In-situ measurement method for unsaturated hydrodynamic dispersion coefficients of soil with structural differences

Abstract

The invention provides an in-situ measurement method for unsaturated hydrodynamic dispersion coefficients of soil with structural differences. The method comprises the following steps: determining structural differences of soil profiles on the basis of soil particle size analysis; enabling water and solutes in soil to enter a redistribution process on the basis of the boundary condition of fixed water head, and determining soil matrix potential and solution concentration profile distribution at different moments by arranging sensors; providing a soil hydrodynamic dispersion coefficient relation equation on the basis of a mass continuity principle in the redistribution process, determining parameters of the soil hydrodynamic dispersion coefficient relation equation with a central difference method according to the soil matrix potential and solution concentration distribution at two adjacent moments, and further determining the unsaturated hydrodynamic dispersion coefficients of the soil with different texture. The method has the advantages of clear physical conception, simple computational formula, easy operation, high measurement precision and direct experimental result, and more importantly, the hydrodynamic dispersion coefficients of the soil with the structural differences can be determined, and the method has originality in the field.

Description

technical field [0001] The invention relates to the field of agricultural technology, and particularly proposes an on-site measurement method for the hydrodynamic diffusion coefficient of unsaturated soil with structural differences. Background technique [0002] With the aggravation of soil pollution and soil salinization, the study of soil solute transport has become an important topic. The movement of soil solutes is a complex process, which is closely related to many factors such as irrigation methods, soil conditions, and the external environment. The movement of chemical fertilizers and pesticides in farmland, the monitoring of water and solute movement in saline-alkali land, and the accurate measurement and monitoring of groundwater resources protection Research matters. The soil diffusion coefficient is an important and indispensable parameter in this process. Soil diffusion coefficient is a parameter that characterizes the migration and diffusion of solutes in soi...

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Problems solved by technology

Therefore, compared to the saturation situation, even under laboratory conditions, it is possible to monitor the migration process of solutes by controlling the boundary conditions. However, it is very difficult to distinguish the convective flux caused by the movement of the water from the flux due to the hydrodynamic dispersion process. , especially in the case of changing water cut, the non-linear variation of water flow motion makes it very difficult to separate the hydrodynamic diffusion flux from the total solute transport flux

[0004] Under field conditions, the inversion of hydrodynamic dispersion parameters based on time-varying monitoring values ​​of solute concentrations at several locations is the main method currently available. One method, which distinguishes convective fluxes from total solute transport fluxes under unsaturated conditions due to the nonlinear flow properties of soils, is very uncertain

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