Phytoremediation Mechanism And Application Of Heavy Metal Cr, Pb, Zn And Cd

The experiment was conducted to study selection of plants in20plants under the condition of6mg/L concentration of Cr (Ⅵ), Pb and lOmg/L concentration of Pb, Zn and Cd composite pollution and choose two plants with growing fast and high enrichment of heavy metals, one in Pb, Zn and Cd different concentration gradient and the other in Cr (Ⅵ) and Pb different concentration gradient. The paper researched their rule of accumulating heavy metals and the influence to the physiological and biochemical characteristics on nutrient solution culture, such as enzyme activity, proline, and malondialde(MDA), and analysis of accumulation of heavy metals and heavy metal stress on soil enzyme activities. The results of the study show that:1. The experiment of selection in6mg/L concentration of Cr (Ⅵ), Pb and lOmg/L concentration of Pb, Zn, Cd composite pollution.(1)The Syngonium podophyllum have a good growth condition, and the accumulation to Cr (Ⅵ), Pb in the overground part of it were569.79mg/kg and787.50mg/kg under the composite pollution of Cr (Ⅵ) and Pb. The Syngonium podophyllum had a high accumulation quantity to Cr (Ⅵ) and Pb.(2)The Plantago asiatica have a good growth condition, and the accumulation to Pb, Zn, Cd in the overground part of it were341.79mg/kg,464.25mg/kg and46.98mg/kg under the composite pollution of Pb, Zn and Cd. The Plantago asiatica had a high accumulation quantity to Pb, Zn and Cd.2. The enrichment regularity for Cr (Ⅵ) and Pb and physiological and biochemical effect of Syngonium podophyllum in single and composite pollution of Cr (Ⅵ) and Pb.(1)Wth the increase of concentratio(0～20mg/L) Cr (Ⅵ) in the solution, the accumulation of Cr (Ⅵ) increased in shoots and roots of Syngonium podophyllum, and the accumulation of Cr (Ⅵ) in shoots was more than it in roots. The maximum amount of the shoot accumulation of Cr (Ⅵ) reached1489.40mg/kg, the maximum amount of the roots reached2263.91mg/kg; With the increasing of Pb concentration (0～50mg/L) in the solution, the accumulation of Pb increased in shoots and roots of Syngonium podophyllum, and the accumulation of Pb in roots was more than it in shoots. The maximum amount of the shoot accumulation of Pb reached1555.46mg/kg, the maximum amount of the roots reached2311.23mg/kg. With the increase of Cr (Ⅵ), Pb concentration, the enrichment coefficient of Cr (Ⅵ), Pb gradually decreases, that indicated heavy metals migrated to plants from the media within a certain range; The transfer coefficient of Cr (Ⅵ) gradually increased, indicated that Syngonium podophyllum promoted Cr (Ⅵ) aboveground transport at higher Cr (Ⅵ) concentration.(2)In Cr (Ⅵ), Pb compound pollution, Stress on the same concentration of Pb, with the increase of Cr (Ⅵ) concentration, the shoots and roots of Syngonium podophyllum accumulated Cr (Ⅵ) was gradually increased, the accumulation of Pb gradually reduced; Stress on the same Cr (Ⅵ) concentration, with the increase of Pb concentration, the shoots accumulated Pb gradually increased. The distribution law of Cr (Ⅵ), Pb in the body of Syngonium podophyllum:roots> shoots.(3)With the increase of Cr (Ⅵ) concentration, the activity of SOD and CAT firstly increased and then reduced, SOD activity reached the maximum481.03U/g,182.95%higher than the control, CAT activity reached maximum399.94mg/(g.min), higher than the control of238.19%, proline content and MDA content increased in the Syngonium podophyllum; With the increase of Pb concentration(0～50mg/L), the activity of SOD and CAT firstly increased and then reduced, SOD activity reached the maximum486.75U/g, higher than the control100.83%, CAT activity reached maximum421.08mg/(g.min), higher than the control149.73%, proline content and MDA content increased.3. The enrichment regularity for Pb, Zn and Cd and physiological and biochemical effect of Plantago asiatica in composite pollution of Pb, Zn and Cd.(1)With the increase of heavy metals concentration, the absorption of heavy metals of Plantago asiatica was gradually increased, and the roots was larger than the shoots. When Pb, Zn and Cd concentrations were less than40mg/L,60mg/L, and2.5mg/L, separatively, Plantago asiatica was basically normal growth. The leaves of Plantago asiatica ended chlorosis, and gradually wither with the high concentrations of Pb, Zn and Cd.(2)Under heavy metals contamination, with the increasing concentration of heavy metals, SOD gradually increased, CAT firstly increased and then reduced, proline and MDA were gradually rising trend overall.4. The enrichment regularity and enzyme activity for Pb, Zn, Cd and Cr (VI), Pb in composite pollution of Pb, Zn, Cd and Cr (Ⅵ), Pb(1)In this study, when Cr, Pb concentration was0-700mg/L,0-1000mg/L respectively, Syngonium podophyllum was normal growth, when Cr (VI) concentration was greater than300mg/kg, Pb concentration was greater than450mg/kg, the fruit of Syngonium podophyllum yellowed; in Pb, Zn, Cd concentration were0-1000mg/L,0-800mg/L,0-5mg/L respectively, Plantago asiatica had normal growth, when the Pb concentration was greater than300mg/kg, Zn concentration was greater than350mg/kg, Cd concentration was greater than1.8mg/kg, the fruit of Plantago asiatica yellowed.(2)With the increase of Cr (Ⅵ), Pb concentration of Syngonium podophyllum, which shoots and roots accumulated Cr (Ⅵ), Pb:the shoots accumulated Cr (Ⅵ), Pb were286.15mg/kg,368.36mg/kg respectively; the roots accumulated Cr (Ⅵ), Pb were1574.48mg/kg,1775.73mg/kg respectively, indicated that Syngonium podophyllum had relatively strong cumulative effect for Cr (Ⅵ), Pb.With the increase of Cr (Ⅵ), Pb concentration, the enrichment coefficient for Cr (VI), Pb haed gradually become smaller, indicated that the concentrations of Cr (Ⅵ), Pb was low, the heavy metals migrated to Syngonium podophyllum from medium within a certain range; the transfer coefficients for Cr (Ⅵ), Pb was gradually reduced, and were low, indicated that two elements of Cr (Ⅵ), Pb were concentrated in the Syngonium podophyllum roots and difficult to transfer to the shoots.(3)With the increase of Pb, Zn and Cd concentration, different parts of Plantago asiatica accumulated Pb, Zn and Cd increased overall, which the shoots accumulated Pb, Zn, Cd were142.38mg/kg,991.75mg/kg,12.37mg/kg respectively; the roots accumulated Pb, Zn and Cd were1020.17mg/kg,1935.62mg/kg,30.89mg/kg respectively, indicated that Plantago asiatica for Pb, Zn, Cd all had relatively strong cumulative effect, and stranded at the roots.With the increase of Pb, Zn and Cd concentration, the enrichment coefficient for Cr Pb, Zn and Cd had gradually become smaller, which indicated Pb, Zn and Cd concentration was low, the heavy metals migrated to Plantago asiatica from medium within a certain range.(4)For catalase activity, in the Cr (Ⅵ), Pb compound contamination, Pb can promote catalase activity, Cr inhibited catalase activity, the correlation of Pb and catalase activity reached extremely significant level. when Cr (Ⅵ), Pb both existed, they can promote catalase activity, and had reached a significant correlation; In the Pb, Zn and Cd compound contamination, Pb can promote catalase activity, Zn, Cd for the inhibition. When Pb, Zn or Zn, Cd both existed, they inhibited catalase activity. When Pb, Cd, or Pb, Zn’both existed, they can promote catalase activity, and had reached a significant correlation.(5) For phosphatase activity, in the Cr (Ⅵ), Pb compound contamination, Cr (Ⅵ) can promote phosphatase activity, Pb inhibited phosphatase activity, the correlation of Cr, Pb and phosphatase activity reached extremely significant level. when Cr (Ⅵ), Pb both existed, they can promote phosphatase activity; In the Pb, Zn and Cd compound contamination, Pb, Zn and Cd can promote phosphatase activity. When Pb-Zn, Pb-Cd or Zn-Cd both existed, they promoted phosphatase activity. When Pb, Zn, Cd existed, they inhibited phosphatase activity.(6)For urease activity, in the Cr (Ⅵ), Pb compound contamination, Pb promoted urease activity, Cr (Ⅵ) inhibited urease activity, the correlation of Pb and urease activity reached a significant level. When Cr (Ⅵ), Pb both existed, they inhibited urease activity, and had reached extremely significant level; In the Pb, Zn and Cd compound contamination, Pb, Zn and Cd inhibited urease activity. When Pb, Zn or Pb, Cd both existed, they promoted urease activity. When Zn, Cd or Pb, Zn, Cd both existed, they inhibited urease activity.