Benefit Estimation Of Land Reclamation And Environment Remediation For The Tailings Pond Of Chaihe Lead-Zinc Mine

The tailings pond formed by mineral separation in non-ferrous metal mines is a potential and high-risk heavy metal pollution source.There are some problems such as dam break risk,heavy metal diffusion and ecological environment pollution after the pond closed.Therefore,the reclamation and remediation measures should be carried out in time after closing the pond.One of the important goals of land reclamation and environment remediation in non-ferrous metal tailings pond is to prevent the heavy metal diffusion and realize the source control of pollution.What measures can be chosen to effectively prevent the heavy metal diffusion and maximize the benefit of reclamation is the key to the reclamation of tailings pond.It is of great significance to construct an appropriate benefit estimation model and accurately estimate the benefit of reclamation measures in tailings pond for optimizing reclamation measures and reasonably determining the investment of reclamation funds.According to the main goal of reclamation of tailings pond,the key measure of reclamation and remediation is soil covering and vegetation restoration.Taking the PSR model as the theoretical basis,article constructs the benefit analysis system of tailings pond reclamation measures based on PSRE model,and systematically analyzes the whole process from the tailings pond closing to the implementation of reclamation measures to producing the benefits.This paper determines the main benefit composition of soil covering and vegetation measures combined with the theory of ecosystem service function.According to the performance of each benefit,determines the method of benefit estimation by reference to the existing relevant research,and constructs the corresponding benefit estimation model.Take the Chaihe lead-zinc mine tailings pond as the research object.According to the situation of reclamation demonstration area.Three different soil covering and vegetation measures,such as 50 cm of soil covering with Amorpha fruticosa L.(measure 1),30 cm of soil covering after geotextile covering with Amorpha fruticosa L.(measure 2)and 150 cm of soil covering with Robinia pseudoacacia and Amorpha fruticosa L.(measure 3),are selected to estimate the benefit of each measure by the direct market method,shadow engineering method,alternative cost method,restoration cost method,ecological service value method and energy value analysis method.The results of the benefit estimation showed that:(1)In the economic benefits,(a)for the production of biological resources,the reclamation of Chaihe lead-zinc mine tailings pond mainly plant the resilient arbors and shrubs.Due to the risk of heavy metal pollution in the vegetation,the benefit is very small,negligible.(b)For the tailings resource preservation,after several years,the tailings resources reused can produce a potential benefit about 97.954 million yuan.(2)In the ecological-environmental benefit,(a)for the underground leaching and diffusion prevention,50 cm of soil covering with Amorpha fruticosa L.can reduce the leaching amount of 80% and its benefit is 29.7524 million yuan per year.30 cm of soil covering after geotextile covering with Amorpha fruticosa L.can reduce the leaching amount of 96% and its benefit is 34.4956 million yuan per year.150 cm of soil covering with Robinia pseudoacacia and Amorpha fruticosa L.can restrain leachate production under normal rainfall condition,and its benefit is 36.0475 million yuan per year.(b)For the surface runoff erosion and diffusion prevention,50 cm of soil covering with Amorpha fruticosa L.and 30 cm of soil covering after geotextile covering with Amorpha fruticosa L.can both reduce 70% runoff erosion,their benefit are 12.2266 and 25.8571 million yuan per year respectively.The key of soil covering is to restrain heavy metal migration and reduce heavy metal content in topsoil.150 cm of soil covering with Robinia pseudoacacia and Amorpha fruticosa L.can reduce 96% runoff erosion,and no heavy metal pollution,its benefit is 25.8675 million yuan per year.(c)For the wind erosion and diffusion prevention,50 cm of soil covering with Amorpha fruticosa L.and 30 cm of soil covering after geotextile covering with Amorpha fruticosa L.can reduce the amount of dust up to 75%,and 150 cm of soil covering with Robinia pseudoacacia and Amorpha fruticosa L.can reduce up to 90%.All of the three measures can effectively control the spread of heavy metal by wind erosion and their benefit are 12.3545,12.3545,12.3786 million yuan per year respectively.(d)The total ecological-environmental benefits of the three measures are 54.3335,72.7072,74.2936 million yuan per year respectively.(3)In the social benefit,(a)for the scientific research and education,the area of the tailings pond after reclamation can be used as the practice test base of colleges and the scientific research demonstration area of scientific research institutions,which has certain scientific research and education benefit,about 3.0978 million yuan per year.(b)For the employment increasing,the reclamation project can provide more employment opportunities for the unemployed,resulting in an increase in employment benefits of 17.3229 million yuan per year.(c)For the health security,reclamation effectively controls the spread of heavy metal pollution and improves the ecological and living environment around the pond area,resulting in a health protection benefit of 3.3067 million yuan per year.(4)The benefits of soil covering and vegetation restoration in reclamation and remediation of Chaihe lead-zinc mine tailings pond are mainly in ecological environment.Among the ecological-environmental benefits,the benefit of underground leaching accounts for about 50%,the benefit of the surface runoff erosion accounts for about 35%,and the benefit of wind erosion accounts for about 15%.The selection of soil covering and vegetation restoration measures should be mainly to control rainfall infiltration and leaching.(5)In terms of comprehensive benefits,30 cm of soil covering after geotextile covering with Amorpha fruticosa L.and 150 cm of soil covering with Robinia pseudoacacia and Amorpha fruticosa L.have relatively better remediation effects.The former can appropriately reduce the thickness of soil after setting up the isolation layer and save the cost of reclamation and remediation.The cost of thick overlying soil of the latter is relatively high,but it can plant the vegetation with deep roots,which is beneficial to the restoration and development of ecological environment in the tailings pond area.