Effects of Nitrogen Fertilizer Types on the Uptake and Translocation of PFAS and Metabolomic Activities of Hydroponically Cultivated Lettuce (Lactuca sativa)

Increasing evidence is showing that per- and polyfluoroalkyl substance (PFAS) replacing compounds are not as safe as they were assumed. This study investigated the plant uptake of two most prevalent PFAS, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic (PFOS) and their replacing compounds, hexafluoropropylene oxide dimer acid (HFPO-DA or GenX) and 6:2 chlorinated polyfluoroalkyl ether sulfonates (Cl-PFESAs) (6:2 Cl-PFAES) by hydroponically grown lettuce in the presence of different nitrogen fertilizers including ammonium sulfate ((NH₄)₂SO₄), potassium nitrate (KNO₃), and urea in a growth chamber. Interestingly, (NH₄)₂SO₄ significantly increased GenX uptake in lettuce shoots by ∼108% and KNO₃ increased the uptake of PFOS and 6:2 Cl-PFAES by 267% and 395%, respectively, suggesting that the nitrogen fertilizer type has a marked impact on the plant uptake of PFAS and that this impact was PFAS-dependent. Our results also showed that (NH₄)₂SO₄ generally resulted in higher PFAS root to shoot transfer than the other two types of nitrogen fertilizers. Metabolomic analysis revealed that amino acids, nucleotides, and antioxidants are the major metabolites that were either significantly increased or decreased in the lettuce shoots. These results showed that nitrogen fertilization management can have a significant impact on PFAS plant uptake and transport, and the impact depends on the types of nitrogen fertilizer and PFAS compounds.