Amendment-Enhanced Phytoextraction of Cadmium from Contaminated Soil Integrating with Ramie as Hyperaccumulator Plant

Enhanced phytoextraction of metals using amendments and hyperaccumulator plants is a promising alternative to expensive traditional remediation techniques. The present study comprehensively investigated the effects of six amendments on both mobility and phytoextraction of Cd and the feasibility of integrating amendment with Ramie as a hyperaccumulator plant on Cd-contaminated soil remediation. The leaching of Cd from contaminated soil was significantly enhanced by two chelating agents (i.e., ethylenediaminetetraacetic acid (EDTA) and ethyleneglycoltetraacetic acid (EGTA)), followed by two natural organic acids (i.e., citric acid and tartaric acid), and lastly, two rhizobacteria (i.e., Bacillus subtilis and Pseudomonas fluorescens). Further, the application of EDTA and EGTA had inhibitory effects on the growth of Ramie. The application of two organic acids and two rhizobacteria increased the dry biomass yields of roots, stems, and leaves. In terms of the dry biomass of Ramie, 32.7, 23.4, 50.6, and 53.1% of increases were obtained from the applications of citric acid, tartaric acid, B. subtilis, and P. fluorescens, respectively, as compared with that without any amendment applied. Meanwhile, the applications of all amendments were observed to increase Cd concentrations in aerial parts of the plants, and they were ranked in descending order of Cd accumulation: EDTA > EGTA > tartaric acid > citric acid > B. subtilis ≈ P. fluorescens. Taking Cd removal efficiency, potential environmental risk, and economic factor into consideration, EDTA and citric acid-enhanced phytoremediation using Ramie were feasible and promising approaches for remediating Cd-contaminated soil in real practice.