Study On The Accumulation Effect Paulownia Fortunei To Heavy Metal In Lead-zinc Slag With Peat Amended

The research team found that the fast-growing tree Paulownia fortunei had good tolerance to the heavy metal stress of lead-zinc slag in the plant and amendment screening test,and peat had good slag amendment effect,but the tolerance mechanism of Paulownia fortunei is still unclear.In this study,Paulownia fortunei seedlings were used as the test material,lead-zinc slag as the matrix,and peat as the amendment(CK:0,T1:10%,T2:20%,T3:30%).The outdoor pot experiment was conducted to explore accumulation of heavy metal in Paulownia fortunei cultivated in lead-zinc slag amended with peat and optimum peat mass ratio.The outdoor pot experiment was conducted again with the optimal peat mass ratio as the treatment group and the red soil and lead-zinc slag as the control group to explore a series of physiological and biochemical responses and microstructure changes of Paulownia fortunei under heavy metal stress.The main results are as follows:1.The study of the heavy metal accumulation of Paulownia fortunei in lead-zinc slag with peat amended(1)The concentration of Pb,Cu and Cd in Paulouwnia fortunei showed the tendency that roots>stems>leaves,and the transportation ability of the three heavy metals were poor.Heavy metal concentration in Paulownia fortunei was significantly reduced and the biomass of Paulownia fortunei was increased with peat amendment.However,the difference of biomass between the experimental groups was not significant.Paulownia fortunei has smaller BCF and TF of heavy metals.The BCF of Pb in Paulownia fortunei was less than 0.01.The BCF of Zn,Cu and Cd in Paulownia fortunei were 0.05-0.08,0.10?0.11,0.02?0.04,respectively.The TF of Pb,Zn,Cu and Cd in Paulownia fortunei were 0.10?0.30,0.30?0.45,0.35?0.50,0.10?0.20,respectively.The TQ of Pb,Zn,Cu and Cd in Paulownia fortunei were 0.10?0.45,0.40?0.50,0.45?0.55,0.10?0.20,respectively.t indicated that Paulownia fortunei was not a hyperaccumulator.The TQ of Paulownia fortunei showed a tendency that the experimental groups>the control group,but there was no significant difference between the experimental groups.(2)According to the subcellular distribution of heavy metals in the organs of Paulownia fortunei,cell wall components and soluble components are the main distribution sites of Pb,Zn,Cu and Cd.The concentration of Pb,Zn,Cu and Cd in cell wall components accounted for 16.4?80.6%,28.6?88.5%,55.7?82.2%,27.0?72.3%,respectively.The concentration of Pb,Zn,Cu and Cd in soluble components accounted for 17.7-82.3%,8.1?57.0%,10.4?33.5%and 17.5?56.4%,respectively.Compared with the control group,the peat amendment enhanced the fixation effect of soluble components on Pb,enhanced the fixation effect of cell wall components on Zn in Paulownia fortunei leaves,enhanced the fixation effect of soluble components on Zn in Paulownia fortunei roots.The effect of peat on Cu and Cd was not obvious.(3)The biomass of Paulownia fortunei and the shoot accumulations of Pb,Zn,Cu and Cd with different mass ratio of peat were used as the screening indexes to obtain the average membership function value of the screening indexes with the optimal application ratio of peat,and the comparison showed that the optimal ratio was 10%.2.Effect of heavy metal stress on Paulouwnia fortunei with peat amended(1)Compared with C group,heavy metal stress inhibited the growth and root development of Paulownia fortunei.The content of chlorophyll in Paulownia fortunei leaves was reduced,and normal life activities such as photosynthesis and transpiration were inhibited.The heavy metal stress was alleviated by the peat amendment.(2)With the increase of heavy metal concentration,MDA content in Paulownia fortunei leaves showed an upward trend.In the early and middle stages of the experiment,the activity of T-SOD,CAT and POD in Paulownia fortunei leaves increased first and then decreased.The activity of T-SOD,CAT and POD in Paulownia fortunei leaves increased in the final stage of the experimental.(3)Compared with C group,the microstructure of roots,stems and leaves of Paulownia fortunei were changed under the stress of heavy metals.Under the stress of high concentration of heavy metals,the cell structure of Paulownia fortunei leaves was destroyed,the cell wall was deformed,and the cytoplasmic membrane was broken in several places.The peat amendment can effectively alleviate the effect of heavy metal stress on the microstructure of Paulownia fortunei.(4)Heavy metal ions can be effectively fixed by sugar,cellulose,organic acid,metallothionein,free amino acid and other substances in Paulownia fortunei.Under the stress of high concentration of heavy metals,sugar,cellulose,organic acid,metallothionein,free amino acid and other substances in Paulownia fortunei could not normally combine with heavy metal ions,resulting in the accumulation of such substances in it.