Per- and polyfluoroalkyl substances (PFAS), also known as “forever chemicals,” have been a key component of industry and consumer products for many years. Due to the strength of carbon-fluorine bonds, PFAS resist degradation in the environment and are likely to bioaccumulate and biomagnify in terrestrial and aquatic environments. Unsurprisingly, PFAS are found within bodies of water globally due to their widespread use. An important mechanism determining environmental fate and transport of organic chemicals (including PFAS) is sorption to soil/sediments in both terrestrial and aquatic systems. Many previous studies have analyzed the soil-water partitioning coefficient, KD, of both legacy PFAS compounds and their present-day replacement compounds. The KD values show a general trend of increased sorption as the presence of soil organic matter is increased. Therefore, this research is focused on the sorption of PFAS to organic matter alone, as many allochthonous inputs to freshwater systems are 100% organic carbon (i.e. leaf litter, decomposing biomass), and it has potential to be a better sorbent than soil alone. Quantifying the potential of organic material to remove bioaccumulative and toxic chemicals from water sources via sorption is important for the remediation of these chemicals which are already present in fresh and saltwater systems. This hypothesis was tested using one legacy PFAS, perfluorooctane sulfonic acid (PFOS) and one replacement PFAS, hexafluoropropylene oxide-dimer acid (HFPO-DA), which differ in their carbon chain lengths, functional headgroups, and ether substitution. A batch sorption method has been developed to quantify the sorption of PFOS or HFPO-DA to leaf litter in a synthetic freshwater system. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used to quantify the free and bound PFOS or HFPO-DA. Preliminary results suggest that polar interactions dominate for HFPO-DA, as it remained in solution and did not sorb appreciably to the leaf litter. For PFOS, a more hydrophobic PFAS, there was a clear trend of increased sorption with increased mass of leaf litter in solution.
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