A plant-derived compound activating agent enhances cadmium phytoextraction by Lantana Camara L

Agent-assisted phytoextraction is an attractive strategy to remove heavy metals from soil. However, there is a lack of effective and sustainable agents. In this study, 10 types of plant extracts were extracted and selected to combined with N, N-bis (carboxymethyl) glutamic acid (GLDA) to prepare the compound activating agent, and its effectiveness and potential risk in enhancing Cd phytoextraction by Lantana camara L. (L. camara) were evaluated. Among the 10 plant extracts, Houttuynia cordata Thunb. extract (HC) showed the highest Cd extraction ability (24.58%). When combined with GLDA (0.9%) in a 1:1 volume ratio, the compound activating agent removed Cd most effectively (79.23%) from soil. In the pot experiment, this agent increased the shoot biomass, Cd concentration, and accumulation in L. camara by 17.45%, 71.43%, and 100.42%, respectively, compared with the Cd treatment. Additionally, soil DOC (+ 17.47%) and available Cd (+ 34.05%) were significantly increased vs. Cd treatment. Acid soluble Cd increased significantly, while the reducible and oxidizable Cd fractions decreased. In the soil column experiment, leached Cd from soils treated with this agent treatment was significantly lower than from EDTA treated soils. Collectively, the compound activating agent enhanced Cd phytoextraction by L. camara through its activation effect and increased soil DOC, which promoted the conversion of oxidizable/reducible Cd to acid soluble Cd and mobilized soil Cd for plant uptake. Thus, the HC extract combined with GLDA compound activating agent is a promising enhancer for Cd phytoextraction.