Function of Submerged Macrophytes in the Distribution of Per- and Polyfluoroalkyl Substances (PFAS) Alternatives in Constructed Wetlands: Role of Extracellular Polymeric Substances (EPS) in the Phyllosphere

Submerged macrophytes in constructed wetlands (CWs) are key to removing PFAS alternatives, which pose serious risks to aquatic ecosystems. Although phyllosphere extracellular polymeric substances (EPS) are crucial for contaminant uptake by submerged macrophytes, the underlying mechanisms remain poorly understood. Here, we show that typical PFAS alternatives, 6:2 chlorinated polyfluoroalkyl ether sulfonate (F-53B) and hexafluoropropylene oxide dimer acid (GenX), accumulated in Vallisneria spinulosa (V. spinulosa) reached 17.49 ± 1.02 and 5.25 ± 0.36 μg/g DW, respectively, approximately 2.70 and 3.16-fold higher than those in Ceratophyllum demersum (C. demersum). Correspondingly, the phyllosphere EPS of V. spinulosa exhibited high accumulation of GenX and F-53B, with concentrations of 124.98 ± 4.70 and 99.53 ± 13.12 μg/g DW, respectively. Crucially, EPS binding with PFAS alternatives increased the hydrophilicity and induced structural reorganization, facilitating contaminant internalization into plant tissues. Meanwhile, metagenomic analysis revealed that the phyllosphere microenvironment selectively enriched microbial functional genes involved in antioxidant defense and EPS biosynthesis, thus supporting sustained contaminant capture in the phyllosphere interface. These findings reveal EPS-mediated mechanisms underlying PFAS alternative uptake by submerged macrophytes in CWs.