PFAS Monitored Retention: A Framework for Managing PFAS-Contaminated Groundwater Sites

Groundwater sites contaminated by per- and polyfluoroalkyl substances (PFAS) present unique and significant challenges, including their widespread occurrence and persistence and stringent remediation objectives. While traditional monitored natural attenuation (MNA) has proven to be an effective remedial option for many degradable contaminants, its direct application to PFAS has been limited due to these chemicals' inherent stability. However, the development of PFAS monitored retention (PMR) broadens the scope of MNA, incorporating an understanding of how retention processes—such as sorption, matrix diffusion, and precursor retention—help to mitigate PFAS mobility and mass discharge in the environment. This paper summarizes PMR, discussing its evolution from traditional MNA, key retention mechanisms, evaluation methodologies, and potential site-specific and broader applications. PMR offers a scientifically robust, economically viable approach for managing PFAS-contaminated groundwater sites when immediate threats to receptors are absent or as an interim remedy pending the development of cost-effective in situ destruction technologies.