| In recent years, the soil heavy metal pollution has been increasingly serious in our country, in addition, many species of heavy mental come into being with uranium, which can interact with each other and lead to some multiple ecological responses. Phytoremediation has been concerned and applied widely for its safety, green, easiness to operate, the further importance was that the phytoremediation never cause any additional pollutions. 29 common species of plants were cultivated into pots, under the uranium concentration of 150 mg/kg, the plants with more biomass, higher accumulating capability and strong resistance under stress of uranium was screened by using the Principal Component Analysis Method. Then these plants were treated as the experimental materials in the second parts to be studyed on their growth, uranium uptook, transfer as well as the physiological and biochemical characters under the stress of U?Cd single and the U-Cd combined pollution. The main results were shown as follows:(1) Under the uranium concentration of 150 mg/kg, the biomass varied because of different species and parts. Uranium could promote the growth of S. kochii,R. sativus and B. juncea while inhibit the S. trifasciata Prain, B. rapa and L. sativa The additional biomass of B. juncea in above-grounds and roots of P. sativum were more than others. The capacity in U uptake, transfer and accumulation among the diverse plants was very different. The highest U content in above-grounds and roots were respectively O. javanica and Z. pendula,the detail number were 1082.06mg/kg and 2543.72mg/kg, meanwhile, the BCF of O. javanica above-grounds 7.21 and Z. pendula under-grounds 16.96 were at the highest level, but their U accumulation were smaller. Except the L. sativa 3.05 and B. juncea 1.25, the TF of all of the plants in this study is less than 1. Thus, the biomass and capacity of accumulation in a U concentration varied from plants to plants, their U transport capacity was poor.(2) By using principal component analysis method combined with membership function method, the indexes of enrichment characteristics for U and biomass accumulation of plant were scientific quantified and evaluated comprehensively, and ultimately determine that Z. pendula and O. javanica were uranium enrichment plant and they had a high comprehensive evaluation of D value, indicateed that the uranium enrichment characteristics of them were better than others, they had great potential in remediation of U contaminated soil.(3) Under the U?Cd single and combined treatment, enrichment plants' growth and development varied because of different kinds of heavy metal elements, different treatmented concentration, different species and parts. U?Cd single treatment inhibited the plant height, stem diameter and biomass of O. javanica and Z. pendula, while, their root length in the treatment of the concentration of 15 mg/kg was promoted, under the conditions of 150mg/kg was inhibited, U inhibition is greater than Cd. Treatmented effect of U-Cd combined treatment and U?Cd single treatment was the same. The growth of enrichment plant under the U-Cd combined treatment was the worst, the performance of U and Cd as antagonistic action. In addition, Z. pendula to U?Cd single and combined treatment tolerance than O. javanica, indicates that Z. pendula has good tolerability of U, Cd element.(4) The absorption, transport and accumulation ability of Cd and U elements in enrichment plant, Under the U ? Cd single and U-Cd combined treatments, plants aboveground parts absorb ability was greater than underground, underground enrichment factor of plant was greater than 1, transfer factor was less than 0.5, The underground part was the main organ of the plant to enrich U and Cd elements. The absorption and enrichment ability of plants to U and Cd elements were different in the types, quantities of heavy metals, the treatmented concentration and composition, the different types and different parts of plants. Under the single stressed of U and Cd, O. javanica was good for the absorption ability of U element,Z. pendula was good for the absorption ability of Cd elements; under the same concentration treatment, O. javanica's bioaccumulation quantity was better than Z. pendula. In addition to U-Cd compound treatment, compare the differences between the content, bioaccumulation factor, transfer coefficient and bioaccumulation quantity of U?Cd, O. javanica was better than Z. pendula. So, O. javanica had good repair potential in U?Cd single and U-Cd combined pollution of contaminated soil, Z. pendula had good repair potential in Cd single and U150+Cd15 compound pollution.(5) Physiological and biochemical characteristics of enrichment plant: with the higher concentration of Cd and U, the stress effect was more significant, and the effect of U was greater than Cd. the root activity of enrichment plants was promoted in low concentration and suppressed in high concentration, with the increase of the concentration, the leaf of chlorophyll content decreased, relative conductivity increased, the cell membrane lipid peroxide process intensified, MDA content increased, cell membrane permeability strengthened, leaf cell membrane structure damaged, antioxidant activity in plants strengthened and SOD, POD, CAT enzyme activity increased. Enrichment plants had a high absorption ability of U and Cd under U and Cd stress. |
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