A Comparative Study On Removal Performance Of Mercury And Cadmium In Agriculture Soils For Several Plants

Soil is not only an important constitution of natural environment, but also an indispensable material basis for human survival and development. With rapid economic development and accelerating urbanization, soil, especially agricultural soil heavy metal pollution become more and more serious. Thus, contaminated soil remediation caused great attention by people. As an environmental treatment technology which was developed in early1980s, phytoremediation had become hot spot of environmental remediation and engineering science frontiers. Comparing with physical and chemical restoration, this technology has incomparable advantage.Agricultural soil heavy metals (Hg, Cd) pollution is one of the most prominent problems in china,.based on the review of phytoremediation of Hg, Cd pollution, in the research conducted for this dissertation, better accumulation effect plant species was chosen, uncontaminated agricultural soil was applied, exogenous add pollutants was added, and pot-culture experiment was used. Remediation effect of Pteris vittata L.,Boehmeria nivea L. and Agrostis matsumurae H. to the soil polluted by Hg and Bidens pilosa L., Sedum polytrichoides, and Mirabilis Jalapa L. to the soil polluted by Cd was studied. Biomass, absorbing amount, enrichment coefficient, and transfer factor of remediation plants was compared in different growth periods (sampling frequency for five times), correlation between biomass above ground and heavy mental absorbing amountwas analyzed, in order to screen species which adapted to local climatic condition and better repair effect to Hg, Cd pollution.The main results as follows: (1) It was showed that Boehmeria nivea L. had the best absorbing effect to Hg pollution. Under low concentration of Hg (2.0mg/kg), the range of Hg concentration in the aboveground part of Boehmeria nivea L. was0.12～0.43μg/g, the absorbing amount0.30～3.12μg/pot, the extraction efficiency0.045‰～0.05%, the enrichment coefficients0.06-0.32, the transfer factor0.67-0.80; Under high concentration of Hg (10.0mg/kg), the range of Hg concentration in the aboveground part of Boehmeria nivea L. was0.27～1.26μg/g, the absorbing amount0.65～9.71μg/pot, the extraction efficiency0.018‰～0.03%, the enrichment coefficients0.03～0.13, the transfer factor0.57-0.91. Under different concentrations level, the growth rates of Boehmeria nivea L. were almost the same. It was suggested that Boehmeria nivea L. had higher pollution resistance, and was the optimization specie for agriculture soil Hg remediation.(2) It was showed that Bidens pilosa L. had the best absorbing effect to Cd pollution. Under low concentration of Cd (1.2mg/kg), the range of Cd concentration in the aboveground part of Bidens pilosaL. was1.00-10.63μg/g, the absorbing amount1.86～194.25μg/pot, the extraction efficiency0.042%～4.44%, the enrichment coefficients0.80～9.84, the transfer factor1.18～4.11; Under high concentration of Cd (12.0mg/kg), the range of Cd concentration in the aboveground part of Bidens pilosa L. was8.12～31.74μg/g, the absorbing amount16.42～609.32μg/pot, the extraction efficiency0.039%～1.45%, the enrichment coefficients0.67～2.71, the transfer factor1.17～2.00. Under different concentrations level, the growth rates of Bidens pilosa L. were almost the same. It was suggested that Bidens pilosa L. had higher pollution resistance, and was the optimization specie for agriculture soil Cd remediation.