Screening Of Heavy Metal Accumulators And Investigation Of Their Heavy Metal Accumulation Characteristics

Phytoremediation of heavy metal-contaminated soils is environment-friendly.More and more scientists are involving in investigation of phytoremediation of heavy metal-contaminated soils.However,a plant which can grow well in local soil and climate must be used for phytoremediation.In this work,wild plants near a lead smelter in Jiyuan were investigated,with the purpose of finding potential heavy metal accumulators.After this,some potential accumulating plants were investigated for the characteristics of germination and absorption of heavy metals.The main results of this work are,i)Totally,80 indigenous plant samples of 22 families and 43 species in Jiyuan and their soils were collected and analyzed for their heavy metal concentrations.The ranges of Cd,Pb,Cu and Zn concentrations in soils were 4.77-199,336-9280,30.3-679 and 89.4-747 mg/kg,respectively,the mean concentrations of these metals were 22.3,1869,139 and 262 mg/kg,respectively.Bioconcentration factors(BCF)of Cd,Pb,Cu and Zn ranged 0.0793?5.39,0.00532?0.484,0.0288?1.07 and 0.0371?1.83,mean values were 1.42,0.128,0.256 and 0.571.Plants with higher BCF values for Cd include D.morifolium'Xiaohuangju'nom.ined.,Salsola collina Pall,Cirsium setosum,Duchesnea indica(Andr.)Focke and Solanum nigrum L..their BCFs for Cd are 5.39,4.7,3.88,3.84 and 2.88,respectively.All the plant species exhibited lower accumulation for Pb,Cu and Zn.The results imply that D.morifolium 'Xiaohuangju 'nom.ined.,Salsola collina Pall,Cirsium setosum,Duchesnea indica(Andr.)Focke and Solanum nigrum L.may be used for phytoremediation of Cd contaminated soils in northern China.ii)The effect of light and seed soaking with deionized water or 20 mg/L potassium nitrate on the germination of Bidens bipinnata,Conyza bonariensis(L.)Cronq,Eclipta prostrata,Abutilon theophrasti Medicus and Solanum nigrum L was investigated.These plant species have been found as potential accumulators of heavy metals in contaminated soil.The results indicated that,the germination of Eclipta prostrata was greatly enhanced by light,soaking with potassium nitrate also helped its germination.Germination rate of Eclipta Prostrata was 91.9%when the seeds was first soaked in potassium nitrate solution then incubated under light,while the value was only 6.21%without light.Bidens bipinnata.and Abutilon theophrasti Medicus had higher germination rates after deionized water soaking than after potassium nitrate soaking,maximum germination rates occurred when the seeds were soaked with deionized water then incubated with light.No significant effect of light or soaking was observed on the germination of Solanum nigrum L.Germination rates of Conyza bonariensis(L.)Cronq was higher with deionized water soaking than with potassium nitrate soaking.The maximum germination rates of the plants ranked Eclipta prostrata>Solanum nigrum>Abutilon theophrasti Medicus>Conyza bonariensis(L.)Cronq>Bidens bipinnata.iii)Hydroponics method was used to study the effects of different concentrations of cadmium(CdCl2)on the growth,root tip,physiological resistance and heavy metal content of Bidens bipinnata L.for 14 months.Provides scientific evidence for contaminated phytoremediation.The results showed that when the concentrations of cadmium(1,5,and 10 mg/L,respectively)stress Bidens bipinnata L.,the growth and root tips of Bidens bipinnata L.increased with the concentration and the severity of the damage.The malondialdehyde content increased first,then decreased,and the chlorophyll content continued to decrease.Peroxidase decreased first,then increased and then decreased.The heavy metal contents in the upper part of the needle and the root system increased with the increase of cadmium concentration,and the content of heavy metals in the above ground.They were 82.1,194,and 358 mg/kg,respectively.The migration coefficients were 3.17,0.609,and 0.432,respectively.The enrichment coefficients were 82.1,38.7,and 35.8,respectively.It can be seen that Bidens bipinnata L.has relatively strong cadmium enrichment characteristics under low concentration conditions,and it has the potential to repair cadmium-contaminated soil.iv)Absorption of heavy metals by Bidens bipinnata Linn,was investigated on six soils,they were a clean calcareous soil(Cd=0.38 mg/kg;Pb=47.3 mg/kg;Zn=42 mg/kg),a heavy metal-spike clean calcareous soil(Cd,Pb and Zn were spiked at 5,500 and 300 mg/kg),a lead smelting polluted calcareous soil(Cd=8.59 mg/kg;Pb=220 mg/kg;Zn=185 mg/kg),a heavy metal-spiked lead smelting polluted calcareous soil(Cd,Pb and Zn were spiked at 3,300 and 100 mg/kg),a heavy metal polluted acid soil(Cd=15.5 mg/kg;Pb=260 mg/kg;Zn=176 mg/kg),and a heavy metal spiked polluted acid soil(Cd,Pb and Zn were spiked at 3,300 and 100 mg/kg).The plant grew 8 months and harvested,and analyzed for heavy metal accumulation.The BCF values of the plant on these six soils were 1.18,2.88,2.00,2.07,3.93 and 3.99,respectively.The ratio between the Cd absorbed by plants and that in soils were 0.792,0.619,0.198,0.223,0.361 and 0.0944%,respectively.The plant had low accumulation of Pb and Zn.The high concentrations of Zn in the polluted acid soil inhibited the growth of the plant.The results indicated that the phytoextraction of Bidens bipinnata Linn,was affected by the soil properties,it had higher accumulation of Cd,the plant cannot be sued for phytoextraction in soils with high heavy metal concentrations.