Study On Influencing Factors Of Heavy Metals Migration In Groundwater Based On FEFLOW Simulation Of Lead-zinc Tailings

The ecological environment is becoming increasingly severe,affecting people’s lives and production.The disposal of the tailings pond after mining in the environment is improper,which will inevitably cause pollution of the surrounding environment and harm to human life.With the development trend of mining industry and the necessary needs of ecological environment,the problem of heavy metal pollution in mining tailings is becoming more and more prominent.With the development trend of mining industry and the necessary demand of the ecological environment,the problem of heavy metal pollution in mining tailings is becoming more and more prominent.However,the corresponding difficulty of governance varies with different types of mines.However,the corresponding difficulty of treatment change with different types of mines areas.And geological conditions also have a very important impact on the migration and diffusion of heavy metals.Therefore,in order to explore the pollution migration mode of heavy metals in tailings ponds,this paper takes the tailings pond of Guangxi OLD factory(lead-zinc mine)as the research object.Preliminary analysis of the corresponding basic properties of the mining area,including the composition of the mining area,the composition of the heavy metals in the mining area,and the hydrological background of the project area.Then use FEFLOW modeling software,Temporal and spatial changes in contaminant migration under specific hydrogeological conditions in the area.This case studies various of different boundaries and initial conditions to simulate various geological scenarios.Those main research results are as follows:(1)The old tailings sample has strong neutralization capacity,NP/AP>3:1 and NAG≤10,which belongs to carbonate-type non-acid tailings in typical karst areas.The main components are silica,alumina,calcium oxide,ferric oxide,etc.,of which SiO2 content is the highest,reaching 57.00%,followed by alumina,calcium oxide and ferric oxide,the total content of which accounts for 22.44%.The main mineral components of tailings are quartz,sericite,a small amount of plagioclase and pyrite,etc.,belonging to iron dolomite tailings.(2)The content of Pb and Zn in tailings samples was the highest,reaching 4068.30mg/kg and4917.20mg/kg,respectively,and the content of Cd was the lowest,only 11.0-14.50mg/kg.The forms of heavy metals in tailings samples showed the rule of residue state > reducible state > oxidizable state > weak acid extraction state.Among the samples with different depth profiles,the upper and middle Pb had higher residual state content,accounting for 83.68% and 85.25% respectively.The content of Zn in the middle layer is the highest,accounting for 69.30%,and the content of residual in the lower layer is the least,accounting for 52.60%.The content of Cd in the middle layer is the highest,accounting for 72.60%.The potential migration ability of heavy metals Pb,Zn and Cd in the tailings sample is Zn>Cd>Pb.(3)The modeling results show that: the increase of precipitation,the increase of contaminant concentration,and the underground structure,such as cracks and discontinuous/displacement layers,willaffect the mode of solute migration and diffusion in saturated groundwater systems.The model of contaminant migration with regular precipitation shows the vertical and horizontal components of the contaminant plume due to diffusion and dispersion effects.The model of contaminant transport without precipitation shows that the plume migration at the edge of the model is primarily horizontal.Although the model of contaminant transport with dual precipitation shows contaminant levels and vertical diffusion.The model of solute concentration affects the migration of contaminants.The increase in concentration expands the area that the contaminant plume reaches in both horizontal and vertical directions.The model of the permeable layer structure significantly changes the path of contaminant transport.The presence of a stopped,water permeable layer with lower hydraulic conductivity creates a physical shield which results in a refraction of the contaminant flow.The presence of faults with different hydraulic parameters makes the pattern more complicated.Due to this phenomenon,the plume of pollutants mainly diffuses above and below the higher concentration of the permeable layer.The simulation results indicate the tendency of the solute to migrate vertically in the low conductivity medium and migrate horizontally in the high conductive layer.