| A pile of mine tailings which released by mining not only occupy a great of land, waste sources, but also brings heavy metals and other harmful elements into environment by leaching, weathering, and oxidation that would destroys the ecosystem, so it is the critical threat of mine environment.The distribution and chemical forms of Cu, Pb, Zn, Mn, Cd in tailings from Cao duikeng tailing reservoir, tailing outlet port and Tie long tailing reservoir in Dabaoshan mine were studied based on mineralogical and chemical analyses as well as sequential extraction. And then the potential migration ability of heavy metals was analyzed on the basis of the speciation of heavy metals, also ecological restoration of Dabaoshan mine was discussed. In summary, the dissertation includes the following contents and conclusions:(1) The main mineral composition of tailings from Dabaoshan mine is goethite, hematite and quartz. Still, clay minerals such as kaolinite, gypsum exist in small smout. The percentage composition of quartz in samples from tailng outlet port is lower than Cao duikeng tailings and Tie long tailings, so the weathering level is lower.(2) The major elements of all the tailings samples are Fe, Si and O, and the sum of the three elements content account for about 80% of the total. The highest content of element in Cao duikeng tailings and fresh tailings is Fe, while the content of Si is higher than Fe in Tielong tailings.(3) All the tailings samples are rich in Cu, Pb, Zn, Mn, Cd. The content of Cu is 3~7 times amouts of the third level criterion of Standard of Soil Environment , and for Pb ti is 2~8 times, for Zn it is 1~4 times. The content of Mn ranges from 20.6 to1562.8 mg / kg, and ti is more than 1000 mg/kg in fresh tailings. The content of Cd ranges from 13.22 to 18.72 mg/ kg..(4) The most of Cu, Pb, Zn, Mn, Cd are in the form of sulfides in surface layer samples from tailng outlet port, and they mainly exist in sulfides. While the dominating chemical forms of Cu, Pb, Zn, Mn, Cd is residual silicates in Cao duikeng tailings. They mainly exist in silicate minerals and residul, and it is hard for them to release to ambientenviroment.(5) The mobility of heavy metals in Cao duikeng tailings and Tie long tailings follows theorder: Mn>Cd>Zn>Cu>Pb, and in fresh tailings the mobility of metals follows theorder: Mn> Cd>Cu>Zn>Pb. The potential migration ability of Cu, Pb for different areas follows theorder: fresh tailings> Tie long tailings> Cao duikeng tailings. And the potential migration ability of Zn, Mn, Cd for different areas follows theorder: Tie long tailings>fresh tailings> Cao duikeng tailings.(6) The methods for ecological remediation of mines have been discussed. The Dabaoshan mine has 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.
|
PDF Full Text Request