Research On Remediation Effect Of Plants On Soil In Bioretention Facility

Heavy metal pollution is a kind of serious soil pollution problems.When this problem occurs in bioretention facilities,it will produce a series of chain reactions,resulting in the complete failure of bioretention facilities.At the same time,the environment near the facilities will also be damaged,resulting in the pollution of soil,water,animals and plants and atmosphere.Aiming at the problem of heavy metal pollution in the soil of bioretention facilities,this study is based on the theoretical basis of the hyperaccumulation of heavy metals by plants.By simulating the pollution caused by heavy metals to the soil in the bioretention system,this study analyzes the effect of plants on the remediation of the soil in bioretention facilities,so as to evaluate the feasibility of plants on the remediation of the soil in bioretention facilities.So as to provide a theoretical basis for the restoration of bioretention facilities in the later stage of operation.In this study,Hylotelephium erythrostictum(Miq.)H.Ohba and Buxus megistophyll Levl.were used as the research objects,and three kinds of soil polluted by heavy metals Pb and Cd with different concentrations were set up.The growth and physiological effects of heavy metals on the two plants and the tolerance of plants to heavy metals Pb and Cd were analyzed.Combined with the difference analysis of the enrichment and transport capacity of the two plants to heavy metals in the soil,the following main conclusions were obtained:(1)Under the soil polluted by different concentrations of heavy metals Cd and Pb,the biomass,root activity,net photosynthetic rate,transpiration rate and chlorophyll SPAD value of Hylotelephium erythrostictum(Miq.)H.Ohba and Buxus megistophyll Levl.were more adversely affected with the increase of heavy metal pollution concentration;Among them,leaf biomass was the least affected by heavy metal pollution,and root biomass was the most affected by heavy metal pollution;Low concentration heavy metal Pb pollution did not significantly promote the transpiration rate of the two plants,and low concentration heavy metal Cd pollution did not inhibit the transpiration rate of Hylotelephium erythrostictum(Miq.)H.Ohba;Low concentration heavy metal Pb pollution has little effect on the chlorophyll SPAD value of the two plants,while medium and high concentration heavy metal Pb pollution has a significant effect on the chlorophyll SPAD value of the two plants and has an obvious inhibitory effect.(2)Generally speaking,Hylotelephium erythrostictum(Miq.)H.Ohba and Buxus megistophyll Levl.have a good tolerance to the pollution of low concentration heavy metals Pb and Cd,a certain tolerance to the pollution of medium concentration heavy metals Pb and Cd,but a poor tolerance to the pollution of high concentration heavy metals Pb and Cd;The tolerance of Hylotelephium erythrostictum(Miq.)H.Ohba and Buxus megistophyll Levl.to heavy metal Cd pollution was worse than that of metal Pb;The tolerance of Hylotelephium erythrostictum(Miq.)H.Ohba to heavy metal pollution is weaker than that of Buxus megistophyll Levl.(3)Hylotelephium erythrostictum(Miq.)H.Ohba is not a super enrichment plant of heavy metals Pb and Cd;Its transfer coefficient is less than 1 in the case of heavy metal Pb pollution,and its transfer ability to heavy metal Pb is poor.The overall transfer coefficient of Hylotelephium erythrostictum(Miq.)H.Ohba is greater than 1 in the case of heavy metal Cd pollution,and its transfer ability to heavy metal Cd is better.Its transfer ability to heavy metal Cd is realized through stems and leaves;The accumulation of heavy metal Pb is mainly concentrated in the root,which is the main organ for the enrichment of heavy metal Pb in Hylotelephium erythrostictum(Miq.)H.Ohba;The accumulation of heavy metal Cd is mainly concentrated in the root and stem,which are the main organs for the enrichment of heavy metal Cd in Hylotelephium erythrostictum(Miq.)H.Ohba.(4)Buxus megistophyll Levl.is similar to the hyperaccumulator of heavy metals Pb and Cd;The overall transfer coefficient of Buxus megistophyll Levl.is greater than1 in the case of low concentration of heavy metal Pb pollution(400mg/kg)and high concentration of heavy metal Pb pollution(1000mg/kg),and close to 1 in the case of medium concentration of heavy metal Pb pollution(800mg/kg),which has a good ability to transfer heavy metal Pb.The overall transfer coefficient of Buxus megistophyll Levl.is greater than 1 in the case of high concentration of heavy metal Cd pollution,which has a certain ability to transfer heavy metal Cd,the ability to transfer heavy metals Pb and Cd is mainly realized by stems;The accumulation of heavy metal Pb in Buxus megistophyll Levl.is mainly concentrated in the root and stem,which are the main organs for the enrichment of heavy metal Pb,and the accumulation of heavy metal Cd is mainly concentrated in the root,which is the main organ for the enrichment of heavy metal Cd.(5)The remediation effect of Hylotelephium erythrostictum(Miq.)H.Ohba on heavy metal Pb contaminated soil is better than that of heavy metal Cd contaminated soil,and the remediation effect of Buxus megistophyll Levl.on heavy metal Pb contaminated soil and heavy metal Cd contaminated soil is similar;In the remediation effect of heavy metal Pb contaminated soil,Buxus megistophyll Levl.is better than Hylotelephium erythrostictum(Miq.)H.Ohba;However,the remediation effect of the two plants on the soil polluted by high concentration heavy metal Pb(1000mg/kg)is not good;In the remediation effect of heavy metal Cd contaminated soil,Buxus megistophyll Levl.is better than Hylotelephium erythrostictum(Miq.)H.Ohba,but Hylotelephium erythrostictum(Miq.)H.Ohba has a better remediation effect on low concentration heavy metal Cd contaminated soil(25mg/kg).