Identification Of Cadmium Hyperaccumulators From Ornamental Plants And Their Chemical Enhancement Techniques

To screen out ideal hyperaccumulators is the main groundwork of phytoremediation, which is also front field of contaminated environment remediation. The species of discovered hyperaccumulators are limited at present, there is no systemic report about ornamentals. If ornamental plants can beautify the environment while remediate contaminated solis at the same time, both economic and ecological benefits will be acquired.Mirabilis jalapa L., Impatiens Balsamina L., Calendula officinalis L. and Althaea rosea Cav. which were selected from preliminary experiment were used in this study to carry out the pot culture gradient experiment of single Cd (Cd≤100 mg kg-1) and the hydroponic experiment of Cd-Pb combined contamination. The results showed that Mirabilis jalapa L. had characteristics as a Cd-hyperaccumulator. Impatiens Balsamina L. and Calendula officinalis L. were not Cd-hyperaccumulators, but they had strong ability of accumulating Cd especially for Calendula officinalis L., therefore they could also act on Cd contaminated soil remediation. Althaea rosea Cav. had potential to be a Cd-hyperaccumulator under appropriate enhancements.Mirabilis jalapa L. was further used to carry out the high concentration of single Cd experiment (100 mg kg-1≤Cd≤500 mg kg-1) and the chemically enhanced experiment for 100 mg kg-1 Cd contaminated soils. The results of the former experiment showed that Mirabilis jalapa L. could tolerate Cd at the level of 300 mg kg-1, i.e. the species did not show any phytotoxicity, the shoot Cd concentration was higher than the critical concentration of Cd-hyperaccumulator, TF and AF values were higher than 1. The results of the latter experiment showed that EGTA and SDS could increase the dry biomass of the plants, EDTA was toxic to the species by restraining the growth, whereas they all could promote Cd accumulation in shoots and roots of the species to a certain extent, moreover, EGTA was more effective than EDTA in enhancing phytoextraction with Mirabilis jalapa L., in particular, there was great efficiency in promoting the Cd accumulation for chelator, or and surfactant treatments when they were applied to contaminated soils in manner of solution 1 month before harvest.Calendula officinalis L. was also further used to carry out the chemically enhanced experiment for 30 and 100 mg kg-1 Cd contaminated soils. The results showed that appropriate EGTA or/and SDS treatments could increase not only the biomass but also the total Cd content of the plants, the total Cd content in shoot was totally higher than that in root, which was greatly beneficial to phytoextraction.Althaea rosea Cav. was also further used to carry out the chemically enhanced experiment for 30 and 100 mg kg-1 Cd contaminated soils. The results showed that the shoot Cd concentration had exceeded the critical concentration of a Cd-hyperaccumulator under appropriate chemical enhancements, and other Cd-hyperaccumulator characteristics were also observed.