Describing the effects of acidification on the level of ecosystems, the acid deposition should be available at the scale of ecosystems or at scales which allow for comparison with critical loads. Several models exist for estimating long range transport of acidifying components on a European scale (EMEP, TREND model). However, the horizontal spatial resolution of these models is too coarse to meet the needs to model the deposition on ecosystems.
In this report a description is given of the EDACS model (European Deposition of Acidifying Components on Small scale), with which the deposition of acidifying components on a small scale over Europe is calculated for 1989. The acidifying components considered in EDACS are sulphur and reduced and oxidized nitrogen compounds. Dry deposition is estimated with the inference method i.e the deposition at the surface is inferred from the concentration and the deposition velocity at the same height. The deposition velocity is calculated using a resistance model in which the transport to and absorption or uptake of a component by the surface are described. Dry deposition velocity fields over Europe are constructed from a detailed land-use map (1/6 degree × 1/6 degree lat/long grid, made by RIVM) and meteorological information using a detailed parameterization of the dry deposition process. These small-scale dry deposition velocity fields are combined with concentration fields from the EMEP Lagrangian long range transport model to yield dry deposition amounts on a small scale.
Wet deposition is also estimated, based on measurements, to obtain a total acidifying deposition map at a European scale. These deposition fields clearly reflect the spatial detailed land-use information and the large-scale concentration pattern over Europe. The presented deposition fields are preliminary because of several shortcomings present in the method to estimate dry deposition and data bases. An update of the deposition fields and calculations for more recent years will be available in 1995. A more thorough uncertainty analysis of the deposition maps and a validation with measurements will also be carried out.The maps of the acidifying components over Europe on a small scale are made in cooperation with the EMEP/MSC-W, Oslo, Norway.