Application of titanium dioxide nanoparticles to promote phytoremediation of Cd-polluted soil: contribution of PGPR inoculation

Abstract

Co-application of titanium dioxide nanoparticles (TiO2 NPs) and plant growth promoting rhizobacteria (PGPR) to promote phytoremediation of Cd contaminated soil was studied. Seedlings of Trifolium repens were exposed to different doses of TiO2 NPs (0, 100, 250, 500 and 1000 mg/kg) and the PGPR, separately and in combination, to investigate the effects on plant growth, Cd uptake and accumulation and chlorophyll content of the plant. Co-application of TiO2 NPs and the PGPR enhanced plant growth and chlorophyll content of T. repens. Cd concentration in roots of T. repens reached 120.3 mg/kg in PGPR + 500 mg/kg TiO2 NPs treatment. Addition of TiO2 NPs to soil significantly increased accumulation capacity of T. repens. The greatest accumulation capacity of 1235 µg/pot was achieved for Cd in PGPR + 500 mg/kg TiO2 NPs treatment. Adverse impacts of using 1000 mg/kg TiO2 NPs were found on plant growth. Co-application of TiO2 NPs and PGPR could reduce the required amounts of TiO2 NPs for phytoremediation of heavy metal polluted soils. Co-application of TiO2 NPs and PGPR promoted growth of T. repens in Cd-contaminated soil and enhanced Cd uptake and accumulation by the plant. Intelligent association of plants, nanomaterials and PGPR have great application prospect in soil remediation.