Characteristic And Environmental Impact Assessment Of Mine Geological Environment In Sichuan Province

Based on the mining geological environment survey of Sichuan Province,this thesis starts with the present situation of exploitation and utilization of mines in Sichuan Province,we creatively introduced eco-geochemical evaluation methods,and carried out multi-scale mine geological environment assessment.We achieved the following results:(1)Oriented by Geological Environment Problem of mines,we creatively established the system of multi-scale mine geological environment assessment methods,which could effectively guide the environmental impact assessment of different types of mines in Sichuan Basin and provide new methods for the National Mines environmental impact assessment.(2)Based on the characteristics of large area of Sichuan Province,wide-spread and multi-issues mines,it is hard to evaluate objectively according to a single metric,This thesis combines the method of big data and adopting the index of superposition model based on GIS which has strong ability of spatial overlay analysis and calculation,Then we use ILWIS software to evaluate the model data superposition,spatial analysis,establish evaluation model,and carry out the safety assessment of mine geological environment impact of Sichuan Province.(3)The results of the mine geological environment impact in Sichuan province indicate that the impact index are most under 0.10,partly distributes range from 0.1 to 0.2,and more than 0.3 is less-distributed.The geological environmental impact regions of the whole province is divided into three large regions,26 sub-regions,of which seriously affected regions account for 5.30% of the area of whole province,more severelier areas account for 17.68%,light impact areas accounts for 77.02%.(4)Aim at the areas of special geological landform landscape background,Based on the established discriminate standard of the extent of soil pollution,we choose representative mines and adopt single factor index method,Nemerow pollution index method and pollution load index method to make a detailed evaluation of surface soil polluted by single element and the comprehensive pollution,we put forward a new idea of computing background values of soil environmental and pollution levels,and establish a suitable method to assess the impacts of regional level applicable mine geological environmental.(5)This thesis first proposed the median of deep soil element content as the background values of soil elements under special geological environment,which can objectively reflect the geochemistry characteristics of soil in this region.The median value is an important indicator of geological environmental impact assessment in regional mining.(6)The results of the assessment of the geological environmental impact of representative mines are as follows: in the view of pollution degree,more than 50% of the representative mine soil is lightly and moderately polluted,and few regions are seriously polluted,and the degree of pollution is different.From the view of characteristics of pollution,the pollution is mainly concentrated in the regions where mine mined and occured,and it combined well with pyrite ore and the strata trend of mining.Bounded by ore bearing strata,seriously polluted soil distributes on both sides of it,and the extension distance is about 4-6km in the southwest,while it extended to 6-8km in the northeast.The source of pollution comes from two respects: the main one is mine exploiting of pyrite,smelt and other mine-related activities and the secondary one is background pollution of the soil which is caused by the special geological and geochemical conditions,and it has adsorption coagulation to heavy metal elements in the pedogenic process of carbonate area.(7)A typical single mine geological environment impact assessment should select the appropriate investigation and evaluation method based on the major mine geological environment problems;the thesis selects a representative copper mine pollution as an example in PanXi region,we use the method of Igeo for the study of single mine geological environmental impact assessment.(8)The single mine geological environment evaluation results shows that heavy metal pollution of soil in a mining region located in southwest of China was rather serious,and the degree of heavy metal ordered from high to low is as follow: Cd>Hg>Cu>Cr>Pb>As.The material sources and distribution of the soil is controlled by the condition of primary geochemistry,and artificial mining also has an important impact on the distribution pattern of heavy metal pollution of mine soil.