Effect and mechanisms of soil functional groups in bacterial-enhanced cadmium contaminated soil phytoremediation

Considering the detrimental impact of heavy metals on agricultural soils, in situ remediation technology has gained considerable attention worldwide. Green materials have emerged as a promising option for enhancing plant-mediated remediation of contaminated soils. In this study, bacteria capable of mobilising cadmium (Cd) and promoting plant growth were screened and isolated. A synergistic system was established by combining bone meal and chitosan as soil amendments with the Cd-mobilising bacteria to improve the extraction of available Cd from soils by plants. The highest Cd accumulation was observed in the bone meal + bacteria, which increased by 131.81% when compared to the control group (CK). The highest available Cd content was observed in the chitosan + bacteria, which increased by 52.31% when compared to CK. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy results revealed that organic compounds, such as hydroxyl and carboxyl groups, and aliphatic compounds in the soil were crucial in mobilising Cd. Cd activation occurred through substitution of protons in the functional groups and chelation, leading to the formation of chelates with Cd2+ and in turn, facilitating Cd mobilisation in the soil. The incorporation of bone meal and chitosan into phytoremediation strategies can enhance the ability of bacteria to mobilise Cd, thereby increasing the effectiveness of phytoremediation.