Phytoremediation Technology On Pollution Control Of Heavy Metals And Soil Improvement In Utilization Of Iron Tailings

With the rapid development of mining and mineral processing of iron mines in China,the discharge of iron tailings has increased dramatically.The amount of iron tailings is increasing because of the low comprehensive utilization rate,leading to the serious environmental pollution and ecological damage.Therefore,the large-scale resource utilization and pollution control of iron tailings are of great significance to break through the technical bottlenecks in the industry.Phytoremediation technology has many advantages such as low cost,good repair efficiency,less on-site disturbance and good capability to integrate with other recovery techniques.It is a promising technology.Based on the comprehensive study and systematic analysis of domestic and foreign research,pot experiment and field application were carried out for the phytoremediation technology research in the process of soil utilization of iron tailings,taking the iron tailings of Dagushan tailings reservoir in Anshan as the research object.On the one hand,the main problems of the soil physical and chemical properties about tailings were improved,including small particle size,defective soil aeration,poor water retention,low organic matter content and serious heavy metal pollution.On the other hand,the heavy metal pollution was effectively controlled.Moreover,the engineering application was realized.The results are as follows:(1)According to comprehensive investigation of plant resources in Anshan area and the related research about phytoremediation,Medicago sativa L.,Kochia scoparia(L.)Schrad.and Suaeda glauca were chosen as typical plants to carry out laboratory and field research.(2)Based on the systematic investigation and on-site monitoring,Cd?Pb?Mn were selected as target heavy metals.A series of Cd,Pb and Mn contaminated soils were planted and pot experiment was carried out.The aboveground biomass,chlorophyll content and catalase activity of plants were measured after ripening to assess their adaptability to the special environment in the proess of soil utilization of iron tailings.The results showed that low concentration of Cd and Mn could stimulate the growth of Alfalfa,while the high concentration of heavy metals had a significant inhibitory effect on its biomass.Biomass of Broom cypress and Suaeda decreased with the increasing concentration of heavy metal.The chlorophyll content of three kinds of plants also decreased with the increasing treatment of heavy metal.Catalase activities in leaves of Alfalfa,Broom cypress and Suaeda were increased at first and then decreased with increasing Cd,Pb and Mn treatments and they were all higher than the respective control.(3)To assess the effects of three kinds of plants on soil improvement,the soil organic matter content,pH value,water content and enzyme activity were measured after plant harvest.The maximum growth rates of soil organic matter content were 49%,45%and 38%,respectively,and the maximum growth rate of soil catalase activity were 66.7%,85.4%and 72.7%,respectively.The soil pH value after Suaeda and Broom cypress introduction decreased by about 0.4,and that decreased by about 0.2 after Alfalfa introduction.The maximum soil water content reached 9.4%,9.5%and 9.1%under Alfalfa,Broom cypress and Suaeda introduction respectively,which increased by about 2%.The improved soil has met the standards for plant growth.(4)Contents of Cd,Pb and Mn in the plant and soil were measured to evaluate the tolerance,enrichment ability of heavy metals about three kinds of plants.Results showed that the enrichment ability of three kinds of plants in Cd is in the order of Suaeda>Alfalfa>Broom cypress.The enrichment ability in Pb is in the order of Broom cypress>Suaeda>Alfalfa.The enrichment ability in Mn is in the order of Suaeda>Broom cypress>Alfalfa.The order of tolerance and enrichment ability of three heavy metals in Alfalfa and Suaeda was Mn>Cd>Pb,while the order in Broom cypress was Pb>Mn>Cd.(5)According to the results of laboratory research and other research results in our studying team,successful application of phytoremediation technology was carried out in the site..Broom cypress,Soybean and Dianthus chinensis was selected.Regular monitoring of plant growth and related index was also carried out.The results showed that the physical and chemical properties of tailings were significantly improved.The pH value in tailing decreased by about 0.6;The water content increased by about 50%,and the organic matter content increased by 70%?109%.The Broom cypress and Soybean growed up to 98cm and 82cm,respectively.The coverage of Dianthus chinensis was 100%.Moreover,the main pollution of heavy metals in the tailings were also effectively controlled.The removal rates of Cd,Pb,Mn,Zn and Cu were up to 13%?49%.