Study On Solute Transport Characteristics Of Shallow Groundwater In Closed Coal Mining Subsidence Area

The paper selects the coal mining subsidence area in the Panxie mining area of Panji District,Huainan as a typical closed coal mining subsidence area,and arranges shallow groundwater sampling points in the study area to conduct shallow groundwater level observation and water quality monitoring for one year.By analyzing the spatial and temporal distribution characteristics of shallow groundwater in the study area,the water quality of shallow groundwater was evaluated by single factor,Nemero,WQI and other weighting methods,combined with GMS software for shallow groundwater flow and solute transport.The simulation was carried out to provide a basis for protecting the water resources in the coal mining subsidence area.The research results are as follows:（1）By selecting 8 water quality indexes such as TDS,pH,NO₃-N and NO₂-N to evaluate the shallow groundwater quality and analyze its variation characteristics,the shallow groundwater quality in the study area is good overall,but there is NH₃-N,TDS,COD_Mn and other problems exceed the standard,and the change of water quality in a year shows a certain time regularity.（2）Using the groundwater numerical simulation method to establish a mathematical model of groundwater flow and groundwater solute transport,and use the relevant modules of GMS software to simulate the groundwater flow field in the region and the contaminant transport and diffusion under different conditions.The overall flow of water in the study area flows from north to south.The water level is stable between19 and 22 m throughout the year.The water level will change with the change of ground recharge.The increase of atmospheric precipitation will cause the groundwater level to rise.（3）F^-and TDS are used as characteristic pollutants under natural and artificial assumptions to simulate the continuous infiltration of pollutants.The migration and diffusion of pollutants in 5,10,15 and 20 years were simulated respectively.With the passage of time,the diffusion range of pollutants in the study area was increasing and the concentration was increasing.After 20 years,the scope of the pollutants has expanded to 2.14 times the area of the subsidence area.The pollution plume extends to the south most,with an extension distance of 1 km.At the same time,the pollution center is also moving southward.The ammonia nitrogen is used as the research object for 60 days.Short-term pollutants were released and simulated the migration of pollutants for 1 year.The pollution range has been increasing within one year.In the first 60 days,contaminants diffused in the aquifers and confined aquifers and the concentration increased due to the continuous release of contaminants.After 60 days,the concentration of pollutants in the polluted center of the stratosphere began to decrease,but due to the slow migration rate of pollutants,the concentration of pollutants in the contaminant aquifer reached the highest in about 120 days,and the concentration of pollutants and the stratosphere The concentration of pollutants in the medium is basically the same.After 120 days,the pollution concentration of the apocalyptic layer and the confined aquifer pollution center decreased continuously,but the speed was slower,and the scope of the pollutants continued to expand.Figure[25]Table[12]Reference[72]...