Experimental Study On Characteristics Of Finger Flow And Pollutant Prioroty Transport In Layerde Soil

The characteristics of the northwest loess is non-homogeneous anisotropic and obviously layer-structured. These characteristics are occurred the basis of preferential flow. The results show that a large number of pollutant transport through preferential flow caused by deep soil and underground water pollution, In order to get to know the influence route of preferential flow has bring for the transportion of water and pollutant, based on National Natural Science Fund Project " Experimental study on the character of structured loess pollutant's preferential transportion", we did non-saturation layer structured soils water infiltrating experiment to study the finger flow and NO3--N transport in the process of water infiltration, using xi'an's loess and sand. We discussed different physical properties of soil influence on simulating finger flow and the finger flow's influence on the transportion of NO3--N in soils. Also, we revealed the basic on finger flow in layer structure of soils and the transportion of NO3--N in soils. The experiment of results supply necessary scientific basis for the further study of finger flow. Based on extensive on finger flow and transport of NO3--N research achievements from domestic and abroad, carrying on some experiment indoors on interior system and using a math model to simulate, we get some achievement as follows:1. We proposed the method for simulating the phenomenon of finger flow in Layered structure of soil,that is, installing the finger flow of mold in experiment and simulating finger flow with sand of different diameters.2. In the process of water infiltrating, if the soil's physical property is different, the affecting factor is also different when simulating finger flow. We use velocity of finger flow to illustrated character of finger flow. If the affecting factor when simulating finger flow is different, the velocity of finger flow will also be different. The velocity of finger flow develops slower if the thickness of the upper-layer soil are more larger and median particle size of matrix sand are more larger. The velocity of finger flow develops faster if the initial moisture content upper soil are more larger.3. The impact of finger flow for transport of NO3--N was researched in the layered structure of soils. With different nature of soils the process of water transport was lcached the different effect of NO3--N.The front of finger flow for concentration of NO3--N distribute smaller if the thickness of the upper soil are more larger. The front of finger flow for concentration of NO3--N distribute smaller with its the leaching effect of NO3--N on the weaker if initial moisture content of soil are more larger. The front of finger flow for concentration of NO3--N distribute smaller if median particle size of matrix sand are more smaller.4. Using two-region model, we divided the infiltration of water into two categories: moving water and immobile water. Then, the math model simulating finger flow can be achieved by Richards equation and mass balance equation. The numerical solution of these equations can simulate the process of finger flow. Comparing the numerical solution with the measured value, we find that the deviation between them is rather small. It proves that this model is of good effect for simulating finger flow.