Metals mobility and bioavailability assessment in the water column caused by dredging operations of polluted sediments

• Ano de defesa: 2023
• Autor(a) principal: Vicente, Murilo de Carvalho
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Palavras-chave em Português: Trace metals; Bioavailability; Sepetiba Bay; Metal traço; Sedimento; Análise de sedimentos; Baía de Sepetiba (RJ); Poluente ambiental; Dragagem; Ambiente costeiro; Metais traço; Biodisponibilidade; Baía de Sepetiba
• Link de acesso: http://app.uff.br/riuff/handle/1/29347

The accumulation of metals can reach degrees capable of representing a coastal environment's risk. However, the bioaccumulation of trace metals through the trophic chain represents also a risk real for human health. The coastal sediments are considered the main receptor and reservoir of pollutants, mostly trace metals. Eventually, these metals reach the coastal region by fluvial transport, commonly associated with organic matter the particles flocculate and settle. In the coastal sea bottom, the trace metals frequently face reducible conditions in sediments capable to decrease mobility, resulting in biounavailable and stabilized chemical species. However, the polluted sediment resuspension by natural or anthropogenic events could result in potential redox and pH changes, influencing directly on the trace metals mobility. Therefore, the trace metals characteristic in different geochemical fractions assessment associated with the sediment physicochemical conditions is crucial to the full comprehension of these pollutants in the coastal environment. For the trace metals assessment in surface sediments of Sepetiba Bay were collected 18 samples. The geochemical fractionation assessment was performed through the BCR-701 sequential extraction, for the determination of pollution extension were applied the Geoaccumulation Index (Igeo), and the Enrichment Factor, and for assessment of pollution risks for the biota were applied the Risk Assessment Code (RAC) and the Risky Pollution Index. A resuspension experiment was used to quantify the amount of metals (Cd, Ni, Cr, Fe, Al, Pb, and Zn), the concentration of the metals were determined in the sediment by ICP-OES and in the water by ICP-MS. A model to predict the concentration of trace metals in the water column after a resuspension event was developed through the geochemical fraction assessment associated with the resuspension experiment results. The Cd and Zn presented approximately 50% of the total in concentration in the exchangeable phase, with relevant enrichment and risk to the biota. The resuspension experiment demonstrated the effectiveness of the potential redox manipulation to metals release, especially for Cd, Pb, and Zn. During the process of changing the reducible to oxidant condition was possible to observe the metals release to solution and reassemble into the different geochemical compartments. The geochemical model for trace metals prediction in the water column presented a relevant tool for planning and/management of activities involving polluted sediments.