A Study On The Evaluation And Accumulation Of Heavy Metal Enrichment Ability Of 18 Trees In Beijing Greenbelt

At present,heavy metal pollution has become an important ecological problem facing cities,and heavy metals in urban soil pollutants are particularly worthy of attention.Relevant research shows that the ecological risks of cadmium(Cd),zinc(Zn),lead(Pd),and copper(Cu)in the soil in Beijing are high,and the heavy metal pollution of road green land shows a high degree,and the problem of heavy metal pollution in the soil needs to be solved urgently.Garden trees are an important part of road green space,and have a certain enrichment effect on heavy metals.However,most of the current research focuses on wild plants and economic crops.There are few studies on the types of garden plants that can be applied to the restoration of urban soil heavy metal pollution.And lack of in-depth study of the enrichment mechanism of heavy metals in garden plants.Therefore,18 kinds of trees commonly used in Beijing's green roads were taken as the research object to study their enrichment level for 4 heavy metals of Cd,Zn,Pd,and Cu,and aimed at 2 heavy metals of Cd and Zn with high pollution among the 4 heavy metals.Tree species with large differences in their enrichment ability were selected,and the differences in their Cd and Zn enrichment characteristics were studied through simulation experiments in seedling pots,and their growth and physiological and biochemical changes under Cd and Zn heavy metal stress were analyzed in detail;And study the accumulation mechanism and transformation mechanism of heavy metals at the cell level to explore the causes of differences in plant enrichment ability.The main findings are as follows:(1)The 18 trees of Beijing's road greenbelt have a comprehensive accumulation capacity of Cd,Zn,Pb,and Cu for four heavy metals.Koelreuteria paniculata,Platanus×acerifolia,Ailanthus altissima,and their membership functions are stronger.The values reached 2.21,1.97,and 1.87,respectively,which is more advantageous for the comprehensive enrichment ability of 4 heavy metals.Cd(1.43)>Zn(0.67)>Pb(0.41)>Cu(0.11)in the heavy metal pollution in the rhizosphere soil of 18 trees on the fourth ring road in Beijing.(2)The annual enrichment ability of Koelreuteria paniculata,Ailanthus altissima and Ginkgo biloba to Cd and Zn is consistent with that of road greenbelts,and the distribution of heavy metals in all organs is generally consistent,with root>branch>leaf.The root is the main enrichment location of Cd and Zn The content of branches was slightly higher than that of leaves,and the contents of Cd and Zn in each organ showed a very significant positive correlation(P<0.01).(3)The weak tolerance of Ginkgo biloba and Koelreuteria paniculata,Ailanthus altissima with high enrichment ability to Cd and Zn stress was significantly different than that of Ginkgo biloba with poor enrichment ability.The inhibitory effects of three kinds of trees on growth and development and physiological and biochemical activities were larger than that of Koelreuteria paniculata and Ailanthus altissima than Ginkgo biloba.Koelreuteria paniculata and Ailanthus altissima have stronger heavy metal enrichment ability but weaker tolerance than Ginkgo biloba with lower enrichment ability.(4)The subcellular distribution and chemical morphology of Koelreuteria paniculata,Ailanthus altissima,and Ginkgo biloba were significantly different.The heavy metals with high enrichment ability accounted for higher percentages of cell wall and cell soluble components than Ginkgo biloba,while Ginkgo biloba accounted for higher percentages of organelles and nuclear components than Koelreuteria paniculata and Ailanthus altissima;heavy metal sodium oxide in leaves and roots of Koelreuteria paniculata and Ailanthus altissima The extraction state and acetic acid extraction state accounted for more than Ginkgo biloba,and Ginkgo biloba accounted for a higher proportion of active and toxic F_Wand F_Ethan Koelreuteria paniculate and Ailanthus altissima.The distribution of heavy metals and the contents of various chemical forms of three kinds of arbor sub-cells showed a very significant positive correlation with their heavy metal enrichment content(P<0.01).The change of subcellular distribution and chemical form is one of the reasons that affect the heavy metal enrichment ability of trees.The research results provide a basis for the restoration of heavy metal pollution in the garden tree species in Beijing...