Constraining PFAS and precursors transport and fate pathways in dune filtration schemes for drinking water supply by modelling

• Applicant: Dr. Anne Imig
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 577360772

Sea spray aerosols (SSA) have been identified as a secondary emission source of per- and polyfluoroalkyl substances (PFAS), overturning the long-held belief that the ocean serves as a final sink for these persistent “forever chemicals” through dilution. Since most PFAS occurring in the environment are harmful to both humans and ecosystems, their re-emission into the atmosphere is creating a substantial issue. In coastal regions such as the Netherlands and Germany, drinking water is often produced through managed aquifer recharge systems (MAR) in dune areas. PFAS are deposited with SSA on the dune surface and transported with infiltrating (rain)water into the groundwater, creating serious challenges for water utilities striving to provide safe drinking water. In Haamstede (Zeeland, the Netherlands), 3.5 million m³/a of drinking water is produced through dune MAR systems, where pretreated water from Lake Haringvliet is infiltrated into dunes across an area of 4 km². Since 2018, 23 PFAS have been monitored monthly; for nine compounds, concentrations in the recovered water exceed regulatory limits. PFAS profiles in the recovered water closely resemble those of the dune topsoil, supporting SSA as a key input pathway. In addition to regulated PFAS, precursors are also detected in SSA but not in dune soils. This suggests that precursors degrade into stable PFAS within soils, thereby representing a long-term contamination source. In this project, I aim to describe the reactive transport of PFAS and their precursors in dune MAR systems such as the Haamstede site through numerical modelling, in order to predict future concentrations in abstracted drinking water. Existing monitoring data from Haamstede will be analysed to trace how PFAS and precursors are transported from the dune surface through the unsaturated and saturated zones to the abstraction wells. An existing 2D MODFLOW6 model of the saturated zone at Haamstede will be extended with the USGT-PFAS module to simulate reactive transport of PFAS and precursors. Building on this, the 2D model will be further developed into a site-specific 3D model calibrated with field data. To the best of my knowledge, this is the first study linking diffuse PFAS emissions from SSA to dune MAR systems used for drinking water production. For the first time, the degradation of PFAS precursors into stable PFAS will also be explicitly considered to quantify their contribution to overall contamination in the drinking water supply system. This modelling approach represents a novel step in PFAS research and will enable predictions of future concentration trends. It will also provide water utilities and decision-makers with a tool to assess risks from SSA-derived PFAS in dunes and dune MAR systems, helping to ensure a safe drinking water supply.

• DFG Programme: WBP Fellowship
• International Connection: Netherlands
• Host: Professor Dr. Boris van Breukelen