Modeling heavy metal concentration distributions in estuarine waters: an application to Suances Estuary (Northern Spain)

Using numerical modeling as a tool to simplify management tasks is a less expensive complementary method to indirectly monitor estuarine zones. Nevertheless, information regarding the sedimentary dynamics and the pollutants present in the area, specifically in the sediment, must be known before a model can be used successfully. The two-dimensional transport model “SOLTOX” allowed the study of the fate and transport of heavy metals in estuarine waters, with particular application to the zinc evolution along the Suances Estuary (Northern Spain) which, historically, has suffered the effects of industrial pollution. As many pollutants can be adsorbed on suspended solids, advection–diffusion transport analyses were tackled to model not only the zinc but also the suspended solids concentration distributions. The importance of specific parameters related with the suspended solids transport modeling was also explored. Using the collected data during a whole tidal cycle for suspended solids and current velocities, a graphical method was applied to obtain the initial values for the calibration and validation of the model main parameters. The model was first calibrated against the field data for suspended solids. The obtained results exhibited the critical shear stress for deposition as the overriding parameter. The model was then used to investigate the zinc transport processes in the Suances Estuary. A reasonable agreement between modeled and measured data was achieved for the suspended solids and zinc. Moreover, the results demonstrated a dependence on the background concentration of the pollutant in the sediment. However, the background concentration in the water column had little effect on the model results.

.