Fluorinated Precursor Compounds in Sediments as a Source of Perfluorinated Alkyl Acids (PFAA) to Biota

Abstract

The environmental behavior of perfluorinated alkyl acids (PFAA) and their precursors was investigated in lake Tyrifjorden, downstream a factory producing paper products coated with per- and polyfluorinated alkyl substances (PFAS). Low water concentrations (max 0.18 ng L–1 linear perfluorooctanesulfonic acid, L-PFOS) compared to biota (mean 149 μg kg–1 L-PFOS in perch livers) resulted in high bioaccumulation factors (L-PFOS BAFPerch liver: 8.05 × 105–5.14 × 106). Sediment concentrations were high, particularly for the PFOS precursor SAmPAP diester (max 1 872 μg kg–1). Biota-sediment accumulation factors (L-PFOS BSAFPerch liver: 22–559) were comparable to elsewhere, and concentrations of PFAA precursors and long chained PFAA in biota were positively correlated to the ratio of carbon isotopes (13C/12C), indicating positive correlations to dietary intake of benthic organisms. The sum fluorine from targeted analyses accounted for 54% of the extractable organic fluorine in sediment, and 9–108% in biota. This, and high trophic magnification factors (TMF, 3.7–9.3 for L-PFOS), suggests that hydrophobic precursors in sediments undergo transformation and are a main source of PFAA accumulation in top predator fish. Due to the combination of water exchange and dilution, transformation of larger hydrophobic precursors in sediments can be a source to PFAA, some of which are normally associated with uptake from water.

The impact of precursors on aquatic exposure assessment for PFAS: Insights from bioaccumulation modeling

“…SAmPAP exposure in food produces somewhat less of an impact on the PFOS BMF, ranging up to approximately 4. BMF values as high as 4 are realistic for such a scenario, based on the PFOS and SAmPAP concentrations measured by Langberg et al ( 2020 ; maximum sediment SAmPAP concentration of 1900 ng/g, PFOS concentration in water approximately 0.3 ng/L, producing a BMF of approximately 4). Finally, PFOSA in water has a smaller effect, increasing the PFOS BMF to approximately 3 at higher PFOSA concentrations, which is an increase of a few percent.…”

“…The BMF values computed by the model, both with and without PreFOS, lie within the range of measured BMFs (Section S6 ). Field‐measured PFOS BMF values range from 0.4 to 31 (g whole‐body wet weight/g whole‐body wet weight; only including studies in which the compared species are reasonably temporally and spatially matched and are considered to be within the same food web [e.g., benthic vs. pelagic]; values provided in Table S6‐1 of the Supporting Information; the Langberg et al [ 2020 ] study was not included because of the clear evidence of a strong influence of PreFOS). The median of the 62 compiled values is 2.0; the arithmetic average is 4.0 ± 5.4 (SD).…”

“…Model testing could be refined further by accounting for the fact that the field‐measured PFOS BMF and TMF values may be inflated owing to the presence of PreFOS. Langberg et al ( 2020 ) measured TMFs and BAFs in a food web strongly impacted by high concentrations of SAmPAP in sediments. PFOS TMFs ranged from 4 to 9 in perch muscle, similar to the range of values computed by the model for SAmPAP exposure.…”

“…SAmPAP was a major component in paper coatings produced in the United States until it was phased out in 2002, although it is likely still produced in other countries (Benskin et al, 2012 ). It has been detected in marine sediment both at concentrations similar to that of PFOS (Benskin et al, 2012 ) and higher than PFOS (Langberg et al, 2020 ). SAmPAP is hydrophobic, with a Log K OW (neutral form) value of 16 (Table S2 ‐1), and its highly sorptive nature is indicated by measurements of sediment concentrations coincident with undetectable concentrations in porewater or surface water (Benskin et al, 2012 ; Langberg et al, 2020 ).…”

“…Field samples have provided evidence of transformation of SAmPAP in freshwater and marine sediments (Benskin et al, 2012 ; Schaanning et al, 2020 ; Zhang et al, 2018 ). SAmPAP transformation products have been found in sediments, surface water, and aquatic organisms (Asher et al, 2012 ; Benskin et al, 2012 ; Franklin, 2016 ; Gebbink et al, 2016 ; Langberg et al, 2020 ; Martin et al, 2004 , 2010 ; Schaanning et al, 2020 ; Sedlak et al, 2017 ; Simmonet‐Laprade et al, 2019 ; Tomy et al, 2009). Some of the intermediates formed in the transformation of SAmPAP to PFOS were also commercially manufactured products and thus may have been discharged directly into the environment (Boulanger et al, 2005 ; Gilljam et al, 2016a , 2016b ; Nascimento et al, 2018 ).…”