Trace Metal Modelling of a Complex River Basin Using the Suite of Models Integrated in the OpenMI Platform

Modelling trace metal dynamics is essential in an integrated modelling framework as trace metals have the potential to be fatal, even when present at low concentrations. Since the degree of bioavailability of a metal depends on its presence in the dissolved phase, it is necessary to keep track of both the dissolved and particulate phase of metals. In general, the well-known partitioning coefficient approach is widely used for trace metal speciation. As such, we applied a parametric approach to relate the partitioning coefficient to several environmental variables. These environmental variables are made available by a suite of physically based models (a hydrologic and diffuse pollution model, Soil and Water Assessment Tool (SWAT): a hydraulic model, Storm Water Management Model (SWMM): a stream temperature model: an in-stream water quality conversion model: and a sediment transport model) integrated using the Open Modelling Interface (OpenMI). For trace metal speciation, two regression techniques, (a) the multi-linear regression (MLR) and (b) the principle component regression (PCR), were used. It is then tested in the Zenne river basin, Belgium, to simulate four trace metals (copper, cadmium, zinc and lead) dynamics. We demonstrated the usefulness of the OpenMI platform to link different model components for integrated trace metal transport modelling of a complex river basin. It was found that the integrated model simulated different metals with ‘satisfactory’ accuracy. The MLR- and PCR-based model results were also comparable. From a management perspective, the river is not heavily polluted except for the level of dissolved zinc. We believe that the availability of such a model will allow for a better understanding of trace metal dynamics, which could be utilized to improve the present condition of the river.