Research On Groundwater Pollution Mechanism And Prevention And Control Technology In Red Mud Yard

Groundwater is an important water source for human production and life and the maintenance of ecosystem operation.However,sometimes groundwater pollution accidents occur due to unreasonable mining and industrial solid waste accumulation.In this thesis,taking the abandoned mine of an aluminum smelter in Shandong Province as an example,the main pollution components of red mud in aluminum smelting are analyzed,and the groundwater"skylight"pollution mechanism of Ordovician limestone aquifer in red mud mine is revealed,and the targeted technical scheme of red mud pollution prevention and control is put forward,which provides scientific research basis and decision-making basis for regional groundwater environment restoration and red mud pollution prevention and control.The main results are as follows:（1）The main components of soil in abandoned mines and the chemical characteristics of regional groundwater were analyzed,and it was found that the main chemical components of red mud in abandoned mines were Al₂O₃,Ca O,Fe₂O₃,Si O₂,Na₂O and TIO₂,which accounted for 60%of the total mass of red mud.～80%;the chemical type of groundwater in the study area is mainly SO₄-Ca Mg type,and TDS,Na⁺,Cl^-,SO₄^2-and F^-concentrations are greatly affected by red mud pollutants.The Nemerow index method was used to evaluate the groundwater pollution degree in the study area on the basis of fully considering the characteristics of the groundwater in the study area,The conclusion is that the groundwater pollution in the study area is serious.（2）Through the laboratory red mud leaching test and leaching test,the influence of soaking time and water volume on the leaching of main anions and cations in red mud was revealed.The release process of red mud pollutants in the yard without anti-seepage treatment under rainfall conditions was simulated.The maximum leaching concentrations of F^-,SO₄^2-and Al³⁺in red mud leaching solution were 54.1 mg/L,259.57 mg/Land 29.20 mg/L respectively.The leaching of metal ions was more affected by water volume than time.In the process of Na⁺migration,ion exchange reaction replaces Ca²⁺and Mg²⁺in the medium,which will combine with F-to form calcium fluoride and magnesium fluoride.The concentration of F^-,Na⁺and TDS in the leachate increases first and then decreases gradually.This study provides a theoretical basis for revealing the mechanism of groundwater pollution in the study area and designing prevention and control programs.（3）FLAC3D numerical simulation software is used to build the floor failure model of open pit bauxite mining.It is concluded that the failure depth of Benxi group shale floor increases with the increase of mining depth.Due to the fragile lithology of mudstone,it will be broken first than limestone.Floor damage depth is about 9 m,broken floor will become a good migration channel between Ordovician limestone water and surface pollutants.Using Hydrus-1D numerical simulation software,the vertical solute transport model of F^-characteristic pollutants under rainfall leaching conditions was constructed.The relationship between F^-concentration in soil leaching solution and infiltration time and infiltration depth was obtained.It takes about 1440days for red mud leaching solution to infiltrate into underground aquifer.Based on the failure characteristics of open pit floor and the vertical migration law of red mud pollutants after landfill,the mechanism of red mud leaching liquid skylight type pollution of Ordovician limestone aquifer under the influence of excavation filling is revealed.（4）According to the depth of the floor failure of the Benxi Formation after open-pit bauxite mining and the migration law of the pollutants in the pit after the pit is filled,combined with the mechanism of groundwater pollution by the red mud pit,based on the existing groundwater pollution prevention and control technology,a comprehensive prevention and control system of groundwater pollution in-situ disposal of vertical anti-seepage walls at the red mud pit—grouting of key aquifers on the floor—surface anti-seepage caps is proposed.The corresponding groundwater pollution remediation technology was proposed to realize the prevention and control scheme combining in-situ disposal and water quality remediation.The thesis includes 62 figures,10 tables,and 100 references.