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

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 mat...

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Bibliographic Details
Published in:Water science and technology 1998-03, Vol.37 (6-7), p.25-31
Main Authors: VALE, C, FERREIRA, A. M, MICAELO, C, CAETANO, M, PEREIRA, E, MADUREIRA, M. J, RAMALHOSA, E
Format: Article
Language:English
Subjects:
Aeration
Anoxia
Anoxic sediments
Bottom trawling
Brackish
Brackishwater environment
Bridge construction
Bridges
Coefficients
Congeners
Contaminants
Dredgers
Dredging
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Estuaries
Estuarine dynamics
Exact sciences and technology
Fractionation
Laboratories
Marine
Metal concentrations
Metals
Mussels
Oxidation
PCB
Pollution, environment geology
Polychlorinated biphenyls
Sediments
Suspended sediments
Turbidity
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Summary: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.
ISSN:0273-1223
1996-9732
DOI:10.2166/wst.1998.0731