离子界面反应对土壤水分入渗的影响
发布时间：2018-08-26 09:13
【摘要】：土壤水分入渗是地球水循环中的一个重要环节,它不仅直接影响土壤水的存储和地表径流的形成,也间接影响降水的资源化利用、土壤侵蚀和农田面源污染的发生,因而引起农业和环境科学研究者的广泛关注。土壤水分入渗是一个极其复杂的过程,长期以来土壤学研究者已经对其进行了大量的定量研究,但对于土壤这个复杂系统而言,现有的土壤水分运动模型对于定量描述水分运动过程还有诸多问题,其中主要问题是经典理论模型不恰当地把土壤结构处理为一种刚性结构,即假定在水分运动过程中土壤结构不发生变化。然而众所周知,水分进入土壤后,土壤结构孔隙都将发生一系列重要变化,从而极大地影响土壤水入渗和土壤水传输。早期研究已经发现,同一土壤,当电解质类型和浓度不同时,土壤水入渗与传输表现出完全不同的特征,但其产生原因不清楚;而后来的研究证实,同一土壤,当电解质类型和浓度不同时,团聚体稳定性也表现不同。由此可以推断,电解质类型和浓度可能是通过影响土壤结构的孔隙状况来影响土壤水运动。近期研究发现,当水分进入土壤后,土壤溶液中电解质被稀释,改变了颗粒表面附近双电层结构,电场强度迅速增大,静电排斥力增强,土壤结构遭到破坏。因此,用于描述土壤颗粒静电学特性的双电层理论和土壤颗粒相互作用的DLVO(Derjaguin-Landau-Verwey-Overbeek)理论或扩展的DLVO理论似乎可以用来描述土壤水的运动。然而,已有研究发现,当水中分别含有KCl和Na Cl时,同一土壤水的运动速度可以出现数倍的差,这一现象被称为离子特异性效应(Specific ion effects)或Hofmeister效应。有关离子特异性效应研究工作受到包括土壤学等各领域科学家的广泛关注,新近研究表明电场-量子涨落耦合作用是离子特异性效应产生的主要原因。因此,本研究从离子界面反应对颗粒表面双电层结构和颗粒间相互作用影响出发,首先理论推导得到单一和混合电解质体系中带电颗粒扩散双电层中滑动层厚度的计算关系表达式,定量表征颗粒表面双电层结构变化对表面电位和静电斥力的影响;其次利用测定得到土壤表面的Stern电位值对颗粒间相互作用力进行定量计算,建立土壤水分入渗速率与颗粒间相互作用力定量关系,分析静电斥力对土壤水分入渗的影响;第三,通过土壤水分入渗离子特异性效应实验,揭示电场-量子涨落耦合作用中离子Hofmeister能量对水分入渗的影响;第四,采用动态光散射技术和工业CT扫描技术表征土壤颗粒凝聚/分散过程和孔隙状况,为进一步解释离子界面反应下颗粒间相互作用对土壤水分入渗的影响提供支撑。通过4个方面的研究工作,阐明离子界面反应下颗粒间相互作用对界面性质及对土壤水分入渗的影响机制。本工作取得的主要结果如下:(1)理论推导得到单一电解质体系中胶体颗粒扩散双电层中滑动层厚度的计算关系表达式,定量表征了离子界面反应对胶体扩散双电层结构和静电斥力的影响。根据单一电解质体系中的Gouy-Chapman方程中电位与距离之间关系的解析解,理论推导得到了单一电解质体系中带电胶体颗粒扩散双电层中滑动层厚的计算关系式。并且通过实验测定,然后计算得到不同电解质体系中蒙脱石和紫色土胶体颗粒扩散双电层中滑动层厚值,在2:1型电解质体系中滑动层厚值远小于1:1型电解质体系。滑动面离均扩散双电层Stern层较远,而与双电层中Gouy层靠近,对胶体扩散双电层结构有了新的认识。基于这种新的认识才能对胶体颗粒表面电位、电场强度和静电斥力进行正确表征,实验测定了蒙脱石矿物和紫色土胶体颗粒的在单一的Stern电位和zeta电位值,发现在不同电解质体系中前者是后者的3~6倍。采用zeta电位值代替Stern电位值将大大降低胶体颗粒表面电场强度值和颗粒间静电斥力,紫色土胶体颗粒间电场强度值和静电排斥力最大分别可降低1~2和4个数量级。因此,对于滑动面在胶体扩散双电层中位置的新认识可以正确表征土壤颗粒表面电位,进而才可以正确反映静电斥力如何影响颗粒间相互作用,最终才能正确揭示颗粒间相互作用对水分入渗的影响。(2)理论推导得到混合电解质体系中胶体颗粒扩散双电层中滑动层厚度的计算关系表达式,定量表征了离子界面反应对胶体扩散双电层结构和电学性质的影响。根据混合电解质体系中电位与距离之间关系的解析解,推导得到混合电解质体系中蒙脱石胶体颗粒扩散双电层中滑动层厚的计算关系式,实验得到蒙脱石矿物胶体扩散双电层中滑动面同样离双电层Stern层较远,而与双电层中Gouy层靠近,并且2价阳离子对其厚度影响远大于1价阳离子。基于胶体扩散双电层结构新的认识,对混合电解质体系中胶体颗粒表面电位和电场强度进行了表征,得到蒙脱石胶体颗粒的在混合电解质体系中的Stern电位绝对值均远大于zeta电位绝对值,是其值的4~5倍。对于混合电解质体系中胶体双电层结构的新认识,可以正确表征胶体颗粒表面电位值,为进一步正确描述混合电解质体系中土壤水分入渗过程奠定了理论基础。(3)离子界面反应下颗粒相互作用决定了土壤水分入渗速率。通过对颗粒间的静电排斥压、范德华引力以及表面水合斥力的定量计算,发现土壤静电斥力决定了土壤团聚体的状态以及土壤水分入渗过程。通过对胶体扩散双电层新认识正确表征了土壤颗粒表面电位,进一步计算得到颗粒间静电斥力。颗粒间静电斥力导致土壤团聚体爆裂,释放的小颗粒不同程度地堵塞土壤孔隙(依赖于静电斥力的强度),从而降低土壤水分入渗速率。相应地,当静电排斥力较弱时,颗粒间表现为净的吸引力,土壤团聚体不发生爆裂过程,土壤孔隙不被堵塞从而使得土壤水分入渗速率提高。理论计算表明,两种离子体系中土壤颗粒间存在一个净引力的临界点,MgCl_2体系下在0.005 mol L~(-1)时出现临界点,Na Cl体系下在0.1 mol L~(-1)时出现临界点。此理论计算得到临界点出现的浓度与土壤水分入渗实验观察的临界点浓度一致。在Mg~(2+)体系下,这种团聚体的膨胀比较弱,而Na~+体系下团聚体的膨胀显著强于Mg~(2+)体系。因此,实验观察的土壤水分入渗速率在团聚体非爆裂阶段仍然表现为Na~+Mg~(2+)。从而我们得出土壤团聚体爆裂或者某种程度的团聚体膨胀影响了土壤水分入渗。离子-颗粒相互作用决定着土壤电场的强弱,进而影响着土壤水分入渗速率的快慢。(4)较系统分析了土壤水分入渗的离子特异性效应,并阐明了该效应产生的机制——“电场-量子涨落”耦合作用。在Li~+,Na~+,K~+,Cs~+离子体系中土壤水分入渗存在强烈的离子特异性效应。对于同一土壤样品,Li~+,Na~+,K~+,Cs~+离子体系中不同浓度条件下的水分入渗最大速率分别为:1.8 cm h~(-1),4.3 cm h~(-1),5.2 cm h~(-1),13.0 cm h~(-1)。颗粒间的DLVO合力加上水合斥力共同决定了土壤水分入渗速率;DLVO合力与水合斥力均存在强烈的离子特异性效应,该效应可通过离子的Hofmeister能量给予定量表征,在Li~+,Na~+,K~+及Cs~+体系下Hofmeister能量分别为:0.06Fφ(0),0.18Fφ(0),0.94Fφ(0)和1.86Fφ(0);只有当考虑“电场-量子涨落”耦合作用的DLVO合力与水合斥力才能正确解释土壤水分入渗中的离子特异性效应。水合斥力来源于土壤颗粒的表面水合与双电层中离子水合的共同作用。颗粒的水合斥力受到电解质浓度的复杂影响,双电层厚度与离子在双电层中的分布均受到离子Hofmeister能量的强烈影响。(5)采用动态光散射技术和工业CT扫描技术探究了离子界面反应下颗粒相互作用对土壤颗粒凝聚/分散过程和孔隙状况的影响。通过这两种分析技术分别表征了不同价离子和相同价离子体系中土壤凝聚/分散过程和孔隙分布状况。紫色土在Na~+和Mg~(2+)体系下的CCC值(临界聚沉浓度)分别为91.6 mmol L~(-1)和4.83 mmol L~(-1),表现为Na~+Mg~(2+),在Li~+,Na~+,K~+和Cs~+体系下的CCC值分别为280.9,91.6,47.8和5.2 mmol L~(-1),表现为Li~+Na~+K~+Cs~+。在Mg~(2+)体系土体中1 mm土壤孔隙体积占所有孔隙比例达到50.4%,1 mm孔隙数量占1.43%;而在Na~+体系土体中1 mm土壤孔隙体积只占40.2%,1 mm孔隙数量仅占1.06%;并且,前者1 mm土壤孔隙体积是后者的1.42倍。Li~+,Na~+,K~+和Cs~+体系下的土体中1 mm土壤孔隙体积占所有孔隙比例分别为22.8%,40.2%,56.4%和59.9%,1 mm孔隙数量所占比例分别为0.32%,1.06%,1.57%,和1.88%。通过进一步计算,可以得到Cs~+体系下土体中1 mm土壤孔隙体积分别为,Li~+,Na~+,K~+体系下的13.7,5.22,2.70倍。通过不同电解质体系中的土壤颗粒凝聚/分散过程和孔隙状况数据可以进一步解释离子界面反应下颗粒相互作用对土壤水分入渗影响的内在机制。综合上述几个方面的研究结果,本研究主要得到如下结论:1)建立了单一和混合电解质体系下带电胶体扩散双电层中滑动面厚度的理论和方法,对胶体扩散双电层结构有了新的认识,并以此确立了须采用Stern电位定量描述颗粒间相互作用才能正确反映其对土壤水分入渗的影响;2)土壤表面电位值决定着水分入渗速率大小,电解质类型和浓度通过调节表面电场强度影响颗粒间相互作用决定着土壤颗粒的凝聚/分散过程,改变土壤小颗粒释放过程,影响土壤孔隙状况,最终改变土壤水分入渗过程;3)土壤水分入渗过程表现出强烈的离子特异性效应,通过电场-量子涨落耦合作用中离子Hofmeister能量影响DLVO合力与水合斥力,使土壤结构稳定性产生差异,影响土壤孔隙状况,最终改变土壤水分入渗过程。综上所述,基于本研究发现土壤水分入渗过程受土壤颗粒间相互作用控制,这为我们提供了一种可能的内部调控途径,即通过调节土壤颗粒间相互作用来控制土壤水分入渗的快慢。
[Abstract]:Soil water infiltration is an important part of the earth's water cycle. It not only directly affects the storage of soil water and the formation of surface runoff, but also indirectly affects the resource utilization of precipitation, soil erosion and the occurrence of non-point source pollution in farmland. Therefore, it has attracted wide attention of agricultural and environmental scientists. For a long time, soil researchers have done a lot of quantitative research on the complex process. However, there are still many problems in describing the process of soil water movement quantitatively with the existing soil water movement model. The main problem is that the classical theoretical model does not properly treat the soil structure as a kind of soil structure. Rigid structure, i.e. the assumption that soil structure does not change during water movement. However, it is well known that when water enters the soil, a series of important changes will occur in soil structure pores, which greatly affect soil water infiltration and soil water transport. Soil water infiltration and transport exhibit completely different characteristics, but the causes are not clear. Later studies have confirmed that the stability of aggregates varies with the type and concentration of electrolytes in the same soil. Recent studies have found that when water enters the soil, electrolytes in the soil solution are diluted, which changes the structure of the double layer near the surface of the particles. The electric field strength increases rapidly, the electrostatic repulsion force increases, and the soil structure is destroyed. VO (Derjaguin-Landau-Verwey-Overbeek) theory or extended DLVO theory seem to be able to describe the movement of soil water. However, it has been found that when the water contains KCl and Na Cl respectively, the velocity of the same soil water can be several times different. This phenomenon is called ion-specific effects or Hofmeist. Recent studies have shown that the coupling of electric field and quantum fluctuation is the main reason for the ion-specific effect. Therefore, this study focuses on the effects of ion-interface reactions on the structure of electric double layer on the surface of particles and the interaction between particles. Firstly, the formula of calculating the thickness of sliding layer in charged particle diffused double layer in single and mixed electrolyte system was deduced theoretically, which quantitatively characterizes the influence of the structure change of double layer on the surface of particles on the surface potential and electrostatic repulsion force. The relationship between soil water infiltration rate and intergranular interaction force was established by quantitative calculation, and the effect of electrostatic repulsion on soil water infiltration was analyzed. Dynamic light scattering (DLS) and industrial computed tomography (ICT) scans were used to characterize the coagulation/dispersion process and pore size distribution of soil particles, which provided support for further explaining the effect of particle-particle interaction on soil water infiltration under ion-interface reaction. The main results obtained in this work are as follows: (1) The formula for calculating the slip layer thickness in the colloidal diffused double layer in a single electrolyte system is derived theoretically, and the effect of ionic interface reaction on the structure and electrostatic repulsion of the colloidal diffused double layer is quantitatively characterized. Analytical solution of the relationship between potential and distance in Gouy-Chapman equation in the system is deduced theoretically. The formula for calculating the slip layer thickness of charged colloidal particles in a single electrolyte system is deduced theoretically. The slip layer thickness in the 2:1 electrolyte system is much less than that in the 1:1 electrolyte system. The slip surface is far from the Stern layer and near the Gouy layer in the double electrolyte layer. A new understanding of the structure of the colloidal diffusion double electrolyte layer can be obtained based on this new understanding. The Stern potential and zeta potential of montmorillonite minerals and purple soil colloidal particles were measured experimentally. It was found that the former was 3-6 times higher than the latter in different electrolyte systems. Therefore, the new understanding of the location of the sliding surface in the colloid diffusion double layer can correctly characterize the surface potential of soil particles, and then can correctly reflect how the electrostatic repulsion affects the interaction between particles, and finally can correctly reveal. (2) Formulas for calculating the thickness of the sliding layer in the colloidal particle diffusion double layer in the mixed electrolyte system were deduced theoretically, which quantitatively characterize the effect of ionic interface reaction on the structure and electrical properties of the colloidal diffusion double layer. The analytical solution of the relationship is derived and the formula for calculating the slip layer thickness in the diffused double layer of montmorillonite colloidal particles in the mixed electrolyte system is derived. The experimental results show that the slip surface in the diffused double layer of Montmorillonite Mineral colloidal particles is also farther away from the double layer Stern layer, but closer to the Gouy layer in the double layer, and the effect of 2 valent cations on its thickness is great. Based on the new understanding of colloidal diffusion double layer structure, the surface potential and electric field intensity of colloidal particles in the mixed electrolyte system were characterized. It was found that the absolute value of Stern potential of montmorillonite colloidal particles in the mixed electrolyte system was much higher than that of zeta potential, which was 4-5 times of that of the mixed electrolyte system. A new understanding of the structure of the colloidal double layer in the system can correctly characterize the surface potential of colloidal particles and lay a theoretical foundation for further describing the process of soil water infiltration in the mixed electrolyte system. (3) Particle interaction in the ionic interface reaction determines the rate of soil water infiltration. Quantitative calculation of Dehua gravity and surface hydration repulsion showed that soil electrostatic repulsion determined the state of soil aggregates and the infiltration process of soil water. When the electrostatic repulsion force is weak, the net attraction between the particles appears, the soil aggregates do not burst, and the soil pores are not blocked so that the soil water infiltrates into the soil. The theoretical calculation shows that there is a critical point of net gravity between the two ionic systems. The critical point appears at 0.005 mol L~(-1) in MgCl_2 system and at 0.1 mol L~(-1) in Na Cl system. In the Mg~ (2+) system, the swelling of the aggregates is relatively weak, and the swelling of the aggregates in the Na~+ system is significantly stronger than that in the Mg~ (2+) system. Therefore, the experimental observation of soil water infiltration rate in the non-bursting stage of the aggregates still shows Na~+Mg~ (2+). Thus we can conclude that the soil aggregates burst or some degree of aggregate expansion. Ion-particle interaction determines the strength of soil electric field, and then affects the speed of soil water infiltration. (4) The ion-specific effect of soil water infiltration is systematically analyzed, and the mechanism of this effect is clarified - "electric field-quantum fluctuation" coupling effect. For the same soil sample, the maximum infiltration rates of Li~+, Na~+, K~+, and Cs~+ under different concentrations are 1.8 cm h~(-1), 4.3 cm h~(-1), 5.2 cm h~(-1) and 13.0 cm h~(-1), respectively. Soil water infiltration rate; DLVO resultant force and hydraulic repulsion force have strong ion-specific effects, which can be quantitatively characterized by the Hofmeister energy of ions. In Li~+, Na~+, K~+ and Cs~+ systems, the Hofmeister energy is 0.06 F phi (0), 0.18 F phi (0), 0.94 F phi (0) and 1.86 F phi (0), respectively; only when the coupling of "electric field-quantum fluctuation" is considered. Hydration repulsion comes from the interaction between surface hydration of soil particles and ionic hydration in the electric double layer. Hydration repulsion of particles is affected by the complex concentration of electrolyte, and the distribution of the thickness and ions in the electric double layer. (5) Dynamic light scattering (DLS) and industrial computed tomography (ICT) were used to investigate the effects of particle interaction on the coagulation/dispersion process and pore size distribution of soil particles under the ion-interface reaction. The CCC values of purple soils in Na~+ and Mg~ (2+) systems (critical concentration of aggregation) are 91.6 mmol L~(-1) and 4.83 mmol L~(-1), respectively. The CCC values of purple soils in Li~+, Na~+, K~+ and Cs~+ systems are 280.9, 91.6, 47.8 and 5.2 mmol ~(-1), respectively. 1 mm soil pore volume accounted for 50.4% of all pore volume, 1 mm soil pore volume accounted for 1.43%; while 1 mm soil pore volume accounted for only 40.2% in Na~+ system, 1 mm soil pore volume accounted for only 1.06%; and the former 1 mm soil pore volume was 1.42 times of the latter 1.42 times. The void fractions were 22.8%, 40.2%, 56.4% and 59.9% respectively, and the void fractions of 1 mm were 0.32%, 1.06%, 1.57% and 1.88% respectively. The dispersion process and pore size data can further explain the intrinsic mechanism of the effect of particle interaction on soil water infiltration under the ionic interface reaction. Based on the above results, the main conclusions are as follows: 1) The thickness of sliding surface in charged colloidal diffusive double layer with single and mixed electrolyte system is established. The theory and method have a new understanding of the structure of colloid diffusion double layer, and it is established that the interaction between particles must be quantitatively described by Stern potential in order to correctly reflect its effect on soil water infiltration; 2) The value of soil surface potential determines the infiltration rate, and the type and concentration of electrolyte can be regulated by adjusting the surface electric field intensity. Degree affects the aggregation/dispersion process of soil particles, changes the release process of soil particles, affects soil porosity, and ultimately changes the infiltration process of soil water; 3) Soil water infiltration process shows strong ion-specific effect, and ionic Hofmeister energy through the coupling of electric field and quantum fluctuation. Influencing DLVO resultant force and hydraulic repulsive force, making the stability of soil structure different, affecting soil porosity, and ultimately changing soil water infiltration
【学位授予单位】：西南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S152.72
，
本文编号：2204399
[Abstract]:Soil water infiltration is an important part of the earth's water cycle. It not only directly affects the storage of soil water and the formation of surface runoff, but also indirectly affects the resource utilization of precipitation, soil erosion and the occurrence of non-point source pollution in farmland. Therefore, it has attracted wide attention of agricultural and environmental scientists. For a long time, soil researchers have done a lot of quantitative research on the complex process. However, there are still many problems in describing the process of soil water movement quantitatively with the existing soil water movement model. The main problem is that the classical theoretical model does not properly treat the soil structure as a kind of soil structure. Rigid structure, i.e. the assumption that soil structure does not change during water movement. However, it is well known that when water enters the soil, a series of important changes will occur in soil structure pores, which greatly affect soil water infiltration and soil water transport. Soil water infiltration and transport exhibit completely different characteristics, but the causes are not clear. Later studies have confirmed that the stability of aggregates varies with the type and concentration of electrolytes in the same soil. Recent studies have found that when water enters the soil, electrolytes in the soil solution are diluted, which changes the structure of the double layer near the surface of the particles. The electric field strength increases rapidly, the electrostatic repulsion force increases, and the soil structure is destroyed. VO (Derjaguin-Landau-Verwey-Overbeek) theory or extended DLVO theory seem to be able to describe the movement of soil water. However, it has been found that when the water contains KCl and Na Cl respectively, the velocity of the same soil water can be several times different. This phenomenon is called ion-specific effects or Hofmeist. Recent studies have shown that the coupling of electric field and quantum fluctuation is the main reason for the ion-specific effect. Therefore, this study focuses on the effects of ion-interface reactions on the structure of electric double layer on the surface of particles and the interaction between particles. Firstly, the formula of calculating the thickness of sliding layer in charged particle diffused double layer in single and mixed electrolyte system was deduced theoretically, which quantitatively characterizes the influence of the structure change of double layer on the surface of particles on the surface potential and electrostatic repulsion force. The relationship between soil water infiltration rate and intergranular interaction force was established by quantitative calculation, and the effect of electrostatic repulsion on soil water infiltration was analyzed. Dynamic light scattering (DLS) and industrial computed tomography (ICT) scans were used to characterize the coagulation/dispersion process and pore size distribution of soil particles, which provided support for further explaining the effect of particle-particle interaction on soil water infiltration under ion-interface reaction. The main results obtained in this work are as follows: (1) The formula for calculating the slip layer thickness in the colloidal diffused double layer in a single electrolyte system is derived theoretically, and the effect of ionic interface reaction on the structure and electrostatic repulsion of the colloidal diffused double layer is quantitatively characterized. Analytical solution of the relationship between potential and distance in Gouy-Chapman equation in the system is deduced theoretically. The formula for calculating the slip layer thickness of charged colloidal particles in a single electrolyte system is deduced theoretically. The slip layer thickness in the 2:1 electrolyte system is much less than that in the 1:1 electrolyte system. The slip surface is far from the Stern layer and near the Gouy layer in the double electrolyte layer. A new understanding of the structure of the colloidal diffusion double electrolyte layer can be obtained based on this new understanding. The Stern potential and zeta potential of montmorillonite minerals and purple soil colloidal particles were measured experimentally. It was found that the former was 3-6 times higher than the latter in different electrolyte systems. Therefore, the new understanding of the location of the sliding surface in the colloid diffusion double layer can correctly characterize the surface potential of soil particles, and then can correctly reflect how the electrostatic repulsion affects the interaction between particles, and finally can correctly reveal. (2) Formulas for calculating the thickness of the sliding layer in the colloidal particle diffusion double layer in the mixed electrolyte system were deduced theoretically, which quantitatively characterize the effect of ionic interface reaction on the structure and electrical properties of the colloidal diffusion double layer. The analytical solution of the relationship is derived and the formula for calculating the slip layer thickness in the diffused double layer of montmorillonite colloidal particles in the mixed electrolyte system is derived. The experimental results show that the slip surface in the diffused double layer of Montmorillonite Mineral colloidal particles is also farther away from the double layer Stern layer, but closer to the Gouy layer in the double layer, and the effect of 2 valent cations on its thickness is great. Based on the new understanding of colloidal diffusion double layer structure, the surface potential and electric field intensity of colloidal particles in the mixed electrolyte system were characterized. It was found that the absolute value of Stern potential of montmorillonite colloidal particles in the mixed electrolyte system was much higher than that of zeta potential, which was 4-5 times of that of the mixed electrolyte system. A new understanding of the structure of the colloidal double layer in the system can correctly characterize the surface potential of colloidal particles and lay a theoretical foundation for further describing the process of soil water infiltration in the mixed electrolyte system. (3) Particle interaction in the ionic interface reaction determines the rate of soil water infiltration. Quantitative calculation of Dehua gravity and surface hydration repulsion showed that soil electrostatic repulsion determined the state of soil aggregates and the infiltration process of soil water. When the electrostatic repulsion force is weak, the net attraction between the particles appears, the soil aggregates do not burst, and the soil pores are not blocked so that the soil water infiltrates into the soil. The theoretical calculation shows that there is a critical point of net gravity between the two ionic systems. The critical point appears at 0.005 mol L~(-1) in MgCl_2 system and at 0.1 mol L~(-1) in Na Cl system. In the Mg~ (2+) system, the swelling of the aggregates is relatively weak, and the swelling of the aggregates in the Na~+ system is significantly stronger than that in the Mg~ (2+) system. Therefore, the experimental observation of soil water infiltration rate in the non-bursting stage of the aggregates still shows Na~+Mg~ (2+). Thus we can conclude that the soil aggregates burst or some degree of aggregate expansion. Ion-particle interaction determines the strength of soil electric field, and then affects the speed of soil water infiltration. (4) The ion-specific effect of soil water infiltration is systematically analyzed, and the mechanism of this effect is clarified - "electric field-quantum fluctuation" coupling effect. For the same soil sample, the maximum infiltration rates of Li~+, Na~+, K~+, and Cs~+ under different concentrations are 1.8 cm h~(-1), 4.3 cm h~(-1), 5.2 cm h~(-1) and 13.0 cm h~(-1), respectively. Soil water infiltration rate; DLVO resultant force and hydraulic repulsion force have strong ion-specific effects, which can be quantitatively characterized by the Hofmeister energy of ions. In Li~+, Na~+, K~+ and Cs~+ systems, the Hofmeister energy is 0.06 F phi (0), 0.18 F phi (0), 0.94 F phi (0) and 1.86 F phi (0), respectively; only when the coupling of "electric field-quantum fluctuation" is considered. Hydration repulsion comes from the interaction between surface hydration of soil particles and ionic hydration in the electric double layer. Hydration repulsion of particles is affected by the complex concentration of electrolyte, and the distribution of the thickness and ions in the electric double layer. (5) Dynamic light scattering (DLS) and industrial computed tomography (ICT) were used to investigate the effects of particle interaction on the coagulation/dispersion process and pore size distribution of soil particles under the ion-interface reaction. The CCC values of purple soils in Na~+ and Mg~ (2+) systems (critical concentration of aggregation) are 91.6 mmol L~(-1) and 4.83 mmol L~(-1), respectively. The CCC values of purple soils in Li~+, Na~+, K~+ and Cs~+ systems are 280.9, 91.6, 47.8 and 5.2 mmol ~(-1), respectively. 1 mm soil pore volume accounted for 50.4% of all pore volume, 1 mm soil pore volume accounted for 1.43%; while 1 mm soil pore volume accounted for only 40.2% in Na~+ system, 1 mm soil pore volume accounted for only 1.06%; and the former 1 mm soil pore volume was 1.42 times of the latter 1.42 times. The void fractions were 22.8%, 40.2%, 56.4% and 59.9% respectively, and the void fractions of 1 mm were 0.32%, 1.06%, 1.57% and 1.88% respectively. The dispersion process and pore size data can further explain the intrinsic mechanism of the effect of particle interaction on soil water infiltration under the ionic interface reaction. Based on the above results, the main conclusions are as follows: 1) The thickness of sliding surface in charged colloidal diffusive double layer with single and mixed electrolyte system is established. The theory and method have a new understanding of the structure of colloid diffusion double layer, and it is established that the interaction between particles must be quantitatively described by Stern potential in order to correctly reflect its effect on soil water infiltration; 2) The value of soil surface potential determines the infiltration rate, and the type and concentration of electrolyte can be regulated by adjusting the surface electric field intensity. Degree affects the aggregation/dispersion process of soil particles, changes the release process of soil particles, affects soil porosity, and ultimately changes the infiltration process of soil water; 3) Soil water infiltration process shows strong ion-specific effect, and ionic Hofmeister energy through the coupling of electric field and quantum fluctuation. Influencing DLVO resultant force and hydraulic repulsive force, making the stability of soil structure different, affecting soil porosity, and ultimately changing soil water infiltration
【学位授予单位】：西南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S152.72
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本文编号：2204399
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