Simultaneous Analysis of Ultrashort- to Long-Chain PFAS in Multisalinity Aquatic Systems: Methodology, Spatial Profiling, and Risk Prioritization

Ultrashort-chain
per- and polyfluoroalkyl substances (PFAS) have
attracted increasing attention due to their rising concentrations
and high mobility in environmental contexts, yet their incorporation
into routine multianalyte workflows remains challenging. This study
established a multidimensional liquid chromatography-tandem mass spectrometry
platform for the simultaneous quantification of 60 PFAS spanning ultrashort-
to long-chain homologues. Large-volume direct injection achieved satisfactory
limits of quantification (≤1 ng/L) for most PFAS, without complex
sample pretreatment. The method was applied to surface waters across
a freshwater-marine salinity gradient from the Xiaoqing River and
Laizhou Bay during two sampling campaigns in 2023 and 2024. Trifluoroacetic
acid (TFA) dominated the PFAS profile, accounting for 87–99%
of total PFAS (∑60PFAS), with a maximum concentration
of 1 467 000 ng/L. In 2024, median concentrations of
TFA and most PFAS decreased by 33–78% downstream of a fluorochemical
industrial park, whereas perfluoro-2,5-dimethyl-3,6-dioxo-heptanoic
acid (C7 HFPO-TA) increased by 170%. An environmental hazard prioritization
index (EHPI) based on persistence, mobility, bioaccumulation, ecotoxicity,
and human health hazards was applied to the 60 target PFAS using in-house
and open-source predictive models, yielding a prioritized pollutant
ranking in Laizhou Bay. TFA and C7 HFPO-TA emerged as the highest-priority
chemicals, indicating an urgent need for strengthened monitoring and
regulatory management.