Granular activated carbon reduces PFAS bioavailability and protects ant colony growth in soil

Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants that pose risks to ecological and human health. Soil stabilisation using sorbents such as granular activated carbon (GAC) can reduce PFAS mobility and bioavailability. Previous studies have focused on plants and earthworms, but bioavailability in species relevant to arid and semi-arid environments remains poorly understood. This study examined the effectiveness of GAC in reducing PFAS bioavailability to tropical fire ants (Solenopsis geminata). Two PFAS-contaminated soils were amended with 1 % or 5 % (w/w) GAC, incubated, then subjected to 5-day and 2-month ant exposure trials. Results showed that GAC reduced leachable ∑29PFAS by 73–100 %, with greater reductions at later post-treatment leaching assessments and at 5 % GAC. PFAS exposure in untreated soils impaired ant colony growth, whereas GAC addition mitigated these effects and reduced PFAS concentrations in ants by < 97 %, with the greatest reductions observed in the sandy soil, consistent with leaching results. Non-target PFAS detected in ants collected from untreated soils were not detected in ants from GAC-treated soils, indicating GAC's broad sorption performance. Risk quotients calculated suggest that GAC can substantially lower potential risk to mammals and birds that feed on ants. Overall, findings underscore the value of soil stabilisation strategies, especially in ecosystems where invertebrates influence contaminant exposure.