Remediation by tissue culture seedlings of Sedum alfredii Hance in Zn-, Cd- and combination-contaminated soils

Sedum alfredii Hance is a typical hyperaccumulator of zinc, cadmium and lead, and is excellent for phytoremediation．In this work Sedum alfredii Hance seedlings were pot cultured in Zn- and Cd-contaminated soils, and removal of Zn and Cd was examined．Tissue culture seedlings were found to preserve completely tolerance to heavy metals, environment adaptability to high concentrations of Zn and Cd was stronger than cut seedlings．In heavily contaminated soil (Zn 2000 mg·kg⁻¹), biomass of tissue culture seedlings was 2.3 times that of control (cut seedlings)．In Cd-contaminated soil (Cd 1344 mg·kg⁻¹), biomass of tissue culture seedlings increased by 16.4% compared to control．Tissue culture seedlings showed strong ability to absorb and accumulate Zn and Cd in compound-contaminated soil．In 2 compound-contaminated soils, enrichment coefficient for Zn was 9.69 and 11.09, for Cd was 12.67 and 85.36, respectively．Zn and Cd in composite contaminated soil were found to interact, which affected absorption and enrichment of Zn and Cd．A low Cd concentration in soil promoted Zn absorption, but Zn inhibited absorption and enrichment of Cd．Distribution of Zn and Cd heavy metals in plants growing in compound-contaminated soil is affected．