Occurrence and fate of PTE, PAH, and PFAS trace contaminants in soils and river suspended particulate matter in three DANUBEAN river catchments

This study aimed to investigate the occurrence and concentration patterns of three groups of trace contaminants-potentially toxic elements (PTEs), polycyclic aromatic hydrocarbons (PAHs), and per- and polyfluoroalkyl substances (PFASs)-in river catchments with contrasting land use and landscape characteristics. A second objective was to relate the concentrations in suspended particulate matter (SPM) to those in soils and to catchment attributes in order to identify dominant transport processes and contaminant sources. A spatially explicit monitoring campaign was conducted in three river catchments of the central Danube River Basin: Zagyva and Koppány in Hungary and Wulka in Austria. Composite soil samples (∼10 per catchment, totaling ∼200 subsamples) were collected from forest, pasture, and cropland areas. SPM was collected using both passive and active samplers under base-flow and high-flow conditions. The results revealed strong spatial variability in concentrations for five of seven PTEs, all PAHs, and eight of 10 PFASs. Substances predominantly deposited atmospherically-such as PAHs and several PFASs-were more concentrated in forest soils compared to pasture and cropland. Base-flow SPM samples were often more contaminated than high-flow samples, especially for PAHs and some PTEs. Concentrations in SPM were generally correlated with soil concentrations, suggesting that erosion-related transport of these chemicals may be significant in rural catchments. However, enrichment patterns and correlation strength varied by substance group and land use type. These findings support the use of parallel SPM and soil sampling for improving empirical emission modeling and source identification in catchments with mixed land use.