Perfluoroalkyl Acid Characterization in US Municipal Organic Solid Waste Composts

Composting the organic fraction of municipal solid waste (OFMSW) creates a nutrient rich soil amendment and reduces the amounts of wastes going to landfills or incineration. However, the occurrence and fate of persistent and challenging per- and polyfluoroalkyl substances (PFAS) in OFMSW composts have not been well studied. The loads and leachability of 17 perfluoroalkyl acids (PFAAs) were analyzed in nine OFMSW commercial composts and one backyard compost. PFAA loads ranged from 28.7 to 75.9 mu g/kg for OFMSW composts that included food packaging and from 2.38 to 7.60 mu g/kg for composts that did not include food packaging. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) were detected in all composts; however, OFMSW composts were dominated by short-chain PFAAs (>64%) and perfluoroalkyl carboxylates (PFCAs, >68%), particularly the C6 PFCA. The total oxidizable precursor assay indicated the presence of PFAS precursors in three OFMSW composts for which 6:2 fluorotelomer sulfonate and 6:2 dipolyfluoroalkyl phosphate ester were identified. Of the total PFAA load in the composts, 25-49% was released to porewater (similar to 1 g/2 mL). PFAA porewater concentrations versus PFAA loads as well as organic carbon-normalized sorption coefficients versus the number of PFAA CF2 units are strongly correlated (R-2 > 0.85).