金属离子界面反应对粘粒水流迁移强度的影响
Clay Migration Intensity Driven by Water Flow as Influenced by Cation-Surface Interactions

土壤颗粒随水迁移常引发水土流失、农田面源污染等一系列环境问题的发生，且雨滴打击等外部作用被普遍认为是降水引发土粒迁移的主导作用，但土粒迁移的内在作用机制仍不十分清楚.本研究从一个新的角度探讨离子界面反应产生的粘粒间的内在作用力对粘粒水迁移的影响.为了能够准确计算粘粒间的作用力强度，以纯的蒙脱石粘土团聚体为材料，用Na⁺和K⁺两种一价阳离子来表征界面反应特征的差异.结果表明：1) Na⁺体系中粘土颗粒迁移强度远远大于同浓度下的K⁺体系；2) K⁺体系下的电场强度远低于同浓度下的Na⁺体系，相应地，Na⁺体系中粘粒间静电排斥力远强于K⁺体系；3)蒙脱石团聚体内部的静电场强度越强，颗粒间的静电排斥压越高，粘粒水迁移强度就越大.研究发现，团聚体中的电场强度主要通过颗粒间的静电排斥力影响粘粒水迁移，但在低电解质浓度下，这个电场还可能通过对水合斥力的影响来影响粘粒的水流迁移强度.本研究提出了在流水运动的外力作用下，引发粘粒迁移的内因驱动力：粘土团聚体中静电场产生的静电效应.由于本研究只考虑了流水的作用而没有考虑雨滴撞击力作用，所以本文并未否定雨滴击打对土壤迁移的重要作用.
Soil particle migration often causes soil erosion, agricultural non-point source pollution and other environmental problems. It is generally acknowledged that soil particle migration during rainfall is mainly attributed to raindrops and other external effects. However, its internal mechanism is still not clear. A study reported herein proposes a new perspective, i. e. how does the internal force between particles influence clay migration intensity? In order to accurately calculate the force between clay particles, pure montmorillonite aggregates were chosen in this experiment as the study material and two monovalent cation species (Na⁺ and K⁺) were employed to characterize the difference of ion-surface interactions. The results obtained were as follows. First, the clay migration intensity for Na⁺ system was higher than that for K⁺ system under the same electrolyte concentration. Second, the electrostatic field strength for K⁺ system was significantly lower than that for Na⁺ system under the same concentration. Correspondingly, the electrostatic repulsive pressure between clay particles for Na⁺ system was much greater than that for K⁺ system. Third, the electrostatic repulsive pressure between particles and the clay migration intensity increased with increasing electrostatic field intensity of montmorillonite. The study indicated that the clay migration intensity was mainly influenced by the electrostatic repulsive pressure from the electrostatic field strength of aggregates, but at low electrolyte concentrations, the electrostatic field also affected the clay migration intensity through the hydration repulsive force. In conclusion, this study suggested that the electrostatic effect generated by the