Predicting pollutant concentrations in the water column during dredging operations: Implications for sediment quality criteria

The development of new dredging techniques that can reduce, or at least predict, the environmental impacts, is in high demand by governments in developing countries. In the present work, a new methodology was developed, to evaluate the level of metals contamination (i.e. cadmium, lead and zinc) of the water column, during a dredging operation. This methodology was used to evaluate the impacts of the construction of a new maritime terminal in Sepetiba Bay, Brazil. The methodology quantifies the amount of resuspended sediments and calculates the expected contaminants concentrations in the water column. The results indicated that sediment quality criteria were not compatible with water quality criteria, because the dredging of contaminated sediments does not necessarily yield contaminated water. It is suggested that the use of sediment quality criteria for dredging operations might be abandoned, and the methodology presented in this study applied to assess dredging's environmental impacts, predicting water contamination levels. - Graphical abstract: A graphic model showing transference of contaminants from the sediments to the water column. The dark sediment area represents the dredged sediments and the arrows emerging from them represent the resuspended sediments affecting the water column. - Highlights: •Developing countries demand for new dredging projects. •A new model evaluates concentrations of metals in the water, caused by dredging. •The model shows that water and sediment quality criteria are not compatible. •Local hydrodynamics have a strong influence on the contamination of the water. •Management of dredging operations reduces environmental contamination.