Joint Remediation For Soil Contaminated With Heavy Metals By Biochar And Herbaceous Plants

Phytoremediation is a better technology for remediation of soils contaminated by heavy metals.However,most of the rehabilitated plants have the drawbacks of long recovery time and low efficiency,which greatly limits the development of phytoremediation technologies.Although there have been some reports of phytoremediation at home and abroad,the effect is unclear.In this paper,we studied the effect of biochar on the stabilization of heavy metals Cd,As,Pb,Cr,Cu and Zn.The eight herbaceous plants and their combination with biochar for phytoremediation of heavy metal contaminated soils were also studied,which provided a scientific basis for biochar fortified herbaceous plants to remediate heavy metal contaminated soils.The main results are as follows:1.Biochar has a passivation effect on heavy metals in soils,and can effectively control the accumulation of heavy metals in rice grains.Compared with the control conventional compound fertilizer,the contents of Cd,As,Pb and Cr in the soil decreased by 37.17%-63.70%,10.77%-39.76%,53.03%-60.62% and 38.47%-66.44% respectively.The enrichment coefficients of heavy metal Cd and As in rice grain decreased by 13.29%-51.31% and 49.80%-71.18%,respectively.The reduction effect of grain on Pb enrichment was the most significant when 10% and 15% treatments were applied,while the enrichment coefficient decreased by 79.82% and 80.96%,respectively.The effect of Cr enrichment coefficient decreased when No.2 recipe was reduced by 15% and 20% The most significant decrease was 43.25% and 39.60%,respectively.2.Among the eight tested herbaceous plants,tall fescue showed the strongest enrichment ability for Cd,As,Pb,Cr,Cu and Zn.Cd,Pb,Cr,Cu and Zn Considering the biomass and the enrichment ability of heavy metals of eight species of herbaceous plants,tall fescue and kentucky bluegrass have great potential for application in remediation of heavy metal contaminated soils in farmland.3.The combination of biochar with tall fescue and kentucky bluegrass enhanced significantly plant growth and heavy metal accumulation.Compared with the control,the plant height of tall fescue and kentucky bluegrass in soil with biochar increased by 37.49% and 36.20%,and the aboveground biomass increased by 34.59% and 29.97% respectively over the 60 d restoration period.In soil with biochar and tall fescue,the enrichment of Cd,As and Cu in tall fescue increased by 49.23%,41.88% and 23.69%,respectively.The enrichment coefficient of biochar and kentucky bluegrass increased significantly by 41.21%.4.Compared with the control,the higtest removal rates of Cd,As,Pb,Cr,Cu and Zn were in the soil with biochar and tall fescue,kentucky bluegrass.Among them,removal rates of Cd,As,Pb,Cr,Cu and Zn by combined remediation of biochar and tall fescue reached 52.45%,44.65%,27.45%,23.98,28.17%,and 31.47%,respectively.The removal rate of heavy metals by the combination of biochar and kentucky bluegrass was 44.07%,30.61%,22.27%,15.16%,22.48% and 27.21%,respectively.In general,the combined effect of biochar and tall fescue on soil heavy metal removal was better than that of biochar and kentucky bluegrass.