<p>Polluted sediments affected by historic discharges of hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), and polycyclic aromatic hydrocarbons (PAHs) pose risks to wildlife due to their bioaccumulative and toxic properties. Here, we propose an analytical method based on gas chromatography coupled to Orbitrap high-resolution mass spectrometry (GC–Orbitrap–HRMS) to investigate the presence of multiple contaminants in sediments from the Flix chlor-alkali plant hotspot and to assess their impact on birds from the Ebro Delta Natural Park using eggs of Audouin’s gull (<i>Larus audouinii</i>) as biomonitors. A combined target/suspect approach was optimised to (i) perform the quantitative analysis of 45 target persistent organic pollutants (POPs) and PAHs and evaluate quality parameters including recoveries, reproducibility, sensitivity, selectivity, and uncertainty measurement, and (ii) apply a suspect screening workflow using the high-resolution NIST library database to identify additional contaminants. Differences in compound patterns were observed between the matrices. In sediments, 4,4′-DDT was the predominant compound detected, reaching a maximum concentration of 49,386 ng g⁻¹ dry weight (dw), while PCB congeners ranged from 0.06 to 1376 ng g⁻¹ dw. In gull eggs, 4,4′-dichlorodiphenyldichloroethylene (4,4′-DDE) was detected from 1426 to 3473 ng g⁻¹ dw, and PCBs levels ranged from 0.40 to 2190 ng g⁻¹ dw. The suspect screening revealed 88 contaminants in the sediments (73 PCBs) and 43 compounds in the gull eggs (33 PCBs). Additional contaminants identified were plasticizers, industrial chemicals, and agrochemicals. This work demonstrates the importance of comprehensive contaminant characterisation in pollution hotspots to improve our understanding of potential impacts on wildlife inhabiting natural ecosystems.</p> Graphical abstract <p></p>