| Astragalus sinicus L., a leguminous plant, was chosen as the experimental material to study the effects of copper(Cu) tailings on the growth, structure, physiological response and the tailing phytoremediation potential of A.sinicus by pot culture. The main research results are as following:1. The effects of different portions of Cu tailings on the growth, leaf and root structure and metals accumulation and trans-location of A.sinicus were studied by pot culture. The results showed that the growth and tolerance index of A.sinicus were in a trend of rise first then fall as the portions of Cu tailings enhanced. The plant height, root length, above-ground and underground part dry weights and tolerance index under pure Cu tailing stress decreased to 37.89%, 17.53%, 59.02%, 26.13% and 17.5% respectively. The trend of photosynthetic pigment contents were the same as the growth index, Chla, Chlb, Cxc contents were reached the lowest level as treated with 100% Cu tailing. Under the stress of Cu tailings, the quantities of chloroplast of some mesophyll cells in both of lamina and petioles were reduced compared with the controls. The root cortex cell accumulated a lot of starch grains, the starch could hydrolyze soluble sugar and improve the osmotic regulation ability of plant cells and reduce the toxicity of the Cu. The Cu2+ contents in root and shoot of A.sinicus dramatically increased with the portions of Cu tailings the enhanced.3. The effects of adding organic acids to Cu tailings on the physiological index of A.sinicus were studied. The results showed that the photosynthetic pigment contents under ethylendiamine tetracetic acid(EDTA) treatment were lower than control leaves, while, the photosynthetic pigment contents under citric acid(CA) and acetic acid(AC) treatments were increased. Under the treatment of EDTA and AC, the O2ยท- contents and conductivity values in the above-ground parts were higher than control. MDA content in AC treatment were higher than control and the content of above-ground parts increased 26.18%. The highest MDA content of underground part was found under the level of 0.1mmo/kg EDTA treatment and increased 38.16% than that of control. POD activity of above-ground part went to the highest levels under 0.1mmo/kg CA treatment and increased 29.23% than that of control. Under the treatments of EDTA and AC, Pro contents in above-ground part were higher than control and underground parts were less than those of control.4. The effects of adding three kinds of organic acids to Cu tailings on the effect of metals accumulation and translocation of A.sinicus were studied. The results showed that under the treatment of organic acids, the dry weight of above-ground and underground part of A.sinicus were lower than the control. Under the low concentration of EDTA and AC treatments, the tolerance indexes were higher than that of control. Cu contents on the above-ground parts under the treatments of AC and CA were significantly decreased. Three organic acids treatment promoted thetrans-location of Pb from roots to the above-ground parts. The maximum Pb contents in the roots were found under the treatment of 1mmol/kg EDTA, while, 1mmol/kg AC treatment promoted significantly Pb contents in the underground part. Under the treatments of AC and CA, translocation rate of Pb were higher than those of control. The mobility rate of Ca under three kinds of organic acid treatment was higher than that of control. The result shows that EDTA with high concentration of AC significantly inhibit the growth of milk vetch, A.sinicus can not only repair Cu pollution of the environment, but also have higher concentration of Pb which can be used for the fixing of Cu tailings dam.The result showed that A.sinicus could grow in Cu tailings environment and improve the environment of the tailings and could be used for Cu contaminated environment remediation and tailings dam fixed. The addition of organic acids could not increase the accumulation of Cu, but could significantly promote the Pb accumulation. |
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