Biologically-Mediated Weathering of minerals from Nanometre Scale to Environmental Systems.

在自然界中，一个由物理、化学和生物过程组成的复杂系统侵蚀着地球表面，并将岩石转化为土壤。由于目前全球侵蚀损失的速度比土壤形成的速度快得多（100倍或更多），主要是由于不可持续的耕作方式，土壤已成为一种有限的资源。尽管土壤对我们的星球及其60亿人口的生存至关重要，但我们对风化的了解有限。这是因为各种科学方法没有充分地整合在一起，以解决发生的许多复杂的相互作用。因此，需要一个多学科的方法来研究土壤的形成速率和过程。土壤真菌似乎利用植物的能量从岩石中挖掘养分，但其中的机制尚不确定。我们想知道生物风化是否由植物光合作用产生的糖流驱动，以换取矿物颗粒中的营养元素（如磷、钾）。森林树木产生的总化学能（糖）的近三分之一直接传递给共生（互利）根真菌。这些真菌完全覆盖在树根上，并在土壤中形成广泛的活丝状网络。实际上，树木吸收的所有营养都是通过这些真菌吸收的。这个研究项目将确定真菌细胞和它们的分泌物如何与矿物表面相互作用，以及如何影响从矿物质到生物体的营养转移速率。将生物过程作为理解矿物如何溶解的分子水平的核心是与现有理论背道而驰的。研究生命系统中的这些基本分子机制使我们能够创造新的概念和数学模型来描述生物风化，并用于土壤风化动力学的计算机模拟。我们建议在三个观察水平上研究这些生化相互作用：1。在分子尺度上，了解活细胞和矿物质之间的相互作用，并量化分解矿物质结构的化学反应。2 .在土壤颗粒尺度上量化真菌、根系和其他生物（如细菌）的活动和空间分布，以及它们对矿物质溶解释放养分速率的影响；在土壤剖面尺度上测试活性真菌和碳能的空间分布及其季节变化和对矿物溶解速率的影响模型。我们将结合许多科学领域的专业知识。生物学家将在真菌和植物培养物存在和缺乏作为营养来源的矿物质的情况下工作，并测量真菌网络中的碳能量通量。表面化学家将使用x射线和红外光束与细胞和矿物表面相互作用，然后使用复杂的传感器进行测量，以提供可能形成的化学键的信息。物理学家将测量真菌细胞和矿物质表面之间的微小作用力，以确定真菌是否真的粘附并形成化学键。材料科学家将使用高度专业化的可视化方法，在几乎原子尺度上观察溶解矿物的形状和组成。地球化学家将研究矿物如何随时间变化以及有多少矿物被溶解。通过几乎从分子到土壤剖面尺度的工作，所获得的数据和理解将被数值建模者用来模拟高等植物、真菌、矿物质、土壤有机质和渗透水之间复杂的相互作用。最后一步是在气候条件和土壤管理变化的一系列情景下模拟土壤剖面风化。预期的成果是对土壤形成的更强的基本理解，特别是生物风化的作用，这样我们就可以改进我们对这一重要自然资源的管理策略。

In nature, a complex system of physical, chemical and biological processes weather the Earth's surface and transform rock into soil. Because global erosion loss is now much faster (100 times or more) than soil formation, largely as a result of unsustainable cultivation practices, soil has become a finite resource. Despite the importance of soil for sustenance of our planet and it 6 billion human inhabitants, our knowledge of weathering is limited. This is because various scientific approaches are not sufficiently integrated to tackle the many, complex interactions that occur. Therefore a multi-disciplinary approach is needed to study soil formation rates and processes. Soil fungi appear to use plant energy to mine nutrients from rock-but the mechanisms involved are uncertain. We want to know if biological weathering is driven by the flow of sugar produced by plant photosynthesis in return for nutrient elements (such as phosphorous, potassium) from the mineral particles. Nearly a third of the total chemical energy (sugar) produced by forest trees passes directly to symbiotic (mutually beneficial) root fungi. These fungi completely cover the tree roots and form extensive networks of living threads through soil. Virtually all nutrients taken up by the trees are absorbed through these fungi. This research programme will identify how fungal cells, and their secretions, interact with mineral surfaces and affect the rates of nutrient transfer from minerals to the organism. Making biological processes central to molecular-level understanding of how minerals dissolve is counter to existing theories. Investigating these fundamental molecular mechanisms in living systems allows us to create new concepts and mathematical models that can describe biological weathering and be used in computer simulations of soil weathering dynamics. We propose to study these biochemical interactions at three levels of observation: 1.At the molecular scale to understand interactions between living cells and minerals and to quantify the chemistry that breaks down the mineral structure, 2.At the soil grain scale to quantify the activity and spatial distribution of the fungi, roots and other organisms (e.g. bacteria) and their effects on the rates at which minerals are dissolved to release nutrients, and 3.At soil profile scale to test models for the spatial distribution of active fungi and carbon energy and their seasonal variability and impact on mineral dissolution rates. We will combine the expertise from many scientific fields. Biologists will work with the fungi and plant cultures in the presence and absence of minerals that are sources of nutrients, and measure carbon energy fluxes in the fungal networks. Surface chemists will use X-Ray and Infrared beams that interact with the cell and mineral surface, and are then measured using sophisticated sensors to provide information on the chemical bonds that can form. Physicists will measure the minuscule forces that operate between fungi cells and minerals surfaces, but determine if fungi actually adhere and form chemical bonds. Materials scientists will use highly specialised visualisation methods to observe the shape and composition of dissolving minerals at almost atomic scale. Geochemists will study how the minerals change over time and how much mineral is dissolved. The data and understanding that is obtained, by working from almost molecular to soil profile scale, will be used by numerical modellers to simulate the complex interactions between higher plants, fungi, minerals, soil organic matter and infiltrating water. A final step is to simulate soil profile weathering under a range of scenarios for changes in climatic conditions and soil management. The anticipated achievement is a much stronger fundamental understanding of soil formation, particularly the role of biological weathering, so that we can improve our management strategies for this important natural resource.