Coupling Of Soil Electric Field And Mechanic Composition On Soil Water Infiltration

Soil water movement is driven by the free energy of soil water or the gradient of soil water potential.In classical theory,the velocity of soil water movement is usually described by the Darcy equation and the Darcy–Richards equation.However,free energy is a thermodynamic concept.Many physical and chemical factors in soil often affect soil water free energy or soil water potential through very complicated methods,and then affect soil water movement.Although there are a large number of models to describe the movement of soil water,all these factors have affected the movement of soil water.The detailed physical mechanism remains unclear.Therefore,the elucidation of how some important physical and chemical factors in soil affect the free energy of soil water is of fundamental importance in the quantitative description of soil water movement.Soil pores are the channels through which soil water moves.Physical and chemical factors such as material composition in the soil,mechanical composition of the soil,surface charge of the particles,electrolyte composition in the soil,non-classical polarization in the ion-interface reaction determine all soil particles in the soil.The interactions between them determine the structure and pore conditions in the soil.In general,long-range molecular forces between soil particles and electrostatic forces?related to surface charges and surface ionic reactions?are the basic forces that interact with soil particles,so that in soil particles In the interaction,the surface charge of the soil,the adsorbed ions on the surface,and the mechanical composition of the soil are coupled to each other.Therefore,in this study,two kinds of soils with different surface charges,different ion-interface reactions and different mechanical compositions were used as experimental materials to study how the coupling of the soil electric field and the mechanical composition of soil affected the infiltration of soil water.Obtain the following research results:?1?In the course of water infiltration,the non-classical polarization of cations has a significant effect on soil water movement,and it does have a strong coupling effect with the mechanical composition of the soil.The non-classical polarization of cations influences the movement of soil water by affecting the strength of the electric field in the soil.When the electric field is strong?depending on the surface charge,the polarization of the adsorbed counterion and the electrolyte concentration?,the net interaction force between the soil particles appears as repulsive force,and the degree of soil aggregate breakdown?it is related to the“electric field-mechanical composition”?.The coupling effect is related to the infiltration of soil moisture.In this case,the study found that:?1?increasing the attraction between soil particles?ie,reducing the repulsive force?will accelerate the infiltration of soil moisture;and?2?soil with higher clay content or lower grain and gravel content,soil moisture infiltration rate is slower.For example,when the net repulsive force of gray brown purple decreases from 2.66 to 0.95atm,the water infiltration rate increases from 45 to 278 cm³ m² min^-1.This also indicates that,under the same electrostatic repulsive conditions,the gray brown purple with higher clay content infiltrates water more slowly than the red brown purple.When the electric field intensity of the soil is very weak,the net force between the soil particles acts as an attractive force.At this time,the soil aggregates will not be broken,and the stability of the soil aggregates alone will determine the soil moisture infiltration.In this case,the study found that:?1?Increasing the attraction between particles does not accelerate the infiltration of soil moisture infiltration;?2?The soil with higher levels or lower levels of silt and gravel,soil moisture infiltration is faster.For example,when the net attractive force of gray-brown purple decreases from 3.52 atm to 5.74 atm,the water infiltration rate increases from 403 cm³ m² min^-11 to 406 cm³ m² min^-1.It shows that the increase of net gravity does not significantly increase the water infiltration rate;this result also shows that when the electric field is weak,under the same interparticle force conditions,the gray brown purple with higher clay content infiltrates water faster than the red brown purple.?2?Even if the repulsive action of the soil electric field on the anions reduces the possibility of anions interacting with the surface in the electric double layer,the effects of Cl^-and NO₃^-interfacial reactions on the stability of the soil aggregates with constant charge are found.Cl^-and NO₃^-There was a difference in the breaking strength of soil aggregates and the infiltration of soil water in the anionic systems.The amount of<10?m micro-aggregates released by the aggregates rupture in the NO₃^-system was much lower than that of the Cl^-system,indicating that the water infiltration process There is also a strong anion-specific effect.Further analysis showed that the difference between the rupture strength and water infiltration of the aggregates of Cl^-and NO₃^-was more obvious in the low concentration range.With the increase of the ion concentration,the stability of soil aggregates gradually increased,and the water infiltration When the ion concentration was higher than 0.1 mol L^-1,the soil aggregates tended to be stable and the rate of water infiltration was close to the maximum,reaching a steady level basically.Based on the above results,we can draw the following conclusions:?1?For soils with uniform mechanical composition,the interaction of soil particles determines the stability of soil aggregates and soil pores,and the stability of soil aggregates and soil pores determines the soil The infiltration rate of water;and for the soil with uniform electric field strength,the mechanical composition of the soil determines the state of the soil pores and thus determines the rate of infiltration of soil water.?2?When the soil electric field is strong,the mechanical composition determines the smoothness of the water infiltration channel;and when the soil electric field is weak,the stability of the aggregate determines the openness of the soil water infiltration channel.?3?Because soil electric charge,solution electrolyte composition,and ion interface reaction determine the strength of the soil electric field,the“coupling of electric field and mechanical components”actually means“soil charge,electrolyte composition,and ion non-ionization in soil water infiltration.The coupling of classical polarization and mechanical composition of soil."...