Application of the SMART2 model to a forested catchment in Finland: comparison to the SMART model and effects of emission reduction scenarios

SMART2, an extended version of the dynamic soil acidification model SMART, was tested with data from a forested catchment in Finland. The catchment belongs to the network of the Integrated Monitoring Programme and is situated in North Karelia (Eastern Finland). The aim of the study was to predict the long-term acidification of soil and runoff water at the study site under different scenarios of future sulphur and nitrogen deposition. Another objective was to study the model behaviour by comparing the results obtained with this extended version to those of SMART. Compared to previous SMART model calibrations, only the nitrate concentration in surface water was clearly closer to the mean observed value. For the specific purposes of the current study, the results did not indicate any great advantage in using the more complex model version SMART2. The scenario runs with both models showed a decline in soil base saturation and surface water pH in response to the rapid increase in acidifying deposition that started in the 1960s. The studied reduction scenarios will result in the cessation of environmental deterioration and the onset of recovery. However, the timing of the response depends on the stringency of the chosen abatement strategy.