Total Oxidizable Precursors Assessments for PFAS Contaminated Soil and Water

Characterization of Polyfluoroalkyl Substances in the Environment
Oral Presentation

Prepared by

Contact Information:; 905-817-5711


Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and related perfluoroalkyl substances (PFAS) continue to receive a substantial amount of attention from environmental practitioners and regulatory bodies, not only because they are recognized as ubiquitous environmental contaminants, but also because these compounds persist, bioaccumulate, cause toxicity in animals and have been shown to produce negative health effects in humans. They have been identified as compounds of environmental concern at an increasing number of sites and drinking water supplies across North America. The emergence of reliable testing protocols in recent years has allowed for investigators and practitioners to not only delineate and assess impact magnitude, but also to investigate biotransformations of PFAS in natural settings and remedial options.

For remediation, aside from the expensive options of high temperature incineration, landfilling or encapsulation, several in-situ or ex-situ options have shown promise in recent years. Foremost among these are adsorption to various forms of carbon and chemical oxidations, typically with persulfate.

Studies have demonstrated in-situ transformation of high molecular weight PFAS precursors to selected, regulated PFAS; typically C4 to C8 perfluoroalkyl acids. This is a concern for site remediation as it suggests that, depending on the nature of high molecular weight precursors present at any given site, natural processes could lead to apparent ‘re-contamination’ of a site after an initially successful remediation, or the remedial processes themselves may cause an increase in target PFAS compounds.

An approach to evaluate the potential magnitude of the precursor pool at a site targeted for remediation was published by Erika Houtz and David Sedlak in 2012.* We implemented this method for routine analysis of impacted soil and water samples in 2017 to assist clients and other stakeholders in more accurately assessing the magnitude of potential liability at an impacted site and in forecasting the intensity of remedial effort required. This presentation will discuss recommended sample collection and submission procedures, lab processes, method limitations, potential matrix interferences and data interpretation. It will also describe findings typically encountered at different types of impacted sites.

*Environ. Sci. Technol., 2012, 46, 9342-9349.