Identification of Novel Iodinated Polyfluoroalkyl Ether Acids and Other Emerging PFAS in Soils Using a Nontargeted Molecular Network Approach

Abstract

Despite advancements in high-resolution screening techniques, the identification of novel perfluoroalkyl and polyfluoroalkyl substances (PFAS) remains challenging without prior structural information. In view of this, we proposed and implemented a new data-driven algorithm to calculate spectral similarity among PFAS, facilitating the generation of molecular networks to screen for unknown compounds. Using this approach, 81 PFAS across 12 distinct classes were identified in soil samples collected near an industrial park in Shandong Province, China, including the first reported occurrence of 12 iodine-substituted PFAS. Among them, the standards of four iodine-substituted polyfluorinated ether sulfonates (I-PFESA) were successfully synthesized, enabling structural confirmation and subsequent quantitative analysis. Although the median concentration of ∑I-PFESA (0.74 ng/g dw) in soil samples was lower than that of ∑H-PFESA (hydrogen-substituted, 61.96 ng/g dw) and ∑Cl-PFESA (chlorine-substituted, 2.98 ng/g dw), embryotoxicity assays in zebrafish revealed that 6:2 I-PFESA exhibited greater toxicity compared to 6:2 Cl-PFESA of the same chain length. This highlights the need for a closer examination of the toxic effects of I-PFESA. Notably, the proposed algorithm, based on novel PFAS spectral similarity, provides new perspectives on the environmental behavior and transformation of I-PFESA, although further investigation is required to elucidate the underlying mechanisms of their toxicity.