Critical loads for the UK are calculated for soil-vegetation systems and lakes and streams. Scientists have chosen appropriate models for the different systems. For soils they are based upon the mineral weathering rate, which determines how fast neutralising elements are released from the soil.
Some vegetation has well-defined chemical thresholds for damage.
These have been used to compute critical loads for particular soil-vegetation systems. A similar approach, but using effects on fish or other aquatic animals, has been used for freshwaters. The maps show the amount of acidity which can be tolerated in different regions. Here we might expect to find damage from acidification. Damage is most likely where the critical loads are small and the excess deposition is high.