Spatial Distribution And Transfer Of Heavy Metals In High-altitude Mountain Industrial Parks

The smelting slag produced in the process of metal recovery contains a large amount of toxic and harmful heavy metals,and simple stacking of its will certainly pose a threat to the surrounding environment.In order to accurately evaluate the impact of smelting waste slag stacking on the surrounding environment in an industrial park,this study analyzed and evaluated the current situation of environmental quality and the spatial distribution of heavy metal pollution in the area.The leaching and release process of heavy metals in soil and waste residues was studied by column experiments,and the migration trend of heavy metals was simulated and predicted by simulation software.The main conclusions are as follows:（1）The main heavy metal pollutants in surface water and groundwater in the study area were Pb,Cd and Zn.The coefficients of variation of Pb,Cd and Zn in surface water were all greater than 0.5,indicating that the spatial distribution of heavy metals was not uniform and obviously affected by human beings.The average pH of the waste residue in the park was 5.68,which is not corrosive.The X-ray diffraction pattern showed that the possible phases of the waste residue included SiO₂,metal oxides,sulfates,phosphates.The content of Pb,Cd and Zn in the waste residue was relatively high,which were 6644 mg/kg,156 mg/kg and 16658 mg/kg,and the leaching toxicity were 2.46 mg/L,40.3 mg/L and 75.0 mg/L.（2）The spatial distribution analysis of soil heavy metal pollution showed that the pollution was concentrated around the slag dump.The environmental risk assessment showed that the Nemerow pollution index was 17.6,the Pollution load index was 2.11,and the degree of heavy metal pollution was mild to moderate.The human health risk assessment showed that the health risks of adults and children were lower than the warning value 1.0×10^-4 stipulated by USEPA.The results of geographic detectors showed that land use type,elevation,terrain slope and soil particle composition had strong explanatory power for the spatial differentiation of the seven heavy metals,reaching 0.39,0.39,0.37,and 0.62,respectively.The detection results of the interaction between the factors showed that the interaction between the two factors was nonlinearly enhanced,and the interaction of factors such as land use type and elevation was stronger.（3）Rainfall leaching experiments showed that lower pH can promote the leaching of heavy metals in soil and waste residues.The leaching and release process of heavy metals conformed to the double constant rate equation,with R~2 above 0.9,indicating that the release process of heavy metals in soil was controlled by many factors.This process was simulated by the solute transport and fluid flow physical field modules of Hydr US-1D and COMSOL software,which was the leaching and migration process of Heavy metals Pb and Cd in waste slag under different pH leaching conditions.The simulation results showed that when the pH was 4.5,Pb and Cd were concentrated within 4 meters of the topsoil after 4 years,the Pb concentration in the topsoil solution was 3.94 mg/L,and the Cd was 224 mg/L;when the pH was 6.0,the concentration was 1.24 mg/L,the Cd was 202 mg/L,and the release amount and mobility of Cd in the waste residue to soil were higher than those of Pb.This study evaluates the current situation of the metal smelting industrial park yard and the surrounding environment,and simulates the migration of heavy metals in the soil and pollution trends under rainfall leaching conditions.