Study On Groundwater Pollution Risk Prediction Of Closed Pit Backfill In Fushun West Open-pit Mine

Under the background of the national promotion of green mine construction and"dual carbon",the treatment of the Fushun West open-pit mine with solid waste backfill not only reduces many geological disasters in the mining area but also improves the resource utilization rate of solid waste materials around the mining area.After solid waste backfilling the open-pit pit,it may cause certain pollution to the surrounding water environment under the action of long-term groundwater immersion and rainfall leaching,which will bring certain safety hazards to the water safety of residents near the mining area,so it is very important to predict and prevent and control the groundwater pollution and risks caused by solid waste backfill.Taking the Fushun West open-pit mine as the research object,according to the specific backfill scheme,the ratio of backfill materials was optimized through laboratory tests,and the release law of backfill material pollutants was explored,and on the basis of on-site investigation and collection of hydrometeorological and borehole geological data around the mining area,the seepage law of groundwater after open-pit mine closure was explored,the solid waste backfill groundwater pollution after open-pit mine closure was predicted by GMS,and the health risk of solid waste backfill groundwater pollution in open-pit mine was predicted by GMS and GIS.The research results are as follows:（1）Through the analysis of the BBD response surface test,the mixing ratio of SWCFB material with the strongest impermeability is:solid mass concentration is 67.50%,alkali slag content accounts for 11.46%of solid mass,steel slag accounts for 51.49%of solid mass,and shale slag accounts for 37.05%of solid mass;The static leaching test results show that the static leaching pollutant concentration of SWCFB material is lower than that of raw materials,which has a certain curing effect on pollutants,and the dynamic column test results show that Fe and Cr have a certain lag in the filtration of soil,mudstone and sandstone,and the adsorption capacity of Fe and Cr of the three media is sorted as soil>mudstone>Sandstone.（2）By establishing a three-dimensional mathematical model of groundwater seepage in the Fushun West open-pit mine,combined with water equilibrium analysis and groundwater level and water flow prediction after the closure of the Fushun West open-pit mine,the results show that the main recharge mode of the mining area is rainfall infiltration,the recharge is 51329m³·d^-1,and the main discharge mode is drainage of each drainage pump room,and the discharge amount can reach 73343 m³·d^-1;After the mine closure stops draining,the groundwater flow field changes from a precipitation funnel that converges towards the center to a stable flow field flowing northwest,and the final groundwater level in the pit will reach+72 m.（3）Multiple linear regression analysis（MLR）was used to establish a solute transport model of groundwater pollution with biological,chemical,and seepage effects,and the groundwater pollution generated by solid waste backfill materials at different times,different backfill heights and different backfill schemes was predicted by GMS,and the results showed that Fe and Cr diffused from the bottom of the pit to the surroundings with the rise of groundwater level,and gradually began to migrate to the northwest in 2060,and Fe will migrate to the south bank of the Hunhe River in 2080,and the diffusion range and distance of organic pollutants naphthalene（Nap）under the action of biodegradation are not significant;The concentrations of Fe,Cr,and Nap in the pit increased with the increase of backfill height,and when the concentration of pollutants in the pit increased significantly,the effect of biodegradation on Nap weakened.Compared with the backfill scheme 1,the greater the backfill height of the SWCFB material at the bottom of the pit,the stronger the anti-seepage ability,and more Fe and Cr will be adsorbed in the water storage stage of the pit,and the microporous structure makes it difficult for the pollutant particles that have invaded the material to dissolve again so that the final concentration of pollutants is reduced.（4）GMS and GIS to predict the health risks caused by solid waste backfill groundwater pollution after open-pit mine closure,the health risks caused by Fe and Nap are low and negligible,although the health risk index of Cr is lower than the acceptable risk limit set by the US EPA,it has reached a medium risk,which should be paid attention to,adult women are slightly higher than men due to pollutants,and children are the most likely to be affected by Cr.The anti-seepage effect of SWCFB material can reduce the health risks caused by solid waste backfill,and the health risk of children affected by Cr can be significantly reduced when the height of SWCFB material is 20 m at the bottom of the pit.The paper has 76 figures,20 tables,and 104 references.