The NERC and CEH trade marks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. Wet deposition of nitrogen and sulphur was found to decrease more slowly than the emissions reductions rate.This is attributed to a number of factors including increases in emissions from international shipping and changing rates of atmospheric oxidation. The modelled time series was extended to a 50 year period from 1970 to 2020. The modelled deposition of SO x , NO y and NH x to the UK was found to fall by 87%, 52% and 25% during this period. The percentage of the United Kingdom surface area for which critical loads are exceeded is estimated to fall from 85% in 1970 to 37% in 2020 for acidic deposition and from 73% to 49% for nutrient nitrogen deposition. The significant reduction in land emissions of SO 2 and NO X focuses further attention in controlling emissions from international shipping. Future policies to control emissions of ammonia from agriculture will be required to effect further significant reductions in nitrogen deposition.

FRAME is a statistical Lagrangian model, which describes the main atmospheric processes (emission, diffusion, chemistry and deposition) taking place in a column of air. The model is used to calculate maps of dry and wet deposition for sulphur and nitrogen. Historical emissions data are used in the model to calculate changes in deposition of sulphur and oxidised and reduced nitrogen for the UK at a 5 km x 5 km resolution for the years 1990-2005. Emissions of SO 2 , NO x and NH 3 in the UK have fallen by 77%, 47% and 18% during this period. FRAME calculated reductions in wet deposition to the UK of 56%, 17% and 16% for SO x , NO y and NH x respectively. Inter-annual variation in meteorology was found to have a significant influence on pollutant transport and the national wet and dry deposition budget. This occurred due to differing wind direction frequency as well as annual precipitation. When using year with specific wind conditions, wet deposition can even change by more than 20%. It was also observed that wind conditions have a greater influence on deposition budget than precipitation data. Modelled trends in nitrogen and sulphur wet deposition have been compared with measurements from the national acid deposition monitoring network during this period. A more comprehensive monitoring network has been used to verify model results for deposition of SO 4 2-, NO 3-, and NH 4+ for the year 2005.