An ecosystem-scale model of PFAS dynamics in stream-to-riparian food webs

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants in aquatic ecosystems, where they bioaccumulate and trophically transfer through food webs. We derived an ecosystem-scale model assessing Σ₁₂PFAS partitioning, bioaccumulation by larval aquatic insects, bioamplification by adult aquatic insects, and trophic transfer from aquatic insects to riparian spiders using data collected across five streams in a mildly impacted watershed. Partitioning involved the greatest PFAS enrichments (range in posterior median log₁₀k_d values = 1.5–2.1), with lesser concentration increases from particulates to larval aquatic insects and from larval to adult aquatic insects, and Σ₁₂PFAS concentration decreases from adult aquatic insects to spiders. Among the 12 compounds, PFOS had the largest proportional contribution to Σ₁₂PFAS concentrations for all sample types, with consistently increasing concentrations from surface water to adult aquatic insects. Σ₁₂PFAS concentrations (5.4–51 ppb wet weight), body burdens (0.44–5.2 ng per individual), and bioamplification factors (0.15–4.9) differed considerably among five common aquatic insect taxa. This study presents a robust modeling framework for PFAS trophodynamics and offers insights into the biological controls that contribute to the context dependency of PFAS at the interfaces of aquatic and terrestrial food webs.