Response of the rhizosphere microenvironment to per(poly)fluoroalkyl substance partitioning induced by submerge-emerge alternation.

Per(poly)fluoroalkyl substances (PFASs) are persistent pollutants with significant environmental risks. However, their partitioning behavior and ecological impacts under dynamic hydrological conditions remain unclear. Our study examined PFAS release, transport, bioaccumulation, and rhizosphere microenvironment responses under submerge-emerge alternation (ASE) compared to continued submergence (CS) and emergence (CE) through indoor simulations. Results showed that ASE significantly promoted the transport and bioaccumulation of PFASs in plant roots. The total PFAS concentration in ASE sediment was 1.54 times that in CS and 0.66 times that in CE at the end of the experiment. The Log bioconcentration factors (Log BCFs) in ASE ranged from -1.09 to 1.02 kg/L, significantly higher than in CS (-1.23 to 0.58 kg/L) and CE (-0.79 to 0.26 kg/L). Substitutes exhibited higher Log BCFs compared to PFOA and PFOS, especially PFBA and PFHxS. Metabolomic analysis revealed that PFAS partitioning under alternating conditions induced the remodeling of root exudates (REs), significantly increasing the secretion of organic acids (9.23 %) and carbohydrates (2.20 %) while decreasing the relative abundance of lipids (24.41 %). Additionally, PFAS partitioning under ASE reduced the abundance of Pseudomonadota (18.10 %) while notably increasing the abundance of Patescibacteria (5.84 %), Thermodesulfobacteriota (4.30 %), and Sphingomonas (1.18 %) in rhizosphere microorganisms (RMs). Co-occurrence network analysis revealed that ASE strengthened the interactions between REs and RMs. Both the mediation of REs and the central role of dominant bacteria within the network were enhanced. Our study elucidates PFAS partitioning behavior under hydrological fluctuations and provides important insights into the management of rhizosphere pollution in submerge-emerge alternating regions.