Abstract: Phytoextraction is a potential, innovative and cost-effective technology for non-destructive remediation of heavy metal-contaminated soils. A field trial was conducted to evaluate the phytoextraction efficiencies of three plants and the effects of EDTA or ammonium addition [(NH₄)₂SO₄ and NH₄NO₃] for assisting heavy metal (Pb, Zn, and Cd) removal from contaminated soil. The tested plants include Viola baoshanensis, Vertiveria zizanioides, and Rumex K-1 (Rumex patientia × R. timschmicus). The application of EDTA soil was the most efficient to enhance the phytoavailability of Pb and Zn, but did not have significant effect on Cd. Lead phytoextraction rates of V. baoshanensis, V. zizanioides and Rumex K-1 were improved by 19, 2, and 13 folds compared with the control treatment, respectively. The application of ammonium did not have obvious effects on phytoextraction of the three metals, except that the accumulations of Zn and Cd in shoot of V. baoshanensis. Among the three tested plants, V. baoshanensis always accumulated the highest concentrations of Pb, Zn, and Cd. The concentrations of Pb, Zn, and Cd in the shoots of V. baoshanensis treated with EDTA were 624, 795, and 25 mg kg^-1, respectively, and the phytoextraction efficiencies of this species for Pb, Zn, and Cd were also the highest among the three species. Results presented here indicated that V. baoshanensis had great potential in phytoremediation of soils contaminated by multiple heavy metals, although the dry weight yield was the lowest among the three plants.

KEY WORDS: phytoextraction; heavy metals; EDTA; ammonium; Viola baoshanensis; Vetiver zizanioides; Rumex K-1 (Rumex patientia × R. timschmicus)