Biogeochemical Weathering of Layer Silicates

本研究将探讨层状硅酸盐风化的无机和生物机制，以及对地球化学循环、土壤肥力和植物营养的影响。具体来说，工作将集中在黑云母、绿泥石、白云母和根际微生物之间的相互作用以及将这些矿物质转化为粘土的反应。这项工作建立在我们之前对无机和生物地球化学介导的链硅酸盐蚀变的研究以及对热液蚀变岩石中硅酸盐层结构、微观结构、化学和反应机制的广泛研究的基础上。部分转化为粘土矿物的层硅酸盐将使用原子分辨率透射电子显微镜和最先进的能量过滤电子显微镜技术进行表征。原子分辨率和低剂量图像捕获能力将用于确定粘土制品的结构细节是否与涉及结构继承的转化机制相一致。我们的工作将使用天然土壤根际风化层硅酸盐和实验室根际风化层硅酸盐。微生物在矿物表面的分布将使用结构域水平和更特异的寡核苷酸探针进行研究。土壤中的微生物通过产生胞外酶（如酶）加速矿物溶解的假说。“矿化酶”（类似于微生物产生的纤维素酶和几丁质酶，用于降解木材、几丁质和相关的有机底物）将进行测试。这项工作包括与Robert Goodman教授（植物病理学，威斯康星大学麦迪逊分校）合作。

9706382 Banfield The proposed research will investigate the inorganic and biological mechanisms by which layer silicates are weathered, with implications for geochemical cycles, soil fertility, and plant nutrition. Specifically, work will focus on interactions between biotite, chlorite, muscovite, and rhizosphere microorganisms and the reactions that convert these minerals to clays. This work builds on our previous studies of inorganically and biogeochemically mediated alteration of chain silicates and extensive studies of layer silicate structures, microstructures, chemistry, and reaction mechanisms in hydrothermally altered rocks. Layer silicates partially transformed to clay minerals will be characterized using atomic-resolution transmission electron microscopy and state of the art energy-filtered electron microscopic techniques. Atomic-resolution and low dose image capture capabilities will be used to determine whether structural details of clay products are consistent with a transformation mechanism that involves structural inheritance. Our work will employ both weathered layer silicates from the rhizosphere region of natural soils and layer silicates weathered in a laboratory rhizosphere. The distribution of microorganisms on mineral surfaces will be studied using domain level and more specific oligonucleotide probes. The hypothesis that microorganisms in soils accelerate mineral dissolution by production of extracellular enzymes (e.g. "mineralases" , analogous to cellulases and chitinases microbes produce to degrade wood, chitin, and related organic substrates) will be tested. This work involves collaboration with Prof. Robert Goodman (Plant Pathology, UW-Madison.