Concepts and methods for developing site-specific soil screening levels for per and polyfluoroalkyl substances

Area of Science:

• Environmental Science
• Geochemistry
• Risk Assessment

Background:

• Soils serve as significant reservoirs for per- and polyfluoroalkyl substances (PFAS), posing risks to groundwater through leaching.
• Soil screening levels (SSLs) are vital for risk-based soil concentration determination, guiding site characterization and remediation efforts.
• Limited research has focused on the specific methodologies for determining SSLs for PFAS-impacted sites.

Purpose of the Study:

• To critically examine the determination of SSLs specifically for sites contaminated with PFAS.
• To present the conceptual framework and application methods for SSLs in the context of PFAS.
• To enhance the understanding and robustness of SSL implementation for environmental protection.

Main Methods:

• Reviewed the conceptual basis and application methods of SSLs for PFAS.
• Analyzed the complexity of porewater concentrations in unsaturated soils and factors influencing them.
• Detailed methods for obtaining SSL input parameters, including estimation, lab, and field data.
• Examined batch leach tests and field measurements for soil and porewater concentrations.
• Discussed data uncertainty, background concentrations, and other relevant factors.

Main Results:

• Porewater concentrations in unsaturated soils are more complex and vary based on PFAS type and other factors.
• Various methods for estimating and measuring SSL input parameters were evaluated.
• The application and limitations of different testing methods (batch leach, field measurements) were assessed.
• Illustrative examples using fictitious and real-world field data were provided.

Conclusions:

• This study provides clarity on both conceptual and practical aspects of SSL determination for PFAS.
• The findings aim to lead to more robust and reliable implementations of SSLs in environmental management.
• Improved SSL determination supports better decision-making for protecting groundwater resources from PFAS contamination.