Growth and metal uptake of three woody species in lead/zinc and copper mine tailing

Mine tailings are known to have environmental perniciousness due to their high concentrations of heavy metals.Phytoremediation can provide a cost-effective,long-lasting and aesthetic solution for the reclamation of mine tailings.However,revegetation on mine tailing areas is a difficult practice because of toxicity of heavy metals and low nutrient levels.As a result,most tailings disposal sites are devoid of vegetation.Hence,plant species with barren tolerance and excess metal tolerance are required.To date,most of studies focused on the potential utilization of grasses in revegetation.Few studies have evaluated the potential of fast growing woody species for revegetation and remediation of mine tailing areas.The objectives of this study were to reveal the adaptation of the selected woody plants to mine tailings and the potential use of woody species for the revegetation of mine tailings areas in China.A greenhouse pot experiment was conducted to evaluate the potential of woody plants for revegetation in copper(Cu) and lead/zinc(Pb/Zn) mine tailings.Three woody plants species(Amorpha fruticosa Linn,Alnus cremastogyne and Pistacia chinensis) were tested to assess their growth,chlorophyll content,chlorophyll fluorescence parameters,root morphology,metal accumulation and translocation in plants.Pb/Zn tailings and Cu tailings contained elevated concentrations of total Pb,Zn and Cu,which imposed stress to species planted.All three species can grow in both Cu tailings and Pb/Zn tailings and show different tolerance to stress of tailings.The N fixing shrub A.fruticosa is the most tolerant species to both tailing areas.P.chinensis was significantly stressed in term of plant growth in Pb/Zn tailing.Heavy metals significantly decreased chlorophyll content of A.cremastogyne.The root morphology parameters of all plants grown in tailings showed no difference from that grown in soil.Despite the high concentrations of heavy metals in the mine tailing,there was a slight transfer of these elements to the aboveground biomass.The accumulated metal contents in the plants varied among species from 58.93 to 333.67(for Zn which grown in Pb/Zn tailing area),49.20 to 199.33(for Zn which grown in Cu tailing area),2.67 to 196.00(Pb) and 17.66 to 55.36 mg/kg(Cu).All plant species have low bioconcentration factor(BCF) and translocation factor(TF) except TF value of Zn(TF=0.84 in Cu tailing areas) of P.chinensis.At day 60,the chlorophyll fluorescence parameters of A.cremastogyne and P.chinensis in two tailings showed no difference compared with control,but the quantum yield of PSⅡphotochemist showed the downward trend.The contents of iron(Fe),magnesium(Mg) and copper(Cu) in leaves increased while manganese(Mn) decreased in A.cremastogyne and P.chinensis grown in tailings than that in control soil.The N-fixing species,A.fruticosa which have the highest tolerance and biomass production,respectively,have great potential application in revegetation in tailings of southern China.