Objective The aim was to evaluate the effectiveness of planting Helianthus annuus for the remediation of composite heavy metal polluted farmland contaminated with cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb) under conditions of Bacillus subtilis biopreparations and the auxiliary effect of Bacillus subtilis, which could help to choose an ideal candidate plant for the remediation of heavy metal polluted farmland soil in Ganzhou, Jiangxi.

Method In the typical heavy metal compound polluted farmland of nonferrous metal mining area in Ganzhou, Jiangxi Province, Helianthus annuus was used as the main test material, solanum nigrum and Bidens bipinnata were used as the contrast materials, and Bacillus subtilis was set up to carry out the plant-microorganism combined remediation test of polluted farmland.

Result The average Cd accumulation in the whole plant of Helianthus annuus reached 1.5 mg plant⁻¹. Calculating based on the planting density of Helianthus annuus in this experiment (83000-84000 plants hm⁻²), it could remove and clear Cd elements from the polluted farmland soil at a rate of 124.5-126 g hm⁻² annually. Helianthus annuus showed relatively weak accumulation and removal abilities for Hg in polluted soil, but a strong accumulation ability for Pb. Furthermore, the application of the biopreparations significantly enhanced the absorption and accumulation ability of oil sunflower roots for Pb. Helianthus annuus exhibited strong accumulation and removal abilities for As, with an average accumulation of 0.14-0.20 mg plant⁻¹. The addition of Bacillus subtilis biopreparations did not significantly affect the As accumulation ability of Helianthus annuus. Helianthus annuus showed significantly better accumulation ability for Cd compared to Black Nightshade and Spanish Needle, while there was no significant difference in the accumulation abilities of the three plants for Hg, As, and Pb. The analysis of the oil extracted from sunflower seeds showed a Cd content of 0.078 mg kg⁻¹, with non-detection of As, Pb, and Hg, meeting national food safety standards. However, the Cd content in the oil cake remaining after oil extraction from Helianthus annuus seeds was 8.27 mg kg⁻¹, which needed to be properly treated as hazardous waste.

Conclusion Compared with the Solanum nigrum and Bidens bipinnata in this experiment, the oil sunflower had a significant advantage in the enrichment and removal efficiency of Cd. In addition, it also had both economic and ornamental value and could be considered an ideal candidate plant for the remediation of heavy metal polluted farmland soil in Ganzhou, Jiangxi.