Study On Heavy Metal Tolerance And Accumulation Characteristics Of Vetiveria Zizanioides L

Heavy metal pollution from coal gangue is an important environmental problem affecting ecological environment and threatening human health.It is very important to use hyperaccumulators or tolerant plants for ecological restoration and revegetation the soil which was polluted by heavy metals.This paper take the Vetiveria zizanioides L.planted on coal gangue for study.The tolerance of Vetiveria zizanioides L.to different concentrations of heavy metals and the characteristics of accumulation,absorption and distribution of different kinds of heavy metals were studied based on the contents of several main heavy metals by Hoaglad hydroponics method.The heavy metals contains Cu,Zn,Cd and Pb which are rich in coal gangue hill of Dahe Coal Mine,Liupanshui.The result shows as follow:(1)Under the single stress of four heavy metals,Cu stress had the greatest effect on the physiological indexes of Vetiveria zizanioides L.With the increase of concentration and stress time of Cu3/30 d,the content of MDA increased gradually,reaching the maximum 77.18 nmol/g at Cu3/30 d,which was 1.71 times higher than that of the control.The activities of CAT,POD,SOD,NPT,GSH and soluble protein decreased gradually,and reached the minimum value at Cu3/30 d,followed by Pb.With the increase of concentration of Pb and stress time,MDA contained.The activity of CAT,POD,SOD,NPT,GSH and soluble protein decreased gradually,and reached the minimum value at Pb3/30 d.Again,the content of MDA increased gradually with the increase of Zn concentration and stress time,and reached the maximum of 65.12 nmol.g-1 at Pb3/30 d.The activity of CAT,POD and SOD decreased gradually.Sex,NPT content,GSH content and soluble protein content increased first and then decreased,and could promote the growth of Vetiveria zizanioides L.at low(Zn1)and medium(Zn2)concentration,while Cd had the least effect on Vetiver grass.Under mixed heavy metal stress,low concentration(CP1)and short time(10d)could promote the growth of vetiver,while medium concentration(CP2)and high concentration(CP3)could inhibit the growth of Vetiveria zizanioides L.(2)The cumulative amount of heavy metals in Vetiveria zizanioides L.showed that the stem and leaf parts were significantly lower than the root part(P<0.05).Under single stress and mixed stress,under the stress of single heavy metal,the content of Cu in stems and leaves and roots increased significantly with the increase of treatment concentration and stress time.The maximum values were obtained when the concentration of Cu3 and CP3 was 30 d.They are: 520.6 mg/kg and 1121.33 mg/kg,476.5 mg/kg and 1367.93 mg/kg.The content of Zn in the stems and roots of Vetiveria zizanioides L.increased gradually with the increase of treatment concentration and stress time,and reached the maximum at 30 d after treatment with Zn3 and CP3 treatment concentrations,respectively,231.37 mg/kg and 532.82 mg/kg,598.85.The difference between mg/kg and 438.00 mg/kg was significant(P<0.05).At the treatment concentration of CP3,the Zn content in stems and leaves was significantly higher than that in roots.The content of Cd in stems,leaves and roots of Vetiveria zizanioides L.increased gradually with the increase of treatment concentration and stress time,and reached the maximum at the concentration of Cd3 and CP3 for 30 days,which were 35.34 mg/kg and 267.42 mg/kg,respectively.The difference between mg/kg and 167.5 mg/kg was significant(P<0.05).Under the condition of single Pb stress,the Pb content in the stems and leaves of Vetiveria zizanioides L.increased with the increase of stress time in the treatment of Pb1 and Pb2 concentrations,and reached the maximum at 90 days after Pb2 treatment concentration stress,which was 90.12 mg/kg.The Pb content in the stems and leaves increased first and then decreased with the increase of stress time,and the Pb content was significantly lower than that of Pb1 and Pb2(P<0.05).The Pb content in roots increased with the treatment concentration and the stress time,and was treated in Pb3.The maximum concentration reached 671.06 mg/kg at 30 days.Under the mixed stress,the Pb content in stems,leaves and roots of vetiver grass increased gradually with the increase of treatment concentration and stress time,and reached the maximum at 30 days after treatment at the concentration of CP3,which were 76.16 mg/kg and 560.02 mg/kg,respectively.The above indicates that the stem,leaf and root of vetiver have the same absorption of Cu,Zn,Cd and Pb,and the specific expression is: Cu > Zn > Pb > Cd.Under the stress of mixed heavy metals,the stems and leaves of vetiver are Cu,Zn and Cd.The absorption of Pb is: Zn > Cu > Cd > Pb;the absorption of Cu,Zn,Cd and Pb by roots is: Cu > Pb > Zn > Cd.When Vetiveria zizanioides L.was used in CP3/10 d,CP3/20 d and CP3/30 d,the content of Zn in stems and leaves was higher than that in roots.(3)Under single heavy metal stress,the transfer coefficient is: Cu > Zn > Pb > Cd.Under mixed heavy metal stress,the transfer coefficient is: Zn > Cd > Cu > Pb.Except for CP3/10 d,CP3/20 d and CP3/30 d,the shift coefficient of Zn is greater than 1,and the transfer coefficients of all other heavy metals are less than 1,indicating that vetiver can transfer more Zn into stems and leaves.