| One of the key technologies for the biological purification of uranium-containing wastewater is the screening of aquatic accumulator plants.Hydroponic solution culture experiments which use Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.as materials are adopted to study the accumulation characteristics and removal ability of U and associated heavy metal Cd,As,and Mn in waste water,and analyze the effects of both physiological and biochemical indices in the test of single contamination.In addition,four-factor regression orthogonal rotation combination design is adopted to study the accumulation laws of U,Cd,As,and Mn in the test of compound contamination.The results of the study are as follows:?1?The accumulation of U by Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.was mainly concentrated in their roots,and the capacity of accumulation and transportation U by the former were greater than the latter.The maximum concentrations of U by the stem-leaf and root of Ipomoea aquatica Forsk.were 626.98mg·kg-11 and3655.49mg·kg-1,respectively.The removal rates of U by Ipomo aquatica Forsk.and Setcreasea purpurea Boom.were the highest under the treatments of 5mg·L-11 U,which were 89.31%and 78.55%,respectively.With the increase of the concentration of U,the growth amounts of fresh weight and photosynthetic performance indexs of Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.decreased gradually,while the activity of SOD and POD and the contents of soluble protein,proline and photosynthetic pigment of leaves increased firstly and then decreased.Under the treatments of 25mg·L-11 U,Ipomoea aquatica Forsk.died,and physiological and biochemical indexes of it were smaller than the control.?2?The transportation coefficient of Cd by Ipomoea aquatica Forsk.was all greater than 0.5.The transportation coefficient of Cd by Setcreasea purpurea Boom.increased with the increase of the concentration of U,and it was greater than 1 under the treatment of 10.8mg·L-11 Cd.The removal rates of Cd by Ipomoea aquatica Forsk.were smaller than that by Setcreasea purpurea Boom.,and the maximum removal rate of Cd by the latter was 77.39%.With the increase of the concentration of Cd,the activity of SOD and POD,and the contents of soluble protein,proline and photosynthetic pigments of Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.increased firstly and then decreased,while the photosynthetic rates and photosynthetic performance indexs decreased gradually.Under the treatments of 10.8mg·L-11 Cd,Ipomoea aquatica Forsk.died,and physiological and biochemical indexes of it were smaller than the control.?3?The accumulation of As by Ipomoea aquatica Forsk.was mainly concentrated in the roots.The transportation coefficient of As by Setcreasea purpurea Boom.was greater than 1,but the total accumulation coefficient and accumulation amounts were not large.The removal rates of As by Ipomoea aquatica Forsk.were greater than that by Setcreasea purpurea Boom,and the maximum removal rate of As by the former was up to 75.11%.With the increase of the concentration of As,the growth amounts of fresh weights,the activity of SOD and the contents of soluble protein of Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.increased firstly and then decreased.Under the treatments of 4mg·L-11 As,Setcreasea purpurea Boom.died,and physiological and biochemical indexes of it were all smaller than the control.?4?Under the treatment of 100mg·L-11 Mn or less,the transportation coefficient of Mn by Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.were all greater than1.The maximum accumulation concentrations in stem-leaf of both were 2315.25mg·kg-1and 2203.53mg·kg-11 respectively.The removal of Mn by Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.were both concentrated in the first 7 days.The removal rates of Mn by them were both greater than 90%.With the increase of the concentration of Mn,the growth amounts of fresh weights,the activity of SOD and POD,the contents of soluble proteine and soluble protein and photosynthetic rate of Ipomoea aquatica Forsk.and Setcreasea purpurea Boom.increased firstly and then decreased.?5?In the test of compound contamination,the accumulation amount of U?r=0.4374*?,Cd?r=0.6672**?,As?r=0.6376**?and Mn?r=0.5854**?by the root of Ipomoea aquatica Forsk.had a significantly positive correlation with their concentrations in the water.Similarly,the accumulation amount of U(r=0.5272**),Cd?r=0.4394*?and As?r=0.4028*?by the stem-leaf of Ipomoea aquatica Forsk.had a significantly positive correlation with the concentration of Mn in the water.However,the accumulation amount of U(r=r=-0.6358**)by the root of Ipomoea aquatica Forsk.had a significantly negative correlation with the concentration of Mn in the water.The accumulation amount of Cd(r=-0.7108**)by the stem-leaf of Ipomoea aquatica Forsk.also had a significantly negative correlation with the concentration of U in the water. |
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