PFAS Dynamics in a Macrotidal Estuary: Insights from Fractionated Particle Components

Area of Science:

• Environmental Chemistry
• Marine Science
• Organic Geochemistry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants (POPs) with increasing environmental presence.
• Estuaries act as critical conduits for transporting land-based pollutants to the sea.
• Suspended particulate matter (SPM) composition, not just size, significantly influences PFAS partitioning and transport.

Purpose of the Study:

• To investigate the dynamics of PFAS associated with size-fractionated SPM in an estuarine turbidity maximum (ETM).
• To understand how tidal forcing and SPM composition affect PFAS partitioning.
• To elucidate the role of nonvolatile organic carbon (NVOC) in PFAS accumulation.

Main Methods:

• Collection of water samples across two tidal cycles in the Jiulong River estuary ETM.
• Analysis of size-fractionated SPM (0.22-1 μm to >63 μm) for composition and PFAS concentration.
• Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) for SPM characterization.

Main Results:

• SPM composition varied by size fraction, with smaller particles potentially organic-rich and larger ones inorganic-rich.
• Disproportionately high PFAS concentrations were found on both the smallest (0.22-1 μm) and largest (>31 μm) SPM fractions.
• Tidal variations induced size-dependent salting-in/salting-out effects for PFAS, linked to electrostatic interactions.
• A positive correlation between bottom-water NVOC and SPM-associated PFAS suggests NVOC facilitates accumulation.

Conclusions:

• Fractionated SPM components differentially regulate PFAS dynamics in estuaries.
• Size-dependent electrostatic interactions and NVOC play crucial roles in estuarine PFAS transport.
• Findings provide critical insights for predicting PFAS transport and assessing environmental risks.