RPG: Effects of Organic Acids on Clay Mineral Dissolution: Integrating Geochemistry from the Atomic--to the Watershed Scale

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9406396 Johnsson Understanding of complex organic/inorganic interactions in forested ecosystems requires an interdisciplinary approach wherein field observations from carefully selected study areas are combined with macroscopic thermodynamic and kinetic investigations and with surface-sensitive technologies (e.g., atomic force microscopy, AFM; scanning tunneling microscopy, STM; X-ray photoelectron spectroscopy, XPS) that are capable of probing the unique structure, composition, and reactivity of the mineral/water interface. This Research Planning Grant proposal outlines two studies wherein an interdisciplinary approach is taken to understanding the effects of organic acids on chemical weathering and trace-metal mobilization in acidic, organic-rich soils and streams. These studies include (1) the effects of simple (oxalate) and complex (humic and fulvic) organic acids on hematite dissolution in mixed-ligand systems, and (2) the effects of organic acids on AL-hydroxide secondary phase formation during the dissolution of phyllosilicates (muscovite and kaolinite). Both of these studies involve integration of geochemical experimentation from the atomic- to the water shed scale. Results of these preliminary studies will be used as background for submission of a large-scale NSF grant, in 1994-95. In addition, establishment of a new field study area, design and construction of a flow-trough reaction vessel attachment to a computerized potentiostat, and development of expertise in the use of 14C- labelled organic acids in competitive sorption experiments will lay the groundwork for additional research efforts involving a wide range of organic/inorganic interactions.