Effects Of Nanoscale Zero-valent Iron Assisted Phytoremediation Of Pb By Lolium Perenne In Sediment

In our country,many rivers or lakes have been polluted by heavy metals,and the sediment environment of rivers has been destroyed,and the environmental quality is declining gradually.Lead(Pb)is one of the most highly toxic heavy metals,and could result in toxic effects on living organisms,which have attracted the extensive attention of scholar at home and abroad.To explore the optimal concentration of starch stabilized nanoscale zero-valent iron(S-nZVI)assisted phytoremediation of Pb in sediment,the effects of 0,100,200,500,1000 and 2000 mg/kg of S-nZVI on plant growth,Pb accumulation and antioxidative responses of Lolium perenne,and the speciation transformation of heavy metals and enzymes activities in sediment were investigated.In this paper,the research included the following three parts.The first part studied the biomass and length of plants with S-nZVI treatment and the accumulation and translocation of Pb in plants through the S-nZVI assisted phytoremediation.The Results showed that the low concentrations of S-nZVI-sediment were favorable for the plant growth,and the increased biomass and length of plant provided the advantages for the accumulation and translocation of Pb in plants.Consequently,the total Pb contents in L.perenne with the treatment of low concentrations of S-nZVI(100,200 and 500 mg/kg)were higher than those in the non-nZVI treatments,and the highest Pb accumulation capacity of 1175.40 ?g per pot was observed in L.perenne with the treatment of 100 mg/kg S-nZVI.However,high concentrations of nZVI(1000 and 2000 mg/kg)sediment caused inhibition effect on L.perenne growth.The second part studied the effects of S-nZVI on physiological structure and oxidative stress of plants after the remediation.The results showed that the low concentrations of S-nZVI slightly relieved the degree of oxidative stress in plants,while the high concentrationsof S-nZVI(1000 and 2000 mg/kg)sediment caused toxic effect on L.perenne growth with severe oxidative stress.This resulted in the decrease of photosynthetic chlorophyll and soluble protein content,which caused the decrease of plant biomass and metal accumulation capacity in plant.The results also showed antioxidant enzymes(SOD,CAT and POD)and antioxidants(GSH)play a critical role in coping up with oxidative stress caused by ROS,but the high concentrations of S-nZVI induced the oxidative damage to antioxidant enzymes.The third part investigated the the speciation transformation of heavy metals and enzymes activities in sediment after the remediation.The results showed the decrease of heavy metals toxicity in sediment indicated by the decreased acid soluble fraction of Pb and increased residual fraction of Pb.S-nZVI play a part in stabilizing the heavy metals in sediment.The similar or increasing enzymes activities in sediment also supported that using S-nZVI to assist phytoremediation was a promising method to remediate Pb-polluted sediment.