Dynamic geochemical models to assess deposition impacts of metals for soils and surface waters

This chapter describes the use of geochemical models to assess the impacts of the deposition of metals on the concentrations of metals in soils and surface waters. We describe three dynamic models: SMART2-metals, SMARTml and CHUM-AM, each with their specific purpose and geographical scale of application. All three models include the most relevant metal fluxes and soil chemical processes, but with various level of detail related to their specific aim and scale. The ability of the models to simulate the long-term trends of metal fate was assessed by comparing model results and observations of either the present metal status, using hind cast simulations with historical deposition trends, or metal pools in chronosequences of afforested agricultural land of different stand age, or metal concentrations observed in a long-term monitoring study. The model simulations show the long times needed to approach equilibrium concentrations of metals due to changes in the atmospheric deposition of metals, sulphur and nitrogen. Dynamic models are therefore indispensable tools for the assessment of metal concentrations at changing levels of metal inputs to soil-water systems.