Soil particle interaction forces/energies control aggregation and breakup/dispersion processes, which further profoundly affect a series of soil micro- and macro-processes. For soils with complex compositions, it is the interaction energy of different particles that determines particle aggregation and aggregate breakdown/dispersion. However, measuring the interaction energy for complex systems remains a challenge. In this study we proposed a method to measure this van der Waals potential energy using the dynamic light scattering technique. Firstly, the mathematic relationship between the mean aggregation rate and van der Waals potential energy was established. The mean aggregation rates of particles for either simple or complex systems can be facilely determined by the dynamic light scattering technique. Secondly, for verifying the availability of the suggested method, montmorillonite suspensions in four different electrolyte solutions (NaCl, KCl, MgCl₂ and CaCl₂) were respectively employed to measure the van der Waals potential energy, which equals −17,817 ± 857 J mol⁻¹ or −7.22 ± 0.304 kT with an average deviation of 4.22%; this directly verified the reliability of the suggested method. Thirdly, the proposed method was also verified indirectly and independently by the ratio of the electrostatic potential energy of particles to the presence of K⁺ and Na⁺, as compared with the ratios from the determined van der Waals potential energy of this study and from cation adsorption selectivity. Considering the dynamic light scattering technique has been widely applied for characterizing soil/clay/humus/microbe aggregation, the proposed method should be appropriate for measuring the van der Waals potential energy for all those systems.

中文翻译：

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动态光散射法测定黏土颗粒相互作用范德华势能的方法

土壤颗粒相互作用力/能量控制聚集和分解/分散过程，这进一步深刻地影响了一系列土壤微观和宏观过程。对于成分复杂的土壤，决定颗粒聚集和聚集体分解/分散的是不同颗粒之间的相互作用能。然而，测量复杂系统的相互作用能仍然是一个挑战。在这项研究中，我们提出了一种使用动态光散射技术测量这种范德华势能的方法。首先，建立了平均聚集率与范德华势能之间的数学关系。无论是简单系统还是复杂系统，粒子的平均聚集率都可以通过动态光散射技术轻松确定。其次，₂和CaCl ₂ ) 分别用于测量范德华势能，其等于-17,817 ± 857 J mol ^-1或-7.22 ± 0.304 kT，平均偏差为4.22%；这直接验证了所建议方法的可靠性。第三，还通过粒子的静电势能与 K ⁺和 Na ⁺的存在之比间接和独立地验证了所提出的方法，与本研究确定的范德华势能和阳离子吸附选择性的比率相比。考虑到动态光散射技术已广泛应用于表征土壤/粘土/腐殖质/微生物聚集体，所提出的方法应该适用于测量所有这些系统的范德华势能。