Polycyclic aromatic hydrocarbons in estuarine sediments as a consequence of the mine tailings remobilization and transport in the Rio Doce basin

• Published in: Integrated environmental assessment and management 2024-01, Vol.20 (1), p.169-178
• Main Authors: Silva, Cesar A., Zacché, Danillo S., Lehrback, Bethânia D., Cagnin, Renata C., Costa, Eduardo S., Longhini, Cybelle M., Bernardino, Angelo F., Sá, Fabian, Neto, Renato R.
• Format: Article
• Language: English
• Subjects: Aquatic ecosystems; Aromatic compounds; Aromatic hydrocarbons; Benthos; Biomass burning; Brackishwater environment; Classification (sedimentation); Contaminants; Contamination; Dam failure; Ecological effects; Estuaries; Estuarine dynamics; Estuarine sediment; Fossil fuels; Mine tailings; Mine wastes; Mining tailings; Polycyclic aromatic hydrocarbons; Rio Doce; Samarco; Sediment; Sediments; Tailings
• ISSN: 1551-3777; 1551-3793
• DOI: 10.1002/ieam.4831

The Fundão dam failure in 2015 severely impaired the economy, the lives of riverine communities, and the aquatic ecosystems of the Rio Doce basin in southeast Brazil. Several contaminants, including polycyclic aromatic hydrocarbons (PAHs), were transported downstream, deposited in the estuary, and released into the Atlantic Ocean. The high concentration of PAHs in estuarine sediments may pose ecological risks and deleterious effects to benthic organisms, so here we aimed at determining the source and fate of these compounds before and after the tailings’ arrival. The mean concentration of the analyzed Σ16PAHs increased from 34.05 µg kg−1 in the prefailure period to 751.77 µg kg−1 one year after the arrival of the tailing. The classification of the sediment quality changed from low to moderate contamination. Our results suggest that there was PAHs remobilization by mine tailings along the Rio Doce basin. The target analytes exhibited mostly a pyrolytic profile from fossil fuel and biomass burning. In addition to other contaminants deposited in the estuary after the arrival of the tailings, this study revealed that the profile change of PAHs in the estuary region is a consequence of the mud's erosive power. Integr Environ Assess Manag 2024;20:169–178. © 2023 SETAC Key Points One year after the tailings arrived at the mouth, the average concentration of polycyclic aromatic hydrocarbons (PAHs) in the estuary increased 20 times. Sediment quality changed significantly from low to moderate and/or high contamination. The sources that contributed to the input of PAHs also changed over time, at first characterized by burning fossil fuels prior to arrival and transitioning to a mixed pyrolytic profile after the tailings arrived at the river's mouth. The compounds carried by the mud appear to be trapped in the estuary, creating a source of chronic contamination for the mouth and adjacent coastal areas.