DATABASE OF CRITICAL LOADS OF ATMOSPHERIC POLLUTANTS

The database comprises estimates of the vulnerability of the land
surface of Great Britain to the effects of atmospheric pollution
(particularly acid deposition), on the basis of air quality and the
sensitivity of receptor soils, geology, freshwaters and vegetation
(trees, semi-natural vegetation and crops).

The Critical Loads Database was developed by the amalgamation of data
sets from the Institute of Terrestrial Ecology, the Soil Survey and
Land Research Centre (SSLRC), Macaulay Land Use Research Institute
(MLURI), and the University of Aberdeen.

The database is managed by the Critical Loads Mapping and Data Centre
(MADC) at Monks Wood and acts as the UK National Focal Centre for the
Critical Loads Advisory Group (CLAG), which was set up in 1991 by the
Department of the Environment to develop a national critical loads and
levels programme.

Data within the basic database correspond to each of the circa 250,000
1 km squares of the British National Grid. The data are held digital
forms within Laserscan Horizon and Arc-Info GIS and within an Oracle
database.

The MADC uses the database to map particular receptor pollutant
combinations which are then combined with current deposition loads or
exposure levels for that pollutant to produce critcal loads or level
exceedance maps.

Areas of potential damage can be quantified from these maps and these
form a basis for relating policy on pollutant emission abatements to
environmental benefits