Abstract
Suspended particulate matter (SPM) from 13 riverine sampling sites of the German Environmental Specimen Bank collected between 2005 and 2019 was retrospectively investigated for per- and polyfluoroalkyl substances (PFAS). The samples were analyzed both by target analysis for 41 PFAS and by a modified total oxidizable precursor (dTOP) assay to capture also unknown precursors. Temporal trends and spatial differences were investigated by generalized linear modeling (GLM). Time trend analysis across all rivers showed decreasing trends for ∑PFCA and ∑PFSA concentrations in SPM. Trends based on target analysis (∑PFCAtarget: -10.0%, ∑PFSAtarget: -8.2%) were more pronounced than in the dTOP analysis (∑PFCAdTOP: -4.2%; ∑PFSAdTOP: -5.3%), suggesting that conventional target analysis overestimated actual decreases as precursors are not considered. ∑PFAS concentrations determined by dTOP assay were 1.3-145 times higher as compared to target analysis, indicating substantial amounts of unknown precursors in the samples. The ∑PFASdTOP/∑PFAStarget ratio increased at all sites between 2005 and 2019. Contamination was highest in SPM from the Elbe tributary Mulde downstream of a large industrial park. The results underscore the need to go beyond conventional target analysis and include precursors when assessing PFAS contamination in the environment. The dTOP assay is a suitable tool for this purpose.
Highlights
Per- and polyfluoroalkyl substances (PFAS) have been identified as a major challenge in chemical management because they are used in many applications, are subject to longrange transport, and the perfluorinated compounds in particular have a very high persistence.[1−3]Currently more than 4700 PFAS are used in technical applications and consumer products,[4] many of them are socalled precursors and are covered by corporate secrecy
To get an impression of the environmental PFAS pollution, the measurement of sum parameters, for example, by the total oxidizable precursors (TOP) assay[12] is discussed, in addition to an increasingly refined target and nontarget analysis based on high-resolution mass spectrometry.[13−17] In the TOP assay, substances that may degrade to perfluorinated compounds under natural conditions, are oxidized to PFCA, while the length of the perfluorinated C-chain is largely preserved
As the mass of original precursors is reduced during this oxidation step, the results of TOP assay underestimate the mass of total PFAS
Summary
Per- and polyfluoroalkyl substances (PFAS) have been identified as a major challenge in chemical management because they are used in many applications, are subject to longrange transport, and the perfluorinated compounds in particular have a very high persistence.[1−3]. The German Environmental Specimen Bank (ESB) collects SPM annually since 2005 in the German parts of the three major streams Rhine, Elbe, and Danube as well as in three of their tributaries and stores well-mixed annual composite samples in the ESB cryo-archive These samples, which are available as ready-for-analysis subsamples, provide the unique opportunity to study time trends and evaluate whether regulatory measures were effective in reducing the environmental pollution. The objectives of the investigation were to (1) demonstrate the added value of the dTOP assay in environmental monitoring and (2) to assess temporal trends as well as spatial differences for PFAS and for precursor substances in SPM to contribute to our understanding of the extent and possible changes of the environmental PFAS contamination
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