| Naturally occurring wetlands that reside in mine waste impacted regions need to be investigated in order to aid in their preservation and to identify mechanisms of contaminant sequestration. Accordingly, an investigation of a mine waste influenced wetland at Cataldo, Idaho was undertaken to determine the aqueous and solid phase distribution of redox dynamic elements such as Fe, As, and Mn. During this research, we developed and tested devices for sampling anoxic environments (Chapter 2), evaluated the effectiveness of selective sequential extractions (SSE) commonly used in soil analysis (Chapter 3), and elucidated Mn, Fe, and As cycling within a natural wetland (Chapters 4 and 5).; Selective chemical extractions provide semi-quantitative information on element partitioning within operationally defined soil fractions. The efficiency of common extraction steps was determined for a mining impacted soil by analyzing solid phase Fe transformations using X-ray diffraction, scanning electron microscopy, and X-ray absorption near edge structure (XANES) spectroscopy (Chapter 3).; Oxides of Mn can have a profound influence on contaminant availability. In response to this possibility we investigated the cycling of Mn within the wetland. We monitored aqueous and solid phase Mn response to changing physicochemical conditions within the system (Chapter 4). Manganese detected in the aqueous phase was highly variable among the sites but occurred at elevated concentrations in the Spring and Summer when pore-waters were supersaturated with respect to Mn carbonate. We identified Mn(II) in the solid phase using X-ray absorption fine structure (XAFS) spectroscopy.; Arsenic is a contaminant associated with regional mine wastes and thus threatens environmental quality. Accordingly, we initiated an investigation of As speciation and its co-distribution with Fe (perceived to be a dominant factor in the cycling of As) in a mine waste impacted wetland (Chapter 5). Aqueous phase Fe and As concentrations were positively correlated in the porewaters of the wetland during the Spring and Summer months, with As occurring at levels an order of magnitude greater than drinking water standards. We used XANES spectroscopy to assess As response to altering soil physicochemical conditions along the periphery and in the deep anoxic part of the site. Soil-solids collected in these regions contained varying proportions of arsenite but mostly arsenate in Spring, a larger fraction of arsenite and orpiment-like (AS2S 3) species in Summer, and more arsenate in Winter.; Wetlands are unique ecosystems that have shown the ability to withstand extensive contamination including those induced by mining activities. (Abstract shortened by UMI.)... |
