POPs Contamination of Aquatic Sediments of the Cerna River Watershed, Romania—Prevalence, Pollution Sources, and Ecological Risk Assessment

This study aims to evaluate the prevalence and pollution sources of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) in sediments of the Cerna River and its main tributaries, and to assess the associated ecological risk on aquatic ecosystem. The compounds were extracted from the dried sediments by ultrasound-assisted extraction and analyzed by gas chromatography coupled with mass spectrometry for PAHs, and with electron capture detector for PCBs and OCPs. Six isomeric and molecular ratios were used to identify the sources of pollution, three for PAHs, and three for OCPs. Ecological risk was assessed using the effects-range low (ERL) and effects-range median (ERM) methods, and health risk using toxic equivalent factors (TEFs). Twenty sediment samples from ten sampling points in two campaigns (October 2023 and August 2024) were collected. Results revealed high concentrations of ƩPAHs, with concentrations between 3.86 and 4450.75 ng/g dw, with values of the isomeric ratios indicating pyrogenic origins. OCPs concentrations ranged between 4.25 and 129.56 ng/g dw. PAHs presented a low biological risk, having concentrations below ERL. Low biological risk was also observed for ƩPCBs, ƩDDTs with values below ERL, and some between ERL and ERM, indicating occasional possible adverse effects.