Heavy Metal Pollution Characteristics Of Three Typical Areas In Shanghai And Assessment Of Heavy Metal Accumulation Capacity Of Common Greening Trees In These Areas

As the largest industrial city in China,Shanghai has developed at high speed in the recent decades.At the same time,heavy metal content in soil increased significantly,and the pollution situation increasingly deteriorated as the cumulative effects of heavy metal in soil.To screen appropriate greening trees for heavy metal polluted area in Shanghai,soil and plant samples were taken from Wenchuan roadside,Wujing thermal power plant and Laogang refuse landfill.The contents of As,Cd,Cr,Cu,Pb and Zn in plants and soils were analyzed through ICP.And the heavy metal pollution situations of these sites were assessed with single factor pollution index,Nemerow comprehensive pollution index and potential ecological risk index.With sand culture,the heavy metal accumulative and transportation capacity of several wood plants were investigated.The main results are as followed:1.Among the three sample fields,the average content of As of Wenchuan roadside was the maximum;it reached 58.82mg/kg.While that of Laogang was only 4.50mg/kg which was the minimum.The range for Cd was 0.60~2.96mg/kg.In Wujing thermal power plant,the highest Cd concentration was recorded.The Cr concentration of soil samples taken from Wenchuan roadside was the highest;its mean value was 219.98mg/kg.Cr content of Laogang refuse landfill was 85.32mg/kg that was lowest among the three sample fields.The Cu content ranged from 29.39~ 44.61 mg/kg,and the highest was found in Laogang refuse landfill.The Pb concentration of soil in Wenchuan roadside was the highest;the mean value reached 86.70mg/kg.And the lowest Pb concentration was recorded in Laogang refuse landfill;its average value was 48.11mg/kg.The Zn concentration ranged from 120.13~205.94 mg/kg,the highest was found in Wenchuan roadside sample field.2.From the single factor pollution index,it was found that Cd,As and Cr in Wenchuan roadside reached middle pollution level.The Nemerow comprehensive ecological risk index of Wujing thermal power plant and Wenchuan roadside were at middle contamination level.While Laogang refuse landfill was clean.But the potential ecological risk index of Laogang refuse landfill reached middle level,and those of Wenchuan roadside and Wujing thermal power plant were at high level and serious level,respectively.In the three sample fields,Cd has the most severe ecological risk among the six heavy metals.3.After comprehensively analyzing the heavy metal concentration,bioaccumulation factors and translocation factors,the trees that adapted to heavy metal polluted fields and had strong heavy metal enrichment and translocation capacities were selected.They were listed as followed: Salix babylonica,Populus canadensis Moench,Bambusamultiplex,Euonymus maackii,Prunus Cerasifera,Distylium racemosum,Edgeworthia chrysantha.,Lagerstroemia indica,Hypericum monogynum,Buxus sinica,Sapindus mukorossi,Platanus acerifolia,Paulownia tomentosa,Malus spectabilis,Hibiscus mutabilis,Hydrangea macrophylla,Broussonetia papyrifera and Morus alba.These trees could be used as greening trees and remediation plants in the heavy metal polluted area.4.The sand cultured Taxodium mucronatum × Cryptomeria fortunei,Ligustrum lucidum,Cornus walteri,Pittosporum tobira and Elaeagnus pungens were treated with 1/4 Hoagland solution containing Cd,Cr,Cu,Pb and Zn.The low concentration treatment was 1 times of national standard level 3,and the high concentration treatment was 3 times of national standard level 3.All of the 5 tree species could grow normally under the heavy metal treatments.The physiological index,such as MDA content,relative electrical conductivity,soluble sugar content and chlorophyll content,of the 2 treatment had no significant difference compared with the control.While the heavy metal concentration in the roots,stems and leaves of the 5 five tree species increased significantly with heavy metals concentration increasing in the Hoagland solution.The results indicated that the 5 tree species could accumulate Cd,Cr,Cu,Pb and Zn to some extent and had relative strong capacity to tolerate heavy metal stress.