Study On The Release And Migration Of Heavy Metals In A Tailings Reservoir Area In Yunnan And Its Impact On Groundwate

As one of the important components of mine production,the tailings reservoir provides storage space for tailings produced in the production process to a certain extent.However,with the increase of time,the number of tailings discharged into the tailings reservoir is increasing.The heavy metals in the tailings are released to the surrounding environment under the leaching of rainwater and the oxidation of air,and to a certain extent,they will migrate with the movement of water flow,which poses a serious threat to the soil,surface water system and even the water environment.Therefore,it is of great significance to understand the release and migration rules of heavy metals in tailings reservoir areas for the prevention and control of the surrounding environment,especially groundwater environment pollution.At present,the research on the release and migration of heavy metals mainly focuses on soil,surface water,and sediments.The research methods are mainly based on on-site sampling detection analysis,indoor small-scale simulation experiment analysis,and simple numerical simulation prediction.The research methods are relatively simple and lack in-depth discussion on the release and migration mechanism of heavy metals in the tailings reservoir area.In this paper,a tailings reservoir area in Yunnan Province is taken as the research object.The field sampling,theoretical analysis,indoor simulation experiment,and numerical simulation are combined to comprehensively explore the release and migration rules of heavy metals in the tailings reservoir area,and the release model of heavy metals in the tailings reservoir with time and the model of heavy metal migration in groundwater are established to predict the migration range of heavy metals in groundwater and the impact on groundwater environment.The research results are as follows :(1)Based on the relationship between the leaching amount and heavy metal release concentration in the leaching experiment,a heavy metal leaching release model was constructed.The results show that the release concentration of heavy metals is inversely proportional to the liquid-solid ratio and tailings height,and the relationship with p H varies with the types of heavy metals.The release concentration of Zn is most affected by p H and is inversely proportional to p H.When the p H was 4 and 6,the release concentration of Pb was the highest,and the release concentration was the lowest among the three.The release concentration of Mn was the highest at p H = 4.The influence of oxidation-reduction is that Zn is easier to leach from tailings in weak oxidation and reduction environment.The leaching concentration of Pb is the highest under high reduction conditions.Mn is greatly affected by high-reduction conditions.The effect of leaching amount on the leaching of three heavy metals is as follows: the release process of three heavy metals includes three stages: rapid rise,rapid decline and gentle decline.The release kinetic characteristics of zinc and lead were well-fitted with the double constant rate equation.The release process of manganese is better described by the modified Elovich equation.(2)The adsorption experiment of heavy metals in soil and the migration experiment of heavy metals in soil were carried out to explore the adsorption characteristics and migration rules of heavy metals in soil.The adsorption kinetics experiments show that the adsorption kinetics characteristics of Zn,Pb and Mn are the highest with the quasi-second-order kinetic model.Isothermal adsorption experiments show that the adsorption process of zinc,lead and manganese in soil is described by Langmuir model.The migration experiment of heavy metals in soil shows that the migration of heavy metals in soil is mainly affected by p H and solution flow rate.The smaller the p H value and the larger the solution flow rate,the shorter the time for heavy metals to penetrate the soil and the faster the migration rate.A soil heavy metal migration model was established,and important parameters such as adsorption distribution coefficient,retardation coefficient and dispersion coefficient were calculated.(3)The Visual Modflow numerical simulation software was used to establish the groundwater solute transport model.The migration process of heavy metals in groundwater was simulated by combining the migration parameters.The migration of Zn,Pb and Mn in groundwater was predicted with time.The results showed that the concentration distribution range of the three heavy metals showed that the concentration of the reservoir area was the largest,centered on the reservoir area,radiated around,and gradually decreased from the inside to the outside.The order of migration speed is : Zn > Mn > Pb.The three heavy metals are affected by the flow direction of groundwater,and the diffusion direction of pollution plume shows a trend of moving from east to west.Therefore,it is necessary to regularly detect the groundwater indicators in the reservoir area and surrounding areas,and to take anti-seepage measures to reduce the risk of groundwater pollution.