| Heavy metal contamination in soil is a worldwide environmental problem,especiallly cadmium and lead.Using phytoremediation,as an efficient technique,to remove heavy metals from contaminated soil is a current research hotspot.This study used a pot experiment with an orthogonal rotated matrix design with three factors?i.e.,Cd,Pb,and pH?and five levels(i.e.,Cd at 9.45,30,60,90 and 110.46?g·g-1;Pb at 195.4,400,700,1000 and 1204.6?g·g-1;and pH at 3,4.1,5.8,7.5 and 8.6),and determined the effects of Panicum virgatum on the growth,physiology,and accumulation characteristics to evaluate the phytoremediation potential of switchgrass for cadmium?Cd?-,lead?Pb?-and pH-polluted soil.The results showed that:1.The root length and shoot length of switchgrass were significantly inhibited under the stress of Cd,Pb,and pH comparing with the control.Moreover,the couple effects of Cd×pH effected significantly the root length of switchgrass,and the corresponding slope was>0,indicating that the couple effects of Cd×pH had a synergistic effect on the root length of switchgrass.2.The activity of superoxide dismutase?SOD?decreased first and then increased under the stress of Cd and Pb as well as the content of malondialdehyde?MDA?.However,there was no significant effect on the peroxidase?POD?activity under three stresses.Moreover,the coupling effects of Cd×pH significantly affected three kinds of physiological indexes,and the ridge lines showed k<0,k>0,k>0,respectively,indicating that Cd×pH had an antagonistic,synergistic and synergistic effect on the activity of SOD,the activity of POD,and the content of MDA.3.The Cd concentration and Pb concentration underground of switchgrass were much higher than that aboveground under three kinds of stresses.In addition,the bioconcentration factor?BCF?of Cd was significantly higher than that of Pb,while the former was more than 1,the latter was less than 1.The translocation factor?TF?of Cd and Pb were no significant correlation with pH.At the same time,that Pb×pH and Cd×pH had a synergistic effect on the BCF of Cd,while Cd×Pb had an antagonistic effect.4.The plant had the highest Cd accumulative ability at ranges of Cd concentration of75.6-94?g·g-1,Pb concentration of 471-645?g·g-1 and pH of 4.8-5.1 after optimal modeling analyses.In conclusion,switchgrass was more suitable in the Cd-polluted soil compared with Pb-polluted soil.Moreover,in the present study,the interaction of Cd and Pb had an antagonistic effect on the accumulation of Cd,whereas either the interaction of pH with Cd or with Pb had synergistic effects on it.Furthermore,the Cd and Pb concentration were mainly factors effected the phytoremediation potential of switchgrass. |
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