Distribution and fate of PAHs across multiple biotic and abiotic compartments in aquatic ecosystems

Aquatic ecosystems are continuously threatened by PAH contamination that represents significant toxicological risks to both environmental and human health. These pollutants enter water bodies mainly through atmospheric deposition or surface runoff, and their environmental fate is governed by complex physico-chemical factors and bioaccumulation processes. To evaluate PAH levels and their distribution patterns, the occurrence of 16 priority compounds was analyzed in various river matrices. The monitoring program included abiotic (bottom sediments, suspended solids, water) and biotic (fish, benthic organisms, biofilm) matrices. Samples were collected at 28 locations covering all major river basins in the Czech Republic during 2025. PAHs were detected in all matrices, with distribution of individual compounds depending on affinity for organic carbon or lipid. Levels of fluoranthene and benzo[a]pyrene in biota exceeded environmental quality standards at a number of monitored locations. Results also revealed spatial variability among the locations, reflecting diverse levels of anthropogenic pressure across the river basins. Overall, multi-matrix monitoring is essential for a comprehensive contamination assessment, as the unique properties of each compartment lead to uneven pollutant distribution in aquatic ecosystems.