Interaction between Per- and Polyfluoroalkyl Substances and Dissolved Organic Matter in Soil: Molecular Variation and Partitioning Behavior

The partitioning and migration of per- and polyfluoroalkyl substances (PFAS) in soil may be regulated by active fractions such as dissolved organic matter (DOM), yet their role in this process has rarely been explored. Herein, the composition and distribution of PFAS and DOM between the soil-porewater phase in field soil were investigated to explore the interaction between PFAS and DOM. In the investigated areas, PFAS display significant spatial differences with the total concentration ranging from 3.14 to 50.92 ng/g. Under relatively high PFAS burden, DOM exhibits higher abundance of lipid/protein/amino-like compounds, indicative of its greater lability and bioavailability. Meanwhile, the relatively high Shannon index of DOM in those soils indicates that the chemodiversity of DOM may be related to the PFAS burden. Particularly, short-chain PFAS are more associated with these observed changes. Additionally, PFAS concentrations in porewater were associated with soil organic carbon content, whereas their soil-porewater partitioning showed no such correlation and was instead dictated by DOM components. Specifically, protein-like components facilitated the partitioning of PFAS into the porewater; in contrast, humic-like components promoted adsorption onto the soil phase. These findings suggest a potential link between PFAS and DOM, offering novel insights into the migration and fate of PFAS in soils.