Trifluoroacetate (TFA) in Precipitation and Surface Waters in Switzerland: Trends, Source Attribution, and Budget

Abstract. Sources and budgets of the persistent, anthropogenic compound trifluoroacetate (TFA) are poorly quantified across different environmental media. Recently, introduction of hydrofluoroolefins and continued use of other fluorinated compounds has increased environmental levels of TFA. Here, we present concentrations of TFA observed in precipitation and surface waters in Switzerland during three years of continuous monitoring and in archived samples, collected since 1984. Atmospheric simulations attribute TFA to precursor gases. Mean observed TFA concentrations were 0.30 to 0.96 μg L^-1 across 14 precipitation sites and 0.33 to 0.88 μg L^-1 across 9 river sites in 2021–2023 – four-to-six-fold increase since 1996/1997. Simulated atmospheric degradation of known TFA precursors accounted for 60–70 % of observed deposition (40–54 % hydrofluoroolefins and 12–17 % long-lived fluorinated gases). Atmospheric deposition amounted to 24.5±9.6 Mg yr^-1. TFA terrestrial inputs in Switzerland from plant protection products (PPP) and veterinary pharmaceuticals, estimated from literature, ranged from 3.9 to 13.2 Mg yr^-1. These inputs were balanced by exports through the major rivers, 31±4 Mg yr^-1. In croplands, TFA inputs from the degradation of PPP were 2.5–3 times larger than those from atmospheric deposition. Archived precipitation samples revealed that TFA was formed in the atmosphere before the introduction of known atmospheric precursors, whereas in the 1990ies TFA deposition increased along with precursors. However, simulated atmospheric degradation underestimates summertime deposition five-fold. Continued use of fluorinated compounds is likely to enhance TFA deposition in the future. Additional environmental monitoring and source attribution studies are paramount for refining the risk assessment of TFA.