Study on the influencing mechanism of biochar and ethylenediaminetetraacetic acid combination on the remediation of Cd polluted soil by Sedum alfredii Hance

Soil amendments and chelating agents play a crucial role in enhancing the uptake of heavy metals by plants. However, the mechanisms by which biochar and ethylenediaminetetraacetic acid (EDTA) affect plants are complex and lack in-depth research. To improve the efficiency of plant remediation in Cd-contaminated soil, Sedum alfredii Hance was used for experimental analysis of bioavailable Cd content to evaluate the effects of biochar and EDTA on the speciation of Cd in the soil. The bio-resistance factor (BRF), bio-concentration factor (BCF), and bio-transfer factor (BTF) were used to assess the plant's capacity to absorb Cd. The results showed that biochar reduced the bioavailable Cd in the soil and promoted the growth and Cd accumulation of S. alfredii. Adding 1 % biochar to the soil reduced the bioavailable Cd content by 31 %. EDTAs inhibitory effect on plant growth intensified with increasing EDTA concentration. When the EDTA concentration was 2.5 mmol center dot kg-1, the biomass of S. alfredii was 76% lower than the CK group. The combined action of biochar and EDTA significantly enhanced the Cd bio-transfer capacity of S. alfredii. The addition of 1 % biochar and 0.5 mmol center dot kg-1 EDTA resulted in the most pronounced increase in the Cd BTF for S. alfredii. Under these conditions, the BTF (1.36) was 3.49 times higher than that of the CK group, and the Cd content in the aboveground parts was 36 % higher than in the underground parts. This study is of great significance in promoting the use of plants for the remediation of heavy metal pollution.