possible to view the lead in analogy to Halliday`s (1985) concept of Theme. Finally, this research paper presents a tentative classification of the leads according to their structure and function, dividing them in four categories: objective, effect phrase, contextualized and intergenre. Statistic tests were applied to the corpus to investigate the variation regarding language, section, newspaper and period. Results point to majority of objective leads, especially in Portuguese. American leads present a variation related to the period of production, intergenre leads being the most frequent during the post-September 11 period. Comparative analysis of American and Brazilian leads shows that leads vary according to the section to which they are written. There is predominance of objective leads in the Business section, while Sports and Culture present more variety. There were also differences between Portuguese and English leads regarding the length of the leads.