PFAS: Forever Chemicals in Soils

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are highly persistent chemicals widely detected in soils around the world. Their resistance to degradation and potential impacts on soil health, groundwater, surface water, and biota make understanding their occurrence and behavior in soil essential for environmental risk assessment and effective remediation strategies.

Objectives and Study Overview

The 2023 monitoring study evaluated the presence and concentration of 20 PFAS compounds in 209 soil samples. These compounds align with regulatory requirements for drinking water monitoring. The primary goal was to determine the frequency of detection, concentration ranges, and compound profiles across various sampling locations.

Methodology and Instrumentation

Soil samples were prepared and analyzed according to a validated standard method (see Table 1 in the original study). Limits of quantification (LOQ) for target PFAS ranged from 0.5 to 5 µg/kg dry weight. Although the specific analytical platform was not detailed, typical workflows involve solid-phase extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to achieve low-level quantification.

Key Results and Discussion

• Approximately 30 % of samples contained PFAS above LOQ, while 70 % were non-detect for all analytes.
• PFOS and PFOA emerged as the most frequently detected and highest-concentration compounds.
• Long-chain PFAS such as PFDA, PFNA, and PFNS were commonly observed, indicating accumulation potential.
• Concentration levels of PFOS reached several µg/kg, significantly exceeding other analytes.
• Spatial variations in PFAS profiles reflected differences in local sources, including firefighting foams, industrial discharges, and atmospheric deposition.

Benefits and Practical Applications

Regular soil monitoring of PFAS supports:

• Accurate risk assessment for human health and ecosystems
• Evidence-based design of remediation and containment measures
• Compliance with emerging regulatory standards
• Identification of contamination hotspots to prioritize interventions

Future Trends and Opportunities

Continued development and application of advanced analytical techniques will enhance detection limits, speed, and throughput. Integration of non-targeted screening and suspect screening workflows may uncover novel PFAS and transformation products. Coupling soil data with hydrological and atmospheric models will improve fate and transport predictions. Emerging in-situ remediation technologies, such as electrochemical oxidation or advanced bioremediation, offer promising avenues for PFAS removal from soils.

Conclusion

This study confirms that soils act as significant reservoirs for PFAS, with PFOS and PFOA dominating positive detections. The findings highlight the need for standardized soil monitoring protocols, refined risk assessment frameworks, and tailored remediation strategies to manage long-term environmental exposure to these persistent contaminants.

References

1. Y. Wang, U. Munir, Q. Huang. Occurrence of per- and polyfluoroalkyl substances (PFAS) in soil: Sources, fate, and remediation. 2023. https://doi.org/10.1016/j.seh.2023.100004
2. M. L. Brusseau, R. H. Anderson, B. Guo. PFAS Concentrations in Soils: Background Levels versus Contaminated Sites. 2020. doi: 10.1016/j.scitotenv.2020.140017
3. DIRECTIVE (EU) 2020/2184 on the quality of water intended for human consumption. 2020.