Recovery from Acidification - Policy Oriented Dynamic Modeling

Sammanfattning: Dynamic biogeochemistry models are important tools for determining the time-scales of recovery from acidification. In the review process of the 1999 UNECE LRTAP Gothenburg protocol, results from dynamic models will probably be included when determining further reductions of acidifying emissions. This thesis describes modeling of recovery from acidification using the dynamic multi-layer soil chemistry model SAFE. Sulfate adsorption was added to SAFE, modeled by a sulfate concentration and pH dependent isotherm. A method to parameterize this isotherm was developed and the isotherm was parameterized for a total of 20 sites, whereof 18 are located in Sweden, 1 in Germany and 1 in Poland. The SAFE model including sulfate adsorption was applied to 19 of these. The addition of sulfate adsorption improved the predictions of sulfate dynamics, especially at sites where there had been large deposition changes and where sulfate adsorption capacity is high. Three of the modeled sites are well-studied single-sites and 16 sites are a part of regional study. Differences in data requirements and model output for the different types of studies are discussed from a policy perspective. The influence of climate driven changes in sea-salt deposition and of changes in forest practices and vegetation on model predictions of recovery is also discussed. The SAFE model applications show that many sites in Sweden and Europe are still severely acidified and that soil recovery will require both further emission reductions and many decades of time.