A Numerical Model for the Transport of Chromium and Fine Sediments |
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Authors: | Alfredo Emilio Trento Ana M Alvarez |
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Institution: | 1.Facultad de Ingeniería y Ciencias Hídricas,Universidad Nacional del Litoral,Santa Fe,Argentina |
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Abstract: | A mathematical model which represents the transport processes of heavy metals and fine sediments in a fluvial stream was developed.
The model consists of a three-equation system: the first one for total chromium concentration in the water column, C
Tw, the second one for total suspended sediment concentration, S
w, and the third one for chromium concentration in bed sediments, r. The third equation represents the chromium exchange between the water column and bed sediments by two processes: diffusion
of soluble chromium and erosion/deposition of chromium sorbed to sediments. The basic assumption of the model is the instantaneous
equilibrium. The main parameters are the partition coefficients in the water column and bed sediments, the depth of the active
bed sediment layer, and the mass transfer coefficient between the water column and sediment pore water. The numerical model
approximates the equations of advection–dispersion for chromium in water and suspended sediments by using a Eulerian third-order
scheme. Numerical vs. analytical solutions were considered satisfactory for different initial, boundary, and sedimentological
conditions. In order to estimate the impact of a chromium side discharge, the model was implemented for the Salado River in
a reach of 65.6-km long (Santa Fe, Argentina). The results showed the effect of chromium discharge on almost the whole reach,
then the vulnerability of the water quality in the Salado River when the flow was low was evidenced. When comparing the computed
and measured results, the former showed a reasonable representation of the presence of chromium in water and bed sediments. |
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