Rapid transfer of per- and polyfluoroalkyl substances through submarine canyons: Sources, pathways and implications

Rapid transfer of per- and polyfluoroalkyl substances through submarine canyons: Sources, pathways and implications

Zesheng Xu1, Ian Kane1, Bart van Dongen1, Holly Shiels2, Richard Kimber2 and Michael Clare3

1. Department of Earth and Environmental Sciences, University of Manchester, Manchester, UK (e-mail: zesheng.xu@manchester.ac.uk) 2. Division of Cardiovascular Sciences, University of Manchester, Manchester, UK 3. National Oceanography Centre, Southampton, UK

Submarine canyons are important conduits for the transfer of terrestrial materials, including pollutants, into the deep ocean, yet their role in mediating the distribution and fate of persistent pollutants such as Per- and polyfluoroalkyl substances (PFAS) remains underexplored. PFAS are globally pervasive as ‘forever chemicals’, which pose significant ecological and health risks due to their persistence, bioaccumulation, and toxicity. The deep sea is therefore a potentially important sink for these compounds but the pathways, processes, and ecological implications of PFAS transport via submarine canyons remain understudied. This study aims to address critical knowledge gaps regarding the transport and distribution of PFAS in submarine canyons, focusing on sedimentary dynamics of PFAS transport and deposition patterns. We present an ongoing case study from the Nazaré Canyon, based on 20 sediment cores collected across the system, together with current-meter and sediment-flux measurements from two canyon-head sites. PFAS in sediments are quantified by LC–MS/MS. The extraction method is adapted from Powley (2005). We add a nitrogen blow-down concentration step to improve sensitivity, and replace HCl/NaOH with acetate-based reagents to better recover short-chain PFAS under milder conditions. Method performance is assessed using estuarine mud from the Liverpool Bay/Mersey system as a reference matrix. This result dataset will be used to test mechanistic links between sediment transport, depositional settings, and PFAS occurrence. In the future, we are using targeted sorption experiments and organic geochemical characterisation to constrain controlling interactions, and the approach will be applied across canyon systems with contrasting sediment feeder mechanisms (Setubal, Whittard and Nazaré canyons) to assess the importance of land-shelf-canyon connectivity. We will also extend measurements to sediments and selected benthic biota to support ecological risk assessment.