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

9406396 Johnsson对森林生态系统中复杂的有机/无机相互作用的理解需要一种跨学科的方法，即从精心选择的研究区域进行的实地观测与宏观热力学和动力学研究相结合，并与能够探测矿物/水界面的独特结构、组成和反应性的表面敏感技术(例如原子力显微镜、扫描隧道显微镜、扫描隧道显微镜、X射线光电子能谱)相结合。这项研究规划资助提案概述了两项研究，其中采用跨学科方法来了解有机酸对酸性、富含有机物质的土壤和溪流中的化学风化和痕量金属活化的影响。这些研究包括(1)简单(草酸盐)和复杂(腐殖酸和富里酸)有机酸对混合配位体系中赤铁矿溶解的影响；(2)有机酸对层状硅酸盐(白云母和高岭石)溶解过程中氢氧化铝第二相形成的影响。这两项研究都涉及从原子尺度到流域尺度的地化实验的整合。这些初步研究的结果将作为1994-95年提交国家科学基金会大规模赠款的背景资料。此外，建立一个新的实地研究区域，设计和建造一个连接到计算机化恒电位仪的流槽反应容器，以及开发在竞争吸附实验中使用14C标记有机酸的专门知识，将为涉及广泛有机/无机相互作用的更多研究工作奠定基础。

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.