Do the UBA results indicate a significant TFA content in the Atlantic Ocean and imply a natural source? Detailed Discussion
Do the results in the UBA report “Analysis of current seawater samples for trifluoroacetic acid” [1] indicate a significant TFA content in the Atlantic Ocean, and if there is a significant TFA content in the Atlantic Ocean, can it all result from industrial sources or does it imply there must be a natural source?
Conclusion: The UBA reported [1] TFA concentration measurements indicate a large content of about 43 million tonnes of TFA in the Atlantic Ocean to a depth of 4000 m. Industrial sources can perhaps only account for about a maximum 1.2 million tonnes in the Atlantic Ocean. This would imply that there is a large natural content of TFA in the Atlantic Ocean.
TFA found at high concentrations over a wide area of the Atlantic Ocean and at depths to 4590 m
It is possible that all the UBA sampling locations and depth profiles coincided with localised high concentrations of TFA and are not representative of other Atlantic Ocean locations. However, it is worth noting that:
- The lowest TFA concentration measured by UBA is 237 ng/L,
- Surface seawater samples were taken over a distance of about 12,000 km,
- Depth profiles were taken over a distance of about 5500 km [2] and
- There is a small fluctuation range of the TFA contents within an individual depth profile and between the depth profiles.
In addition, Scott et al. [3] reported TFA concentrations up to 190 ng/L (to 1000 m depth, 28-190 ng/L) and 150 ng/L (to 947 m, 17 to 150 ng/L) in two locations, not sampled for the UBA study, in the North Atlantic (closer to the USA) and about 4000 km from one of the UBA depth profiles. Jordan and Frank [4] reported TFA concentrations measured in 1995 in ocean surface waters taken directly from the shore at 70 ng/L at Mace Head, Ireland, 250 ng/L at Ile d’Yeu, France, and 160 ng/L at Cape Point, South Africa. Scott et al. also reported high TFA concentrations (to 1500 m depth, 34 -181 ng/L; and to 3000 m depth, 61 -172 ng/L) in two locations in the Arctic Ocean (Canadian Basin). Therefore, it seems unlikely that for the Atlantic Ocean, TFA would only be in high concentrations in the locations sampled by the UBA, Frank and Scott.
If the average concentration measurement, reported by the UBA (278.5 ng/L), is representative for the whole of the Atlantic Ocean to 4000 m depth [5], then the TFA content for this volume of water would be about 43 million tonnes in 2022/23 (from 278.5 ng/L TFA and an Atlantic Ocean 0-4000 m volume [6] of 155 x 106 km3 , which is about 46% of the total volume of the Atlantic Ocean ).
TFA content in the Atlantic Ocean, resulting from industrial sources
An inventory of fluorspar industrial use estimated TFA emissions as 230,000 to 470,000 tonnes in the period 1930 to 1999 [7]. About 54,000 tonnes of this total is due to degradation of fluorocarbon emissions in the atmosphere with most being deposited globally due to the atmospheric lifetimes of the fluorocarbons. A further 30,000 tonnes is potentially due to the TFA manufacture, assuming all TFA manufactured equals TFA emissions (unlikely, but represents the worst case scenario). Pesticides and pharmaceuticals account for a maximum 145,000 to 385,000 tonnes assuming complete degradation to TFA, but this is unlikely (but represents the worst case scenario). No other significant industrial sources of TFA were identified.
Preliminary results (not yet published) from an updated inventory for 2000 to 2020 [8], indicate that fluorocarbon emissions to the atmosphere could have resulted in about 440,000 tonnes of TFA emissions in this period, with most being globally deposited due to the atmospheric lifetimes of the fluorocarbons. The manufacture of TFA in the period 2000 to 2020 is estimated as 350,000 tonnes, which could result in a maximum of 350,000 tonnes emissions assuming all TFA manufactured equals TFA emissions (unlikely but represents the worst case scenario). It is difficult to estimate pesticide use in this period that could result in TFA formation. An initial indicative estimate suggests that a maximum of 1 million tonnes TFA emissions globally and assuming complete degradation to TFA (unlikely, but represents the worst case scenario).
Pesticide degradation: The Environmental Effects Assessment Panel in 2022 [9] reported that the dependence of the formation of TFA on environmental conditions and substituents on the other parts of the molecule likely applies to other pesticides and to pharmaceuticals and other potential precursors of TFA. Breakdown of some of these pesticides to TFA has been investigated. For example, ozonation (4 mg/L) of solutions of trembotrione, flufenacet, flurtamone and fluopyram (at 100 μg/Lfor times between 5 and 60 min resulted in 5, 20, 43, and 32% production of TFA on a molar basis. Whether ozonation is a good model for the formation of TFA from pesticides in agricultural soils or not is unknown. The yield of TFA from the degradation of pesticides is dependent on the other substituents on the molecule and the environmental conditions. Studies on the photolysis of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) used to control the sea lamprey in the North American Great Lakes have shown that photolysis (365 nm) results in the formation of TFA. Yields were dependent on the pH of the solution and ranged from 5–18%. Conversion of the nitro-group to an amino-group increased the rate of conversion but not the yield. In another study, yields of TFA from photolysis of the penoxsulam (a herbicide) and sulfoxaflor (an insecticide) exposed to UV radiation in river water were less than 5% under laboratory conditions. Yields of TFA from penoxsulam were greater in river water than in distilled water at pH 7.
In summary, an initial indicative estimate, from the published 1930-1999 inventory [7] and the preliminary results (not yet published) from an updated inventory for 2000 to 2020 suggests a maximum 2.3 million tonnes of TFA emissions from industrial sources in the period 1930 to 2020. Most of these TFA emissions would be either deposited globally (for TFA produced from fluorocarbons with atmospheric lifetimes ≥ 1 year) or dispersed in surface waters (pesticides, pharmaceuticals). Subsequent transfer would be to all the oceans and not just the Atlantic Ocean [10].
Industrial sources can perhaps only account for about a maximum 1.2 million tonnes of TFA in the Atlantic Ocean assuming about 50% of the total 2.3 million tonnes of TFA produced from industrial sources is transferred to the Atlantic Ocean [10]. This can be compared with the estimate of 43 million tonnes of TFA in the Atlantic Ocean to a depth of 4000 m based on the UBA 2024 report [1]. This would imply that there is a large natural content of TFA in the Atlantic Ocean.
Evidence from precipitation and surface water TFA concentrations measurements supporting estimates of industrial emissions
Available data for concentrations of TFA in precipitation and surface waters in remote areas is consistent with the estimated emissions of TFA from fluorocarbons having atmospheric lifetimes ≥ 1 year (HCFCs, HFCs, anaesthetics) in the 1990s and 2020.
TFA Emissions in 1999: According to the published inventory [7], total emissions of TFA from the degradation of HCFCs, HFCs, and anaesthetics emitted to atmosphere are estimated at about 8000 tonnes/year [11] in 1999 and would have been precipitated globally [12]. The Scientific Assessment of Ozone Depletion: 2022 (SAP 2022) [13] states a total global precipitation volume of 5.5x1017 litres. In 1999, assuming 8000 tonnes/year TFA is deposited through wet deposition only [14], results in a global average TFA concentration in precipitation of about 15 ng/L. This is consistent with the TFA concentrations measured in remote precipitation and rivers in the 1990s which are shown in Table 1.
Table 1. Reported concentrations of TFA in precipitation and surface waters in the 1990s
| Location | Precipitation/River | Concentration ng/L | Date | Reference |
| Mace Head, Ireland | Rain | <15 | 1995 | [15] |
| Mace Head, Ireland | Rain | 62, 58, 4, 17, 93, 8, 14, 2 | 1996 | [16] |
| Resolute, Canada | Snow | 33, 3, 7, 2 | 1996 | |
| Queen Maud Land, Anarctica | Snow | 2, 9 | 1996 | |
| Mount Cooke, New Zealand | Snow | 3 | 1996 | |
| Interior Alaska | Surface waters | Median 21.7 (<9.5-63.0) | 1998 | [17] |
| Chile (rural) | rain | 12 | 1999 | [18] |
| Malawi | rain | 9 | 1999 |
In the 1990s, surface waters and precipitation in populated/industrial areas were higher than in remote regions. For example, River Rhine, Duisburg-Ruhrort (630 ng/L, 1995), River Elbe, Wittenberg (200 ng/L, 1995) [3]; East San Francisco Bay Area (145 ng/L, 1998) [17]; Algoma, Canada (1999, precipitation, 94 ng/L) [18]. TFA concentration measurements for the Detroit River, in the Great Lakes system, in a highly industrialised area were measured as 0.051-0.099 µg/L (51-99 ng/L) in 1998 [19].
TFA Emissions in 2020: Preliminary results from the updated inventory (not yet published) indicate that estimated TFA emissions from emissions of fluorocarbons with atmospheric lifetimes ≥ 1 year (HCFCs, HFCs, anaesthetics) were about 30,000 tonnes in 2020, with emissions of short lifetime HFOs not being significant until about 2015. This is consistent with SAP 2022 [13], which provides estimates of TFA emissions due to HFC-134a (10,000 -30,000 tonnes) and HFO-1234yf (30,000 tonnes) in 2020, and notes that other fluorocarbons containing a CF3 group, also have the potential of being degraded to TFA in the atmosphere, albeit with a lower influence, as they currently have very small atmospheric mixing ratios and lower conversion rates to TFA.
Preliminary results from the updated inventory indicate that HFC-134a accounts for about 80% (about 24,000 tonnes) of the estimated 30,000 tonnes of TFA emissions from fluorocarbons (HCFCs, HFCs, anaesthetics) in 2020. According to Madronich et al. [20] the global flux of TFA in 2020 from HFC-134a and HFO-1234yf oxidation is estimated to be 10,000 to 30,000 tonnes/year and 30,000 tonnes/year, respectively. As discussed by Madronich et al., “Assuming uniform deposition across the global scale this corresponds to average deposition fluxes of 20–60 g/km2 year from HFC-134a and 60 g/km2 year from HFO-1234yf. The measured deposition flux of TFA in precipitation in Arctic ice cores in 2007–2018 of ca. 10 g/km2 year is consistent with that expected for the atmospheric degradation of HFC-134a in 2020 after accounting for the lower average photochemical activity of OH radical in the Arctic. The measured deposition flux of 51 g/ km2 year in 2018–2019 in the catchment area of Lake Vattern, Sweden is consistent with that expected from oxidation of HFC-134a and may also contain a contribution from oxidation of HFO-1234yf.”
References and Notes
[1] Examination of current seawater samples for trifluoroacetic acid | Federal Environment Agency (umweltbundesamt.de), Texte 35/2024, F. Freeling, and A Mangels
[2] The Atlantic Ocean is over 13,000 km long and varies in width from about 3000 to 5000 km
[3] Trifluoroacetate Profiles in the Arctic, Atlantic, and Pacific Oceans, Scott, B. F., Macdonald, R. W., Kannan, K., Fisk, A., Witter, A., & Yamashita, N., et al., Environmental Science & Technology, 2005, 39(17), 6555–6560. https://doi.org/10.1021/es047975u
[4] Trifluoroacetate in the Environment. Evidence for Sources Other Than HFC/HCFCs, A. Jordan and H. Frank, Environ. Sci. Technol. 1999, 33, 522-527
[5] UBA, Frank and Scott all reported TFA concentrations to about this depth
[6] Volumes cited in Trifluoroacetate Profiles in the Arctic, Atlantic and Pacific Oceans, Scott, B. F., Macdonald, R. W., Kannan, K., Fisk, A., Witter, A., & Yamashita, N., et al., Environmental Science & Technology, 2005, 39(17), 6555–6560. https://doi.org/10.1021/es047975u
[7] An Inventory of Fluorspar Production, Industrial Use, and Emissions of Trifluoroacetic Acid (TFA) in the Period 1930 to 1999, A.A. Lindley, Journal of Geoscience and Environment Protection > Vol.11 No.3, March 2023, https://doi.org/10.4236/gep.2023.113001
[8] 2020 was selected as the end date for the updated inventory because emission estimates for fluorocarbons derived from atmospheric monitoring are currently available up to 2020
[9] UNEP 2022 Assessment Report of the Environmental Effects Assessment Panel, available from http://ozone.unep.org/science/eeap
[10] The Atlantic Ocean and its associated continental drainage basin is similar in size to the Pacific Ocean and its associated continental drainage basin. See Figure 1 in ESD - Water transport among the world ocean basins within the water cycle (copernicus.org) and Largest Drainage Basins in the World - WorldAtlas
[11] In 1998, TFA total due to degradation of fluorocarbon emissions in the atmosphere is estimated at about 6500 tonnes.
[12] The inventory estimates that a minor quantity of TFA emissions from the degradation of fluorocarbons would be regional due to emissions of hexafluoropropene, with a lifetime measured in days.
[13] World Meteorological Organization (WMO). Scientific Assessment of Ozone Depletion: 2022, GAW Report No. 278, 509 pp.; WMO: Geneva, 2022. Available at: https://ozone.unep.org/science/assessment/sap 7.2.5.1 Trifluoroacetic Acid (TFA) page 408
[14] Wet deposition is the most substantial loss process of atmospheric TFA by a significant margin, being responsible for approximately 80% of total atmospheric TFA loss according to Trifluoroacetic Acid: Toxicity, Sources, Sinks and Future Prospects, M. de los Angeles Garavagno, R. Holland, M. A. H. Khan, A. J. Orr-Ewing and D. E. Shallcross, Sustainability 2024, 16(6), 2382; https://doi.org/10.3390/su16062382
[15] Frank, H. and Klein, A. 1997. Trifluoroacetic Acid: Assessment of Environmental Relevance. Final Report to AFEAS by Univ. Bayreuth (Project SP91–18.19/BP94-26). Reported in Environmental Risk Assessment of Trifluoroacetic Acid, J. C. Boutonnet et al. Article in Human and Ecological Risk Assessment · February 1999, https://doi.org/10.1080/10807039991289644
[16] Grimvall A., Borén, H., von Sydow, L., and Laniewski, K. 1997. Analysis of TFA in samples of rain, snow and ice collected at remote sites. Presentation to AFEAS, Washington, DC. Reported in Environmental Risk Assessment of Trifluoroacetic Acid, J. C. Boutonnet et al. Article in Human and Ecological Risk Assessment · February 1999, https://doi.org/10.1080/10807039991289644
[17] Increases in Trifluoroacetate Concentrations in Surface Waters over Two Decades, T. M. Cahill, Environmental Science & Technology 2022 56 (13), 9428-9434 DOI: 10.1021/acs.est.2c01826
[18] Comparison of Haloacetic Acids in the Environment of the Northern and Southern Hemispheres, B. F. Scott, C. Spencer, J. W. Martin, R. Barra, H. A. Bootsma, K. C. Jones, A. E. Johnston, and D. C. G. Muir, Environmental Science & Technology 2005 39 (22), 8664-8670, DOI: 10.1021/es050118l
[19] Distribution of Haloacetic Acids in the Water Columns of the Laurentian Great Lakes and Lake Malawi B. F. Scott, C. Spencer, C. H. Marvin, D. C. MacTavish, and D. C. G. Muir, Environ. Sci. Technol. 2002, 36, 9, 1893–1898 https://doi.org/10.1021/es011156h
[20] Continuing benefits of the Montreal Protocol and protection of the stratospheric ozone layer for human health and the environment, S. Madronich et al. Photochemical & Photobiological Sciences 2024 https://doi.org/10.1007/s43630-024-00577-8, section 6.3 Environmental concentrations and estimations of fluxes of TFA from chemicals under the purview of the Montreal Protocol