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SELF-ORGANIZED CHEMICAL PRECIPITATES:
LABORATORY AND FIELD STUDIES
by
Laura Marie J. Barge
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(GEOLOGICAL SCIENCES)
December 2009
Copyright 2009 Laura Marie J. Barge
Object Description
| Title | Self-organized chemical precipitates: laboratory and field studies |
| Author | Barge, Laura Marie J. |
| Author email | laurie.barge@gmail.com; barge@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Geological Sciences |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2009-06-03 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-10-16 |
| Advisor (committee chair) | Nealson, Kenneth H. |
| Advisor (committee member) |
Petruska, John Hammond, Douglas Corsetti, Frank Bottjer, David |
| Abstract | Self-organized patterns can be formed in diffusion experiments where two interdiffusing electrolytes react to form an insoluble precipitate in a medium (such as gelatin) that permits diffusive motion of ions, but prevents product particles from moving from their site of formation. Various pattern morphologies such as periodic bands, dendritic crystals, and continuous precipitates can be formed in many types of diffusion media. We hypothesized that interfering ions that are not part of the dominant precipitation reaction could affect the formation of self-organized patterns in a reproducible fashion, and that the same precipitation reaction occurring in different diffusion media would produce different pattern morphologies (depending on the physical and chemical properties of that medium).; To initially characterize the patterns formed by various diffusion/reaction systems, we performed experiments with ferrous carbonate, phosphate, and hydroxide precipitation in agarose gel. Ferrous compounds were precipitated under reducing conditions, forming self-organized patterns such as periodic bands, and were subsequently oxidized as atmospheric oxygen diffused into the gel. Mineral replacement occurred upon introduction of a reactant that formed a more insoluble compound than the one already present, and after replacement the banding pattern remained unaltered, allowing identification of the original precipitate.; We also characterized the effects of the diffusion medium and interfering ions on self-organized precipitation in silver nitrate/potassium chromate and silver nitrate/potassium dichromate reaction systems. We observed that precipitate morphology was characteristic of the reactants that were initially present and the type of gel medium in which they precipitated. It was found that soluble impurities in agarose gel were responsible for the slight banding produced in silver chromate precipitation experiments. We then tested the effects of organic compounds (simple amino acids and their N-acetylated derivatives) on morphologies of silver chromate precipitates in purified agarose gel. High concentrations of pure amino acids caused periodic banding of crystals, and N-acetyl amino acids were more effective than pure amino acids, because of their negative charge. We hypothesized that the length and orientation of the neutral side chain of the amino acids, as well as charge, affects the degree of binding to the crystal surface, and hence the ability to induce banded patterns.; To better apply these studies to self-organized patterns that form in natural systems, where the diffusion medium may be inhomogeneous (such as sand or sandstone), we studied laboratory and field examples of self-organized mineral precipitates in porous media. Silver chromate precipitation experiments in tubes of glass beads and glass bead/gel mixtures produced structures such as finger fluid fronts, periodic banding, and millimeter-size spherules. The spheroidal precipitates produced in our experiments nucleated via self-organizing processes throughout the glass bead medium, and bear morphological resemblance to iron oxide concretions formed via self-organizing processes in the Navajo Sandstone, UT, that preserve records of fluid flow events in a porous and permeable sandstone. |
| Keyword | Liesegang bands; silver chromate |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m2672 |
| Rights | Barge, Laura Marie J. |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Barge-3330 |
| Archival file | uscthesesreloadpub_Volume26/etd-Barge-3330.pdf |
Description
| Title | Page 1 |
| Full text | SELF-ORGANIZED CHEMICAL PRECIPITATES: LABORATORY AND FIELD STUDIES by Laura Marie J. Barge A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (GEOLOGICAL SCIENCES) December 2009 Copyright 2009 Laura Marie J. Barge |
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