Fate and transport of PFAS, conceptual and numerical models

Since the industry has become aware of the hazards and issues associated with per- and poly-fluorinated alkyl substances (PFAS), our understanding of their fate and transport in the environment has evolved. Numerous field and academic studies have led to a greater understanding of how PFAS migrates and what attenuation mechanisms may be important. These have led to a better understanding of how assessment works should proceed and what we should be sampling for. The main mechanism for assisting in this process and for communicating ideas about PFAS fate and transport is the Conceptual Site Model (CSM). CSMs initially assumed PFOS in particular had a high solubility and was essentially a conservative compound migrating inexorably towards the nearest aquatic receptor or production bore with potentially dire consequences for all. Further studies have shown this to be a simplification. Numerical modelling is often utilised to predict future contaminant migration and remediation system performance. PFAS are the only known group of water soluble organic bio-accumulator chemicals, which presents some challenges when existing numerical models are used to predict their future behavior in groundwater systems. This paper combines our conceptual knowledge of PFAS with an assessment of their fate and transport in the environment in the context of existing commonly used analytical and numerical models to predict fate and transport. (author)