Unveiling the impact of lipophilic brominated flame retardants in Danube River sediments: a deep dive into pollution sources and distribution

Aquatic sediments serve as both a major sink and a potential secondary source of polybrominated diphenyl ethers (PBDEs), a class of persistent, bioaccumulative, and toxic pollutants. This study assessed ten PBDE congeners in Danube River sediments (Serbia), addressing their occurrence, spatial distribution, and potential sources. Σ10PBDE concentrations ranged from 0.52 µg/kg dry weight (War Island) to 31.21 µg/kg dry weight (Neštin), with BDE-209 as the predominant congener. Localized dominance of hepta- and penta-BDEs at Neštin and Šangaj suggested site-specific contamination patterns. Comparative analysis indicated levels comparable to or exceeding those in other industrialized regions, implicating anthropogenic activities as key contributors. Source apportionment using Principal Component Analysis identified three major pathways: (1) transport and debro-mination of higher-brominated congeners, (2) direct anthropogenic discharge, and (3) improper waste manage-ment. Hierarchical cluster analysis and Kohonen’s self-organizing maps pinpointed Neštin as a pollution hotspot. This study provides the most comprehensive dataset on PBDE contamination in Serbian Danube sediments, establishing a critical baseline for future monitoring and regulatory actions.