Elucidating the role of surface alteration and dynamic relocation for the formation and maturation of microaggregates in the soil-parent rock continuum

阐明表面蚀变和动态迁移对土壤母质岩石连续体中微团聚体形成和成熟的作用

• 批准号: 418749388
• 负责人: Professor Dr. Kai Uwe Totsche
• 金额: --
• 依托单位: Lehrstuhl für Hydrogeologie
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/418749388?language=en
• 关键词: Elucidating; role; surface; alteration; dynamic

Aggregation and the build-up of aggregates is one of the unique features of soils. It results in a non-random spatial arrangement of the solid phase already at the submicron scale. Within this system, microaggregates are considered the fundamental building blocks for the aggregated structure in almost all soils, including those with an aggregate hierarchy. Soil microaggregates are defined as compound structures smaller <0.25mm, comprising the colloidal-sized and nanoparticulate composite building units and the organo-mineral composites. Noteworthy, microaggregates, may be present as suspended or colloidally-dispersed components of the mobile phase. As such, they are prone to transport with the seepage and may affect the surface and pore-space properties. Surface alteration by interactions of seepage components with immobile surfaces is likely an important, yet essentially unexplored pathway triggering formation of microaggregates in the soil-parent rock continuum. In matured soils, the commonly found associations of clays with other, often poorly crystallized but highly reactive minerals and organic matter is the consequence of nucleation in the chemically heterogeneous soil suspension. Both pathways coexist and can be studied in the soil-parent-rock transition zone were weathering and formation/alteration of secondary mineral phases are still in the early stage. The stability of microaggregates and their interactions are dependent on wetting-drying and in turn by hydration-dehydration cycles. Such moisture-related dynamics regularly take place in soils of the temperate regions even down to the soil-parent-rock transition zone and suggests that the hydraulic and osmotic stress and their history results in attachment, detachment, translocation and accumulation. With this project we intend to close fundamental knowledge gaps in the understanding of the formation and stability of microaggregates in the soil-parent rock continuum. The research program comprises studies in-situ (profile analysis loess pedosequence in a space-for-time approach), in-vitro (dynamic relocation experiments) and in-silico (numerical simulations of hetero-aggregation). We focus on two so far ignored formation pathways of microaggregates and composite building units, i.e. the "geochemical inheritance" and "heteroaggregation from Suspension", thereby considering the role of dynamic relocation of composite building units and microaggregate forming materials from upstream compartments. With the research in this subproject, we aim for a quantitative understanding of the interplay and interdependence of the formation pathways in space and time, the controlling processes and underlying mechanism by the exploration of the resulting phenomena. Our improved understanding will ultimately fuel our endeavor for the development of a quantitative theoretical framework of microaggregate formation and function in soils guided and realized within the coordination project.

团聚体和团聚体的形成是土壤的独特特征之一。它导致固相的非随机空间排列已经在亚微米级。在这个系统中，微团聚体被认为是几乎所有土壤中团聚体结构的基本组成部分，包括具有团聚体层次的土壤。土壤微团聚体是指粒径小于0.25mm的复合结构，由胶体和纳米颗粒组成的复合结构单元和有机-无机复合结构单元组成。值得注意的是，微聚集体可以作为移动的相的悬浮或胶体分散组分存在。因此，它们易于随渗流迁移，并可能影响表面和孔隙空间性质。通过渗流组分与固定表面的相互作用进行的表面改变可能是一个重要的，但基本上未探索的途径，触发土壤-母岩连续体中微团聚体的形成。在成熟土壤中，粘土与其他通常结晶不良但活性高的矿物和有机质的结合是化学非均匀土壤悬浮液中成核的结果。这两种途径共存，可以在土壤-母岩过渡带进行研究，风化和次生矿物相的形成/蚀变仍处于早期阶段。微团聚体的稳定性及其相互作用取决于湿-干循环，而湿-干循环又取决于水化-脱水循环。这种与水分有关的动力学规律发生在温带地区的土壤中，甚至到土壤-母岩-岩石过渡带，表明水力和渗透应力及其历史导致附着、分离、移位和积累。通过这个项目，我们打算缩小在理解土壤-母岩连续体中微团聚体的形成和稳定性方面的基本知识差距。该研究计划包括原位研究（时空方法中的黄土剖面分析），体外研究（动态迁移实验）和计算机模拟（异质聚集的数值模拟）。我们专注于两个迄今为止被忽视的形成途径的微团聚体和复合建筑单元，即“地球化学遗传”和“从悬浮液的异质聚集”，从而考虑的作用，动态搬迁的复合建筑单元和微团聚体形成材料从上游隔间。通过本子项目的研究，我们的目标是通过对所产生的现象的探索，定量地了解空间和时间形成途径的相互作用和相互依赖性，控制过程和潜在机制。我们对微团聚体形成和功能的理解的提高最终将推动我们在协调项目的指导和实现下开发土壤微团聚体形成和功能的定量理论框架的奋进。