Persistent and semivolatile contaminants in sediments of Nutrias Lagoon (Uruguay): historical trends and potential ecological implications

Sediments provide long-term archives of environmental change and are critical for reconstructing historical contaminant dynamics in aquatic systems. This study analyzed polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), mercury (Hg), and previously reported polycyclic aromatic hydrocarbons (PAHs) in a dated sediment core from Nutrias Lagoon, a small, shallow, and low-impact coastal lagoon in southeastern Uruguay. The site’s protected status and minimal local anthropogenic pressure make it an ideal reference system to evaluate diffuse and long-range pollution inputs. Results show that PCB 52 was sporadically detected, particularly in layers corresponding to the late 20th and early 21st centuries, consistent with historical global production and atmospheric redistribution. PBDEs were not detected, suggesting negligible inputs to the region. Mercury concentrations remained relatively stable (65–85 µg kg⁻¹) throughout the core and consistently below international sediment quality guidelines, reinforcing the interpretation of atmospheric deposition as the dominant source. In contrast, PAHs were more consistently present, with light compounds enriched toward the surface and isolated exceedances of ecotoxicological thresholds, indicating potential localized risks for benthic organisms. The temporal overlap between PAH maxima, PCB 52 detections, and the highest Hg values suggests periods of enhanced contaminant influx likely linked to regional or global emission events. Overall, the findings highlight that even protected, low-impact lagoons are susceptible to diffuse atmospheric contamination. Nutrias Lagoon thus provides a valuable paleoenvironmental baseline for assessing contaminant dynamics in South American coastal systems and underscores the need for continued monitoring under scenarios of global environmental change.