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WP3 Metals in the Environment: Chemistry and Fate Issues
() Extension of coupled multispecies metal TRANsport and SPECiation (TRANSPEC) model to soil compartment.
Bhavsar, S1, Diamond, M1, Gandhi, N1, 1 University of Toronto, Toronto, ON, Canada
ABSTRACT- A coupled multispecies metal fate-TRANsport and SPECiation/complexation (TRANSPEC) model was developed for surface aquatic systems and used to assess the movement of multiple metals in various lakes that ranged from eutrophic to oligotrophic and mine-impacted to pristine. We now extend TRANSPEC model to estimate metal movement in soil and the metal input from the soil compartment to the aquatic system. The extended model includes two soil layers, surficial and deeper, in addition to water column, surficial and deeper sediments. The extended TRANSPEC model estimates the partition coefficient, Kd, between solid and soluble phases of soil using semi-mechanistic regression models that consider chemistry parameters such as pH, total metal concentrations, and the organic matter content of soil. A geochemical speciation/complexation module is used to calculate species fractions in dissolved and colloidal (operationally defined as DOM) phases of soil solution. The module also estimates partition coefficients, Kd, and species fractions in dissolved, colloidal and solid phases of water and sediments. Multispecies fugacity/aquivalence based on the fate-transport module then estimates inter-media transport rates such as leaching from soil, soil runoff to an aquatic system, and diffusive and particulate exchanges between water and sediments of each metal species. The model is applied to a unit world environment and used to demonstrate the fate of metals under various environmental conditions.
Key words: coupled model, speciation and fate, metals in soil and lake, multispecies metal
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