Production of perfluoroalkyl acids (PFAAs) from precursors in contaminated agricultural soils: Batch and leaching experiments

• Published in: The Science of the total environment 2023-12, Vol.902, p.166555-166555, Article 166555
• Main Authors: Röhler, Klaus, Susset, Bernd, Grathwohl, Peter
• Format: Article
• Language: English
• Subjects: Agricultural soils; Batch-test; Column leaching test; dTOP assay; PFAA; PFAS; Precursor transformation
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.166555

Contamination of soils with per- and polyfluoroalkyl substances (PFAS) (e.g., aqueous film forming foams (AFFFs) or PFAS containing biosolids applied to agricultural soils) can lead to large scale groundwater pollution. For site management, knowledge about the extent and time scales of PFAS contamination is crucial. At such sites, often persistent perfluoroalkyl acids (PFAAs) and so-called precursors, which can be transformed into PFAAs, co-occur. In this study, the release of PFAAs from 14 soil samples from an agricultural site in southwest Germany contaminated via compost/paper sludge was investigated. Rapid leaching of C4-C8 perfluoroalkyl carboxylic acids (PFCA) was observed in saturated column tests, while slowing down with increasing chain-length (≥ C9 PFCAs). Two selected samples were further incubated in batch-tests after removal of existing C4-C8 PFCAs in extensive column leaching tests until a liquid-solid ratio of 10 l/kg. During 60 days of incubation, aqueous concentrations of C4-C8 PFCAs increased linearly by a factor of 29–222, indicating continuous production by transformation of precursors. The potential PFAA-precursor reservoir was estimated by the direct total oxidizable precursor (dTOP) assay. PFCA concentrations after the dTOP increased up to two orders of magnitude. Production rates determined in batch-tests combined with the results of dTOP assay were used to estimate time scales for the duration of C4-C8 PFCAs emission from the contaminated agricultural soils which likely will last for several decades. [Display omitted] •Rapid leaching of short-chain PFAAs in column tests is followed by continuous tailing.•C4-C8 PFCA concentrations in batch incubation tests increased by a factor 29–222 after 60 days.•PFCA patterns in batch incubation tests match field observations in groundwater.•PFCA production from precursors in paper-sludge amended soils may continue for several decades.