Abstract Recent studies have shown that, soil particle interaction forces strongly affect soil water movement. Classically, humus could increase the attractive forces through the complex interactions between humus and clay particles, but in the meanwhile humus could increase soil electric field and thus increase electrostatic repulsive forces due to surface charges of humus. On the other hand, electrolyte concentrations could affect soil particle interactions through the influence on soil electric field and osmotic pressure. Therefore, the effect of humus and electrolyte concentration would be coupled in soil water movement. In this study, the coupling effects were explored with a purple soil under different humus contents and MgCl2 concentrations. The results showed that: (i) the total repulsive energies among soil particles would increase with increasing humus content, and soil aggregate stability as well as the soil water transportation and infiltration would correspondingly decrease; (ii) a critical MgCl2 concentration was observed, and at the critical concentration the total repulsive energy was the lowest, while both the soil aggregate stability and soil water movement were the highest; (iii) humus content did not significantly change the critical concentrations. The analysis of water movement changing with soil particle interaction energy showed that, both of them decreased linearly with increasing total repulsive energies between soil particles, and different humus contents obeyed the same linear relationship for water movement. We concluded that, (i) the total repulsive energies between soil particles control soil water movement through their effect on soil aggregate stability; (ii) humus affected soil water movement mainly through its effect on the total repulsive energy between soil particles; (iii) the total repulsive energy was mainly from the electrostatic repulsive force among soil particles as MgCl2 concentration was lower than the critical concentration, while it was mainly from the osmotic pressure when the MgCl2 concentration was higher than the critical concentration.

中文翻译：

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腐殖质与2:1型电解质对土壤水分运动的耦合作用

摘要 近年来的研究表明，土壤颗粒相互作用力强烈影响土壤水分运动。传统上，腐殖质可以通过腐殖质和粘土颗粒之间的复杂相互作用来增加吸引力，但同时腐殖质可以增加土壤电场，从而由于腐殖质表面电荷而增加静电排斥力。另一方面，电解质浓度可以通过影响土壤电场和渗透压来影响土壤颗粒相互作用。因此，腐殖质和电解质浓度的影响将在土壤水分运动中耦合。在这项研究中，在不同腐殖质含量和 MgCl2 浓度下，用紫色土壤探索了耦合效应。结果表明：(i) 土壤颗粒间的总排斥能随着腐殖质含量的增加而增加，土壤团聚体稳定性以及土壤水分输送和入渗量相应降低；(ii) 观察到临界 MgCl2 浓度，在临界浓度下，总排斥能最低，而土壤团聚体稳定性和土壤水分运动均最高；(iii) 腐殖质含量没有显着改变临界浓度。水分运动随土壤颗粒相互作用能变化的分析表明，两者均随土壤颗粒间总排斥能的增加呈线性下降，且不同腐殖质含量对水分运动具有相同的线性关系。我们得出的结论是，(i) 土壤颗粒之间的总排斥能通过它们对土壤团聚体稳定性的影响来控制土壤水分运动；(ii) 腐殖质主要通过其对土壤颗粒间总排斥能的影响来影响土壤水分运动；(iii)当MgCl2浓度低于临界浓度时，总排斥能主要来自土壤颗粒之间的静电排斥力，而当MgCl2浓度高于临界浓度时，它主要来自渗透压。