| Phytoremediation of soil polluted with heavy metals is the hot spot in environmental management at home and abroad recently,which makes use of the tolerant plants or hyperaccumulators to uptake one or several kinds of heavy metals,then the heavy metals will decrease from soil.Yunnan is known as the kingdom of non-ferrous metals,also the kingdom of plant in China.The external condition is well advantageous to carry out research on phytoremediation.In present study,it was studied the uptake and accumulation of Neyraudia reynaudiana(kunth)Keng for Pb,tolerance and the effect of different additive agents on enhancing the accumulation of plant through a series field surveys and pot trials on laboratory condition.The major results are as follows:(1)The Pb,Zn,Cd,Cu and Mn concentrations in thirty-five plant species belonging to twenty families and their associated soils were determined.The results show that Neyraudia reynaudiana(kunth) Keng can accumulate and translocate Pb.Growing at tailings wasteland,the average Pb concentration in shoots of Neyraudia reynaudiana(kunth)Keng is 346.07 mg·kg-1,the BFCs are 0.19～1.69 which is higher than the general plants' BFCs,and the TFs are 3.13～21.24.(2)In the pot trials,The Pb concentrations in shoots and roots of Neyraudia reynaudiana(kunth) Keng increase with the increase of Pb contents in soils.The maximum concentration is 681.97 mg·kg-1in shoots when the Pb treatment concentration is 1500 mg·kg-1,and the maximum concentration in roots is 515.87 mg·kg-1at the 1000 mg·kg-1.The distribution of Pb in Neyraudia reynaudiana(kunth)Keng is: shoots＞roots,which indicates that this plant has a better ability to translocate Pb.(3)It was found that biomass of Neyraudia reynaudiana(kunth)Keng is high through field surveys and pot trials.Its average biomass can reach 59.51g individual(dry weight)growing at tailings wasteland.In the pot trails,the biomass is 6.99g individual(dw)when the plants grow sixty days at the stress of Pb.Because of its high biomass,the total heavy metal translocated is also high.The results indicate that the total heavy metal translocated is 6.63mg individual(dw),which attain the maximum concentration when the disposal concentration is 700mg·kg-1.(4)In order to ensure the tolerance of Neyraudia reynaudiana(kunth)Keng to Pb,the biomass, height,the root activity,chlorophyll contents,total sugar contents and CAT are determined.The results show that the effect of lead on all physiological indexs are not significant when the concentration of Pb in soil is lower than 1000 mg·kg-1.So the tolerance critical content of Neyraudia reynaudiana(kunth) Keng in soils was 1000 mg·kg-1.In addition,Neyraudia reynaudiana(kunth)Keng has a better accumulation for Pb when the Pb concentration in soils ranges from 700 mg·kg-1to 1000 mg·kg-1.Thus, Neyraudia reynaudiana(kunth)Keng may be suitable for phytoremediation of contaminated soils with medium contamination of Pb.(5)The accumulation of Neyraudia reynaudiana(Kunth)Keng for Pb is different at each growth periods.The maximum concentration in shoots and roots are 1012.32mg·kg-1,565.45 mg·kg-1 respectively,and the total heavy metal translocated of plants is 19.22mg individual when they grow one hundred and eighty days.However,it can attain a better remediation efficiency when the plants grow ninety days by using Neyraudia reynaudiana(Kunth)in Pb pollution soils' remediation.Treating with combined pollution of Pb,Zn,Cd and Cu,the growth response and lead accumulation of Neyraudia reynaudiana(kunth)Keng compared with the contrast did not significantly when the Zn,Cd,Cu concentration were below 1500 mg·kg-1,15 mg·kg-1,800 mg·kg-1.Neyraudia reynaudiana(kunth)Keng may be latent to remediate the soil pollution of Pb,in which the Zn,Cd,Cu concentrations are not very high.(6)Using EDTA,OA,CA,DL-MA and nutrition elements were conducted to study the additive agents enhancement of the mobility and phytoextraction of Pb.The results show EDTA is most effective. The concentration of Pb in Neyraudia reynaudiana(kunth)Keng and total heavy metal translocated increased significantly when addition of EDTA(8 mmol.kg-1).Because EDTA may lead to some environmental risks,it must control its concentration.Considering accelerating remediation and decreasing environmental risks,0.500～1.000 mmol·kg-1EDTA may be appropriate,and it needs to avoid applying EDTA during periods of high rainfall.
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