Abstract Clay minerals and Fe- and Al-oxyhydroxides are considered as the most important materials for the formation of microaggregate building units in soils. The mode of aggregation and the resulting structure and stability are largely determined by their size, aspect ratio (AR), differences in surface charge (SC), and mixing ratio. Here, the impact of these parameters on the formation of microaggregate building units (BUs) was elucidated with a mechanistic model, i.e. using a twophase cellular automaton method, in which prototypes of illite and goethite were implemented. The simulations allowed assessing the formation of particle arrangements during aggregation, moreover building unit diameters, and the number of discrete particles. The contact area between particles was evaluated as a quantitative measure for stability. Homoaggregation of illite under the sole influence of attracting van der Waals forces enabling face-to-face as well as edge-to-face contacts, resulted in compact structures with a small mean diameter and specific surface area. In contrast, electrostatic attraction between negatively charged faces and positively charged edges favored formation of larger card-house structures, where low contact areas indicated the low stability of the resulting BUs. At constant AR, homoaggregation of illite of different particle size led to BUs of different stability, more precisely smaller particle sizes led to more stable BUs. Variation of the AR of illite, while keeping the particle size constant, revealed that most stable BUs arose from illite with smallest AR. Shielding of coarse goethite particles due to attachment of fine illite with negatively charged edges increased the number of discrete fine illite particles not aggregated. Aggregation of illite with positively charged edges was in fundamental difference to results from simulations with negative edges because of electrostatic attraction between illite particles. The simulation setting, without using fitting parameters resulted in an appropriate approximation of laboratory findings. The simulation clearly facilitated the understanding of microaggregate building unit formation and stability by illuminating turnover dynamics and provision of quantitative data.

中文翻译：

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力学模型评价针铁矿和伊利石的微团聚体

摘要 粘土矿物和铁和铝的羟基氧化物被认为是形成土壤微团聚体结构单元的最重要材料。聚集方式以及由此产生的结构和稳定性在很大程度上取决于它们的大小、纵横比 (AR)、表面电荷差异 (SC) 和混合比。在这里，这些参数对微集料构建单元 (BU) 形成的影响通过机械模型阐明，即使用两相元胞自动机方法，其中实施伊利石和针铁矿的原型。模拟允许评估聚集过程中粒子排列的形成，此外构建单位直径和离散粒子的数量。颗粒之间的接触面积被评估为稳定性的定量测量。在吸引范德华力的唯一影响下，伊利石的均聚能够实现面对面和边缘到面对面的接触，从而形成具有小平均直径和比表面积的紧凑结构。相比之下，带负电的面和带正电的边缘之间的静电吸引力有利于形成更大的卡屋结构，其中低接触面积表明所得 BU 的稳定性低。在恒定 AR 下，不同粒径伊利石的均聚导致不同稳定性的 BU，更准确地说，较小的粒径导致更稳定的 BU。在保持粒度不变的情况下，伊利石的 AR 变化表明最稳定的 BU 来自具有最小 AR 的伊利石。由于细伊利石附着在带负电荷的边缘而屏蔽粗针铁矿颗粒增加了未聚集的离散细伊利石颗粒的数量。由于伊利石颗粒之间的静电引力，带正电边缘的伊利石聚集与带负电边缘的模拟结果存在根本差异。不使用拟合参数的模拟设置导致了实验室结果的适当近似。通过阐明周转动态和提供定量数据，模拟清楚地促进了对微聚集建筑单元形成和稳定性的理解。由于伊利石颗粒之间的静电引力，带正电边缘的伊利石聚集与带负电边缘的模拟结果存在根本差异。不使用拟合参数的模拟设置导致了实验室结果的适当近似。通过阐明周转动态和提供定量数据，模拟清楚地促进了对微聚集建筑单元形成和稳定性的理解。由于伊利石颗粒之间的静电引力，带正电边缘的伊利石聚集与带负电边缘的模拟结果存在根本差异。不使用拟合参数的模拟设置导致了实验室结果的适当近似。通过阐明周转动态和提供定量数据，模拟清楚地促进了对微聚集建筑单元形成和稳定性的理解。