How Important Is Solid Phase PFAS Release from Legacy Coastal Landfills to the Water Environment?

Historical landfills in coastal environments are at increasing risk of erosion under changing climate conditions. Various studies have highlighted pollutant release associated with potentially toxic elements and flame retardants from such erosional processes, but there has been little focus on per- and poly-fluoroalkyl substance (PFAS) release as a result of physical erosion at such sites, despite landfills being highlighted as a key source of PFAS to the water environment. This study presents a rapid screening approach that could be adopted at scale by regulators to assess the presence and potential flux of PFAS released at three historical municipal waste landfill sites in the UK. The sites selected cover a range of epochs prior to rigorous environmental regulation from the second half of the twentieth century. At the older waste deposits (Withernsea: 1950s–1960s; Hessle: 1930s–1970s), all 52 PFAS analysed in solid materials were below the detection limits except for two samples where modest concentrations (0.92–1.98 ng/g) of perfluorooctane sulfonate (PFOS) and perfluoroethylcyclohexane sulfonate (PFecHS) were detected. At the more recently operational site (Crosby: 1970s–1980s), the legacy PFAS chemicals, PFOS and perfluorooctanoic acid (PFOA), were present in all samples in modest concentrations (6.01–8.22 ng/g for PFOS; 0.62–1.20ng/g for PFOA) below contaminated land thresholds. At this site, it was possible to model the flux of PFAS release based on LiDAR surveys of the eroding waste terrace over an 18-year period. This showed an annualised total solid phase PFAS (PFOS plus PFOA in this case) flux in the region of 2.5–16.9 g/yr, which is towards the lower end of the reported landfill leachate flux at inland sites. While such releases are relatively modest on an individual site basis, in transitional and coastal waters in heavily urbanised and (post-)industrial regions, the aggregated solid phase PFAS flux from the large number of eroding historical landfills (n = 114) could be significant.