European critical loads of cadmium, lead and mercury and their exceedances

Critical loads of cadmium (Cd), lead (Pb) and mercury (Hg) were computed by 17, 17, and 10 countries, respectively. The methodology used for calculating critical loads of heavy metals has been carefully reviewed and is documented in the Mapping Manual of the ICP on Modelling and Mapping. The methodology enabled the assessment of ecosystem specific critical loads to protect human or environmental health.

These critical loads were compared to preliminary computations of ecosystem specific deposition of the respective metals in 1990 and 2000. The robustness of deposition results can not yet well be established due to the many uncertainties. Bearing these uncertainties in mind, atmospheric deposition of Cd did not cause widespread risk in 2000, that the risk of Pb deposition decreased after 1990 but was still widespread in 2000 and, finally, that the risk caused by Hg did not change much from 1990 to 2000 in most of the countries that provided data on mercury.

Agricultural input of Cd causes exceedance in a single grid cell. For Pb fertilisation alone does exceed critical loads, especially in the Netherlands. Added to atmospheric deposition, however, the critical load of Pb is exceeded also in central Germany.