The Mine Environmental Pollution And Remediation In Large Metal Mines

The environmental problems around mine have not been paid much attention for a long time due to its regionality. The living standard has been raised as a result of economic growth and social development, which make the people pay more and more attention to ecological and environmental problems and also to the environmental geologic problems of mine. The environmental pollution and ecological destruction caused by mining and smelting is a global event which has become an important research field for environmental geochemistry.Jinchang city and Baiyin city are the typical mining cities based on exploitation of Jinchuan Ni-Cu magmatic sulfide deposit and Baiyin Cu-multi-metals deposits. They are also the important manufacture bases of nonferrous multi-metals in China. However, in the past half century, eco-environmental problems caused by the mining and smelting of Jinchuan and Baiyin mines were devoid of corresponding recognition and comprehensive study. Through general data collection and the field studies and lab analyses, the study focused on the characteristics of environmental geochemistry of heavy metals in mine tailings, waste dump, soil, water system, sediments and plants.The research reveals that the forms, releasing, migration, transform and mobility in different mediums and their ecological effects. Furthermore, the potential environmental harm of heavy metals on soil, water system and sediments has been assessed. In the end, the releasing, migrating and transforming models of heavy metals among different mediums are constructed. In summary, the dissertation includes the following contents and conclusions:(1) Environmental pollution of Jinchuan and Baiyin is very serious. The SO₂ pollution in the atmosphere and heavy metals contamination are the main pollution problems in Jinchuan. Except for two kinds of pollution above, acid mine drainage (AMD) formed by sulfide minerals oxidation is particularly more serious in Baiyin. The contamination is original from AMD produced by waste slagheap and tailings oxidation, the weathering and atmospheric deposition and pollution irrigation.(2) The concentration of heavy metals in tailings and waste slagheap is very high, which is also the main source of contaminants for heavy metals releasing and AMD forming. Heavy metal contaminations are mainly from Cu and Ni in Jinchuan and Cd, Cu, Pb and Zn in Baiyin. Analyzed results of chemical forms of heavy metals show that Ni in tailings of Jinchuan and Pb in waste slagheap of Baiyin have strong mobility, which suggested that Ni and Pb have the great potential harm to the surroundings.(3) Water bodies in the mines are not only direct objects of heavy metal pollution, but also the important carriers of heavy metal transportation. The water bodies in Jinchuan, mainly containing Cu and Ni, were moderately polluted. While for the water bodies in Baiyin were heavily polluted by all the heavy metals except Pb which was in the alerting level.(4) In contrast to water bodies, the sediments in Jinchuang and Baiyin have more highly concentrated heavy metals. Because of effect of tailings, the concentration of Cu and Ni in Jinchuan is ten to tens times of the third class of National Soil Quality Standard values. The highest concentrations of Pb and Zn in Baiyin is 20 times of the third class of National Soil Quality Standard values, which indicate a great account of heavy metals have deposited from water to sediments which become the potential secondary source of pollution.(5) Cu and Ni as the main soil pollutants in Jinchuan are distributed in southeast and northwest, whose contamination level is greater in the southeast than in the northwest. The soil contamination in Baiyin is distributed in east and southeast, particularly, Cd is seriously contaminated in the whole region due to pollution irrigation. The analysis of chemical forms of soil heavy metals show the mobility of heavy metals in the descending order: Ni>Cu>Pb>Zn>Cr in Jinchuan and Cd>P b>Cu>As>Zn in Baiyin.(6) Ecological risk and heavy metals pollution evaluation using Nemerow index and potential Ecological Risk index show potential ecological risk is light in Jinchuan, but the most dangerous in Baiyin. The Ecological Risk factor in soil of the mine area is Ni, followed by Cu, Cd, Cr, Pb and Zn in Jinchuan and Cd, followed by Cu, Pb and Zn in Baiyin.(7) The releasing and transport models of AMD and heavy metals have been established through the studies of the storage, transport, transformation, and conditions of the mine exploration, as well as the recycling and accumulation of heavy metals in various environmental mediums.(8) The methods for ecological remediation of mines have been discussed. The mines have been classified into three remediation areas and the remediation process has been divided into three steps. By improving the soil environmental qualities, the suitable ecological conditions and structures for plants will be created, the dynamic balance for ecological system of mines will be established, to obtain the sustainable remediation of ecological systems for mine area.