DOM forms PFAS nanoclusters and lowers phytotoxicity

What the study found: The study reports that per- and polyfluoroalkyl substances (PFAS) can form nanoclusters when interacting with dissolved organic matter (DOM, natural organic material in water), rather than remaining only as individual molecules. It also reports that this nanocluster formation is associated with reduced phytotoxicity (toxicity to plants) in rice seedlings.

Why the authors say this matters: The authors conclude that DOM-induced nanoclustering is a critical interface process that affects PFAS bioaccessibility (how available a substance is to living organisms) and risk. They suggest this offers a different perspective for environmental assessment and remediation of PFAS.

What the researchers tested: The researchers used newly established in situ atomic force microscope (AFM, a type of microscope that can image surfaces at very small scales) techniques to visualize PFAS behavior at the interface of naturally extracted DOM. They also examined intermolecular interactions and performed plant exposure experiments in rice seedlings.

What worked and what didn't: The AFM observations showed dynamic formation of PFAS nanoclusters at the DOM interface. Strong binding forces between PFAS molecules and specific DOM functional groups produced many small nanoclusters, while weaker interactions produced larger, sparser nanoclusters; this relationship was reported across nonionic, anionic, cationic, and zwitterionic PFAS structures, with a strong negative correlation between nanocluster size and abundance (R = -0.983, P = 0.017). Compared with molecularly dispersed PFAS, the nanoclustered PFAS showed significantly reduced uptake in rice seedlings and were sequestered on root surfaces as a physical barrier.

What to keep in mind: The abstract does not describe detailed experimental conditions beyond the use of naturally extracted DOM, AFM imaging, and rice seedling exposure tests. It also does not provide broader field or environmental measurements beyond the systems tested here.

Key points

• PFAS formed nanoclusters when they interacted with dissolved organic matter (DOM).
• Strong PFAS-DOM binding produced many small nanoclusters; weaker interactions produced larger, sparser ones.
• The nanocluster size and abundance showed a strong negative correlation (R = -0.983, P = 0.017).
• In rice seedlings, nanoclustered PFAS had reduced uptake compared with molecularly dispersed PFAS.
• The authors say DOM-induced nanoclustering may affect PFAS bioaccessibility and environmental risk.