| Due to historical excessive open-pit mining,the lead-zinc wasteland has high heavy metal content and serious soil erosion.Scientific selection of appropriate phytoremediation modes can not only ensure plant biomass but also adsorb heavy metals in the soil.which is very important for the remediation of lead-zinc mine wasteland.At present,the phytoremediation work of mining wasteland is mostly focused on field investigation and pot experiment,but there are few reports on the phytoremediation mode and type of wasteland under actual reclamation and restoration conditions.This paper took a lead-zinc mine wasteland in Nanling,northern Guangdong Province as the research object.Based on field investigations and experiments,classical statistics,geostatistics,principal components,entropy and TOPSIS models were used,the analysis of the characteristics and sources of heavy metal pollution in the wasteland was carried out to reveal the plant diversity and soil-plant heavy metal enrichment and migration characteristics under different ecological restoration modes.The study put forward the optimal phytoremediation model for the abandoned land of Nanling lead-zinc mine in northern Guangdong.The research conclusions were as follows:(1)Except for Ni,the contents of As,Zn,Cu,Pb,and Cd in soil surface layer and profile of the study area exceed the soil environmental background values in Guangdong Province.The soil heavy metals in the study area gradually decreased from the north-central to the east-west,and the pH value was higher in the north and the south Low.The pollution evaluation results showed that Ni was in a clean state,Zn was in a moderately polluted state,and other elements heavily polluted.The potential ecological risk assessment showed that As,Pb and Cd were in a high-risk state.Both evaluation methods showed that the comprehensive pollution degree of the study area was relatively high.From the source point of view,As,Pb and Cd may originate from the oxidative release process of pyrite;Zn and Cu may be affected by the chemical reaction process of chalcopyrite and sphalerite;Ni may come from soil parent material and weathering accumulation.(2)There were 8 families and 10 species of living plants in different ecological restoration modes.Ligustrum lucidum,Slash pine,ramie,crape myrtle and plantain were the dominant plants under different ecological restoration modes.Slash pine and crape myrtle leaf stems had a Cd-enriched transfer coefficient close to or more than 1,which was a Cd-rich plant.The heavy metals of plantain and Ligustrum lucidum were mainly concentrated in the roots and belonged to root hoarding plants.Ramie had a low content in all parts and belonged to an evasive plant.The diversity index of plant community under different ecological restoration modes was as follows:arbor-shrub-grass>shrub-grass>arbor-grass>grass.The plant coverage of the arbor-shrub-grass community reached 100%,and the plant survival rate of the arbor-shrub-grass community was the highest(>69%),Qiaocao district was the lowest(<60%).(3)A vegetation effect evaluation system covering 11 indicators under different ecological restoration modes had been constructed.The evaluation results were arbor,shrub,shrub,shrub,arbor,and grass from good to bad.The important value and enrichment migration of plants under each ecological restoration mode were comprehensively considered.Slash pine,shrub crape myrtle and herb plantain can be used as target plants for ecological restoration of lead-zinc mine wasteland.Combined with the results of plant research,a three-dimensional ecological restoration technology model based on soil matrix reconstruction technology,ecological bag slope protection technology,three-dimensional vegetation recovery technology and plant maintenance technology was proposed.Figure[14]Table[24]Reference[128]... |
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