| Carrying out soil ecological environment assessment is an important content of mine ecological engineering construction.At present,the assessment results of mine soil are limited to a single pollution index assessment,and there is no comprehensive and feasible assessment system to support the prevention and control of mine soil.Therefore,this artice takes a lead-zinc mine in Hunan Province as the research site,divides it into six functional areas,and focuses on selecting the typical heavy metal pollutants Pb,Zn,and Cd in the mine soil as the research objects.Historical inquiry,on-site inspection,etc.,to select a reasonable sampling plan for soil collection.After that,soil column experiments were carried out combined with numerical simulation technology to delineate the migration range of heavy metal pollutants;Secondly,the degree and level of contamination of heavy metal pollutants in the soil within each functional area is studied by integrating the geoaccumulation index method and the improved hierarchical analysis method,and furthermore,the spatiotemporal distribution pattern of heavy metals and the degree of soil pollutants risk in lead-zinc mines is analyzed by coupling numerical simulation based on the potential ecological index method,finally,carry out the analysis of soil pollution sources.The research results are as follows:(1)The soil column experiment shows that the migration and content of heavy metal pollutants in lead-zinc mine soil are controlled by five forms of heavy metals,among which exchangeable speciation、fe-mn oxides bound and residual form are the main changes in the process of migration and transformation.Numerical simulations show that: when the pollutants migrate for 15 days,the pollution diffusion in the range of 0-40 cm tends to be stable,of which 0-30 cm is a highly polluted area,and 0-10 cm is a heavily polluted area.The results of soil column experiment and numerical simulation combined show that the soil migration rule of lead-zinc mine is 0-20 cm,which is the most polluted area during the migration process,especially 0-10 cm is the most serious.(2)The characteristic analysis and spatial distribution of heavy metal pollution show that among the six functional areas,the mining area is the most polluted,among the three heavy metals,Cd pollution is the most prominent,the spatial distribution results reflect that the sewage treatment of the sewage plant area and the smelting behavior of the mining area have a great influence on the surrounding soil.In addition,the results of the study based on the improved hierarchical analysis method showed that the highest pollution index was found in mining area among the six functional areas,the pollution level of 100 % of the soil in the farmland and residential areas has reached the standard of extremely serious pollution,the pollution level of 95 % of the soil in the mining and tailings area reaches the standard of very serious pollution,and 75 % of the soil in the sewage plant area and reclamation area has reached the standard of extremely serious pollution.(3)The risk characteristics and spatial distribution of heavy metals show that the soil of lead-zinc mines is generally at a very high environmental risk level,among them,according to the six functional areas,priority should be given to mining areas as risk pollution source area,according to the classification of three heavy metals,the heavy metal Cd should be regarded as the priority control source of soil pollution risk in the study area.The spatiotemporal distribution shows that lead-zinc mines will reach a risk balance period on the 20 th day,and when the time exceeds 20 day,the pollution risk will increase sharply,among them,according to different functional areas,the mining area is the highest risk area,and the surrounding risk distribution shows a decreasing trend,secondly,there are still three high pollution risk areas,which are located in the north and east of the mine,and the pollution risk distribution presents an ’8’ shape.The ecological risk level of middle soil in lead-zinc mines will be significantly higher than that of surface soil.(4)The source analysis of heavy metals shows that the mining area is the total source type in the six different functional areas of the lead-zinc mine,there is a significant correlation between Zn and Cd in the three heavy metals.PMF analysis shows that there is a positive correlation between heavy metals Zn and Cd,among which the artificial factors that cause heavy metal Zn and Cd pollution in mine soil are blind mining and tailings stacking;The human factors causing heavy metal Pb pollution in mine soil are ore transportation and smelting sewage.Based on the above,the research results can put forward a clear pollution scope for mine soil pollution assessment,and also propose a reliable scientific method and technical means for mine soil pollution assessment system;On this basis,new insights on the migration law and risk characteristics of heavy metal pollutants are further put forward,which provides a new idea for soil environmental assessment in lead-zinc mines. |
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