The transportation and driven mechanisms of per- and polyfluoroalkyl substances (PFAS) in various saline vadose environments

Abstract

The ubiquitous presence of per- and polyfluoroalkyl substances (PFAS) is causing significant concern due to their hazardous and long-lasting properties. Large amounts of PFAS have been preserved in the vadose zone after years of accumulation from both direct and indirect sources, possibly posing a threat to the groundwater. Extreme weather events, such as heavy rainfall and severe drought, have become more often in recent years as a result of global climate change, causing fluctuations in the groundwater table and changes in soil structure and function. A primary outcome is soil salinization, which is associated with substantial uncertainty regarding the transport and fate of PFAS. Salinization leads to soil compaction, reduced porosity, diminished aeration, and impaired permeability, hence increasing solid-phase PFAS adsorption. Salt ions can enhance the hydrophobic effect of PFAS by affecting electrostatic interactions, bridge bonding, and competitive adsorption between PFAS and the medium surface. Furthermore, as the concentration of salt ions increases, the adsorption of PFAS at the air–water interface strengthens. The paper investigates PFAS deposition, transport, and driving mechanisms in several natural salty habitats, such as coastal zones, saline agricultural land, and salt lake regions. A summary of numerical models suitable for describing PFAS behavior under normal salinity settings is provided. The current research gaps and prospective research dimensions are examined. This review improves our understanding of PFAS behavioral characteristics in natural saline environments. It would provide both theoretical and practical recommendations for reducing PFAS pollution in saline soil and groundwater environments.