Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2023

Sorption and transfer behaviour of perfluoroalkyl acids (PFAAs) and polyfluoroalkyl phosphate diesters (diPAPs) in the soil-plant pathway for hazard assessment and evaluation of  per- and polyfluoroalkyl substances (PFAS) contamination (#49)

Mark Buecking 1 2 , Bernd Goeckener 1 , Janine Kowalczyk 3 , Hildegard Just 3 , Jörn Breuer 4 , Eva Weidemann 5 , Matthias Gaßmann 5 , Thorsten Stahl 6 , René Laemmer 1
  1. Fraunhofer IME, Schmallenberg, NRW, Germany
  2. Monash University, Melbourne, Australia
  3. German Federal Institute for Risk Assessment, Berlin, Germany
  4. Agricultural Technology Centre Augustenberg , Karlsruhe, Germany
  5. University Kassel , Kassel, Germany
  6. Chemisches und Veterinäruntersuchungsamt Münsterland-Emscher-Lippe (CVUA-MEL), Münster, Germany

The background of the research project was a major environmental pollution event in southwest Germany, where several hundred hectares of agricultural land were contaminated by paper sludge containing PFAS.

Leachte and plant transfer studies with maize plants were carried out under both natural and laboratory conditions.

For all studies, a target method as well the direct total oxidizable precursor dTOP assay as described by Göckener et al. was used as a sum parameter. It is a modification of the originally implemented TOP assay by Houtz and Sedlak without prior extraction step.

Results on the PFAS content in leachate showed comparable substance courses in the differently contaminated soils between the experiments under laboratory conditions and near-natural conditions. The short-chain perfluoroalkylcarboxylic acids (PFCAs) perfluoropentanoic acid and perfluorohexanoic acid were the main compounds in the leachate samples of the 6:2 diPAP-spiked lysimeters and soil columns and those filled with contaminated field soil. For the 8:2 diPAP variants, perfluorooctanoic acid (PFOA) showed the highest concentrations in the leachate.

PFAS levels in maize plants showed a transfer into the different plant compartments (leaves > stem > spindle) in both the field study and the study under controlled conditions.

 The detection of PFCAs with chain lengths ≤ C6 (6:2 diPAP application) or chain lengths ≤ C8 (8:2 diPAP application) in the leachate and maize compartments shows the degradation of diPAPs into persistent PFCAs in the environment and their subsequent PFCA-transport into deeper soil horizons. The diPAPs themselves mainly remain in the upper soil layer and are hardly taken up by the plants showing a high level of immobility.

Furthermore, the uptake of PFAS into maize plants can be seen as a potential pathway of PFCAs into the food chain.

Additional studies will be necessary to understand the environmental behaviour of PFAS precursors more thoroughly.

  1. Göckener, B., Eichhorn, M., Lämmer, R., Kotthoff, M., Kowalczyk, J., Numata, J., Schafft, H., Lahrssen-Wiederholt, M., Bücking, M. (2020) Transfer of Per- and Polyfluoroalkyl Substances (PFAS) from Feed into the Eggs of Laying Hens. Part 1: Analytical Results Including a Modified Total Oxidizable Precursor Assay. Journal of Agricultural and Food Chemistry 68:12527-12538.
  2. Houtz, E. F. and Sedlak, D. L. (2012) Oxidative conversion as a means of detecting precursors to perfluoroalkyl acids in urban runoff. Environ Sci Technol 46:9342-9.