Study On Allocation Model Of Phytoremediation Of Urban Copper Contaminates The Soil

Soil heavy metal pollution is a prominent pollution characteristic in the process of brown field restoration,and it is also a problem that must be paid attention to in the urbanization development.Although heavy metal copper is an essential element for the growth of animals and plants,if the copper content in the soil exceeds 200mg/kg,it will pollute the soil,so the remediation of copper polluted soil is also an important link in the process of soil restoration.Compared with traditional heavy metal remediation technology,phytoremediation technology has been widely recognized as an economic,efficient and environmentally friendly remediation method.However,due to the impact of the surrounding environment on the growth of plants,the heavy metal enrichment ability of plants is greatly reduced.Therefore,how to improve the efficiency of plant extraction of heavy metals is the main research focus of phytoremediation technology.It is also the research hotspot of landscape architecture.The intensive measures of phytoremediation technology can not only improve the physical and chemical properties of soil and enhance soil fertility,but also promote plant growth and increase the amount of heavy metals extracted from plants.Meanwhile,reasonable plant allocation pattern can also make full use of natural resources between different ecological niches,create a good growth environment for plants,thus promoting plant growth and increasing the amount of heavy metals extracted from plants.Based on this,in order to repair heavy metal copper in soil more efficiently,this paper combined the above two methods and adopted field orthogonal experiment to carry out intensive experimental study on phytoremediation of copper-contaminated soil in the heavy metal pollution phytoremediation test site in Songjiang District,Shanghai,to explore the effects of different ratios of three substrates on soil physical and chemical properties,tree biomass and heavy metal copper extraction.And the effects of four different life types of green plants on biomass and heavy metal copper extraction,in order to screen out enhanced matrix matching measures that can improve soil physical and chemical properties and promote plant growth and plant allocation models that extract higher copper content in soil,so as to provide references for ecological restoration and landscape allocation of urban brownfield.The main results of this study are as follows:(1)In plant compost,wood chips and EM microbial agent(referred to as matrix A,matrix B and matrix C,respectively),matrix A had the greatest effect on the biomass of trees and the amount of copper in soil,followed by matrix B and matrix C.The addition of 30% matrix A and appropriate matrix B can make the soil loose and porous and enhance the fertility.Adding15% of matrix A and 500 dilution of matrix C can increase the content of water soluble copper in soil and increase the enrichment ability of heavy metal copper in plants.The addition of30% matrix A in each ratio could promote the growth of elevation diameter of Fraxinus chinensis and S.matsudana ×alba,increase the biomass per unit area of Fraxinus chinensis and S.Matsudana × Alba,and increase the extraction amount of heavy metal copper per unit area.Among the 16 substrates proportioned treatments,T15 was the treatment with the highest amount of heavy metal copper extraction per unit area,and the proportioned treatments were plant compost 30%,wood chip 7.5% and EM microbial agent 250 times diluent.T16 was the treatment with the highest extraction amount of heavy metal copper per unit area,and the ratio was plant compost 30% and wood chips 15%.(2)The complex planting of plants in different ecological niches can effectively improve the biomass per unit area and the heavy metal copper extraction.The Fraxinus chinensis in woody plants is better than S.Matsudana × Alba,and the superenriched Commelina communis is better than the shrub Forsythia suspensa.The order of copper extraction from high to low in the six plant allocation patterns was as follows: Fraxinus chinensis + Commelina communis > Fraxinus chinensis + Forsythia suspensa > Fraxinus chinensis > S.Matsudana× Alba + Forsythia suspensa > S.Matsudana × Alba > S.Matsudana × Alba + Commelina communis.(3)Based on the above studies,three plant configuration modes for remediation of copper-contaminated brownfieldl were proposed,which were as follows:(1)Severe soil pollution remediation modes: Fraxinus chinensis + Commelina communis or Fraxinus chinensis + Forsythia suspensa,and the enhanced matrix ratio measureratio for soil improvement before planting was treatment T15;(2)Remediation mode of moderate soil pollution: Fraxinus chinensis monopcropping or S.Matsudana × Alba + Forsythia suspensa complex planting,the enhanced matrix ratio measureratio of Fraxinus chinensis monopcropping was treatment T15,and that of S.Matsudana × Alba + Forsythia suspensa complex planting was treatment T16.(3)The remediation mode of soil mild pollution: S.Matsudana × Alba + Commelina communis were combined,and the enhanced matrix ratio measureratio was treated T13.