Research On Migration And Restoration Of Heavymetal In The Typical Irontailings Region Of Shaanxi Province,China

Mineral processing activity and tailing dump caused serious pollution to the surrounding soil and water which posed a threat to the ecosystem and human health,the pollution was paid more attention,but the oxidation of magnetite area environmental problems often were ignored. Therefore, in this thesis,the typical magnetite tailings in southern shaanxi area was as the research object, using morphological analysis of heavy metals, the ecological risk assessment, analysis of soil microbial community, soil column leaching, such as research methods, heavy metals pollution condition of soil aroud the tailings area and the adsorption and migration pattern of the typical metal in the soil were studied, and the research on ecological restoration of the tailings soil was done.The results were shown below:（1） It wascomparatively studied the heavy metal pollution of soil around 30 a using tailings area and 10 a used tailings area, the results showed that:the all heavy metals（Fe, Mn, V, Cu, Ni,Zn,Co,Cd,Ti） in soil around 10 a used tailing areas were no pollution; however, all metals except Ti in the soil around 30 a using tailing area reached moderate pollution levels.The geo-accumulation index suggested that Cd,Ni and Cu polluted soil around 30 a using tailings area seriously which posed a remarkable pollution level. The risk assessment results performed that Mn showed moderate potential ecological risk and other metals showed low potential risk in the soil aroud the two tailings area. The average contents of metal in the 2 m profile were all beyond the local soil background values,Mn was the strongest potential migration ability metal in the tailings which was harm to groundwater potentially.（2） By adopting Biolog method combining with principal component analysis（ PCA）, it was found that the metabolic characteristics of different soil microbial communities varied significantly with increasing soil heavy metals pollution level.The variation was mainly manifested in the metabolic patterns of carbon sources such as by polymer and amino acids.In slightly and moderately polluted soils,the utilization of carbon sources by soil microbial communities was activated; while in heavily polluted soils,the carbon sources utilization was inhibited.McIntosh index could well reflect the degree of soil heavy metal pollution, and could be used as a sensitive indicator of mining area of soil heavy metal pollution. The activities of soil urease,alkaline phosphatase,catalase and dehydrogenase all tended to decline with intensifying soil heavy metals pollution level.The contentof As in soils impacted on urease,alkaline phosphatase,catalase negatively correlated,andthe content ofCd was significantly negative correlation with urease activity.（3）The adsorption behavior of typical soil which were including browns soil and rice paddies sand, towards Mn²⁺,Ni²⁺,Cu²⁺ and Cd²⁺were studied and simulated the adsorption kinetics process by mathematical model.The results showed that in two kinds of soilthe adsorption isotherm of Mn²⁺ and Ni²⁺,Freundlich equation was superior to the Langmuir adsorption isotherm equation,whearas the Langmuir equation was better for adsorption isotherm of Cu²⁺ and Cd²⁺.The equilibrium adsorption of heavy metals by soil was positively related with soil organic matter, cation exchange capacity, and clay content.（4）It was studied that the Mn²⁺, Ni²⁺, Cu²⁺ and Cd²⁺migrated patterns in the browns soil and rice paddies sand, and the equilibrium CDE model fitted the migration process in the soil column.Soil column leaching experiments proved that the soil had a great influence for the migration of the metal, due to browns soil hadstrong ability of adsorption ofheavy metal, it was slow migration process of heavy metals in the brown soil column, sand ability of adsorption for heavy metal was weak, the migration process ofheavy metals in the sand column was faster than in the brown soil column.Mn²⁺ mobility was strong, and Cu²⁺ mobility was weak in the research soils.Except Cu²⁺ equilibrium CDE model could simulate the other three metal migration in the two kinds of soil, and the fitting results were close to the actual experimental process.（5）The potted experiment results showed that the concentration of Mn²⁺ and Ni²⁺ could affect plant germination, growth situation.Thephosphatase activity and urease activity of infected soil changed with the plant growth and the infected concentration of soil.The phosphatase and urease activity was activate in the low concentration of Mn²⁺ and Ni²⁺ in the soil, inhibition in high concentration.Themicrobial community structure of infected soil was analysised, the results showed that the concentration of Mn²⁺ in soil had a certain influence onthe microbial community structure of soil.Principal component analysis showed that the soil microbial community structure stability would be affected obviously when the concentration of Mn²⁺ manganese was greater than 300 mg/kg in the soil.（6）The experiment of ecological restoration of iron tailings which modified iron tailings by soil conditioner showedthat :the urban sludge as a soil conditioner could improved soil physical and chemical properties whichreachedthe soil quality secondary standards.In the modified iron tailings plants could sprout, and growth normally, but excess sludge still need to deal with the sludge which reduced effective state content of heavy metals in sewage sludge, and prevent the migration to the plant.