Evaluation of environmental risk caused by PAHs presence in river sediments − A multi-method approach using the example of the Odra River

The study provides a comprehensive assessment of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Odra River (Central Europe) using three complementary ecological risk evaluation methods. Official monitoring data from 18 sites along the river (samples collected 2022 - 2023) were analyzed using Sediment Quality Guidelines (SQGs), the Risk Quotient (RQ) method with negligible and permissible concentration benchmarks, and a probabilistic multi-substance potentially affected fraction (msPAF). PAH pollution was found to be significant, especially in the Upper Odra: total PAH concentration in 2023 reached ∼ 277,000 μg/kg d.m. at the most contaminated site; 4-6 ring compounds dominated in PAH profiles. Diagnostic ratios pointed to a predominantly pyrogenic origin of the PAHs All assessment methods indicated at least moderate ecological risk at the majority of sites, with the highest in the industrialized upper course. The msPAF results suggest that virtually all benthic species are adversely affected by PAH mixtures. The use of multiple risk assessment methods provided consistent evidence of PAH hotspots in the Odra catchment. The findings underscore an urgent need for targeted remediation of the most polluted sediment sites and the implementation of routine monitoring (including biological effect measures) to mitigate PAH risks in the Odra River ecosystem. • The ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) is a priority, given their mutagenic, carcinogenic and teratogenic effects on aquatic organisms. • The methods employed in the ecological risk assessment have confirmed the presence of a moderate ecological risk, attributable to the presence of PAHs (polycyclic aromatic hydrocarbons) in the sediment of the river Oder. • An exceptionally high environmental risk was identified in the upper reaches of the Oder River, specifically in the vicinity of industrial areas. • It was determined that in the upper reaches of the Oder, the vast majority of benthic species, estimated at approximately 100%, could be susceptible to risk due to exposure to PAHs (Polycyclic Aromatic Hydrocarbons). • The compounds exhibiting the highest concentrations were primarily fluoranthene, phenanthrene and benzo(b)fluoranthene. • The investigation revealed that the predominant PAH sources in the sediments were of a pyrogenic nature, with urban-industrial runoffs being a significant contributing factor.