Multi-compound PFAS transport in the unsaturated zone during infiltration cycles
Samuel Oluwaseun Kolade1, Avner Ronen1, Tuvia Turkeltaub1
1Department of Environmental Hydrology and Microbiology, Zuckerberg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 84990, Israel.
Water Research
|September 18, 2025
Summary
Short-chain Per- and Polyfluoroalkyl substances (PFAS) move quickly through soil, while long-chain PFAS stick to sediment. Transient flow conditions significantly impact PFAS transport and retention in the subsurface.
Area of Science:
- Environmental Science
- Geochemistry
- Hydrogeology
Background:
- Per- and Polyfluoroalkyl substances (PFAS) are persistent contaminants with long-term retention in subsurface environments.
- Understanding PFAS transport dynamics is crucial for assessing environmental risks and developing remediation strategies.
Purpose of the Study:
- To investigate the simultaneous transport of long- and short-chain PFAS under transient flow conditions simulating episodic infiltration.
- To evaluate the influence of dynamic water content fluctuations on PFAS adsorption-desorption processes.
- To assess the limitations of equilibrium-based models in predicting PFAS transport in the unsaturated zone.
Main Methods:
- Conducted large column experiments (3 m) simulating unsaturated zone flow with episodic infiltration cycles.
- Simultaneously tracked the transport of long-chain (PFOS, PFOA) and short-chain (PFHxA, PFPeA) PFAS, alongside a conservative tracer (Bromide).
- Utilized flow and transport modeling incorporating equilibrium-based solid phase and air-water interfacial adsorption parameters (KAWI and Kd).
Main Results:
- Short-chain PFAS (PFHxA, PFPeA) exhibited high mobility, closely matching conservative tracer transport.
- Long-chain PFAS (PFOS, PFOA) showed significant retention and delayed breakthrough, with concentration fluctuations linked to wetting/drainage cycles.
- Equilibrium-based models underestimated the complex transport behavior of long-chain PFAS under transient flow.
Conclusions:
- Infiltration-driven wetting and drainage cycles critically influence PFAS partitioning and mobility in the unsaturated zone.
- Non-equilibrium sorption kinetics must be incorporated into models for accurate PFAS transport prediction under transient flow.
- Findings provide crucial insights into PFAS fate, migration, and remediation in contaminated subsurface environments.
Related Concept Videos
01:17Pore Transport and Ion-Pair Transport
Pore transport and ion-pair formation are critical mechanisms for the absorption and distribution of drugs in the body.
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...
01:25Microbial Bioremediation of Uranium
Microorganisms play a critical role in the transformation and immobilization of uranium in contaminated environments through four main pathways: bioreduction, biosorption, bioaccumulation, and biomineralization. These mechanisms reduce uranium’s toxicity and prevent its migration through groundwater systems, offering sustainable approaches for in situ bioremediation.Bioreduction of UraniumBioreduction is driven by anaerobic bacteria such as certain strains of Geobacter and Shewanella, which use...
01:28Microbial Bioremediation of Pesticides
Pesticides often feature structurally complex chemical architectures, incorporating halogen groups and multiple aromatic rings. These characteristics confer high chemical stability, rendering many pesticides resistant to natural degradation processes. This resistance poses significant environmental concerns, as persistent pesticide residues can accumulate in ecosystems and affect non-target organisms.Despite the inherent stability of many pesticides, certain microorganisms possess the metabolic...
01:30Microbial Wastewater Treatment
Microbial communities in aquatic ecosystems play a key role in the natural breakdown of contaminants introduced through domestic and industrial effluents. Acting as biological catalysts, these microbes change and mineralize a wide range of organic and inorganic pollutants under different redox conditions.In oxygen-rich surface waters, aerobic heterotrophs lead organic matter breakdown, using oxygen as the terminal electron acceptor to efficiently oxidize substrates to carbon dioxide and water.