In situ phytoremediation of copper and cadmium in a co-contaminated soil and its biological and physical effects

Phytoremediation is a potential cost-effective technology for remediating heavy metal-contaminated soils. This method was used to evaluate the biomass and accumulation of copper (Cu) and cadmium (Cd) of plant species grown in contaminated soil and their biological and physical effects on the soil. In co-contaminated soils with copper (Cu) and cadmium (Cd), a three-year field experiment was conducted by planting four plant species in the co-contaminated acidic soil treated with hydroxyapatite. The four species produced different amounts of biomass in this order: Pennisetum sp. > Elsholtzia splendens > Setaria lutescens > Sedum plumbizincicola. Over three growing seasons, the best accumulators of Cu and Cd were Elsholtzia splendens and Sedum plumbizincicola, respectively. Overall, Pennisetum sp. was the best species for Cu and Cd removal when biomass was considered. The four plant treatments could improve the content of >0.25 mm mechanically stable (DR(0.25)) and water-stable (WR(0.25)) aggregates and significantly improve the aggregate mean mass diameter (MWD) and the geometric mean diameter (GMD). The largest increase was with the treatment of Pennisetum sinese, while the fractal dimension (FD) of mechanically stable aggregates could be significantly reduced by the treatment of Pennisetum sp. Hydroxyapatite and phytoremediation could improve the soil enzyme activity, and Elsholtzia splendens had the best effect in this respect. This study will provide a better understanding of the remediation of heavy metal contaminated soil.