Remediation And Evaluation Of Different Plants On Typical Heavy Metal Contaminated Sediment

The problem of heavy metal pollution in river sediments has been more serious.More and more attention has been attracted due to the sediment’s characteristics oflong-term, concealment and irreversibility, etc. Phytoremediation technology hasbecome a hotspot in the remediation of heavy metal contaminated sediments andgradually become mature.Maize, Lolium perenne L, Festuca arundinacea, Helianthus annuus, Sedumalfredii Hance and Trifolium were selected for phytoremediation. Phytoremediationefficiency of heavy metals contaminated river sediments was studied by potexperiment. Through comparison and analysis, we screened out the best proportion ofsediment and nutrient soil as well as the best plants for heavy metal remediation. Theexperiment mainly aimed at the following results: the change of contents and forms ofheavy metals in the sediments after planting, the effect on existing forms of heavymetals and sediment structure due to planting, the change of enzyme activity affectedby heavy metals and the effect on the forms of heavy metals after adding differentcomponents of humic acid. Main conclusions of this paper were as follows:Heavy metal removal effects were different based on the different kinds of plantsand different ratios of sediment and nutrient soil. For the ratio of1:2, Maize showedthe optimal remediation effect among Maize, Lolium perenne L and Festucaarundinacea. Therefore, sediment of the ratio of1:2was chosen as the soil used forthe later experiment. Compared with other three plants, Trifolium had the best abilityof accumulation heavy metals.The contents and existing forms of heavy metals had changed after planting. Thetotal amount of heavy metals decreased on the whole, which indicated that plantscould change the existing forms of heavy metals and promote activation andabsorption of heavy metals.The activities of urease and catalase were sensitive to concentration of heavymetals. Relationship between the two could be summarized as the more amount ofheavy metals, the more strongly enzyme activities were inhibited. After planting, bothof the urease and catalase activities recovered greatly. Compared with catalase, ureaseactivity recovered faster.After adding humic acid, the total amount of heavy metals decreased and theforms of heavy metal changed more significantly with higher amount of humic acid, while equilibrium was reached after some amount of humic acid was added. FAactivated the heavy metals in segments and increased the contents of dissoluble phase.HA passivated the heavy metals, which transformed bioavailable phase of heavymetals into unavailable phase, leading to less risk of being absorbed by plants.