Evaluating the hypothesis of per- and polyfluoroalkyl substances (PFAS) presence in HDPE geomembranes

• PFPrA was found in all examined geomembranes, with concentrations ranging from < limit of quantification (LOQ) to 0.44 µg/g. • Higher methanol concentrations (100 % methanol) improved extraction efficiency, yielding PFPrA levels up to 0.44 µg/g compared to 0.09 µg/g in 10 % methanol solutions. • PFPrA concentrations varied by production facility, with geomembrane 1 exhibiting levels about one order of magnitude higher than geomembranes 2 and 3. • Total fluorine measurements were consistently below LOQ, suggesting minimal presence of other PFAS than PFPrA. This study examines the presence of per- and polyfluoroalkyl substances (PFAS) in high-density polyethylene (HDPE) geomembranes, which are commonly utilised in waste containment facilities, hydraulic infrastructure and other engineering applications. Three different HDPE geomembranes (GMBs) were analysed for PFAS content using targeted detection of six specific analytes and total fluorine (TF) measurements. To assess PFAS leachability under different conditions, extraction experiments were conducted using solutions with varying methanol concentrations. The results showed that perfluoropropionic acid (PFPrA), an ultra-short-chain PFAS, was detected in all tested geomembranes at concentrations ranging from below the limit of quantification (LOQ) to 0.44 µg/g. Importantly, PFPrA concentrations in two geomembranes (GMB2 and GMB3) manufactured at the same facility were comparable, whereas GMB1, produced at a different plant, exhibited concentrations nearly an order of magnitude higher. This disparity suggests potential differences in polymer processing aid (PPA) formulations, PFAS-containing additives, or variations in manufacturing processes. TF measurements for all samples fell below the reporting limit, indicating that large quantities of other PFAS were unlikely to be present. However, the high limit of quantification (LOQ) of 5 mg/kg for TF analysis likely resulted in excessive data censoring, highlighting the need for more sensitive TF detection methods. As regulatory pressures drive a transition toward PFAS-free polymer processing aids, a significant issue may arise if unregulated or unknown PFAS substitutes are used in place of regulated or guideline-referenced PFAS chemicals. Future research should investigate a broader range of geomembrane types and PFAS analytes, enabling more generalised conclusions to be drawn regarding the presence of PFAS in geomembranes.