Studies On The Lead Leaching Liquid Tolerance And Phytoremediation Of Nelunbo Nucifera

(1) The effects of different concentrations of Pb tailing leaching liquid on theseeds germination and seedlings growth of lotus Nelumbo nucifera Gaertn. werestudied by liquid culture. Different concentrations of Pb tailing leaching liquid inhibitedthe lotus seed germination and seedling growth, and the inhibition increased with theincrease of the concentration of Pb tailing leaching liquid. The seed germination ratedecreased lower as the concentration of Pb tailing leaching liquid lower than75%. Thegermination rate was only20%under100%Pb tailing leaching liquid and seedgermination index and vigor index was significantly lower than the control. Toxicityexcitement of stems and leaves was found at25%Pb tailing leaching liquid and thegrowth of them were little fast than control. When the Pb tailing leaching liquid reached50%, the root, stem and leaf of the seedlings was inhibited and decreased by17%,18%and29%, respectively, compared with the control. As treatment time extended, plantroot length significantly restrained. After13d’s seed germination, root lengths under75%and pure Pb tailing leaching liquid treatment were decreased47%and65%,respectively, compared with that of control. Leaf diameters treated with75%Pb andpure tailing leaching liquid were significantly lower than the control (P <O.05). Thelotus root growth significantly inhibited by Pb stress. Therefore, the changes of rootlength can be taken as an important indicator of the toxic effects of heavy metals. Theseedling growth was better reflected the harmful levels of Pb toxicity than seedgermination.2The anatomical structure and physiological indicators of lotus were studiedunder the stress of Pb tailing leaching liquid. The results show that the anatomicalstructure of the root, petiole and blade were affected with the increase of Pb tailingleaching liquid. The chlorophyll content of lotus leaf was first increased and thendecreased with increase of the liquid concentration. The relative conductivity, thecontents of MDA, AsA and GSH of various parts of the lotus increased as the Pb tailingleaching liquid increased. The highest values of relative conductivity was found at puretailing leaching liquid treatment and the relative conductivity of root, rhizome and leafwere58%,59%and64%, respectively, higher than the control. High concentration ofPb tailing leaching fluids promoted the accumulation of MDA. The contents of AsA andGSH increased under Pb tailing leaching fluid stress. GSH contents in the lotus leafwere significantly greater than the content of the rhizomes, showing that the GSH played an important role in the lotus leaf to lower reactive oxygen injury under Pbtailing leaching liquid stress. The results indicated that lotus seedlings had the tolerantpotential to Pb tailing leaching fluid stress, which laid a foundation for further study onthe phytoremediation of the comtaminated environment of Pb tailing leaching fluid.3The seedlings growth and accumulation of Pb, Cu, Cd, K and Zn of lotus werestudied under the stress of different portion of Pb tailing leaching liquid by pot culture.The results show that the root dry mass of lotus decreased67%under stress of Pbtailing leaching liquid, while, the leaf dry mass of lotus50%Pb tailing leaching liquidstress decreased only0.8%compared with the control, indicating that aboveground partof lotus have a certain tolerance to low concentrations of Pb tailing leaching liquid. Pbcontents in the leaves, roots and rhizomes were10.8times,11.1times and10.83times,respectively, of the control. The Cu absorption of lotus aboveground part wasproportional to the rise with the amount of Pb tailing waste concentration. Kaccumulation in the lotus aboveground part was significantly higher than theunderground part, and had a positive role with Pb tailing waste liquid level.Accumulation of Zn was not changed significantly at25%Pb tailing leaching liquidtreatment, which indicated that low concentrations of Pb tailing leaching liquidimpacted plant absorption of Zn. Translocation factor of Pb at the treatment of100%Pbtailing leaching liquid was1.27times of the control. The results showed that highconcentrations of Pb tailing leaching liquid could significantly promote Pb translocationfrom the underground part to the aerial parts.4Different concentration of N and P was applied to the pure tailing leachingliquid and the numbers of lotus root and leaf, the lengths of root and leaf were enhancedand greater than those of the control with the applied N and P. The highest value of theroot number found in5mg/LN/0.5mg/L P treatment and root number was2.8times ofthe control. The reaction of root length to the applied N and P was not significantly. Thecell membrane damage reduced after N and P applying and leaf cell membrane damagewas lower than the roots. The contents of chlorophyll, POD, AsA and Pb in the lotusincreased first and then decreased as the concentrations of nitrogen and phosphorusincreased. The contents of chla, chlb Cxc increased by59%,56%,59%under2.5mg/LN/2.5mg/LP treatment. AsA content in the root increased most significant. Thecontent of Pb in the plants at this concentration was reached peak value and the contentsof Pb in the roots, rhizomes and leaves under2.5mg/LN/2.5mg/LP treatment increased42%,38%,51%, respectively, compared with the control. POD activities were highest in the roots, stems and leaves, and were30%,46%,61%, respectively, more than thoseof the controls. However, POD activities under highest concentration of N and Ptreatment decreased by18%,15%,37%, respectively, of the control. The applying of Nand P improve the SOD activity in the rhizomes and leaves, SOD activity in5mg/LN/2.5mg/L P treatment increased significantly, and was59%more than that ofthe control. The results indicated that applying N and P could promote the lotus seedlinggrowth and enhance the ability of the phytoremediation of the Pb tailing leaching liquid.