Heavy Metal Uptake and Extraction Potential of Two Bechmeria nivea (L.) Gaud. (Ramie) Varieties Associated with Chemical Reagents

Two varieties of Bechmeria nivea (L.) Gaud. (Ramie), namely, triploid Tri-2 and diploid Xiangzhu-3, were potted with soils from Guangdong for 15 weeks and treated with 10 mmol kg−1 EDTA or EGTA before harvest at 17th week. Lead, Zn, and Cd in plant and soil materials were analyzed, and their potential ecological risk in soils was simultaneously evaluated. These three metals in soils was found to be above 14.4, 3.0, and 29.9 times higher than the national (China) background value, 10.9, 6.19, and 96.7 times higher than the local (Guangdong) background value, and 1.25, 1.20, and 9.67 times higher than the maximum permissible concentration for soils, respectively. An ecological risk analysis of metals using Häkanson's method indicated an extremely high contamination and a significantly high potential ecological risk by these three metals in soils. The both ramie varieties contained respective concentration exceeding the concentration of <10, <80, and <0.27 mg kg−1, respectively, for Pb, Zn, and Cd in normal plants, suggesting they were multimetal tolerant. Tri-2 generally contained higher Pb, Zn, and Cd than Xiangzhu-3. Treatment with EDTA or EGTA applied at 10 mmol kg−1 generally promoted Pb or Cd concentration in both plants while the uptake of Zn was depressed. The ramie variety of Tri-2 and Xiangzhu-3 could extract 0.161 and 0.147 t ha−1 of Cd, respectively, equaling to the 0.17 t Cd per hectare by Cd-hyperaccumulating species Viola baoshanensis. Therefore, two ramie varieties in this study had a higher extracting potential for removal of Cd from contaminated soils.