Abstract: Variations in the environmental conditions in marine and estuarine environments can lead to the release of metal fractions from the sediment to the seawater phase. The risk of release of potential pollutants from soils and sediment to the aqueous phase is well-assessed through leaching tests. In this work, a mathematical description of the kinetics of Pb and Zn release from marine sediment of the Suances estuary (northern Spain) with CO2 acidified seawater at pH values of 5, 6, 7 and 8 using leaching tests is proposed. The model considers the external mass transfer from the bulk liquid phase to the particle surface and the effective diffusion within the particle itself. Using Aspen Custom Modeler software, the effective solid diffusion values for Zn and Pb are obtained: Def,Zn=1.21×10-12 m2/s and Def,Pb=1.56×10-13 m2/s. Finally, the solid surface diffusion values for each pH studied value are also calculated. The obtained results would be useful as a line of evidence input for the risk assessment of potential carbon capture and a sequestration site where an advective flow of acidified fluid seawater at different concentrations of CO2 is in contact with recent contaminated sediment.

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