The comparative potential of four Compositae plants for phytoremediation of karst lead/zinc mine tailings contaminated soil

A tailings concentration gradient experiment was done to demonstrate the comparative evaluation of phytoremediation for Cd, Pb, and Zn in karst lead/zinc mine tailings contaminated soil by four Compositae plants (Crassocephalum crepidioides, Bidens pilosa, Ageratum conyzoides, and Cosmos bipinnatus). The results indicated that the four species grown in the dose-gradient mine tailings were tolerant to these metals to varying degrees. C. crepidioides and B. pilosa were more tolerant to heavy metals, while C. bipinnatus was the most sensitive species. Despite the high concentrations of Pb and Zn in the culture substrate, there was only a small increase in the concentration of these elements in the plant organs compared to the control. However, all species were observed to be shoot accumulators for Cd. C. crepidioides accumulated a maximum of 132.1 and 159.1 mg·kg-1 of Cd in leaves and stems, respectively, and these results were higher than those in the roots (67.2 mg·kg-1) and soil (75.8 mg·kg-1). C. crepidioides can be regarded as a Cd-hyperaccumulator, with a Cd removal of 4.56% to 9.97% from the soil polluted by lead/zinc mine tailings after single season cultivation. The comprehensive analysis result indicated that C. crepidioides exhibited the highest tolerance, biomass production, and removal of heavy metals, indicating its ability in the phytoremediation of contaminated soil in Pb/Zn tailings affected area.