Water quality in dynamic redox environments : coupled hydrologic-biogeochemical controls on metal contaminant mobility
- Rising population and changing climate threaten to amplify the risks posed by metal contaminants to our freshwater resources. Altered hydrologic cycles and increased demand for freshwater will shift biogeochemical conditions in soils and sediments, potentially transforming metal contaminants from stationary (solid) phases to mobile forms, which are subject to transport and human consumption. Often, redox processes control partitioning of metal contaminants, whether by changing the redox state of the metal itself, or by transforming the metal host(s). In soils and sediments, these redox processes are commonly driven by hydrologic conditions. My research seeks to understand how redox-associated biogeochemical processes arising from and coupled to hydrologic conditions impact metal contaminant partitioning and mobilization. I employ a combination of experimental, spectroscopic, field and modeling approaches to study the partitioning of U, Pb and Cd to solid and dissolved phases in dynamic redox environments. In my first chapter, I find that the calcium-uranyl-carbonato species kinetically limit U(VI) reduction by Fe(II)(aq), thereby impeding transformation of U from a soluble form to an insoluble form. In my second chapter, I show that the stability of Pb in a range of bonding environments limits dissolved Pb concentrations in contaminated floodplain sediments, despite redox-driven dissolution of Pb hosts. In my third chapter, I reveal that soil redox conditions influence the metal-binding properties of dissolved organic matter, leading to increased complexation of Cd by soft ligands in reduced environments. Finally, in my fourth chapter, I find that the impacts of beaver dams on hyporheic biogeochemical activity dwarfs that of seasonal hydrologic dynamics. Overall, my work both furthers our understanding of the biogeochemical cycles of U, Pb, and Cd and deepens our understanding of how changes in hydrology couple with biogeochemical redox processes to determine water quality
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource
|Dewey, Christian William
|Degree committee member
|Degree committee member
|Stanford University, Department of Earth System Science
|Statement of responsibility
|Submitted to the Department of Earth System Science
|Thesis Ph.D. Stanford University 2020
- © 2020 by Christian William Dewey
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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