Mobility of contaminants in relation to dredging operations in a mesotidal estuary (Tagus Estuary, Portugal)

• Autor(a) principal: Vale, Carlos
• Data de Publicação: 1998
• Outros Autores: Ferreira, Ana M., Micaelo, Cristina, Caetano, Miguel, Pereira, Eduarda, Madureira, Maria J., Ramalhosa, Elsa
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10198/3940
• topic: Dredging operations; Mesotidal estuary; Metals; PCB congeners; Suspended sediments; Turbidity

During the construction of a New Bridge over the Tagus estuary 2.5 million tons of sediments were dredged, part of this quantity being contaminated material. The extension and intensity of the water turbidity associated with dredging operating varied with the tidal conditions but the resuspended material collected near the bucket dredger did not present a concentration increment in metals and PCB, when compared to the estuarine suspended sediments. The calculated distribution coefficients suggest that some contaminants in solids near the dredger were not in equilibrium with the water. A 24-hour laboratory experiment demonstrated the complexity and quickness of anoxic sediments oxidation. In such a short period of time metals in the solids change their fractionation. A second laboratory simulation showed that mussels accumulate metals and PCB congeners when placed in turbid aerated water.