Hu Feinan, Li Hang, Liu Xinmin, Li Song, Ding Wuquan, Xu Chenyang, Li Yue, Zhu Longhui
Chongqing Key Laboratory of Soil Multi-Scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing, China.
PLoS One. 2015 Apr 15;10(4):e0122460. doi: 10.1371/journal.pone.0122460. eCollection 2015.
Soil particle interactions are strongly influenced by the concentration, valence and ion species and the pH of the bulk solution, which will also affect aggregate stability and particle transport. In this study, we investigated clay aggregate stability in the presence of different alkali ions (Li+, Na+, K+, and Cs+) at concentrations from10-5 to 10-1 mol L-1. Strong specific ion effects on clay aggregate stability were observed, and showed the order Cs+>K+>Na+>Li+. We found that it was not the effects of ion size, hydration, and dispersion forces in the cation-surface interactions but strong non-classic polarization of adsorbed cations that resulted in these specific effects. In this study, the non-classic dipole moments of each cation species resulting from the non-classic polarization were estimated. By comparing non-classic dipole moments with classic values, the observed dipole moments of adsorbed cations were up to 104 times larger than the classic values for the same cation. The observed non-classic dipole moments sharply increased with decreasing electrolyte concentration. We conclude that strong non-classic polarization could significantly suppress the thickness of the diffuse layer, thereby weakening the electric field near the clay surface and resulting in improved clay aggregate stability. Even though we only demonstrated specific ion effects on aggregate stability with several alkali ions, our results indicate that these effects could be universally important in soil aggregate stability.
土壤颗粒间的相互作用受本体溶液的浓度、价态、离子种类及pH值的强烈影响，这些因素也会影响团聚体稳定性和颗粒迁移。在本研究中，我们研究了在浓度为10⁻⁵至10⁻¹ mol L⁻¹的不同碱金属离子（Li⁺、Na⁺、K⁺和Cs⁺）存在下黏土团聚体的稳定性。观察到特定离子对黏土团聚体稳定性有强烈影响，其顺序为Cs⁺>K⁺>Na⁺>Li⁺。我们发现，导致这些特定效应的并非阳离子-表面相互作用中离子大小、水合作用和分散力的影响，而是吸附阳离子的强烈非经典极化作用。在本研究中，估算了由非经典极化作用导致的各阳离子物种的非经典偶极矩。通过将非经典偶极矩与经典值进行比较，发现吸附阳离子的观测偶极矩比相同阳离子的经典值大10⁴倍。观测到的非经典偶极矩随电解质浓度降低而急剧增加。我们得出结论，强烈的非经典极化作用可显著抑制扩散层厚度，从而减弱黏土表面附近的电场，提高黏土团聚体稳定性。尽管我们仅用几种碱金属离子证明了特定离子对团聚体稳定性的影响，但我们的结果表明，这些效应在土壤团聚体稳定性方面可能普遍具有重要意义。
