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Experimental Study on Characteristics of Macropore Flow and Solute Preferential Transport in Unsaturated Soils

Author: WuJiQiang
Tutor: ZhangJianFeng
School: Xi'an University of Technology
Course: Hydrology and Water Resources
Keywords: Simulation of large pores Preferential flow Macropore flow. Solute transport Unsaturated soil
CLC: S152.7
Type: Master's thesis
Year: 2010
Downloads: 184
Quote: 1
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Abstract


Preferential flow in recent years, a new concept for soil water movement, it is a more common form of soil water movement and soil infiltration, surface and underground water quality is closely related to macropore flow is a typical preferential flow phenomenon. Macropore flow due to the prevalence of large pores in the soil, water and solute priority through these channels formed within the soil moisture and solute transport has a very significant impact. The paper through the indoor physical simulation test and mathematical model for simulation of large pores regular water and solute transport in the unsaturated soil from the two aspects of the depth and effective surface porosity of macropores. Achieved the following results: (1) study analog characteristics of the pore domain indicators - large pore depth and the concept of the effective surface porosity, the test results show that the indicators proposed are reasonable. Gravel using a certain range of particle size is simulated in a special test apparatus and the mold a the macropores domain of different depths and different effective surface porosity. (2) analysis of the water in the same analog effective surface porosity (Φ = 1.8370%), the different simulated depth pore domain unsaturated soil priority migration law. The findings of the trial conditions characterized by transition time Tp cumulative the infiltration, characterized wetting front and instantaneous infiltration rate significant priority Migration Characteristics. The concept of the different analog depth pore water infiltration increment and unit pore area of ??water infiltration incremental ratio, and a quantitative analysis and validation. (3) analysis of the water in the same analog depth (Z = 15 cm), different simulated effective surface porosity pore domain of unsaturated soil migration law, draw water infiltration process characteristic transition time TPE, moisture accumulation infiltration, characterized quantitative relationship of the wetting front and the effective surface porosity under the test conditions, and give validation to good effect; analysis of instantaneous infiltration rate of water infiltration process has a significant preferential flow phenomena. (4) analysis of water and solute leakage of effluent water quantity and water solute concentration variation in the effective surface porosity of the different analog depth and analog unsaturated soil pore domain, analog pore depth and effective quantitative mathematical relationship between the surface porosity and cumulative water quantity of water and solute cumulative harvest; obtained under specific test conditions the solute containing analog longitudinal distribution of large-pore domain of unsaturated soil with obvious double and shortened solute transport in the soil deep and solutes in the unsaturated soil radial distribution of large-pore domain law, that is, with the center of a large pore domain radially increasing regularity in the radial direction. (5) diffusion of water transport in the unsaturated soil analog pore domain dual permeability conceptual model, combined with the test conditions to be simplified. ADI difference method for solving finite difference calculation simplified mathematical model and the initial and boundary conditions. Using the mathematical model the combination of HYDRUS-2D software water containing analog characteristics of large-pore domain of unsaturated soil wetting front and cross-sectional wetting front over the course was simulated and measured values ??were compared, the results show that the effect is good.

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CLC: > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil physics > Soil moisture
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