Investigation of Current and Future Nitrogen Depositions and Their Impact on Sensitive Ecosystems in Europe

Abstract

Eutrophication and acidification due to anthropogenic emissions is a major threat for bio diversity in vulnerable ecosystems. The combined impact of N and S deposition can be evaluated using ecosystem dependent critical load masses. Here, we used modelled N and S deposition fields from the CCLM-CMAQ chemistry transport model (CTM) to calculate the annual load. We compared the modelled loads with geo-referenced critical load (CL) maps from the Coordination Centre for Effects (CCE). We found that in central Europe around 25% of the areas defined in the CCE-CL database currently exceed their critical loads due to anthropogenic emissions. Expected NH3 emission reductions in the agricultural sector in the next decade showed little reduction potential in the area with critical load exceedance. A source receptor study of major N and S sources in Europe gave that SO2 emission reductions have a larger potential to decrease critical load exceedances than NH3 emission reductions. The most effective measure was the reduction of SO2 emissions from coal fired power plants. However, each source exhibited a different regional distribution which indicates that there is no general approach to reduce critical load exceedances. Moreover, we found a non-linear relationship between emission reductions and reductions in critical load exceedances. Furthermore, the reduction of only one of the two elements lead to diminishing returns without a reduction of the other.