Dynamic Geochemical Models to Assess Deposition Impacts and Target Loads of Acidity for Soils and Surface Waters

This chapter presents four geochemical dynamic models (VSD, MAGIC, ForSAFE and SMARTml) that have been used to assess impacts of nitrogen and acidity inputs on soil and soil solution chemistry. These models differ in their complexity and description of some processes. Some models can be used to calculate effects on surface waters as well. For all models this chapter shows examples of site-scale applications at intensively monitored forested plots in the UK, Germany, Switzerland and Norway, illustrating the adequacy of the model behaviour. Impacts of legislated emission reductions and forest harvest scenarios on soil solution chemistry are illustrated with a MAGIC model application. Besides scenario analyses, dynamic models can also be used to determine target loads, i.e. the deposition to reach a prescribed condition within a given time frame. This chapter introduces the target load concept and presents target load calculations with the MAGIC and the VSD model.