Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2021

Sorption behaviour of per- and polyfluoroalkyl substances (PFAS) as affected by the properties of coastal estuarine sediments (#76)

Divina Navarro 1 , Danielle Oliver 1 , Jeff Baldock 1 , Stuart Simpson 2 , Rai Kookana 1
  1. CSIRO, Urrbrae, SA, Australia
  2. CSIRO, Lucas Heights, NSW, Australia

The widespread use of perfluoroalkyl substances (PFAS) and their persistence in the environment means PFAS concentrations from past and current uses have resulted in increasing levels of environmental contamination. However, despite their long use, the understanding of their risks and over-all behaviour in the environment is still quite poor. This study investigated the sorption-desorption behaviour of three of the most commonly detected PFAS in the environment, perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS), in 19 coastal sediments. Sediment-water partitioning values (Kd) were evaluated to determine properties that are important in controlling their sorption. The median average (n=19) Kd value found for PFOS (30.4 L/kg) was 8 times higher than for PFOA (3.3 L/kg) and PFHxS (2.8 L/kg).  Results revealed significant linear relationships between Kd and organic carbon (OC) content of sediments with r2 values ranging from 0.87 to 0.91. These trends were consistent with subsequent desorption experiments on 5 sediments, where the amount of PFAS leached decreased with increasing OC content of the sediment. Generally, the greatest desorption of PFAS occurred in the first 24 h following contact with PFAS-free seawater. The amount of PFAS desorbed ranged from 33% to 91% for PFOA and 43% to 116% for PFHxS, whilst the amount of PFOS desorbed was lower and had a wider range across sediments (9-69% 24 h desorption). Over-all, the results highlight the importance of OC in keeping PFOS, PFOA and PFHxS retained in sediments, with high salinity environments appearing to be beneficial for contaminated sediments such that release of these PFAS to the aquatic environment is limited.