Brominated flame retardants and perfluoroalkyl substances in landfill leachate from Ireland

Between June and November 2017, leachate samples were collected from 40 landfills across the Republic of Ireland. Concentrations of perfluoroalkyl substances (PFASs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDD) determined in these samples were within the range previously reported in other countries. Average concentrations of PFASs exceeded those of PBDEs and HBCDD; likely due to the higher water solubility of PFASs. Log-transformed concentrations of BDEs-47, 100, 153, and 183, as well as perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorobutane sulfonate (PFBS) were significantly (p < 0.05) higher in leachate from newer, lined landfills than in samples from unlined landfills. These higher concentrations in lined landfills are likely related to the fact that lined landfills are found to retain organic matter leading to a higher organic content of leachate from such landfills. This is evidenced by the significant (p < 0.05) correlation between log-transformed concentrations in leachate of most of the same contaminants and those of chemical oxygen demand (COD). Concentrations of the less water-soluble, higher molecular weight BDE-209 were not correlated with leachate COD, nor landfill age or the presence of a landfill liner. This suggests that the presence of BDE-209 in landfill leachate is driven more by physical abrasion of particles and fibres from waste articles, than dissolution into the aqueous phase. The higher concentrations of some PFASs and PBDEs in leachate from lined landfills present a challenge with respect to leachate disposal, when leachate is sent to wastewater treatment plants that do not necessarily have mechanisms in place to remove or destroy these chemicals prior to discharge into the environment. Moreover, the presence of these persistent organic chemicals in leachate from unlined landfills raises concerns about releases to the environment including groundwater over the lifetime of such landfills and beyond.