Phytoremediation Potential of Azolla filiculoides: Uptake and Toxicity of Seven Per‐ and Polyfluoroalkyl Substances (PFAS) at Environmentally Relevant Water Concentrations

Abstract

Environmental contamination of aquatic systems by per‐ and polyfluoroalkyl substances (PFAS) has generated significant health concerns. Remediation of contaminated sites such as the fire‐fighting emergency training grounds that use aqueous film‐forming foams is a high priority. Phytoremediation may help play a part in removing PFAS from such contaminated waters. We investigated the potential of the water fern Azolla filiculoides, which is used for phytoremediation of a wide range of contaminants, to uptake seven common PFAS (perfluorobutanoic acid [PFBA], perfluorobutane sulfonic acid [PFBS], perfluoroheptanoic acid [PFHpA], perfluorohexanoic acid [PFHxA], perfluorohexane sulfonic acid [PFHxS], perfluorooctanoic acid [PFOA], and perfluoropentanoic acid [PFPeA]), during a 12‐day exposure to environmentally relevant concentrations delivered as equimolar mixtures: low (∑PFAS = 0.0123 ± 1.89 μmol L−1), medium (∑PFAS = 0.123 ± 2.88 μmol L−1), and high (∑PFAS = 1.39 μmol L−1) treatments, equivalent to approximately 5, 50, and 500 µg L−1 total PFAS, respectively. The possible phytotoxic effects of PFAS were measured at 3‐day intervals using chlorophyll a content, photosystem II efficiency (Fv/Fm), performance index, and specific growth rate. The PFAS concentrations in plant tissue and water were also measured every 3 days using ultra‐high‐performance liquid chromatography—tandem mass spectrometry. Treatments with PFAS did not lead to any detectable phytotoxic effects. All seven PFAS were detected in plant tissue, with the greatest uptake occurring during the first 6 days of exposure. After 12 days of exposure, a maximum bioconcentration factor was recorded for PFBA of 1.30 and a minimum of 0.192 for PFBS. Consequently, the application of Azolla spp. as a stand‐alone system for phytoremediation of PFAS in aquatic environments is not sufficient to substantially reduce PFAS concentrations. Environ Toxicol Chem 2024;00:1–12. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.