Review on Methods for Assessing and Predicting Leaching of PFAS from Solid Matrices

Purpose of Review

Per- and poly-fluoroalkyl substances (PFAS) are prevalent environmental contaminants detected in materials such as soils, biosolids, and wastes. Understanding PFAS leaching is crucial for assessing risks associated with leaving impacted material in place, reuse, or disposal. However, there is limited guidance on laboratory methods to measure extent and rate of leaching. This review aims to identify the best methods for assessing PFAS leaching that are reflective of relevant release scenarios.

Recent Findings

Various methods have been applied to assess PFAS leaching from contaminated materials. The most common are batch leaching methods that simulate particular conditions (e.g. rainfall, landfill), with the intention of providing conservative estimates (worst-case scenarios) of cumulative PFAS release over time. Columns, static leaching, and rainfall simulators are also used to simulate less aggressive field-like conditions. While less common, pan and suction lysimeters have been used to measure PFAS leaching in situ. Most methods use saturated conditions that do not account for the possible influence of air–water interface accumulation and wetting–drying cycles on leaching. A notable gap is the scarcity of data benchmarking laboratory-leached concentrations with real-world PFAS concentrations. Establishing this relationship is crucial for reliable laboratory protocols.

Summary

This article reviews methods for estimating leaching of PFAS from contaminated materials. Given the variety of methods, selecting those that best simulate assessment objectives is essential. Specific scenarios requiring PFAS leaching assessment, such as leaving materials in place, reuse, and disposal, are discussed. The knowledge gaps presented could be used to improve existing leaching methods for better predictions and understanding of PFAS leachability.

Graphical Abstract