Study On Transport Processes Of Solute In Unsaturated Zone Of Different Vegetation Recovery Modes In Coal Mining Area

The process of soil water and solute transport is inevitably changed in the process of ecological restoration in coal mine area.Soil water in unsaturated zone is the main carrier of solute transport.Pollutants in coal mine area migrate with soil water,polluting soil and even groundwater.Solute transport is affected by soil hydrological properties,characteristics of soil water movement,vegetation status,and a series of physical and chemical reactions occurring in the process of transport.Recognizing and describing the solute transport process in unsaturated zone is one of the key scientific issues in the process of ecosystem restoration in mining area.In this study,herbaceous,shrubs,arbors,shrubs and grasses vegetation restoration areas and abandoned wasteland in Gujiao mining area of Shanxi Province were taken as the research objects.By monitoring soil physical and chemical properties and hydraulic parameters under different vegetation restoration modes,the changing laws of soil physical and chemical properties in vegetation restoration areas were revealed.The transport characteristics of chloride ion in soils under different vegetation restoration modes were clarified,and the parameters were simulated and shadowed using CDE,TRM and SC models,and simulation and prediction of migration process of sulfate ion in soil.The results showed that after vegetation restoration,the contents of organic matter,total nitrogen,total carbon,nitrate nitrogen and soil water holding capacity increased significantly,and the bulk density of 20-40 cm soil layer was the largest,while that of below 40 cm soil layer gradually decreased.In the process of ecological restoration in mining area,herbaceous plants should be chosen as the main vegetation restoration method to ripen the soil,and then the combination of arbor,shrub and grass should be adopted to improve the ecosystem function and stability.Soil adsorption experiments show that the adsorption of sulfate ion in mining area is mainly non-uniform.The simulation results show that when the sulfate ion concentration in surface soil is 0.411 mg/cm~3,the sulfate ion concentration will reach the same level 3 m away from the surface after 51.90 days.Sulfate ions migrate downward at a faster rate in unsaturated zones,and certain anti-seepage measures should be taken to prevent contamination of groundwater.The best fitting effect of CDE model for chloride ion transport process in soil is obtained.Convection is the main transport mode of solute in soil in the study area.Volume weight and sand content are the main factors affecting soil solute transport in mining area.Mean pore velocity,dispersion coefficient and dispersion decrease with the increase of bulk density,while dispersion coefficient and dispersion increase with the decrease of sand content.