Sources Of Acid Wsatewater From Alum Ore And Migration Of Heavy Meatals In Soil And Simulation

The rapid development of China’s economy has greatly increased the amount of ore mined,and heavy metals in waste tailings are leached by liquid and migrate with surface runoff or seepage,which will pollute the surface water and groundwater,at the same time,the content of heavy metals in agricultural soil will increase after being eroded by soil.Once the water and soil are polluted,it is difficult to control and recover,which seriously threatens the ecological environment and human health.Therefore,the problem of heavy metal pollution in mining areas has attracted more and more attention from scholars.This research takes the Fanshan mining area in Lujiang,Anhui Province as the research area,and takes the slag,ore,and natural water bodies in the mining area as the research objects.The source of acid mining wastewater,the dissolution law of heavy metal elements in ore slag under soaking and leaching conditions,the water quality evaluation of mining area and the risk of heavy metal leaching have been systematically studied.The results are as follows:(1)Through hydrogen and oxygen stable isotope tracing,the relationship between different water bodies has been clarified,indicating that the accumulation of water in the mining subsidence area is mainly derived from atmospheric precipitation.As water,fissure water,trench water,rainwater have similar isotopic characteristics with the east and west cave water,they may provide the main water source for the supply of mine cave water.The MixSIAR model is used to analyze the percentage of shallow groundwater,gully water and rainwater in the mine cave water.Through three sampling analyses,the results show that the groundwater replenishes the mine cave water more.Rainwater and channel water will replenish the underground roadway through fast passages such as subsidence openings and mining pits during the confluence of slopes.Therefore,due to the difference in rainfall,the proportion of rainwater in the three samplings in the mine cave water is quite different.On this basis,combined with the detection results of the water quality,alum ore and slag composition in the mining area,it is shown that the acidification of the mine cave water quality is not directly related to the replenishment water source of Dafanshan and Xiaofanshan,and the main cause mechanism of the hydrolysis of alum into acidic wastewater.In addition,pyrite is also one of the reasons for the generation of acid mine cave wastewater.The goaf above the mine cave provides sufficient oxygen and water,which provides a good environment for the formation of acid water.(2)Through the indoor static immersion experiment analysis,it is shown that the release of heavy metals in the slag increases with the increase of the solid-liquid ratio,but the precipitation concentration of each ion in the sintered slag is always lower than that of the waste slag,which is related to the background value and the existence form of the heavy metal content in the slag.And through an outdoor simulated rainfall experiment,it is concluded that the heavy metal with the highest amount of heavy metal dissolved in the slope runoff of the waste slag and the vertical seepage of the sintered slag is Al.The leaching rate of heavy metals in the waste slag is Cd,Ni,Cr,Mn,Cu,Al,Fe in descending order,and the leaching rate of heavy metals in the slag after sintering is Ni,Mn,Cd,Cr,Cu,Fe,Al in descending order.The water quality of the water collected from different locations in the mining area was evaluated,and the results showed that the water in the mining area was closely affected by mining activities.Dongping mine cave,Xiping mine cave,Dafanshan shaft and tailing pit water are all seriously polluted water bodies.The carcinogens Cr,Cd and non-carcinogen Cu in the surface water and groundwater of the mining area have exceeded the maximum acceptable risk level recommended by the International Radiation Protection Committee.The direct comparison and analysis of the leaching concentration of heavy metals in the slag and the "Surface Water Environmental Quality Standards" Class III water quality standards show that the heavy metal elements in the leaching liquid will pollute the environment.(3)Through the soil column leaching experiment,the migration law of Cu and Cd in the soil is obtained,that is,the external heavy metals Cu and Cd are mainly adsorbed on the surface after entering the soil,the adsorption capacity of soil to Cu is stronger than that of Cd;the downward migration ability of Cu is weaker,and as the amount of leaching increases,the migration risk of Cd in the soil is greater than that of Cu,and the Cd content of the bottom soil is higher than that of the surface.Using the Hydrus software to simulate the migration and accumulation of heavy metals Cd in the soil,it shows that the distribution trend of Cd in the soil profile is closer to the actual results,that is,Hydrus can simulate the migration process of Cd well.