Linking Ammonia Emission Trends to Measured Concentrations and Deposition of Reduced Nitrogen at Different Scales

This document builds on the Bern Background Document (Sutton et al. 2003), which was used to facilitate the discussion about following emission trends by means of measurement data at the UN/ECE Ammonia Expert Group meeting in Bern (Switzerland) in 2000. It is now 6 years since the Bern Workshop and major new datasets on European NH3 and NH4+ monitorin gand their relationship to estimated NH3 emissions have become available for the following countries: UK, Germany, Hungary, Switzerland, Denmark, the Netherlands, North Carolina. Slovak Republic, Norway and Croatia. Based on these datasets our current scientific understanding about the different issues is updated. In particular, input will be given to questions like: is there still an "Ammonia Gap" in the Netherlands, does such a gap exist in other countries, can we be confident of the effectiveness of ammonia mitigation policies and how can we best address the relationships between emission and deposition using atmospheric modelling and improved monitoring activities.