Study on the regulatory effect of biochar-based materials on the migration and accumulation of perfluoroalkyl substances in paddy soil-water-plant systems

Perfluoroalkyl substances (PFAS), as persistent emerging contaminants, can migrate into rice systems through the soil-water interface (SWI) during irrigation, threatening food security and human health. However, the diffusion characteristics of PFAS at the SWI under carbon-based material regulation and their solute exchange kinetics remain unclear, particularly the quantitative differences between short-chain (PFBA) and long-chain (PFOA) PFAS behaviors. To address this, this study innovatively integrated molecularly imprinted polymer-diffusive gradients in thin films (MIP-DGT) and high-resolution pore water sampling (HR-Peeper) techniques to systematically investigate the regulatory mechanisms of control (WBC), rice husk biochar (RBC), and montmorillonite-modified biochar (MBC) on the migration and accumulation of PFBA and PFOA in the paddy sediment-water-plant system. The results showed that in WBC-treated soil, the surface C DGT -PFBA and C DGT -PFOA concentrations were 6.76 ± 1.44 ng L −1 and 7.21 ± 2.14 ng L −1 , respectively, while biochar treatments significantly inhibited PFAS migration to deeper layers. Compared to WBC, RBC reduced C DGT -PFBA and C DGT -PFOA in deeper soil layers by 32.80 % and 87.50 %, respectively, with modified biochar exhibiting even stronger retention effects. The constructed 2D-DIFS (DGT-induced fluxes in soils/sediments) model indicated that PFAS re-supply capacity (R-value) from soil to pore water declined with irrigation cycles. PFBA had shorter response times (T c ) and higher mobility, while PFOA was more immobilized due to higher adsorption rate (k −1 ) and partition coefficient (K d ). Notably, compared to WBC, RBC reduced PFBA and PFOA accumulation in rice organs by 24.21 ~ 26.26 %, confirming the dual role of carbon-based materials in altering PFAS interfacial behavior and thereby inhibiting plant uptake. This study clarifies PFAS migration and biotransport responses to carbon-based materials under irrigation, supporting strategies to mitigate PFAS contamination in farmland. • Enhanced MIP-DGT technology efficiently identifies and quantifies PFAS. • Biochar inhibits PFAS migration from overlying water to deeper soil layers. • Carbon-based materials can effectively alleviate PFAS pollution in plant organs. • PFOA tends to persist in soil, whereas PFBA is readily accumulated by plants. • PFAS re-supply capacity from soil solids to pore water diminishes over time.