Investigation of Cadmium Uptake and Transfer Ability of Three Ornamental Plants for Remediation of Cadmium Contaminated Soils

The remediation of heavy metal in contaminated soils using ornamental plants presents a suitable solution for decontamination, especially in urban areas. In order to investigate the ability of ornamental plants to refine contaminated soils, an experiment was conducted in the greenhouse using six levels of soil cadmium (0, 5, 10, 20, 40, and 80 mg/kg), three species of ornamental plants (Calendula officinalis L., Helianthus annuus L., and Celosia argentea L.) and three replications. The results showed with increasing cadmium levels in the soil, cadmium concentration in the plant tissues increases, so that, the highest and the lowest concentrations of cadmium were measured in the shoot of Calendula officinalis L. and Helianthus annuus L. respectively with a difference of 50.2%. However, the highest and the lowest cadmium concentration in the root were found in the Helianthus annuus L. and Calendula officinalis L., respectively with a difference level of 4.2%. The cadmium uptake of the shoot in Calendula officinalis L. was at least 27.63% more than those in the other species. The chlorophyll index of the leaf and the number of flowers in Calendula officinalis L. were respectively 17.33% and 34% more than those in the other species. The translocation factor of Celosia argentea L. was equal to one (1.0) and those of Calendula officinalis L. and Helianthus annuus L. were less than one (0.5 and 0.3), but the bioconcentration factors for all species were found to be more than one. With respect to high cadmium uptake, high cadmium concentration of shoot, high biomass and high beauty indices (chlorophyll index and the number of flowers) of the Calendula officinalis L., this species is recommended for remediation of cadmium contaminated soils.