From Waste Collection Vehicles to Landfills: Indication of Per- and Polyfluoroalkyl Substance (PFAS) Transformation

Abstract

Municipal solid waste contain diverse and significant amounts of per-and polyfluoroalkyl substances (PFAS), and these compounds may transform throughout the "landfilling" process from transport through landfill degradation. Fresh vehicle leachates, from commercial and residential waste collection vehicles at a transfer station, were measured for 51 PFAS. Results were compared to PFAS levels obtained from aged landfill leachate at the disposal facility. The landfill leachate was dominated by perfluoroalkyl acids (PFAAs, including perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs); 86% of the total PFAS, by median mass concentration), while the majority of PFAS present in commercial and residential waste vehicle leachate were PFAA-precursors (70% and 56% of the total PFAS, by median mass concentration, respectively), suggesting precursor transformation to PFAAs during the course of landfill disposal. In addition, several PFAS, which are not routinely monitoredperfluoropropane sulfonic acid (PFPrS), 8-chloro-perfluoro-1-octane sulfonic acid (8Cl-PFOS), chlorinated polyfluoroether sulfonic acids (6:2, 8:2 Cl-PFESAs), sodium dodecafluoro-3H-4,8dioxanonanoate (NaDONA), and perfluoro-4-ethylcyclohexanesulfonate (PFECHS)were detected. Potential degradation pathways were proposed based on published studies: transformation of polyfluoroalkyl phosphate diester (diPAPs) and fluorotelomer sulfonic acids (FTS) to form PFCAs via formation of intermediate products such as fluorotelomer carboxylic acids (FTCAs).

Electrochemical Transformations of Perfluoroalkyl Acid (PFAA) Precursors and PFAAs in Landfill Leachates

“…Some of the cyclic PFAS presented isomers (Figures S2 and S3). The compound PFEtCHxS (traditionally used as an erosion inhibitor) is the only cyclic PFAS that has been previously detected in landfill leachates . The ECF derivatives F5S-PFPeA, H-PFAS, UPFAS, and PFASi have been found in commercial products and AFFF-impacted groundwater …”

“…14,15 Some of the most common PFAS classes detected in leachates include perfluoroalkyl acids (PFAAs) (e.g., PFCAs, PFSAs) and multiple PFAA precursors such as saturated (n:2 FTCA, n:3 FTCA) and unsaturated (n:2 UFTCA) fluorotelomer carboxylic acids, fluorotelomer sulfonates ( FTSs), perfluoroalkyl sulfonamide-based substances (perfluoroalkane sulfonamides (FASAs), perfluoroalkane sulfonamido acetic acids (FASAAs), and N-alkyl FASAAs), and polyfluoroalkyl phosphate esters (PAPs). 18,19 The PFAA precursors are ultimately transformed to PFAAs. 12,20−22 Some of the effective technologies to remove PFAS from drinking water include granular activated carbon (GAC), ionexchange resins (IX), nanofiltration (NF), and reverse osmosis (RO).…”

“…Masoner et al estimated that the contribution of total PFAS load from landfill leachates corresponded to 18% of the total PFAS load in the influent of WWTPs, rendering landfill leachates a significant secondary source of PFAS to the environment . Concentrations of PFAS ranging from nanograms per liter to micrograms per liter are detected in landfill leachates worldwide, with PFCAs and fluorotelomer carboxylates (FTCAs) accounting for the classes with the highest concentrations. − The broad concentration range is attributed to the heterogeneity of waste, landfill age, and climate conditions. , Some of the most common PFAS classes detected in leachates include perfluoroalkyl acids (PFAAs) (e.g., PFCAs, PFSAs) and multiple PFAA precursors such as saturated ( n :2 FTCA, n :3 FTCA) and unsaturated ( n :2 UFTCA) fluorotelomer carboxylic acids, fluorotelomer sulfonates ( FTSs), perfluoroalkyl sulfonamide-based substances (perfluoroalkane sulfonamides (FASAs), perfluoroalkane sulfonamido acetic acids (FASAAs), and N -alkyl FASAAs), and polyfluoroalkyl phosphate esters (PAPs). , The PFAA precursors are ultimately transformed to PFAAs. ,− …”

Formation of soot in the disposal of municipal solid waste

“…The induction period of the soot formation process is determined by 1/a. Let us assume that the first nucleus radicals are formed as a result of a monomolecular reaction of hydrogen decomposition [14]. Let us write down an expression for determining the rate of spontaneous nucleation of radical-nuclei:…”

Under-reporting Potential of Perfluorooctanesulfonic Acid (PFOS) under High-Ionic Strength Conditions

“…PFOS is sometimes present under high-ionic strength conditions when accurate detection and monitoring are important. For example, in situ chemical oxidation (ISCO) often employs potassium or sodium persulfate concentrations as high as 0.7 M for remediation of chlorinated volatile organic compounds (cVOCs), which often co-occur with PFOS contamination. − Salt and PFOS are also present in brines from reverse osmosis (RO) and ion exchange (IX) treatments, − and landfill leachate often contains high PFOS levels under high-ionic strength conditions . In addition, PFOS may be present in saltwater-impacted sites with high ionic strengths .…”