Field Application of Layered Double Hydroxides to Reduce Cd Bioavailability and Uptake in Artemisia argyi Grown in Severely Contaminated Soil

Non-food cropping provides a practical strategy for the safe utilization of severely cadmium (Cd)-contaminated farmland. In this study, a field experiment was conducted to evaluate the effectiveness of layered double hydroxides (LDHs) in reducing Cd transfer from soil to Artemisia argyi, a plant used for non-food applications, and to estimate Cd release potential during moxa burning. Our results demonstrated that the application of LDHs increased soil pH and decreased the extractable Cd concentration based on CaCl2 extraction, suggesting a reduction in Cd bioavailability. Furthermore, BCR fractionation analysis indicated a shift of Cd from more active to more stable forms, further supporting the reduction in Cd bioavailability in the soil. SEM–EDS and FTIR confirmed the lamellar morphology, CaAl composition, and hydroxyl-rich functional groups of the LDH conditioner. Plant growth was not negatively affected by LDH treatment, and Cd concentrations in roots, stems, and leaves were significantly reduced. LDHs also reduced Cd levels in processed moxa and the mass-balance-based estimate of Cd release during combustion. These findings suggest that LDHs application may help reduce Cd transfer in non-food cropping systems on severely contaminated farmland.