THE EFFECTS OF SCALE AND RESOLUTION IN DEVELOPING PERCENTILE MAPS OF CRITICAL LOADS FOR THE UK

Critical loads are estimated in the UK by the Department of Environmen t's Critical Loads Advisory Group and sub-groups. The Mapping and Data Centre at ITE Monks wood acts as the National Focal Centre for the UN ECE programme for mapping critical loads. The centre is responsible fo r the generation of UK data sets and their application for national an d European purposes. To make effective use of these data, it is necess ary to draw upon other environmental data and examine the issues of sc ale, uncertainty and the way that data are presented This paper outlin es the methodologies which have been employed to derive national maps. Early critical load maps were not vegetation specific, but now critic al loads for acidity and for nutrient nitrogen for soils, critical lev els maps for ozone and sulphur dioxide, and sulphur deposition maps, h ave been generated on a vegetation or ecosystem specific basis. These have been used to derive a number of different types of critical load and exceedance maps. The results show the importance of the method sel ected and the data used for the interpretation. The visualisation of c ritical loads and the corresponding exceedance data is an important as pect in producing information for pollution abatement strategies.